1
Q
nutrition is the science of
A
food
nutrients and substances in food
their action, interaction and balance in relation to health and disease
the process of ingesting, digesting, absorbing, transporting, utilizing and excreting food substances
2
Q
what is an essential nutrient
A
a chemical that is required for metabolism but cant be synthesized (or not quickly enough) to meet the needs of the animal or human for one or more physiological functions
3
Q
nutrients are essential to the human diet if
A
- removing the nutrient causes a deficiency and decline in health
- putting the nutrient back into diet corrects the problem and health returns
4
Q
when do nutritional deficiencies occur
A
when a persons nutrient intake consistently falls below the recommended requirement
5
Q
what happens if there is a deficiency in iron, folate and/or vit B12
A
Anemia: not enough rbc to transport oxygen
6
Q
what happens if there is a deficiency in thiamine B1
A
beriberi: defective energy production, abnormalities in nervous system
7
Q
what happens if there is a deficiency of vitamin d
A
rickets in kids, osteomalacia in adults: defective bone growth, upset homeostasis
8
Q
what happens if there is a deficiency in vitamin c
A
scurvy: defective collagen production, haemorrhaging, bleeding of gums, etc.
9
Q
what is the difference between deficiency and below nutrient requirements
A
deficiency: prevent disease
nutritional requirement: ensure optimal health
10
Q
_____ and ______ are used to establish nutrient requirements
A
nutrition research and statistics
11
Q
what is the % daily value
A
based on 2000 cal diet, simplified way to provide consumers with info
12
Q
what is used to make % daily values
A
dietary reference intakes
13
Q
what is dietary reference intake (DRI)
A
umbrella term that refers to a set of reference values for nutrients (EAR, RDA, AI and UL)
14
Q
what is a nutrient requirement
A
range of nutrient intakes required by individuals in a population subset (eg. age, gender groups) to achieve the same end point of growth, storage or health
15
Q
estimated average requirement EAR
A
the needs of 50% of the population are met
16
Q
recommended dietary allowance RDA
A
the needs of 97% of the population are met
17
Q
tolerable upper limit
A
the highest level of continuous daily nutrient intake that causes no risk of adverse effects
18
Q
adequate intake AI
A
when sufficient scientific evidence is not available to establish and EAR and RDA
determined based on intake in healthy people who are assumed to have an adequate nutritional status
expected to meet or exceed the needs of most
19
Q
outcomes of starvation
A
weight loss, irritability, dizziness, tiredness, hair loss, reduced sex drive, depression
some effects were not reversed for 1 year rehab
20
Q
what 4 characteristics does a nutritious diet have
A
adequate: enough cals, essential nutrients, fibre, etc. to keep you healthy
moderate: ensuring you do not consume excessive cals or eat more of one food group than recommended
balanced: foods are nutrient dense, rather than poor
varied: wide selection to get necessary nutrients
21
Q
how are nutrient recommendations created
A
cell culture models
animal models
human studies: epidemiological cohort studies (prospective and retrospective), intervention (randomized control trial *)
22
Q
what is the major issues with nutrient recommendations
A
variables: genetics, lifestyle, cultural habits, etc.
23
Q
what are organic nutrients
A
contain carbon in structure
24
Q
macronutrients
A
carbs and fibre
lipid
protein
25
micronutrients
minerals and vitamins
26
which macro and micronutrients are organic
carbs
lipids
proteins
vitamins
27
which macro and micronutrients are inorganic
minerals and water
28
which macro and micronutrients are NOT stored in the body in large amounts
minerals, proteins, carbs
29
what makes up majority of the body weight
water and fat
30
anabolism
building things such as storage components (fat to triglycerides, glucose to glycogen, etc)
under hormonal control (insulin)
31
catabolism
breaking down structures
in fasted state and need glucose from glycogen
hormone controlled (glucagon)
32
average adult human water intake
2.7-3.7L/day
~20% from food
33
functions of water in the body
solvent in biochemical reactions
catabolism (hydrolysis rxns)
maintains vascular volume (blood)
nutrient transport
temperature regulation
34
when does water toxicity happen
when water intake exceeds the kidney's ability to process (~0.9 L/h)
excessive fluid intake
under replacement of sodium
35
hyponatremia
water sodium imbalance
36
how is hyponatremia typically avoided
urination
37
what are the consequences of hyponatremia
central nervous system edema and muscle weakness
38
food analysis
the development, application and study of analytical methods for characterizing foods and their constituents
39
why is food analysis important
info about safety and nutrients, allow consumer to make informed decisions
40
what is the governments role in food analysis
maintain quality, ensure safety, high quality, fair competition, eliminate economic fraud
41
what are the 5 steps of proximate analysis
1. moisture
2. ether extract
3. ash
4. nitrogen
5. crude fibre
42
how is water removed during the first step of proximate analysis
weigh sample
put in oven until dry matter
weigh sample and find difference for water content
43
why is determining water content in feed important
weight
storage conditions (shelf life vs. enjoyability)
dilutes energy and nutrient in food
optimal water intake in animals
44
what are potential sources of error in the moisture content step of proximate analysis
drying could remove volatile compounds such as short chain fatty acids and minerals
could cause slight under estimation of dry matter weight (more than just water removed)
(wet weight - dry weight) / wet weight x 100%
45
how is the fat content found in proximate analysis
ether extract
dry matter is added to organic solvent ether extraction to solubilize lipids
solution is dried down resulting in precipitate of fat
weight of ether extract/wet weight of sample x100%
46
potential error in the crude fat step of proximate analysis
other things are soluble in organic solvents
eg. chlorophyll, resins, waxes in plants
could cause over estimate of crude fat
47
what newer method is used to find crude fat in proximate analysis
gas chromatography
finds amount of each lipid (saturated, trans, omega 3, etc.)
