1
Q
When are nutrients considered to be essential to the human diet?
(2)
A
- Removing the nutrient causes a deficiency & decline in health
- Putting the nutrient back into the diet corrects the problem & health returns
2
Q
When do nutritional deficiencies occur?
A
Nutritional deficiencies occur when a person’s nutrient intake consistently falls below the recommended requirement.
*Note: amount of time to see a deficiency depends on the nutrient.
3
Q
A deficiency in iron, folate, and/or Vitamin B12 causes _________.
What occurs in this deficiency?
A
A deficiency in iron, folate, and/or Vitamin B12 causes ANEMIA.
- Not enough RBC to transport O2 around the body
- important at key stages of development (e.g., pregnancy and infancy)
4
Q
A deficiency in ______ is called Beriberi.
What are some of the results of this deficiency?
A
A deficiency in THIAMINE (VITAMIN B1) is called Beriberi.
- Defective energy production
- Abnormalities in the nervous system
5
Q
Defective collagen production & hemorrhaging/ bleeding of gums are symptoms of the deficiency of what nutrient? What is this deficiency called?
A
These are symptoms of a Vitamin C deficiency. This deficiency is called scurvy.
6
Q
Vitamin D is obtained from the diet and made by the body via UV radiation. What happens when there is a deficiency in this nutrient? What is this deficiency called?
A
Deficiency in Vitamin D: Rickets
- causes defective bone growth
7
Q
Most Canadians have a Vitamin D deficiency. True or False?
A
True.
Survey says 2/3 Canadians have less Vitamin D than necessary.
8
Q
What is the difference between a deficiency and a nutritional requirement?
A
Deficiency –> amount needed to prevent disease
Nutritional requirement –> amount needed to ensure optimal health
9
Q
What was the original use of nutritional requirements intended for?
A
Nutritional requirements were made in WWI when rationing food for soldiers.
10
Q
What were the limitations with the first set of nutritional requirement recommendations?
A
Didn’t take into account:
- Age
- Gender
- Body Size
- Physical activity
11
Q
Nutrition research and statistics are used to establish nutrient requirements. True or False?
A
True.
12
Q
What is the purpose of % DV?
A
%DV are a simplified way for governments to provide consumers with information about the daily requirement for each nutrient.
*based on 2000 calorie/ day diet.
13
Q
Daily Values are made using _________.
(Hint: DRI)
A
Daily Values are made using DIETARY REFERENCE INTAKE.
14
Q
Daily reference intake, unlike %Daily Value takes into account lifestyle (athletes). True or False?
A
False.
15
Q
What is the definition of Dietary Reference Intake?
A
DRI –> umbrella term that refers to a set of reference values for nutrients (EAR, RDA, AI, UL).
They were introduced in 1997.
16
Q
What are “Nutrient Requirements”?
A
Nutrient requirements –> range of nutrient intakes required by individuals in a population subset to achieve the same end point of growth, storage, health.
17
Q
What are nutrient requirements based on?
2
A
Based on:
- Estimated Average requirement (needs of 50% of the population are met)
- Recommended Dietary Allowance (needs of 97% of the population are met)
18
Q
The highest level of continuous daily nutrient intake that causes no risk of adverse effects is called ________.
A
The highest level of continuous daily nutrient intake that causes no risk of adverse effects is called the TOLERABLE UPPER LIMIT (UL).
19
Q
The adequate intake, on the nutrition curve, is found between the _____ and the _____.
It is based on the nutrient intake of healthy people (who are assumed to have adequate nutritional status).
A
The adequate intake, on the nutrition curve, is found between the RDA and the UL.
*(Recommended Dietary Allowance and Upper Limit)
20
Q
What was the Minnesota Starvation Experiment led by Ancel Keys in 1944?
What were the effects of the study on the participants?
A
Studied physical & mental effects of starvation in 36 healthy men.
3 months @ 3200 kcal/day
6 months @ 1800 kcal/ day
3 months rehabilitation
Results:
- Weight loss, irritability, dizziness, tiredness, hair loss, reduced sex drive, depression, etc.
21
Q
What are the 4 characteristics of a nutritious diet? Give a brief description of each.
A
- Adequate
- provides enough calories, essential nutrients, and fibers to keep you healthy - Moderate
- ensuring you don’t consume excessive calories, or eat more of one food/ food group than recommended - Balanced
- Making sure you eat nutrient-dense foods rather than nutrient-poor foods - Varied
- eating a wide selection of foods to get the necessary nutrients
22
Q
What are some methods of studying nutrition?
(4)
What is the main challenge for studying nutrition?
A
- Cell culture models
- Animal models (rodents, pigs, etc.)
- Epidemiological cohort studies (studies based on exposure)
- Prospective vs. Retrospective - Intervention studies
- Randomized Control Trial (RCT)
Main challenge : adding human variability
(genetics, lifestyle, cultural habits, etc.)
23
Q
What are two ways of classifying nutrients?
A
- Macronutrients & micronutrients
- Oranic & Inorganic
*2nd is useful because it allows the classification of water
24
Q
How much of our body is water? (%)
A
About 60% of our body is water.
25
Anabolism + Catabolism = ________
Anabolism + Catabolism = METABOLISM
26
What is the average water intake of an adult human?
2.7L-3.7L / day.
27
What are some major functions of water?
| 5
- Solvent in biochemical reactions
- Catabolism (hydrolysis)
- Maintains vascular volume
- Nutrient transport
- Temperature regulation
28
When does water toxicity occur?
Water toxicity occurs when water intake is greater than the kidney's ability to process it (aroun 0.9L/ hour).
*The body tries to establish a new equilibrium by moving water into cells, leading to hyponatremia.
29
What is hyponatremia? When can it occur?
Hyponatremia --> a water/ sodium imbalance
Occurs from excess fluid intake, under-replacement of sodium, or both.
*Avoided with urination. Causes CNS edema and muscle weakness.
30
What is the definition of food analysis?
The development, application and study
of analytical methods for characterizing foods and their
constituents.
31
Food analysis is important because it allows the consumer to make informed decisions about their food. True or False?
True.
32
Food analysis is driven by government regulations. What do these regulations ensure?
(4)
- Maintain quality of foods
- Ensure food industry makes safe foods with high quality
- Fair competition between companies
- Eliminate economic fraud
33
What is the purpose of quality control?
- Ensure food composition doesn’t change
| - characterize raw materials
34
Calorie content is more important than food composition. True or False?
False.
| Food composition is more important than calorie content.
35
Caloric content predicts nutrient content in foods. True or False?
False.
| Caloric content DOES NOT predict nutrient content in foods.
36
What are the 5 steps of proximate analysis?
1. Moisture (water)
2. Ether Extract (lipids)
3. Ash (minerals)
4. Nitrogen (protein)
5. Crude Fiber (fiber)
37
What is the process for determining water content in proximate analysis?
Air dry.
38
Why is it important to determine water content in feed?
| give 3 reasons
- Water is weight and is part of the price of feed + shipement (more water = higher costs)
- Plays a role in storage conditions
- Too much = food spoils quickly
- Too little = food is less palatable
- Moisture dilutes energy and nutrients in food
- Moisture important for optimum intake and performance of animals
39
What is the formula to determine % moisture?
| What is the formula to determine % dry matter?
% moisture = [(wet weight – dry weight)/ wet weight] ×100%
% dry matter = 100 - % moisture
40
What is a potential error/ limitation of determining moisture content?
- Drying can remove other volatile compounds, like SCFA and some minerals
* This can cause under-estimation of dry weight
41
What is the difference between human food industry and agriculture industry when it comes to % moisture?
Agriculture industry --> interested in composition of dry matter
Human food labelling --> Based on wet weight
42
What is the process for determining crude fat in proximate analysis (ether extract)?
(General and step by step)
General: Ether extraction
Steps:
1. Take sample of dry matter, mix it with salt
- This makes all the fats soluble, anything that is not a fat will be drained out
2. Take solution out of tube
- Resulting precipitate is the fat
43
What is the formula to determine % crude fat? (Proximate analysis)
% crude fat = (weight of ether extract /wet weight of sample) ×100%
44
What are some limitations of finding crude fat % through ether extract?
-There can be other things that are soluble in ether extracts that are not nutrients
(Chlorophyll, resin, waxes in plants)
- This over-estimates crude fat determination
*Industry doesn't care how MUCH fat is in a food sample, they care what KIND of fats are in a sample --> can be determined through chromatography
45
What is the process to determine the ash in proximate analysis?