48
what is the precipitate from the ether extract used for in proximate analysis
it is ignited to ash to be measured for mineral content (total, not in individual elements)
weight of ash/wet weight of sample x 100%
49
why is measuring ash content important in proximate analysis
nutrition label
quality and taste
microbiological stability
nutritional requirements
manufacturer processing
50
what are limitations of mineral content analysis in proximate analysis
volatile minerals may be lost when burning
no info about individual minerals
51
what 2 assumptions are made for the Kjeldahl analysis
all nitrogen is in protein
all protein contains 16% protein
52
what does the nitrogen step of proximate analysis measure
protein
53
3 steps to kjeldahl analysis
1. digestions with sulfuric acid, converting nitrogen to ammonia
2. distillation to separate ammonia
3. titration to quantify the amount of ammonia
54
how is crude protein calculated
[nitrogen in sample x (100 / %nitrogen in sample)] /wet weight of sample x 100
use 6.25 unless specified as we are assuming 16% nitrogen
55
sources of error in kjeldahl analysis
assumes 16% protein when normal range is 13-19
doesn't consider other sources of nitrogen (nitrates, nitrites, urea, nucleic acids in food sample)
would over estimate crude protein content
56
how is crude fiber found in proximate analysis
mimicking digestion
boil in acid, keep precipitate
boil residue in alkali
ignite precipitate at 600˚C to burn off organic material and calculate what was burned off
[(wt of ash+crude fibre) -(wt of ash)] / wet weight of sample x 100%
57
why is crude fibre not the same as dietary fibre
crude fibre is cellulose and lignan content
dietary fibre is all fibre (soluble and insoluble)
58
sources of error when finding crude fibre in proximate analysis
unable to distinguish diff fibre components
soluble fibres are lost during proximate analysis
59
what are potential sources of error when calculating NFE in proximate analysis
NFE accumulates ALL errors that exist for other parts of the proximate analysis
maximum error is in this calculation
60
what is the equation for NFE in proximate analysis
100-(%moisture+%crude fat+%ash+%crude protein+%crude fibre)
61
proximate analysis gives no information on the _________ of food
digestibility
so we don't know what will actually be absorbed by an organism
62
what is dietary fibre
non digestible complex carbohydrates
structural part of plants
incl insoluble and soluble fibre
63
what is insoluble fibre and 3 examples
lignin, cellulose, hemicellulose
remains intact through the intestinal tract
does not dissolve in water
64
what is soluble fibre and 3 examples
pectins, gums and mucilages
forms gel and can dissolve in water
65
what are 2 more accurate fibre analysis that complement the proximate analysis
van soest method
southgate method
66
what does the van soest method do well?
differentiates bw insoluble fibres (lignin is poorly fermented and prevents fermentation of other fibres)
determines fermentable and non-fermentable carbs
67
what is done poorly in the van soest method
poorly differentiates bw sugars, starches and soluble fibres
68
which method of fibre analysis is best for human food analysis and which is best for agricultural applications
van soest is best for ag purposes
southgate is best for human food analysis
69
what is good about the southgate method
provides info about sugar, starch and various fibres
useful for human nutrition and food labeling
70
what is done poorly in the southgate method
does not differentiate bw various insoluble fibre components
71
If wondering the solubility regarding carbohydrate ask?
is a CHO soluble in the aqueous environment of the digestive tract
determined by physiochemical properties of CHO
72
what is digestability
does the host organism have the enzymes necessary to digest a CHO
determined by host digestive enzymes
73
what is fermentability
do gut bacteria have the enzymes necessary to break down a CHO
determined by gut bacteria
74
what are the key features of a simple digestive system without caecum
monogastric
non-functional caecum
considered a hindgut fermenter
suitable for a nutrient dense, low fibre diet
75
what digestion is done in the oral cavity
food is chewed
food is mixed with saliva
76
what 2 enzymes are released from the salivary gland
alpha amylase: target CHO
lingual lipase: target fats
77
what are the 4 parts of the stomach
cardia, fundus, body and antrum
78
what is the volume of the monogastric stomach empty vs filled
empty: 50mL
filled: 1-1.5L
79
what is the time from for gastric emptying of the monogastric stomach and what factors can change the time
2-6 hours
depends of activity, type of food, sleeping, etc.