Ignite the residue from the ether extraction. What's left is inorganic (minerals)
46
Why is it important to measure mineral content in proximate analysis?
(5)
- Nutritional labelling
- Quality and taste of food
- Microbiological stability
- Nutritional requirements
- Manufacturer processing (want to know quality & characteristics of food)
47
What is the formula to determine % ash in proximate analysis?
% Ash = (weight of ash/ wet weight of sample) ×100%
48
What are some errors/ limitations when determining mineral content in proximate analysis?
- Volatile minerals may be lost when burning the residue
- No information about individual minerals
*Note: It is now mandatory for food labels to indicate sodium content
49
What is the process to determine nitrogen content in proximate analysis?
(Hint: 1 word)
Kjeldahl.
50
What are two assumptions that need to be made for the Kjeldahl analysis?
1. All nitrogen is in protein
| 2. All protein contains 16% nitrogen
51
What are the three main steps in the Kjeldahl Analysis? Give a brief description of each.
```
1. Digestion
– A food sample is mixed with sulfuric acid, which converts
nitrogen into ammonia
2. Distillation
– separates the ammonia
3. Titration
– quantifies the amount of ammonia
```
52
What is the formula to determine crude protein %? (proximate analysis).
% crude protein = [(N in sample ×6.25)/ wet weight of sample] ×100%
53
In the proximate analysis crude protein formula, where does the 6.25 come from?
100% (total protein) ÷ 16% (nitrogen) = 6.25
**Note: will change depending on the protein nitrogen content
54
What are some potential errors/ limitations of the kjeldahl analysis?
1. Assumes all proteins have 16% nitrogen
2. There are other sources of nitrogen in foods (nitrates, nitrites, urea, nucelic acids)
- This slightly over estimates crude protein content
55
What is the formula to determine % crude fiber of a food sample? (Proximate analysis)
% Crude Fiber = [ (weight of ASH + crude Fiber) - (weight of ash)] / wet weight of sample x 100%
56
What is the difference between crude fiber and dietary fiber?
Crude fiber --> insoluble fibers left after proximate analysis (mainly cellulose & ligand)
Dietary fiber --> all fiber (soluble and insoluble)
- to estimate this better, need further analysis
- usually non-digestible complex CHO, structural part of plants
57
What are some potential errors of determining crude fiber?
1. Unable to distinguish different fibre components
2. Measuring crude fibre under-estimates the actual dietary fibre content
of feed by up to 50%.
– Dietary fibre includes cellulose, hemicellulose, pectin, mucilages, gums, lignin,
etc. Soluble fibres are lost during the proximate analysis.
58
Nitrogen Free Extract (NFE) = Digestible Carbohydrate (CHO)
| True or False?
True.
| NFE estimates starch & sugar content
59
What is the formula to determine % NFE?
% NFE = 100 - (% moisture + % Crude Fat + % ASH + % Crude protein + % Crude Fibre)
*Has highest potential error because accumulates errors of all the other components
60
Proximate analysis is used for food labeling and tells us the digestibility of food.
True or False?
False.
Although it is used for food labeling, proximate analysis gives no information of the "digestibility" of a food.
- We don't know what actually gets absorbed.
61
Dietary fiber can be soluble or insoluble. Give examples of each and a brief description.
1. Insoluble:
- cellulose, lignin, hemicellulose
- remains intact through intestinal tract (doesn't dissolve in water)
2. Soluble
- Pectin, Gums, Mucilages
- forms gel ( dissolves in water)
62
What are the two fibre analyses to complement the proximate analysis?
1. Van Soest Method (detergent fiber analysis)
| 2. Southgate Method
63
What is the purpose of the Van Soest Method of Fiber analysis?
(2)
1. Differentiates between insoluble fibres
- Cellulose & Hemicellulose
- Lignin (poorly fermented, prevents fermentation of other fibres)
2. Determines fermentable and non-fermentable CHO
- Very important for agricultural applications!
*Note: Poorly differentiates sugars, starches, & soluble fibres
64
What is the purpose of the Southgate Method of Fiber analysis?
(2)
1. Provides information about sugars, starch and
various fibres.
2. Useful for human nutrition and food labeling
*Note: Does not differentiate between various fibre
components adequately, so this method is not used
for agricultural applications.
65
What are the 4 different types of Digestive Systems?
1. Simple system (w/o caecum)
2. Simple system (w/ functional caecum)
3. Ruminant system
4. Avian system
66
The Gastrointestinal Tract has 7 components. What are they?
1. Mouth
2. Esophagus
3. Stomach
4. Small Intestine
5. Large Intestine
6. Caecum
7. Rectum
67
The addition of what components differentiates the GIT from the digestive system?
(4)
1. Salivary glands
2. Liver
3. Gall Bladder
4. Pancreas
*These are peripheral tissues that are important for digestion
68
What is the difference between digestability and fermentability?
Main difference: WHO has the enzymes to break down/ digest CHO (human or gut bacteria).
Digestibility --> if host has enzymes to digest CHO
Fermentability --> if gut bacteria have enzymes to break down CHO.
69
Human, pig, cat, dog have what kind of digestive system?
Simple system without caecum.
70
What are some key features of a simple digestive system without a caecum?
(3)
1. Monogastric
2. Non-functional caecum
3. Suited for a nutrient dense, low fibre diet
71
What is the role of the oral cavity (Simple system w/o caecum)?
1. Food is chewed (mechanical breakdown)
2. Food is mixed with saliva
- Two enzymes released: α-amylase (starch breakdown) and lingual lipase (triglyceride breakdown)
72
What is the role of the stomach (Simple system w/o caecum)?
1. pH of stomach is acidic ~ 2
2. Food become “chyme”
3. Gastric glands secrete gastric juice.
-signals are released through enzymes that create gastric juice that will begin digestion
gastric juice: water, electrolytes, HCl, enzymes
- Empty = 50mL, Filled = 1-1.5L
- Gastric emptying = 2-6 hrs
73
The stomach of humans has 4 different regions. True or False?
True.
1. cardia
2. fundus
3. body
4. antrum
74
What is the role of the small intestine (Simple system w/o caecum)?
1. Main site for nutrient digestion and absorption
2. Chyme acidity neutralized by pancreatic juice
3. Food digested by pancreatic juice (pancreas bicarbonate) and bile acids
Surface area = 30m2
75
The small intestine has two types of muscles. What are they and what is their function?
Intestinal motility controlled by:
1. longitudinal muscles (movement down line)
2. circular
muscles (mixing of food, better absorption)
76
What is the function of the large intestine (Simple system w/o caecum)?
1. Site of fermentation
- Production of short chain fatty acids (SCFA) (also known as volatile fatty acids (VFA))
2. Site for water absorption
77
What are three mechanisms in the small intestine that increase its surface area? Give a small description of each.
1. Kerckring folds
- overall muscle folds of small intestine
2. Villi (&Crypts)
- Bloodstream & lymphatic drainage found here
- Once food is absorbed, transporters are found @ the top & bottom
3. Microvilli
- Brush border membrane
78
What are the 3 characteristics of a nutrient that determines its transport mechanism?
1. Solubility
2. Concentration gradient
3. Molecular size
79
What are the different nutrient transport mechanisms?
| 3
1. Diffusion (passive)
2. Facilitate diffusion (passive)
3. Active transport
*Passive --> works with the concentration gradient
Active --> works against the concentration gradient
80
Bacteria in the intestine are found in a 1000:1 ratio. True or False?
False.
| That was thought before, but it's now believed to be 1:1.
81
What are the functions of the bacterial species in large intestine?
1. Fermentation
| 2. Production of B vitamins
82
Bacteria are very important in fermentation of non-digestible CHO. They produce SCFA & Lactate. True or False?
True.
83
Horse, rabbit, hamster have what kind of digestive system?
Simple System w/ functional caecum
84
What are the key features of a simple digestive system with a function caecum?
(4)
1. ‘Pseudo-ruminant’
2. Functional caecum
3. All other regions of the gut function similar to the monogastric
system
4. Suited for a diet with large amounts of fodder
85
Where is the caecum of horses found?
Caecum is found between the small and large intestine.
86
SCFA from gut bacteria produce 50% of total energy in horses. True or False?
False. SCFA produce around 70% of total energy.
87
What is a sign of nutrient deficiency in horses?
Coprophagy (eating feces).
88
Why aren't indigestible fibers fermentable?