80
chyme
food mixed by gastric juice in the monogastric stomach
81
what is the pH of the stomach
2
82
what is secreted by gastric glands? what is in it?
gastric juice
contains: water, electrolytes, HCL (protein inactivation) and enzymes
83
what increases the secretion of gastric juice
food or saliva entering body
84
parts of the small intestine
duodenum, jejunum and ileum
85
how is the pH raised when it enters the small intestine from the stomach
bicarbonates from the pancreas juice
86
small intestine is the main site for what?
nutrient digestion and absorption
87
what controls intestinal motility in the small intestine
longitudinal and circular muscles
88
food continues being digested in the small intestine by what?
pancreatic juice and bile acids
89
large intestine is the site of what 2 main things
fermentation and water absorption
90
what do bacteria in the large intestine produce and why
produce short chain fatty acids (volatile fatty acids) for their own energy, however the leftovers can be used by the host
91
in the small intestine, the surface area is expected to be about 30 meters squared. how is this possible
1. kerckring folds
2. villi and crypts
3. microvilli / brush border membrane
92
what is an enterocyte
cellular cytoplasm of an absorptive cell
93
what are the 3 types of nutrient transport mechanisms
1. diffusion
2. facilitated diffusion
3. active transport
94
what about the nutrient affects which transport mechanism would be used
1. solubility (water vs lipid soluble)
2. concentration/electrochemical gradient
3. molecular size and polarity
95
how does the number of species in a persons gut differ between people
500-1000 species identified per person
different species but similar core functions
96
what is the ratio of anaerobic to aerobic bacteria in the gut
1000:1
97
what influences the bacterial numbers in the different areas of the digestive system
regional oxygen level
ph
bile
gut transit time
mucus
immune factors
98
what is the purpose of a functional caecum
enormous hindgut (20-30L capacity) filled with bacteria
short chain fatty acids provide ~70% of total energy needs for host
site for the production of vitamins
99
what are the signs of an energy or nutrient deficiency
coprophagy (eating feces)
young animals eating feces colonize their guts with bacteria
100
what are examples of animals with a simple digestive system and a functional caecum
horse, rabbit and hamster
101
what is absorbed in the small intestine of horse
glucose, amino acids and fatty acids
102
what is absorbed in the large intestine and caecum of horse
short chain fatty acid (from bacteria), amino acids and lactic acid (high starch diet, bacteria break down anerobically = colic)
103
example of what has a ruminant digestive system
cattle, sheep, goat
104
key features of stomach of ruminant
4 regions
1. reticulum
2. rumen
3. omasum
4. abomasum
105
what is a ruminant digestive system designed to eat
high quantity of fodder and forage plant materials
106
why is there a difference between horses and cows
horses can run away from predators, so can't have 4 stomachs full of food weighing them down. cattle are in herds
107
what happens in the reticulum of the stomach in ruminants
capture nutrients and trap foreign materials (wire, nails, etc.) that are accidently swallowed to prevent perforations (hardware disease)
rich in bacteria = fermentation vat
108
what happens in the rumen of the stomach in ruminants
largest section
rich in bacteria = fermentation vat
food is temporarily mixed and partially broken down
temporary storage
109
where is 60-80% of total energy produced in ruminant?
rumen of stomach, as SCFA
110
what is the role of rumen papillae
increases surface area of the rumen for absorption
111
what happens in the omasum of the stomach in ruminants
resorption of water and some electrolytes
filters large particles and send back to rumen
112
what happens in the abomasum of the stomach in ruminants
digestive enzymes secreted from gastric glands (HCl, mucin, pepsinogen, lipase, etc.
stomach most similar to monogastric animals
113
a ruminant is a fore or hindgut fermenter
foregut
fermentation before intestines
114
what are the 2 steps that occur while food is in ruminant stomach
1. rumination: chew, swallow, regurgitate
2. eructation (belching): expel methane (biproduct of fermentation
115
advantages of a ruminant system
vitamin synthesis (B, K)
non-protein nitrogen used for making protein (poor quality protein can be used in feed= cheaper)
116
disadvantages of a ruminant system
carbs degrades into gases and lost through eructation (methane, bad for environment)
heat production: fermentation creates, can be uncomfortable to animals
117
distinct features of an avian digestive system
beaks and claws important for breaking up food into smaller pieces that birds can swallow (no teeth)
rapid digestion: get food, fly away, need light weight. easy to starve, need food constantly
crop used to regurgitate food for young
118
how many chambers are in an avian stomach
2: proventriculus and gizzard
119
explain the role of the crop in avian digestive systems
enlarged area of esophagus
temporary storage location for food
softened and regurgitated to feed offspring
120
explain the role of the 2 chamber stomach in avian digestion
glandular portion (proventriculus): gastric enzymes and HCl secreted (monogastric stomach like)
muscular portion (gizzard): mechanical breakdown to grind (rocks swallowed work here to break down)
121
explain the role of the ceca in avian digestion
minor site of bacterial fermentation
not a big contributer
small so can fly away easily
122
role of large intestine in avian digestion
very short, prodominantly used to connect small intestine and cloaca
small amount of storage, water absorption
123
role of cloaca in avian digestion
digestive, urinary and reproduction system meet here for excretion
124
definition of digestibility
fraction of a specific nutrient (or energy) that is exracted by the GIT
calculated from the amount of nutrient in diet and amount in feces
125
why is digestibility important
prevent deficiency and ensure essential nutrients are available to the organism
126
what is the total collection method
laborous
allow adaptation to diet or 7-21 days
isolate for quantitative analysis
measure intact and feces over 3-10 days, analyze nutrient of interest
127
limitations of the total collection method
accuracy in measuring intake (crumbs, left over, etc)
metabolic cage creates anxiety, abnormal behaviour
labour intensive
animals confined in costly equipment
not feasible for captive wild animals (eg. elephants)
128
what is the indicator method
way to measure digestibility
requires a marker (marker technique)
adapt animal to test diet containing marker
collect feed and fecal sample (dont need everything)
analyze marker and nutrient of interest relative to indicator
129
what are the types and characteristics of a marker (digestibility)
internal (natural component of feed)
external (component added to feed)
1. non-absorbable
2. must not be affected by or affect GIT (cant change digestion)
3. must mix easily with food (not change taste, texture, etc. shouldn't know its there)
4. easily and accurately acquired in sample
130
examples of markers used to measure digestibility
ferric oxide, chromic oxide, silica and lignin
131
advantages of indicator method
less labour intensive, ideal for wild animals
132
how is apparent digestibility different from true digestibility
apparent digestibility under-estimates true digestibility
133
what is not considered when calculating apparent digestibility
endogenous secretions: like epithelial cells, fatty acids released from dying intestinal cells
bacterial growth in gut: nutrient synthesis eg. biotin produced by gut bacteria
digestive enzymes like protein secretions (digestive enzymes released by cells)
134
how is true digestibility measured
1. preform 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 from the test
135
what is the cellular source of energy where is supplied from
atp
supplied by macronutrients in the diet
136
what is the energy value of a food
calorie
137
what is the difference bw a chemistry calorie and a food calorie
1000 chem cals = 1 food cal
1 food cal = 1kcal = 4.18KJ
138
what is a food calorie definition
the energy required to raise the temperature of 1kg (1L) of water by 1˚C
139
chronic positive energy balance is
energy in>energy out
can lead to weight gain, infertility, increased blood lipids, insulin resistance
140
chronic negative energy balance
energy in< energy out
can lead to weight loss, infection, loss of performance, reduced bone mass
141
how were calories discovered historically (3 men)
antoine lavoisier (1700s): heat production vs co2 production of guinea pig, ice calorimeter, co2 formed from rxn of oxygen and organic matter
justin liebig: recognized that protein, carb and fats are oxidized in body
max rubner: measured energy values of foods to determine caloric content
142
calorimetry
measurement of heat production
amount of energy stored in the chemical bonds C-H of foods
143
what is a bomb calorimeter
principle of direct calorimeter
directly measures the amount of energy stored in chemical bonds of foods
144
explain the process of bomb calorimetry
dry and weigh sample 1g, place in enclosed chamber with oxygen
sample ignited
heat released is absorbed by water outside chamber and measured
heat of combusion = max energy
145
potential errors of bomb calorimetry
overestimate energy: cant digest fiber
doesn't take into accoun energy needed for digestion and absorption
146
Atwater values of cho, fat and protein
cho: 4kcal/g
fat: 9kcal/g
protein: 4kcal/g
147
atwater/ physiological values
available energy
metabolizable energy
takes into account incomplete digestibility
148
why is fat the highest in kcal/g
chemical structure influences the heat of combustion
CHO: rate of H to O= 2:1 (fewer C-H bonds to break)
protein: has nitrogen, eliminated as urea, this loss of hydrogen affects heat of combustion
fat: less oxidized than cho and protein, ratio of H to O much higher than 2:1, lots of C-H bonds to break, releases lots of energy
149
what factors affect heat of combustion of fatty acids
chain length: longer chain = more energy, more C-H bonds
degree of unsaturation: more double bonds = less energy released, fewer C-H bonds
150
heat increment of feeding HIF
thermic effect of food
energy used for digestion, absorption, distribution and storage of nutrients
5-30% of daily energy use
used to determine NET energy
151
what is net energy
= metabolizable energy - HIF
supports basal metabolism, physical activity, growth, pregnancy
152
order of partitioning energy from foods
gross energy
digestible energy
metabolizable energy
net energy
excess energy
153
3 primary components to energy expenditure
basal metabolic rate
thermic effect of food
physical activity energy expenditure
thermoregulation plays a very small/neglibible role in humans
154
how is BMR measured
shortly after waking
post absorptive state
lying down
completely relaxed
comfortable room temo
155
what is BMR and what tissues are most reflective of it?
kcal per 24 hours, based on metabolic weight (fat free mass, body weight and Kleibers law = 0.75)
muscle and bone are most reflective
156
what factors can affect BMR
genetics (fast or slow metabolic rate)
age (young vs old)
sex (men>women)
exercise changes tissue proportions (fat vs muscle)
temperature (thermoregulation)
157
what metabolic activity does fat, muscle, brain, liver, heart and kidney have
brain, liver, heart and kidney take up 60% of metabolic activity
fat = 5%
muscle = 25%
158
what are the 2 ways to measure total energy expenditure
direct calorimetry or indirect calorimetry
159
what is being measured when measuring total energy expenditure
all metabolic processes in the body - they all generate heat
heat production can be used as a measure of energy expenditure
160
direct calorimetry measures what
the heat a person generates
total heat loss
very expensive and impractical
161
indirect calorimetry measures
energy-releasing reactions in the body
energy requirements are estimated by measuring oxygen consumption (L), carbon dioxide production (L) and urinary nitrogen loss (g if being super accurate)
162
what does indirect calorimetry NOT account for
anaerobic processes (lactic acid production from glucose during intense exercise)
163
is indirect or direct calorimetry better
there is less than 1% difference
very comparable
164
advantages and disadvantages of indirect calorimetry
advantages: animal use, determine the type of substrate oxidized, more practical, moved around on a cart
disadvantages: hyperventilation (then gas balance not about metabolism), hard to get an airtight seal, masks are impractical
165
respiratory quotient provides information on what
energy expenditure, biological substrate being oxidized
ratio of metabolic gas exchange
co2 produced/o2 consumed
166
why does RQ vary for different macronutrients
differences in chemical composition mean that there is a different amount of oxygen intake in relation to co2 produced for each macronutrient
167
what assumptions are made when calculating RQ to determine energy expenditure
only CHO and fat are metabolized
no synthesis taking place at the same time as breakdown
amount of co2 exhaled = the amount of co2 produced by tissues
168
which type of exercise uses lipids vs cho?