They're not fermentable because they have not been converted by bacteria.
89
Cattle, sheep, goats have what kind of digestive system?
Ruminant system.
90
What are the key features of a ruminant digestive system?
| 3
1. Large stomach divided into 4 regions
2. System highly suited for animals that eat a high quantity of fodder.
3. All other regions of the gut function similar to the monogastric
system
91
What are the 4 sections of the ruminant stomach?
1. Reticulum
2. Rumen
3. Omasum
4. Abomasum
92
Describe the reticulum.
| 2
1. Honeycomb appearance in order to capture nutrients and trap foreign
materials (wire, nails, etc)
2. Rich in bacteria (fermentation vat)
93
What is the largest part of the ruminant stomach?
The rumen.
94
Describe the rumen.
| 4
1. Rich in bacteria (fermentation vat)
2. Rumen papillae--> increases surface area for absorption (like microvilli in the human intestine)
3. Food is mixed & partially broken down, and stored temporarily
4. 60-80% of total energy produced here as SCFA
95
Describe the omasum.
| 2
1. Resorption of water and some electrolytes
| 2. Filters large particles
96
Describe the Abomasum.
| 1
1. Digestive enzymes secreted from gastric
glands (HCl, mucin, pepsinogen, lipase, etc)
*Considered the "True stomach" of the ruminant --> closest to the monograstric stomach.
97
In ruminants, fermentation occurs before entering the intestine. This is called ______.
In ruminants, fermentation occurs before entering the intestine. This is called FOREGUT DIGESTION.
*Nutrients produced by bacteria are now available for digestion & absorption by ruminant.
98
What are two processes specific to ruminants when it comes to digestion. What are they?
1. Rumination
- Regurgitating, chewing, swallowing again
2. Eructation (belching)
- Large amounts of Methane gas produced
99
Give 2 examples of advantages & disadvantages of a ruminant system?
Advantages:
1. Vitamin synthesis (e.g., B Vitamins, Vitamin K)
2. Non-protein nitrogen used for making protein
(low quality food broken down, made into high quality proteins by bacteria)
Disadvantages:
1. Carbohydrates degraded into gases and lost through eructation
2. Heat production
100
What are the distinct features of the avian system?
| 2
1. Beaks and claws are important for breaking up foods into smaller pieces
that birds can swallow.
2. Rapid digestion
– Birds can starve if deprived of food for even a short time (i.e., hours)
101
What is the function of a crop?
| 4
1. Enlarged area of the esophagus
2. Well developed in most species, but not all
3. Temporary storage location for food
4. Food is softened here, and often
regurgitated to feed offspring
102
What are the two parts of an avian stomach? What is their function?
1. Glandular portion = proventriculus
- "True stomach" --> gastric enzymes & HCL are secreted
2. Muscular portion = gizzard
- grind & digest tough foods
103
What digestive system has 2 functional caeca in the small intestine?
The avian system.
104
The ceca in the avian digestive system is the major site of bacterial fermentation. True or False?
False. The ceca of avian system is the MINOR site of bacterial fermentation.
(It's too small, but still important)
105
Describe the large intestine of the avian system.
| 3
1. Very short, and serves predominantly to connect the small intestine and cloaca
2. A bit of storage of undigested material
3. Water absorption
106
What three systems meet at the cloaca of birds?
Digestive, urinary and reproductive
| systems meet.
107
______ is the measure of the fraction of a specific nutrient (or
of energy) that is extracted by the GI tract.
DIGESTIBILITY is the measure of the fraction of a specific nutrient (or
of energy) that is extracted by the GI tract.
*Calculated from the amount of nutrient in the diet and the amount appearing in the feces.
-Represents a combination of nutrient release from the food matrix, microbial fermentation, and
absorption.
108
Why is it important to calculate digestibility?
Prevent deficiency and ensure essential nutrients are
| available to the organism.
109
What are the two methods of determining digestibility?
1. Total collection Method
| 2. Indicator method
110
Describe the Total collection method.
| 5
- Allow the animal to adapt to the diet over a 7-21 day period
- Isolate animal for quantitative analyses
- Measure intake over a 3-10 day period
- Collect and weigh all feces
- Analyze for nutrient of interest
111
What is the formula to determine apparent digestibility coefficient?
Apparent Digestibility
| Coefficient = (Total Intake – Total Feces)/ Total Intake
112
What are some limitations of the total collection method?
| 5
- Accuracy in measuring food intake
- Metabolic cages creates anxiety in animals, which may then behave abnormally
- Labour intensive
- Animals confined in costly equipment
- Not feasible for captive wild animals
113
What is the funciton of a metabolic cage?
Metabolic cages --> collect & analyze urine & feces
114
The indicator method to determine digestibility requires a marker. What are the characteristics of a marker?
(4)
1. Non-absorbable --> needs to be independent
2. Must not affect or be affected by the GIT (shouldn't affect the eating of the animal or now the GIT function; if GIT can digest or convert marker, shouldn't work)
3. Must mix easily with food (or else animals won't eat it)
4. Easily & accurately measured in samples
115
Ferric oxide, chromic oxide, silica, lignan are examples or markers in the _____ method to determine digestibility.
Ferric oxide, chromic oxide, silica, lignan are examples or markers in the INDICATOR method to determine digestibility.
116
What are the steps to determine digestibility in the indicator method?
(3)
1. Adapt animal to test diet (which contains a marker)
2. Collect a feed and fecal sample
3. Analyze each for marker and nutrient of interest relative to your indicator
117
What is the formula to determine the apparent digestibility coefficient using the indicator method?
Apparent Digestibility Coefficient = (A – B) / A
```
A= Nutrient%/ Marker% (in feed)
B= Nutrient% / Marker% (in feces)
```
118
What are the advantages of using the indicator method to determine the digestibility.
1. Less labour intensive
| 2. Ideal for wild animals
119
Apparent digestibility overestimates true digestibility. True or False?
False.
| Apparent digestibility UNDER-ESTIMATES true digestibility.
120
What are things not considered when calculating apparent digestibility?
1. Endogenous secretions (epithelial cells)
- fatty acids released from dying intestinal cells
- Cell & all its components are secreted
2. Bacterial growth in gut (nutrient synthesis)
- Bitotin produced by gut bacteria
- SCFA from bacteria
3. Digestive enzymes (protein secretion)
- digestive enzymes released by cells
121
What is the process of determining TRUE digestibility?
1. Perform digestibility study using a TEST DIET.
2. Switch to diet containing none of the nutrient of interest (ZERO NUTRIENT DIET).
3. Analyze feces after TEST DIET is cleared.
4. Subtract level of nutrient in feces of animals fed the ZERO NUTRIENT DIET from the TEST
DIET.
122
What is the formula to determine True Digestibility Coefficient?
True Digestibility Coefficient = [A- (B-C)]/ A
C= Nutrient/ Marker in feces AFTER ZERO DIET
123
Give some examples of factors that affect digestibility.
- Feed intake
- Particle size
- Chemical composition
- Climate
- Age
Fact
124
1 Food Calorie = 1 chemistry calorie
| True or False?
False.
| 1 Food Calorie = 1000 chemistry calories (1kcal)
125
What is the definition of a food calorie?
Calorie --> energy required to raise the temp of 1kg (L) of water by 1 degree celcius
126
Energy balance: Energy in = energy out
| True or False?
True.
127
What is the result of a positive energy balance?
* Weight gain / obesity
* Infertility
* Increased blood lipids
* Insulin resistance
128
What is the result of a negative energy balance?
* Weight loss
* Infection
* Loss of performance
* Reduced bone mass
129
Antoine Lavoisier, Justin Liebig, and Max Rubner contributed to the development of what?
They all contributed to the development of the calorimeter.
130
Calorimetry uses what as an indicator of the energy stored in chemical bonds of food?
Uses heat as an indicator.
131
What are the steps of using a bomb calorimeter?
| (4)
```
1. Dry and weigh sample (~1g), and
place in enclosed chamber (the
‘bomb’) with oxygen
2. Sample ignited
3. Heat released is absorbed by water and measured
4. Heat of combustion (gross
energy)
Gross energy = maximum energy
```
132
What are the potential errors of bomb calorimetry?
| 2
1. overestimates energy content of food
- we don't digest food like a bomb calorimeter (ex. fiber will produce E in calorimeter, but we don't digest it)
2. Doesn't take into account the energy needed for digestion & absorption (bomb calorimeter will
always give you max. amount of E you can get from a food)
133
How are physiological fuel values calculated? (Formula)
Physiological fuel value = (Gross energy - energy lost from urine) x apparent digestibility
OR
=(available energy)/ (metabolizable energy)
* this gives ATWATER VALUES
* It takes into account incomplete digestion
134
Why do fats provide more kcal per gram than CHO and Proteins?