endurance=lipid
high intensity = cho
169
what type of carbohydrate is naturally occuring
monosaccharides
170
when are monosaccharides considering reducing sugars?
when the anomeric carbon is free
171
in a disaccharide, what type of bond connects the 2 monosaccharides
glycosidic bond (acetyl bond)
172
what are the 2 types of polysaccharides
homo - one type of monosaccharide
hetero - diff types
173
what is the ratio of H:O for all carbohydrates
2:1
174
3C monosaccharide is called
triose - metabolite of glucose
175
5C monosaccharide is called
pentose - components of dna and rna
176
6C monosaccharide is called
hexose - nutritionally the most important
177
how do stereoisomers differ
same molecular formula, different 3D space due to chiral carbons resulting in L and D isoforms
178
what is a chiral carbon
mirror images
a carbon attached to 4 diff atoms or groups
179
which isoform of CHO are nutritionally important and why
D monosaccharides, because digestive enzymes are stereospecific for D sugars
180
how do you determine if the cho is in D or L isoform
highest chiral carbon has an OH on the right = D
highest chiral carbon has an OH on the left = L
181
what are the types of glycosidic bond
alpha or beta
configuration of the OH on the anomeric carbon determines whether the disaccharide is alpha or beta
possible
182
what bond does sucrose have
glucose alpha 1-2 fructose
non reducing
183
what bond does lactose have
galactose beta 1-4 glucose
reducing
184
what bond does maltose have
glucose alpha 1-4 glucose
reducing
185
starch contains what
amylose and amylopectin
186
is there an advantage in branching in polysaccharides
yes provides larger number of ends from which to cleave glucose when energy is needed
187
what bond causes branches in amylopectin
alpha 1-4 and 1-6 are used
188
is amylose or amylopectin branched
amylopectin
189
is glycogen branched
yes
190
examples of insoluble fiber
lignin, cellulose, hemicellulose
191
examples of soluble fibre
gums, pectins, mucilages
192
dietary fibre is what
non digestible complex cho
structural part of plants
193
what are the characteristics of solubility
water holding ability: does it hold water and become a viscous solution
absorptive ability: ability of fibre to bind enzymes and nutrients (affecting digestion)
194
insoluble fibre
remains intact throughout digestive system
reduce transit time (move quickly)
increases fecal bulk - stim muscle contractions
195
soluble fibre
forms a gel
delays gastric emptying, increases transit time
slows down the rate of nutrient absorption
196
cellulose
dietary and functional fibre
poorly fermented by human gut bacteria
found in bran, legumes, nuts, peas, etc.
197
what type of cho is cellulose
homopolysaccharide of beta1-4 glucose units
198
hemicellulose
solubility and fermentability depends on the sugar composition
found in bran, whole grain, nuts and some fruits/veg
199
what kind of cho is hemicellulose
heteropolysaccharide of alpha and beta linkages
contains pentose and hexoses (Xylose is the most common monosaccharide)
200
pectin
dietary and functional fibre
part of the primary cell wall of plants
highly fermented by gut bacteria
good bulking agent in animal feeds
rich in fruits, apples, oranges, lemons, grapefruit
201
resistant starch
4 types: RS1-4
found in plant cell walls
resistant to amylase activity
some advantages of soluble and insoluble fibres (eg. green banana ripening = resistant starch break down to simple sugars)
202
health benefits of fibre
maintains function and health of the gut
reduces constipation (insoluble fibre): stim contractions, decrease risk of infection, keeps things moving)
increases satiety (soluble fibre): delays gastric emptying, slows down nutrient absorption
203
how does soluble fibre decrease risk of cardiovascular disease
lowers cholesterol
forms a gel which binds cholesterol in the small intestine and send it out in feces
204
where does carb digestion occur
mouth, stomach, small intestine
205
what enzymes break down cho in the mouth
alpha amylase: breaks down alpha 1-4 glycosidic bonds
206
what cho are not broken down in the mouth
cellulose, lignin and alpha 1-6 bonds
207
what enzymes break down cho in the stomach
alpha amylase digestion continues until pH drops, then the enzyme is inactivated
208
what type of cho is left in the stomach once the pH has dropped
small polysaccharides and maltose
209
what enzymes break down cho in the small intestine
alpha amylase from the pancreas
210
what cho are still not broken down in the small intestine
alpha 1-6 bonds, and produce isomaltose
211
what specific enzymes are present at the brush border for cho digestion
isomaltase / alpha dextrinase: breaks down disaccharides such as maltose and dextrines from starch
invertase / sucrease: breaks down sucrose (glucose + fructose)
lactase: breaks down lactose (glucose + galactose)
212
what transporters are present at the brush border membrane
glucose
fructose
galactose transporters
213
factors known to influence lactase enzyme activity
age (ability to digest lactose decreases with age)
ethnicity (asian vs northern europeans)
genetics (variation in the LCT gene which encodes the lactase enzyme)
214
what happens in lactose intolerance
lactose should be broken down into glucose and galactose in the small intestine brush border enzymes
in lactose intolerance, it is not broken down and is fermented by bacteria in the large intestine causing irritation, increased motility, gas
215
what happens to glucose when monosaccharides are absorbed by enterocytes
small amounts leak back out into the lumen
small amounts diffuse in blood through basolateral membrane
majority goes to blood through GLUT2
216
how are glucose and galactose transported from the lumen to blood
basolateral Na-K ATPase
217
how is fructose transported from lumen to blood
taken up by facilitated transport GLUT5 on apical surface
218
how do glucose, galactose and fructose get from enterocyte to the bloodstream
GLUT2
219
what is the role of SGLT1
monosaccharide transporter on apical surface of enterocyte Na -glucose symporter
220
functions of glucose in the body
primary source of energy for cells - brain and rbc
spare protein - preserves biological function of proteins build, repair and maintain body tissue
prevent ketosis- ketones can cause pH of the body to become slightly acidic
221
is glycogenolysis anabolic or catabolic
catabolic
222
is glycogenesis catabolic or anabolic
anabolic
223
is glycolysis catabolic or anabolic
catabolic
224
is hexose monophosphate shunt catabolic or anabolic
oxidative phase is catabolic
225
is krebs catabolic or anabolic
both = amphibolic
226
what are the 3 fates of glucose in the cells
enters glycogenesis for energy storage
enters glycolysis for energy production
enters hexose monophosphate shunt to generate precursors for biogenesis
227
how glucose is used by the cell depends on
the cell and its requirements at the time
228
what is glycogenin
an enzyme that serves as a scaffold on which to attach glucose molecules to build glycogen in glycogenesis
229
what enzyme takes over for glycogenin to continue growing the glycogen store
glycogen synthase
230
is energy required to make glycogen?
yes
231
what enzyme is used to release glucose from glycogen
glycogen phosphorylase
232
how do insulin and glucagon maintain blood glucose homeostasis
influence numerous pathways in key metabolic tissues to store or release energy as needed
233
where is energy produced in the cell
substrate level phosphorylation: in mitchondria (krebs) and cytoplasm (glycolysis)
oxidative phosphorylation in mitochondria (ETC)
234
where are glycolytic enzymes found?
in cell cytoplasm, location of glycolysis
235
the endpoint of glycolysis depends on what
the availability of oxygen in the cell (aerobic vs anaerobic)
236
what type of cells can only use glycolysis to produce atp and why is this the only option?
red blood cells
they have no mitochondria
237
what is the first committed step in glycolysis
phosphofructokinase
238
what is the net energy yield of glycolysis from 1 glucose molecule
2 NADH and 2 ATP (equivalent to 8 ATP)
239
what is produced from pyruvate (from glycolysis) in an anaerobic state and where does this happen
lactic acid
in cells cytosol
240
when lactate is produced what is regenerated to allow glycolysis to continue and what is the net energy produced
regenerates NAD+
2 ATP produced
241
how does ethanol production differ from lactic acid production? what is the same?
human body does not produce ethanol
yeast breaks down pyruvate into CO2 and ethanol
also regenerates NAD+ which allows glycolysis to continue
242
when does the cori cycle occur?
when oxygen is unavailable leading to the production of lactate
lactate goes back to the liver, where gluconeogenesis allows for conversion of pyruvate back to glucose
243
what is the net energy production from the cori cycle and why is this number important
2ATP are produced, however 6ATP are consumed to convert lactate back to pyruvate and then glucose in the liver, so it is not sustainable
more energy consumed that produced
244
what is produced from the hexose monophosphate shunt and where does it occur
NADPH and ribose (precursors of nucleotides) synthesis
occurs in cytoplasm of cell
245
what are the phases of the hexose monophosphate shunt
oxidative and non oxidative
246
which cells use which phase of the hexose monophosphate shunt
all cells use the nonoxidative phase
only cells that preform biosynthesis use the oxidative phase
247
which pathway would be used if:
the cell needs ATP?
the cell has abundant ATP?
needs nucleotides?
the cell needs ATP? glycolysis
the cell has abundant ATP? glyconeogenesis
needs nucleotides?hexose monophosphate shunt
248
what enzyme is the gatekeeper to the krebs cycle and why
pyruvate dehydrogenase
converts pyruvate to acetyl coA
249
what cofactors are needed for the enzymes required for pyruvate dehydrogenase complex
thiamine
niacin
riboflavin
pantothenic acid
250
how much energy is generated by the pyruvate dehydrogenase complex
net energy 6ATP
(2x [1NADH/pyruvate])
251
how much energy in food is release in the krebs cycle
over 90%
252
where does the krebs cycle take place
mitochondrial matrix
253
what is the energy yield from 1 acetyl coA in the krebs cycle
12 ATP
(3NADH, 1FADH2, 1GTP)
254
how much atp is produced total from 1 molecule of glucose
38 atp
255
gluconeogenesis is active when
glucose is needed in the body
256
where does gluconeogenesis occur
liver
kidney during starvation
257
what tissues do not have the enzymes for gluconeogenesis
muscle and adipose tissue
258
what are the 3 irreversible steps in glycolysis and what enzymes are used to bypass this during glyconeogenesis
1. glucokinase/hexokinase: bypassed by glucose 6-phosphatase
2. phosphofructokinase: bypassed by fructose 1,6-bisphosphatase
3. pyruvate kinase: bypassed by pyruvate carboxylase and PEP carboxykinase
259
how does pyruvate get into the mitochondria
transporter: pyruvate translocase
260
why is oxaloacetate converted to malate and then recoverted in gluconeogenesis
oxaloacetate cant leave the mitochondria, malate can cross the mitochondrial membrane and once in the cytosol, malate is converted back to oxaloacetate
261
lipids are soluble in _______ solvents such as ether, chloroform, acetone
organic
262
lipids are a major component of what?