CHO:
- ratio of hydrogen to oxygen = 2:1
(oxygen rich)
Protein:
- has nitrogen, which contributes to gross energy.
(However, our bodies don’t use nitrogen for energy)
Lipid:
- lipids are less oxidized than CHO and protein
- ratio of hydrogen to oxygen much greater than 2:1
- lipids have lots of hydrogen atoms available for cleavage
and oxidation for energy
*LCFA have a lot more E compared to SCFA
135
Order the following fatty acids from highest to lowest energy. What affects the amount of calories in them?
Steric acid, oleic acid, linoleic acid.
Stearic (18:0) > oleic acid (18:1) > linoleic acid (18:2)
more double bonds = less calories
136
What are factors that affect heat of combustion of fatty acids?
1. chain length
- longer chain length releases more energy
2. degree of unsaturation
- the more double bonds, the less energy released (for equivalent length fatty acids)
137
What is the Heat Increment of Feeding (HIF)?
-Also called the thermic effect of food
- Energy used for the digestion, absorption,
distribution & storage of nutrients
- Comprises 5-30% of daily energy usage
- Used to determine Net Energy
138
What is the net energy of a food? How is it calculated?
Net Energy: supports basal metabolism, physical activity, growth, pregnancy, etc.
(Net Energy = Metabolizable Energy – HIF)
*allows us to understand BMR and see if we're in a positive or negative energy balance
139
If someone is doing intermittent fasting, how would that affect their HIF?
Intermittent fasting = decrease of HIF
140
How is energy lost between Gross energy and digestible energy?
Energy lost in feces (not 100% digestible)
141
How is energy lost between digestible energy and metabolizable energy?
- Gases (ruminants)
| - Energy lost in urine (birds)
142
How is energy lost between metabolizable energy and net energy?
Heat increment of Feeding
143
____ Energy allows us to understand Basal Metabolic activity.
NET Energy allows us to understand Basal Metabolic activity.
144
Why is it difficult to determine the difference between digestible & metabolizable energy in birds?
Their cloaca is digestion, reproduction, urination system, so is hard to determine what exactly is from digestive.
145
What are the 4 components to energy expenditure?
1. Basal metabolic rate (BMR)
2. Thermic Effect of Food (same thing as “HIF”)
3. Physical Activity Energy Expenditure (PAEE)
4. (Thermoregulation)
146
When it comes to total energy expenditure, why is thermoregulation not as important in humans?
Humans can adapt to their environment with clotes.
147
How is Basal Metabolic Rate measured? (conditions and what machine reads)
(5)
-Shortly after waking
- Post-absorptive state
- Lying down
- Completely relaxed
- Comfortable room
temperature
-Machine measures O2 consumed vs CO2 released.
148
BMR calculates the amount of calories needed per ____ hours.
BMR calculates the amount of calories needed per 24 hours.
149
What tissues are most reflective of BMR?
Muscle & bone.
| Tissues comprise a lot of our body; tissues are highly metabolic (a lot of turnover)
150
What is the formula to determine Crude BMR?
BMR = A×[M^0.75] kcal/day
```
A = Metabolically active tissue (70 for humans)
M= weight in kg
0.75= Kleiber's Law (constant for all vertebrates)
```
151
How is the Harris-Benedict Equation different from the crude method to determine BMR?
HBE --> uses height, weight, age to determine BMR
*Can also incorporate physical activity level by multiplying by a number.
152
What is the difference between BMR and RMR (resting metabolic rate)
RMR:
-Takes about 1-2 hours
BMR:
-Takes over 24 hours
Both pretty much calculate the same thing, but BMR will always be more accurate because the participant is more accustomed to the environment.
153
What are some factoors that affect BMR?
| 5
• Genetics
– Inheritance of a fast or slow metabolic rate
• Age
– Young > old (greater muscle mass)
• Sex
– Men > women (Greater muscle mass)
• Exercise (changes body tissue proportions)
-Fat tissue (20% body weight, 5% metabolic activity)
-Muscle (30-40% body weight, 25% metabolic activity)
-Brain, liver, heart & kidney (5% body weight, 60% metabolic
activity) --> but the size of these organs doesn’t change with
exercise!
• Temperature (maintaining thermoregulation)
-Maintaining heart rate, maintaining breathing
154
Gain/ Loss of Muscle drastically changes BMR. True or False?
True. Since muscle has a much higher metabolic activity, it will change BMR drastically.
155
Can you use body fat % to calculate BMR?
Yes, you can use the Natch-Mcardle BMR equation.
* Same for men and women
* More accurate
156
All metabolic processes in the body generate heat.
| True or False?
True.
157
Heat production can be used as a measure of energy expenditure.
True or False?
True.
158
The general combustion equation is as follows:
FUEL + O2 -----> CO2 + H2O + HEAT
Which of the components are used to calculate indirect and direct calorimetry?
Indirect : O2 & CO2
| Direct : HEAT
159
How was Direct Calorimetry calculated in the past?
| Is it still calculated?
Direct calorimetry --> Measures the heat a person generates; total heat loss
- In a room surrounded by a layer of water which measures heat change
-Not used today because: Very expensive & impractical
160
When calculating indirect calorimetry, what are 3 things that need to be measured?
1. Oxygen consumption (L)
2. Carbon dioxide production (L)
3. {Urinary nitrogen loss (g)}
- People don't usually use protein for metabolic functions; if you do, you start to lose structures/ function of the body
161
Indirect calorimetry can be used for anaerobic and aerobic processes.
True or False?
False.
| This method cannot account for the production of lactic acid (lactate) from glucose during intense exercise.
162
What are some advantages (3) and disadvantages (2) indirect calorimetry?
Disadvantages:
- Hyperventilation (higher CO2 production)
- Hard to get an airtight seal
- Masks are impractical
Advantages:
- Useful with animals
- Can determine the type of substrate being oxidized
163
What is a Respiratory Quotient? How is it calculated?
RQ --> Ratio of metabolic gas exchange
RQ = CO2 produced / O2 consumed
164
The way we calculate RQ doesn't incorporate protein. Why?
Non-protein RQ --> because protein contributes little to energy metabolism
165
RQ provides information about two things. What are they?
1. Energy expenditure
2. Biological substrate being oxidized
(Carbs, Fats, or both)
166
Each macronutrient requires a different amount of O2 intake in relation to CO2 production. What does this ratio depend on?
This ratio depends on chemical composition.
167
What assumptions are made using the RQ value table?
1. Only CHO and fat are metabolized.
(no protein)
2. No synthesis is taking place at the same time as breakdown.
3. Amount of CO2 exhaled = amount of CO2 produced by tissues
168
What is the crossover point (in regards to RQ)?
Crossover point --> the moment when someone starts to use more CHO than Fat
169
How does training change the crossover point of RQ?
Training changes the biochemistry of our muscles. We will have a crossover point closer to the right. (More fat burned at higher intensities)
170
When it comes to the crossover concept chart (RQ), low intensity exercise means more _____ usage, while high intensity exercise means more _____ usage.
When it comes to the crossover concept chart (RQ), low intensity exercise means more FAT usage, while high intensity exercise means more CHO usage.
171
What are the types of simple and complex carbohydrates?
Simple:
- Monosaccharide
- Disaccharide
Complex:
- Oligosaccharides
- Polysaccharides
172
What is the most common monosaccharide? What is the most common disaccharide?
Mono: Glucose
Di: Sucrose
173
Give a brief description of Monosaccharides.
| 3
- Naturally occurring
- Cannot be hydrolyzed into a smaller unit
- Considered a “reducing sugar” when the anomeric carbon is free
174
A disaccharide is 2 monosaccharides joined. What is the name of the bond that joins them?
Acetyl bond (glycosidic bond)
175
What are the polysaccharides found in plants? Animals?
Animal: Glycogen
Plants: Starch & cellulose
176
All CHO have a H:O ratio of 2:1.
| True or False?
True.
177
Monosaccharides can be found in triose, pentose, and hexose form. Give a brief description of each.