cell and organelle membranes
263
8 functions of lipids
1. concentrated source of energy 9kcal/g
2. palatability of foods and increase satiety
3. source of essential fatty acids
4. source of fat soluble vitamins
5. necessary for growth and development
6. important precursors for production of hormones
7. affect inflammation and blood clotting
8. key roles in disease development : atherosclerosis, diabetes, obesity
264
what 2 configurations are possible for unsaturated fatty acids
cis or trans
265
what end does numbering start in the omega naming system
methyl end CH3
266
what end does numbering start in the delta naming system
carboxyl end COOH
267
explain the essential fatty acid discovery
george and mildred barr fed rates diets that were fat free
stunted growth, lost fur, inflamed and scaly tails
humans: infants fed differing fat diets, <0.1% linoleic acid had poor growth and dry skin
268
what are the omega 3 and 6 essential fatty acids
linoleic acid = omega 6
alpha linolenic acid = omega 3
269
why are omega 3 and 6 fatty acids essential
humans lack the enzymes necessary to insert double bonds beyond the delta 9 position
delta 12 and delta 15 FA are produced in plants
270
signs of omega 6 deficiency
dermatitis
reduced growth
reduced repro maturity
271
signs of omega 3 deficiency
decreased IQ
decreased visual acuity
272
who is susceptible to essential fatty acid deficiency
infants (formula specifically but rare)
hospitalized with feeding through IV also rare
273
how has dietary fatty acid intake changed in industrial society
increased trans fats
increased omega 6
lower omega 3
274
what is the purpose of the EFA desaturation and elongation pathway
eicosanoid production pro-inflam (omega 6) and anti inflam (omega 3)
275
steps of EFA desaturation and elongation
desaturation delta 6 desaturase
elongation elongase 5
desaturation delta 5 desaturase
276
what happens in the desaturation step of efa desaturation and elongation
new double bond added at the 6th position (delta 6 desaturase) or 5th position (delta 5 desaturase) of the carbon backbone from the carboxyl end
277
why are dogs and cats susceptible to omega 3 deficiency
dogs: can convert ala to epa but not dha
cats: lack enzymes to make any long chain FA
278
3 types of eicosanoids
prostaglandins
thromboxanes
leukotrienes
279
eicosanoids are metabolites of any ___ carbon fatty acids but mostly _____ and _____
20
arachidonic acid (AA) and eicosapentaenoic acid (EPA)
280
what do eicosanoids have a role in
inflammation, platelet aggregation, blood pressure
implications for diseases characterized by inflammation
281
TAGs are the main _____ and _____ lipid
dietary and storage
282
what processes involve TAGs
de novo lipogenesis
cellular storage and lipolysis
transported in lipoproteins
283
what type of bond is used to connect the glyceride to the 3 FA in a TAG
ester bonds
284
what important structural feature is different in phospholipids compared to TAGs
more polar due to hydrophillic phosphate group
285
primary functions of phospholipids
membrane component
source of physiologically active FA for eicosanoid synthesis
anchors membrane proteins
intracellular signalling
286
structural features of sterols
free or esterfied with a fatty acid - cholesterol ester
287
sources of cholesterol
diet: meat and eggs 40%
endogenous production 60%
288
primary functions of sterols
essential component of membranes
precursor for: bile acid production, steroid sex hormone production, vitamin D synthesis
289
what enzyme is in the mouth for digestion of lipids
lingual lipase
290
what enzyme is present in the stomach to break down lipids
gastric lipase (stable at low pH)
291
what is the livers role in lipid digestion
bile acid production for emulsification of fat
292
what is the gallbladders role in lipid digestion
storage of bile salts, release of bile triggered by hormones
293
what lipid digestion happens in the small intestine
pancreatic enzymes include: pancreatic lipase and cholesterol esterase
294
how are bile salts different from bile acid
conjugated with taurine or glycine in the liver
greater solubility in the intestinal lumen
295
what are mixed micelles
small, spherical complexes containing lipid digestion products and bile salts
size enables them to access space between microvilli in the intestine
296
how are bile salts recycled and what is this process called
deconjugated by gut bacteria and reabsorbed and recycled
enterohepatic circulation
297
what reduces the efficiency of enterohepatic circulation and why
holds on to bile acids, which are then secreted in the feces
298
what digestive enzymes work on lipids
pancreatic lipase, cholesterol esterase, phospholipase
299
simply, how are lipids absorbed by enterocytes
TAG broken down into monoacylglycerols and FFA
with cholesterol absorbed via mixed micelles
through endoplasmic reticulum to reform TAG
exocytosis via chylomicron
300
lipoprotein classification is determined by
1. ratio of lipid to protein (affects density)
2. specific apolipoprotein content (which affects receptor interactions)
301
how are chylomicrons classified?