Triose:
- Metabolites of glucose
- Intermediates of glycolysis; glycerol in triglycerides
Pentose:
-Components of DNA/RNA
Hexose:
- Nutritionally most important
- Glucose
178
Why is stereoisomerism so important in biological systems?
Biological systems are stereospecific.
*Stereoisomers --> Same molecular formula and sequence, but differ in 3D space due to chiral carbon atoms
– “L” and “D” isoforms
179
What is a chiral carbon?
A carbon attached to 4 different atoms or groups.
180
What are the two types of stereoisomers?
1. Enantiomers
(mirror image)
2. Diastereomers
(not a mirror)
181
What is an anomeric carbon?
Anomeric carbon --> carbon with carbonyl group
182
In the Fisher projection, what carbon do you consider C1?
Counting always begins at the anomeric carbon (carbonyl).
183
The Fisher Projection of a molecule has 2 forms which is determined by the -OH group on the last chiral carbon. What are these forms called?
- OH on the right = D
| - OH on the left = L
184
How do you calculate the number of stereoisomers for a molecule?
```
# of stereoisomers for molecule = 2^n
(where n = # chiral carbons)
```
185
In nature, are there more alpha or beta configurations of molecules?
Beta configurations
186
Why are D-monosaccharides nutritionally more important?
D-monosaccharides are nutritionally more important because digestive enzymes are stereospecific for D sugars.
187
When you convert a Fisher Projection to a Haworth model, the linear projection becomes cyclical.
A _______ is made from an aldose, a _____ is made from a ketose.
A HEMIACETAL is made from an aldose, a HEMIKETAL is made from a ketose.
188
What are the rules for turning a fisher projection into a haworth model?
(3)
1. CH2OH always points up
2. If on Left = Above
3. If Beta = Above
189
Disaccharides are 2 monosaccharides attached by a glycosidic bond between a hydroxyl group and a carboxyl group.
True or False?
False.
| A glycosidic bond is between TWO HYDROXYL GROUPS.
190
What determines whether a disaccharide is alpha or beta?
| What are the possible outcomes?
Configuration of the -OH group on the anomeric
carbon determines whether the disaccharide is α or β.
Possible outcomes: [α(1,4), α(1,6), β(1,4), β(1,6)]
191
What are the 3 most common disaccharides? Give a brief description of each.
1. Sucrose
- Found in sugar cane, fruits
- glucose + fructose
- Non-reducing! (both anomeric carbons used)
2. Lactose
- Found in milk
- galactose + glucose
- Reducing! Free anomeric carbon
3. Maltose
- Found in beer & liquor
- glucose + glucose
- Reducing! Free anomeric carbon
192
What is a polysaccharide?
| min. # of Cs?
Polysaccharide --> Long strings or branches of monosaccharides (min. of 6) attached by glycosidic bonds
193
Both Homopolysaccharides and Heteropolysaccharides
| exist in nature, but which ones are more abundant in food?
Homopolysaccharide are more abundant in food.
194
Starch forms Amylose and Amylopectin are both forms of _______ polymers.
Starch forms Amylose and Amylopectin are both forms of D-GLUCOSE polymers.
195
What is the advantage of glycogen branching?
Branching provides a large # of ends from which to cleave glucose when energy is needed.
196
Give a brief description of dietary fiber. (2)
| Are humans able to digest this food?
- Non-digestible complex CHO
- Structural part of plants
Humans are unable to digest because we don't have the enzymes necessary to break down these fibers.
197
What are the two types of dietary fibers?
1. Insoluble
| 2. Soluble
198
What are the characteristics of solubility?
| 2
1. Water-holding ability
- Ability of a fibre to hold water (becomes a viscous solution)
–
2. Adsorptive ability
- Ability of a fibre to bind enzymes and nutrients
199
Give some examples and a brief description of insoluble dietary fibers.
ex. cellulose, lignin, some hemicelluloses
- Remain intact throughout the digestive system
- Reduce transit time (i.e., things move quickly through the gut)
- Increases fecal bulk
200
Give some examples and a brief description of soluble dietary fibers.
ex. pectins, gums, β-glucans, some hemicelluloses
- Forms a gel
- Delays gastric emptying, increases transit time
- Slows down the rate of nutrient absorption
201
Cellulose is a dietary fiber, but not found as a functional fiber.
True or False?
False.
| Cellulose is both a dietary fiber and a funcitonal fiber.
202
What is the difference between a dietary fiber and a functional fiber?
Dietary fiber --> naturally occurs in food
| Functional Fiber --> natural fiber that's added to a food that doesn't normally have it
203
Cellulose is a homopolysaccharide of _______ glucose units in a linear chain.
Cellulose is a homopolysaccharide of β-1,4 glucose units in a linear chain.
204
Where is cellulose found? How is it fermented by the human gut bateria?
Found in: bran, legumes, nuts, peas, etc.
Poorly fermented by human gut because we lack cellulose-fermenting microbes in our gut-microbiome (lack metanogens)
205
Hemicellulose is a mixture of α and β glycosidic linkages, meaning it is a __________.
Hemicellulose is a mixture of α and β glycosidic linkages, meaning it is a HETEROPOLYSACCHARIDE.
206
Hemicellulose contains both pentoses and hexoses.
| True or False?
True.
| *Xylose is the most common monosaccharide in hemicellulose.
207
Where is hemicellulose found and what does its solubility/ fermentability depend on?
- Found in bran, whole grains, nuts, and some vegetables/fruits
- The solubility and fermentability of hemicellulose depends on the sugar composition
208
Hemicellulose is found in both ____ and linear structures.
Hemicellulose is found in both BRANCHED and linear structures.
209
Pectin is both a dietary and a functional fiber.
| True or False?
True.
210
______ is the polysaccharide that is part of the primary cell wall of plants.
PECTIN is the polysaccharide that is part of the primary cell wall of plants.
211
_____ is the backbone of unbranched α-1,4-linked-D galacturonic acid.
PECTIN is the backbone of unbranched α-1,4-linked-D galacturonic acid.
212
Is pectin stable at high pH?
No. Pectin is stable at low pH.
213
Where is pectin found? How is it digested?
- Found in fruits, such as apples, oranges, lemons, and grapefruit
-Highly fermented by gut bacteria
(food bulking agent in animal feed)
214
How many types of resistant starch are there?
4 types. (RS1-4)
215
Give some characteristics of resistant starch.
| 3
- Typically found in plant cells walls
- Resistant to amylase activity
- Conveys some advantages of both soluble and insoluble fibres
216
What are the health benefits of fiber?
| 3
1. Maintains function & health of the gut
2. Decreases constipation (insoluble fibre)
- Stimulates muscle contraction to break down waste
- Decreases risk of bacterial infections
3. Increases satiety (soluble fibre)
- Delays gastric emptying
- slows down nutrient uptake
(creates viscous solution, slows everything down; binds with various nutrients which slows down their absorption)
217
Soluble fiber decreases CVD risk by lowering blood cholesterol. How does this occur?
1. Soluble fiber + cholesterol from food reach the stomach & small intestine
2. Soluble fiber forms gel which binds to some cholesterole, and prevents its uptake into the blood stream
218
Soluble fibers can decrease the risk of type 2 diabetes by binding to glucose in the GIT.
True or False?
True.
219
Explain the Carbohydrate Digestion processes that occur in the mouth.
(3)
1. Saliva (α-amylase breaks down α-1,4-glycosidic bonds)
- Produces only a few monosaccharides
- Cellulose and lactose are resistant, as are α-1,6-bonds
220
Explain the Carbohydrate Digestion processes that occur in the stomach.
(2)
- α-amylase digestion continues until pH drops, then enzyme is deactivated
- At this point, the pool of dietary CHO consists of small polysaccharides and maltose
221
Explain the Carbohydrate Digestion processes that occur in the small intestine.
(3)
- Pancreatic α-amylase
- Active at a neutral pH
- α-1,6 bonds are resistant and eventually produce isomaltose
222
The brush border of the small intestine has 4 different enzymes. What do they break down?
Sucrase (invertase):
Sucrose --> Glucose + fructose
Lactase:
Lactose --> Glucose + Galactose
Isomaltase (alpha-dextrinase):
Isomaltose --> Glucose + Glucose
Maltase:
Maltose --> Glucose + Glucose
223
How do monosaccharides get into the epithelial cells of the small intestine?
The brush border of the small intestine takes up monosaccharides by intestinal cells.
224
Lactose intolerance is caused by a decrease of lactase activity. What are some factors know to influence lactase enzyme activity?
(2)
1. Age ( ability to digest decreases with age)
| 2. Ethnicity (genetics, variants in LCT gene)
225
What causes the discomfort / gases associated with lactose intolerance?
Gut bacteria have a lot more new sugars that they didn't have before --> they create more gases as they ferment the lactose.
226
In the small intestine, most monosaccharides are taken up by _____.
In the small intestine, most monosaccharides are taken up by ENTEROCYTES.
227
What is the enterocyte that takes up glucose? Where is it found?
SGLT1 (sodium glucose transporter 1) is found on the apical side of the intestine (interacts with the lumen).
228
What happens when the glucose is taken up by the SGLT1?
| 3
1. Small amounts leak back out into the lumen from the enterocyte
2. Small amounts diffuse into the blood through the basolateral membrane
3. Majority of clucose is transported into the blood through the GLUT2 basolateral transporter
*Note: galactose & fructose also enter the blood via basolateral GLUT2
229
How is fructose taken up into the intestine on the apical surface?
Fructose is taken up by factilitate transport (GLUT5 on apical surface)
*in contrast to SGLT1
230
The transport of glucose and galactose from the lumen into the blood is dependent on what enzyme activity?
(Hint: on basolateral side)
Transport of glucose and galactose from
lumen into blood is dependent on
basolateral Na-K ATPase activity.
231
What are the functions of Carbohydrates in the body?
| 3
1. Glucose is the primary source of energy for cells (especially for RBC and Brain)
2. Carbohydrates “spare” protein
- Prevents breakdown of protein for energy
- Allows protein to concentrate on building, repairing, and maintaining body tissue
3. Carbohydrates prevent ketosis (breakdown of fats for energy)
- Ketosis leads to the production of ketone bodies, causing the body’s pH to become slightly acidic
232
Carbohydrate Metabolism can go in 6 directions. What are they?
1. Glycogenesis (production of stores)
2. Glycogenolysis (Breakdown of stores)
3. Gluconeogenesis
4. Glycolysis
5. Hexose Monophosphate Shunt
6. Kreb's Cycle
233
In a cell, glucose has 3 fates. What are they?
1) Enters glycogenesis for energy storage
(Glycogenesis)
2) Enters glycolysis for energy production
(Glycolysis)
3) Enters hexose monophosphate shunt to generate precursors for biogenesis
*How the cell will use glucose depends on its requirements at the time (energy vs. biosynthesis)
234
Why is the conversion of glucose to glycogen so important during the take up of glucose?
If glucose is transported into the cell, its gradient is destroyed.
If it turns into glycogen, it maintains the gradient while lowering blood glucose.
235
Insulin influences 3 enzymes that promote glycogenesis. What are they?
1. Hexokinase (muscle)
2. Glucokinase (liver)
3. Glycogen Syntahse
236
What is the difference between hexokinase and glucokinase?
They do the same thing, but hexokinase is inhibited by high glucose levels.
- we need to limit the amount of glucose in muscle because they are the 1st responder for high blood glucose
237
What is glycogenin? What is its role?
Glycogenin --> enzyme that serves as a scaffold on which glucose attaches to build glycogen ("primer")
- Initally attaches molecules to itself before glycogen synthase is able to help.
238
What are two methods energy can be produced in the cell?
| Hint: Types of phosphorylation
1. Substrate-level phosphorylation
- ADP --> ATP
- In mitochondria (krebs) and in cytoplasm (glycolysis)
2. Oxidative phosphorylation
- ETC
239
Where are the enzymes for glycolysis found?
In the cytoplasm.
240
Most life on earth performs glycolysis.
| True or False?
False.
| ALL life on earth performs glycolysis.
241
The endpoint of glycolysis depends on ________ in the cell.
The endpoint of glycolysis depends on AVAILABLE O2 in the cell.
242
Why is glycolysis the only way cells can generate ATP?
RBC have no mitochondria.
243
What enzyme is considered the first committed step of glycolysis?
Phosphofructokinase
| this step is irreversible in glycolysis
244
______ (hormone) and ____ inactivate the activity of phosphofructokinase, allowing the fructose to convert back to glucose and be transported into other cells.
GLUCAGON (hormone) and ATP inactivate the activity of phosphofructokinase, allowing the fructose to convert back to glucose and be transported into other cells.
245
What is the net energy of glycolysis?
Net energy: 2 NADH, 2 ATP
| around 8 ATP
246
What are the two events that can occur in the anaerobic metabolism of glucose?
(Hint: human vs plant)
1. Lactic acid production
| 2. Ethanol production
247
Give a brief description of Lactic acid production.
| 4
- Occurs in muscle (prolonged exercise) and in red
blood cells
- Pyruvate is converted into lactic acid in the cell’s cytosol
- Regenerates NAD+, which allows glycolysis to continue
- Net: 2 ATP produced when glucose is converted to lactic acid
248
Give a brief description of ethanol production.
| 4
- Doesn’t happen in the body
- Yeast breaks down pyruvate into CO2 and ethanol
- Basis of fermentation when you make wine and beer
- Regenerates NAD+, which allows glucose to continue being broken down in glycolysis
249
When and where does the Cori Cycle take place? Is it sustainable?
In an anaerobic state, lactate is taken to the liver where it's converted back to glucose, then taken to muscle.
This is not sustainable long-term because it requires more ATP than it produces.
250
The Hexose Monophosphate shunt is important for _____ production and ____ synthesis.
The Hexose Monophosphate shunt is important for NADPH production and ribose synthesis.
251
Concerning the hexose monophosphate shunt, all cells use the oxidative phase, but only cells that perform biosynthesis will use the nonoxidative phase.
True or False?
False.
| All cells use the nonoxidative phase, but only cells that perform biosynthesis will use the oxidative phase.
252
What is the NADPH from the hexose monophosphate shunt used for?
NADPH is used for the biosynthesis of fatty acids and antioxidant production.
253
What enzyme is considered the "gatekeeper" to the krebs cycle?
Pyruvate dehydrogenase.
254
What are the cofactors of the pyruvate dehydrogenase complex?
(Hint: 4, vitamin Bs)
1. Thiamine
2. Niacin
3. Riboflavin
4. Pantothenic acid.
255
What is the net energy yield of converting pyruvate into acetyl coA?
Net: 2 NADH
| around 6 ATP
256
Over 90% of the energy in food is released in what biochemical process?
Krebs Cycle.
257
Where does the krebs cycle take place?
Mitochondrial matrix.
258
The Krebs cycle is a common and final catabolic pathway for products of protein, lipid, and carbohydrates.
True or False?
True.
259
What is the net energy of the Krebs cycle?
Net: (3 NADH, 1 FADH2, 1 GTP) x 2 pyruvate
| (12 ATP) x2
260
What is the total energy from 1 glucose molecule?
| Explain by breaking down every step.
Glycolysis = 2 ATP + 2 NADH
(8 ATP)
Puruvate dehydrogenation = (1 NADH) x2 pyruvate
(6 ATP)
Krebs cycle: (3 NADH, 1 FADH2, 1 GTP) x 2 pyruvate
(24 ATP)
261
What is gluconeogenesis, where does it occur, and how does physical activity affect it?
- Pathway activated when we need glucose (during fasting)
- Very active in liver, can also occur in kidney during starvation
- Increase of physical activity = muscle lactate that travels to the liver in the cori cycle
262
Muscle and adipose tissue lack enzymes for the _______ process.
Muscle and adipose tissue lack enzymes for the GLUCONEOGENESIS process.
263
What are the 3 irreversible steps (enzymes) of Glycolysis? What are the 3 enzymes of gluconeogenesis that bypass those irreversible steps?
glycolysis:
1. Glucokinase / hexokinase
2. Phosphofructokianse
3. Pyruvate kinase
Glucongeogenesis:
1. Pyruvate carboxylase & PEP carboxykinase
2. Fructose 6-phosphatase
3. Glucose 6-phosphatase
264
What enzyme converts oxaloacetate to phosphoenol pyruvate and allows it to continue in glycolysis?
PEP carboxykinase.
265
Oxaloacetate can't leave the mitochondria so it is converted to ______.
Oxaloacetate can't leave the mitochondria so it is converted to malate.
266
What are things we need to consider when thinking about the direction a molecule will metabolize?