carry lipid from the diet
high lipid, low protein
has ApoB-48, ApoC and ApoE
302
how is very low density lipoprotein VLDL classified
drops fat off at different tissues, becomes IDL then VDL
high lipid low protein
contains ApoB-100, ApoC, ApoE
303
how are IDL and LDL classified
bad cholesterol
protein to lipid ratio increases relative to VLDL
contains ApoB-100, ApoC, ApoE
304
how is high density lipoprotein HDL classified
good cholesterol
low lipid high protein
ApoA
brings cholesterol to liver for excretion
305
when do chylomicrons increase in the blood
after a meal
peaks 30min-3hours
306
what is the order of dietary lipids available to tissue and why
available to muscle and adipose before the liver
because chylomicrons enter the lymphatic system before entering the blood
307
where is LPL lipoprotein lipase located
on the surface of endothelial cells lining small blood vessels and capillaries
not expressed in the liver
expressed by adipose and muscle
308
what activated LPL in chylomicrons
ApoC
only in chylomicrons
309
what does LPL do
hydrolyzes TAG in chylomicrons into 2 monoglycerol and 2 FA
turns chylomicrons into chylomicron reminant
310
how are chylomicron reminants removed from circulation once depleted
ApoE mediated interactions with a receptor in the liver
311
how is LDL cholesterol removed from circulation
taken up by liver via LDL receptors (receptor mediated endocytosis) then broken down and recycled
312
how does HDL pick up cholesterol
extracted from plasma membranes and then esterfied directly on HDL
most blood cholesterol is esterfied with a FA
313
what does HDL do
reverse cholesterol transport
picks up cholesterol around the body and brings it to the liver
314
what enzyme esterfied a fatty acid to cholesterol
Lecithin-cholesterol acyltransferase LCAT
315
what enzyme transports cholesterol from HDL into the liver
SR-B1 (scavenger receptor class B1)
316
what enzyme transfers cholesterol from HDL to VLDL and or LDL
CETP cholesterol ester transfer protein
317
what are the 3 fates of cholesterol in the liver
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
318
where does de novo cholesterol ester and TAG synthesis happen
liver
319
what is the major endpoint of lipids in the adipose cell
triglyceride pool
320
where do lipids fit in metabolic pathways
gluconeogenesis: glycerol backbone is glucogenic - can be used to make glucose
krebs cycle: energy production, fat oxidation via acetyl coA
321
lipases hydrolyse what
ester linkages
322
what does hormone sensitive lipase do in adipose tissue
cleaves a fatty acid from the glycerol backbone
inhibited by insulin
323
what pathway do fatty acids enter for energy production
beta oxidation to acetyl coA and then can anter TCA as citric acid or become ketone bodies
323
steps of beta oxidation
1. dehydrogenation
2. hydration
3. oxidation
4. thiolysis
324
after each round of beta oxidation, what is removed and what is produced
removes 2 carbons from the fatty acid chain and produces 1NADH and 1FADH2
325
how many times does a 10 carbon fatty acid go through beta oxidation?
how many ATP equivalents are produced by complete oxidation?
4x resulting in 2 acetyl coA
5 acetyl coA, 4NADH, 4FADH2 = 80ATP
326
what percent of protein, carb and fat is recommended of daily calories
protein: 10-35%
carb: 45-65%
fat: 20-35%
327
how does limiting dietary cholesterol affect blood cholesterol in healthy vs those with high cholesterol
healthy: not much change
high cholesterol: reduces LDL
328
what are trans fatty acids
unsaturated fa with at least one double bond in the trans configuration
industrial and natural trans fats exist
329
how are industrial trans fats produced
hydrogenation of vegetable oils
to increase stability, longer shelf life, palatability
330
partial vs complete hydrogenation
partial: double bonds converted from cis to trans
complete: all double bonds become fully saturated
331
where are trans fats found naturally
ruminant fat
milk fat = 4-8% trans
made in the rumen through bacterial fermentation
332
what effect does high intake of industrial trans fats have on CVD risk
increase LDL
increase total cholesterol
increase inflammation
decrease HDL
333
what increases the risk of cardiovascular disease more than any other nutrient on a per calorie basis
industrial trans fats
334
what is the mediteranean diet high in? what effect does it have on the body
monounsaturated fats
decrease risk of heart disease, metabolic syndrome and certain cancers
335
what is fish high in? what effect does it have on the body
omega 3, decrease disk of heart disease, arthritis, reduce inflammation
336
proteins 3 possible uses
provide amino acids for protein synthesis
source of energy if needed
substrate for glucose synthesis
337
do humans need proteins
no necessarily, but we need the amino acids in protein
338
how proteinogenic amino acids are there in humans
21, including selenocysteine
non-proteinogenic aas also exist but are not used to make protein
339
how many aas are essential for humans
9
340
where is protein highest in the body
blood, connective tissue, eye lens
341
true or false, percent protein is generally higher in animal derived food than plants
true
342
parts of aa structure
alpha carbon in the center
carboxyl terminal COOH
side chain with variable composition
amino terminal NH2
343
what are the 2 types of amino acids in the body
standard - all used to make protein, 20 AAs in genetic code + selenocysteine
non-standard: rarely used to make protein, eg. intermediates or formed by post translational mods
344
NUTR 3210
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