(2)
1. Are we in a fed or fasted state? (different pathways)
2. Hormonal regulations
(certain hormones produce certain pathways)
267
What are some characteristics of lipids?
| 4
```
1. Soluble in organic solvents
– e.g. ether, chloroform, acetone
2. Wide variety of structures and functions
– 10,000 different lipid species characterized
3. Source of energy
4. Major component of cell and organelle
membranes
(dietary lipids)
```
268
Where are most lipids stored?
Lipids are mostly stored as triglycerides in adipose tissue (lipid droplets)
269
What are the function of Lipids?
| 8
1. Concentrated source of energy
- 9 kcal/g
2. Palatability of foods & increase satiety
(trans fats)
3. Source of essential fatty acids
- α-linolenic acid (omega-3), linoleic acid (omega-6)
4. Carrier of fat-soluble vitamins
- (A, D, E, and K)
5. Necessary for growth and development
6. Important precursors for the production of hormones
7. Affect inflammation and blood clotting
8. Key roles in disease development
- Atherosclerosis, diabetes, obesity, etc...
270
What are the two types of fatty acids? Give a brief description of each.
1. Saturated
- Maximum # of H
atoms
- Only single bonds
2. Unsaturated
- “Missing” H atoms
- Double bonds
(Monounsaturated or Polyunsaturated)
- cis or trans
configuration
271
Give an example of a saturated, monounsaturated, and polyunsaturated fatty acid.
Saturated:
- Butyric acid
- Palmitic acid
Monounsaturated:
- Oleic acid (cis)
- Elaidic acid (trans)
Polyunsaturate:
- cis-9,12- Linoleic Acid
- cis-9,trans-11-CLA
- Arachidonic Acid
272
What kinds of fatty acids play an important role in membrane fluidity?
Monounsaturated and polyunsaturated.
273
Which kinds of unsaturated fats are more stable? Why?
| cis vs trans
Trans unsaturated fats are more stable because they're not oxidizing or degrading; meaning they have a longer shelf life
274
What are the two nomenclature systems for fatty acids?
| Give a brief description of each.
1. Delta System (Δ)
- Numbering starts from carboxyl end of fatty acid
- 18:2 Δ ^9,12
2. Omega System (ω)
- Numbering starts from methyl end of fatty acid
- 18:2 n-6 or 18:2 ω-6
* only care about 1st DB
275
What were the two experiments that led to understanding essential fatty acids?
1. 1929, George and Mildred Barr fed rats diets that were completely fat free
- Stunted growth, lost fur, inflamed & scaly tails
2. 1963, infants were fed diets that differed in fat content.
- Diets with <0.1% linoleic acid had poor growth and thickened dry skin
276
What are the essential fatty acids? Where can we get them?
1. Linoleic Acid (18:2 n-6)
- Nuts, seeds, vegetable oils, etc
2. Alpha Linolenic Acid (18:3 n-3)
- Fatty fish, canola oil, almonds, etc
277
Why are there essential fatty acids?
- Humans lack the enzymes necessary to insert double bonds beyond the delta-9 position of a fatty acid
- The delta-12 and delta-15 fatty acids found in plants
278
n-6 deficiencies affect what?
| 3
Skin: dermatitis
Growth: lower
Reproductive maturity: lower
(2-3% of energy)
279
n-3 deficiencies affect what?
| 2
CNS development: lower IQ
Retinal development: lower visual acuity
(1% of energy)
280
What was the n-6:n-3 ratio in the 1800s? What is it now?
Before: 2:1
Now: 20:1
281
Pets can be susceptible to EFA deficiency. How do dogs and cats differ in this department?
Dogs --> can convert ALA to EPA but not DHA (need DHA in their diet)
Cats--> lack ENZYMES to make LCFA (require the enzymes in their diet)
Result of deficiency:
Impaired reproductive efficiency, impaired wound healing, dry coat, scaly skin.
282
EFA are converted to eicosanoids through 3 processes. What are these processes and what are the enzymes/ functions associated with them?
1. Desaturation
- delta-6 desaturase
- New DN added at the 6th position from carboxyl end
2. Elongation
- Elongase 5
- 2 carbons added at carboxyl end (all DB get shifted)
3. Desaturation
- Delta-5 desaturase
- New DB added at 5th position from carboxyl end
283
Give a few characteristics of Eicosanoids.
| 3 +examples
1. Metabolites of 20-carbon fatty acids (primarily AA and EPA)
2. Produced by most cells in the body
3. Hormone-like, function locally
- Role in inflammation, platelet aggregation,
blood pressure, etc.
- Implications for disease
ex. prostaglandins, thromboxanes, leukotrienes
284
After conversion, eicosanoids (AA) can go down 3 different pathways. What are the pathways and what are the enzymes associated with these pathways?
1. Cyclooxygenase pathway
- Cyclic
- COX enzyme
- (negative feedback by aspirin)
2. Epoxidase pathway
- Cyp450 enzyme
3. Lipoxygenase Pathway
- Linear
- LOX enzyme
*Pathway depends on needs of the cell
285
What is the enzyme that converts a 20C phospholipid into AA? What inhibits this enzyme?
PLA2 (Phospholipase A2)
*it removes the fatty acid (AA) from the phospholipid
Inhibited by coriticosteroids.
286
AA is a _______ molecule, while EPA is an ______ molecule.
AA is a proinflammatory molecule, while EPA is an anti-inflammatory molecule.
287
By inhibiting the acridonic acid pathway, asipirin and corticosteroids act as _____ molecules.
(Hint: proinflammatory or anti-inflammatory)
By inhibiting the acridonic acid pathway, asipirin and corticosteroids act as ANTI-INFLAMMATORY molecules.
288
Triglycerides are a major source of dietary and storage lipids.
True or False?
True.
289
Triglycerides are key in what pathways?
| 3
1. Lipogenesis (production of fatty acids)
2. Lipolysis (release of fatty acids)
3. Transport in lipoproteins
290
_________ composition determines the physicochemical properties of TAGs.
FATTY ACID composition determines the physicochemical properties of TAGs.
291
What is the bond in lipids called?
Ester bond.
292
Phospholipids are more polar than TAGs. Why?
Hydrophilic phosphate head group makes them more polar.
293
What are the principle functions of phospholipids?
| 4
1. Components of membranes
2. Source of physiologically active fatty acids for eicosanoid synthesis
3. Anchors membrane proteins
4. Intracellular signaling
294
______ is the most common sterol.
CHOLESTEROL is the most common sterol.
295
Steroid alcohols are also called ______ alcohols.
Steroid alcohols are also called MONOHYDROXY alcohols.
296
What is a structural feature of sterols?
| Hint: Cholesterol ester
Are free/ esterified with a fatty acid.
297
What are some sources of cholesterol?
1. Diet: meat & eggs (~40%)
| 2. Endogenous production (~60%)
298
Sterols are essential components of membranes.
| True or False?
True.
299
Sterols are precursors for what?
| 3
1. Bile acid production
2. Steroid sex hormone production
3. Vitamin D synthesis
300
Explain the lipid digestion process that occurs in the mouth.
(2)
- lingual lipase
| - continuously secreted
301
Explain the lipid digestion process that occurs in the stomach. (3)
- gastric lipase
- continuously secreted
- lipases stable at low pH
302
Explain the lipid digestion process that occurs in the gallbladder (2).
- Storage of bile acids
| - Release of bile triggered by hormones
303
Explain the lipid digestion process that occurs in the small intestine (1).
- Pancreatic enzymes include pancreatic lipase, cholesterol esterase
304
Mixed Micelles are an important mediated step of digestion. What are they and what are they important?
(5)
- Digested lipids are emulsified by bile acids
- Small, spherical complexes containing lipid digestion products plus bile acids
- Can access the spaces between microvilli in the intestine
- Bile acids are reabsorbed in our digestive tract
- Originally thought that digested lipids were delivered into intestinal enterocyte cells by passive diffusion, but carrier-mediated transporters have now been identified
305
Soluble fibers increase the efficiency of enterohepatic circulation by holding onto bile acids, which are then secreted in feces.
True or False?
False.
Soluble fibers DECREASE the efficiency of enterohepatic circulation by holding onto bile acids, which are then secreted in feces.
306
What are the 3 brush border enzymes?
1. Pancreatic lipase
2. Cholesterol esterase
3. Phospholipase
307
What is the classification of lipoproteins (from largest to smallest)?
1. Chylomicron (chylomicron remnant) (1000nm)
2. Very low density lipoprotein (VLDL) (70nm)
3. Intermediate Density Lipoprotein (IDL) (40nm)
4. Low Densit Lipoprotein (LDL) (20nm)
5. High Density Lipoprotein (HDL) (10nm)
308
ApoB-48 is specifically made for _______.
ApoB-48 is specifically made for CHYLOMICRONS.
309
ApoB-100 is specifically made for ____, ____, and _____.
ApoB-100 is specifically made for VLDL, IDL, and LDL.
310
ApoC and ApoE are made for "___" cholesterol.
ApoC and ApoE are made for "BAD" cholesterol.
311
ApoA is specifically made for ____.
ApoA is specifically made for HDL.
312
As the Protein:Lipid ratio increases, the amount of ApoB-100, ApoC, and ApoE _____.
As the Protein:Lipid ratio increases, the amount of ApoB-100, ApoC, and ApoE INCREASES.
313
What is lipoprotein classification determined by?
| 2
1. Ratio of Lipid-to-Protein (which affects density)
2. Specific apolipoprotein (Apo)
content (which affects receptor interactions)
314
Where is chylomicron made?
It is made in the small intestine.
315
What is the difference between LDL and HDL?
LDL and HDL are structurally identical, but LDL DEPOSITS fats, while HDL ACQUIRES fats.
316
How are chylomicrons able to deposit dietary lipids to adipose tissue and muscle before arriving at the liver?
Chylomicrons enter the lymphatic system before entering the blood, meaning they pass adipose and muscle before reaching the liver.
317
Chylomicrons increase in circulation after a meal, but they enter at a slow rate. When is the peak time to see chylomicrons?
30mins-3hrs post meal is chylomicron peak.
318
Where is Lipoprotein Lipase (LPL) located?
Lipoprotein lipase (LPL) is located on the surface of endothelial cells lining small blood vessels and capillaries.
319
What are some characteristics of LPL?
| 3
1. LPL not expressed in liver, but is expressed by adipose tissue and muscle
2. LPL is activated by ApoC in chylomicrons
3. LPL hydrolyzes the TAG in chylomicrons
320
What happens when chyomicrons become TAG-depleted?
- referred to as a “chylomicron remnant” (CR)
| - CR are removed from circulation through ApoE-mediated interactions with a receptor in the liver
321
VLDL is the main transporter of newly synthesized hepatic TAG. What happens to the TAG when the VLDL is converted to LDL?
TAG is either stored or used for energy.
322
How is LDL taken up by the liver?
LDL taken up by the liver via LDL-receptors (i.e., receptor mediated
endocytosis)
323
What enzyme is responsible for esterfying a fatty acid to cholesterol on HDL?
Lecithin-Cholesterol Acyltransferase (LCAT)
324
Most blood cholesterol is esterified with fatty acids.
| True or False?
True.
325
What is Reverse Cholesterol Transport?
This occurs when HDL picks up cholesterol around the body, and brings it to the liver.
326
What is the scavenger receptor class B1 (SRBI)?
SRBI --> HDL receptor in the liver
327
What is the function of the cholesterol ester transfer protein (CETP)?
Enzyme responsible for moving cholesterol esters & TAGs between VLDL, LDL, & HDL.
*Lower CETP levels promote HDL formation.
328
In the liver, cholesterol has 3 fates. What are they?
1. Converted into bile acids to replenish the bile acid pool
2. Secreted “as is” directly with bile, to be eliminated in feces
3. Packaged into VLDL and sent around the body
329
Give the summary of how lipids/cholesterols interact with the body (liver, cells, digestive).
(5)
1. Chylomicrons are assembled in the intestine (rich in dietary TAGs, and less cholesterol esters).
Chylomicrons enter the lymphatic system, deliver TAGs to tissues (become chylomicron remnants).
2. De novo cholesterol ester (CE) and TAG synthesis.
3. VLDL circulate to peripheral tissue (TAGs hydrolyzed by LPL) and become IDL; either taken up by hepatic LDL-R or further hydrolyzed into LDL (CE rich particles).
4. Reverse cholesterol transport.
HDL carries cholesterol to the liver or CETP mediates the transfer of CEs to LDL.
5. Cholesterol is eliminated from the body by conversion to bile acids or secretion into gut as is.
330
Higher HDL levels means more cholesterol returning to the liver.
True or False?
True.
331
What happens in the liver following a meal?
| lipid metabolism
- De novo lipogenesis
| - Enterohepatic circulation
332
What happens in the adipose cell following a meal? (lipid metabolism)
-Triglyceride pool
333
How do lipids fit into the carbohydrate metabolic pathways?
| 2
1. GLUCONEOGENESIS:
The glycerol backbone is glucogenic
2. KREB’S CYCLE:
Fat oxidation via acetyl CoA
334
Lipases hydrolyze ester linkages in lipolysis.
| True or False?
True.
335
What happens to lipids in adipose tissue?
| 2
1. HSL (hormone sensitive lipase)
| 2. Cleaves a fatty acid from the glycerol backbone
336
The complete breakdown of a TAG molecule releases ____ glycerol and ____ fatty acids.
The complete breakdown of a TAG molecule releases 1 glycerol and 3 fatty acids.
337
Fatty acids can undergo _______ and used be to generate energy (in Krebs cycle).
Fatty acids can undergo β-oxidation and used be to generate energy (in Krebs cycle).
338
There are 4 steps of β-oxidation that a fatty acid has to take before entering the krebs cycle. What are they?
1. Dehydrogenation (FADH2)
2. Hydration
3. Oxidation (NADH)
4. Thiolysis
*End with acetyl coA
339
*Each round of B-oxidation removes 2 _______ (acetyl CoA), and produces ___ NADH + ___ FADH2.
Each round of B-oxidation removes 2 CARBONS (acetyl CoA), and produces 1 NADH + 1 FADH2.
340
What is the recommended caloric intake for men vs. women?
Men: 2500kcal/day
Women: 2000 kcal/day
341
How much of each macronutrient should be a part of your daily diet (%), as recommended by Dieticians of Canada?
- Protein: 10-35% of daily calories (218g max)
- Carbohydrate: 45-65% of daily calories (406g max)
- Fat: 20-35% daily calories (97g max)
342
Decreasing the dietary cholesterol of a healthy person drastically improves their health by lowering blood cholesterol.
True or False?
False.
For healthy people, there is usually no effect, but for people with high cholesterol levels, decreasing dietary cholesterol will decrease LDL levels.
343
Plant sterols compete with cholesterol for uptake by _____ in the small intestine.
Plant sterols compete with cholesterol for uptake by NPC1L1 in the small intestine.
344
When plant sterols are taken up by NPC1L1, they are then pumped back into the lumen by _________ apical transporters.
When plant sterols are taken up by NPC1L1, they are then pumped back into the lumen by ABCG5/G8 apical transporters.
345
Industrial trans fats are produced during the hydrogenation of vegetable oils.
Why do industries do this and how does it affect the oil?
1. Companies do this to increase stability during cooking, longer shelf-life, & for palatability
2. Hydrogen atoms are added catalytically across double bonds
- Partial hydrogenation: double bonds converted from cis --> trans
- Complete hydrogenation: all double bonds become full saturated
3. ↑ the amount of hydrogenation, ↑ degree of saturation
346
Trans fats are found naturally in ruminant fat.
| True or False?
True.
- Milk fat contains 4-8% trans fat (aka conjugated linoleic acid – CLA)
- Natural trans fats are made in the rumen through bacterial fermentation.
347
A high intake of industrial trans fatty acids has 4 effects.
What are they?
1. ↑ LDL - cholesterol
2. ↑ total - cholesterol
3. ↑ inflammation
4. ↓ HDL - cholesterol
348
On a per-calorie basis, trans fats appear to increase the risk of CVD more than any other nutrient.
True or False?
True.
349
What are the health outcomes of a Trans Fat diet (processed foods)?
(heart disease, inflammation, diabetes)
1. ↑ Risk for Heart Disease
2. ↑ Inflammation
3. ↑ Diabetes?
350
What are the health outcomes of a monounsaturated (Mediterranean) diet?
(heart disease, metabolic syndrome, some cancers)
1. ↓ Risk for Heart Disease
2. ↓ Risk for Metabolic Syndrome
3. ↓ Risk for certain cancers
351
What are the health outcomes of a polyunsaturated (fish, fish oil) diet?
(heart disease, arthritis, inflammation)
1. ↓ Risk for Heart Disease
2. ↓ Risk of Arthritis
3. ↓ Reduce inflammation
NUTR*3210
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