1
Q
what is nutrigenomics?
A
a new branch of nutrition that considers people as individuals who will respond uniquely to nutrient status based on their genetic makeup.
2
Q
what is a positive energy balance?
A
excess of calories over an extended period of time causing a gain in body mass
3
Q
what is the definition of nutrition?
A
the science of food and food systems, their nutrients and their constituents, and their interactions within and between all relevant biological, social, and environmental systems
4
Q
what are the current challenges regarding nutrition?
A
- over population
- obesity
- effects of climate change on food security
- advances in nutrigenomics
5
Q
what is the main goal regarding nutrition?
A
understand process by which the organism ingest, digest, absorb, transport, utilize, and excrete food
6
Q
what are essential nutrients?
A
a chemical that is required for optimal metabolism, but cannot be synthesized to meet the needs of the organism
7
Q
what are the 2 steps in determining if something is an essential nutrient?
A
- removing the nutrient from the diet causes a deficiency that affects biochemical processes and symptoms that indicate a decline in health
- putting the nutrient back into the diet corrects the problem and health will return provided there are no permanent damages
8
Q
what is cretinism?
A
a disorder caused by nutritional deficiency of iodine in a pregnant mother
9
Q
what can deficiency of iron, folate, and/or vitamin B12 cause?
A
anemia
10
Q
what is anemia?
A
low circulating red blood cell volume that causes fatigue
11
Q
what can deficiency of vitamin D cause?
A
rickets or osteomalacia
12
Q
what does rickets or osteomalacia cause?
A
deformed legs as an infant of fractures in adults
13
Q
what can deficiency of vitamin B1 (thiamine) cause?
A
beriberi
14
Q
what is beriberi?
A
abnormalities in the nervous system, weakness and pain in limbs, irregular heart beat
prevents appropriate energy production
15
Q
what can deficiency of vitamin C cause?
A
scurvy
16
Q
what is scurvy?
A
prevents proper collagen formation and triggers haemorrhaging, bleeding of gums, skin ulcers
17
Q
what can deficiency of vitamin B3 (niacin) cause?
A
pellagra
18
Q
what is pellagra?
A
sun sensitive skin, dementia, diarrhea
19
Q
how many nutrients are essential?
A
40/5000
20
Q
how many essential nutrients are carbs?
A
0
21
Q
what are the 2 essential nutrients that are fats?
A
linoleic acid and alpha-linolenic acid
22
Q
what are the 10 essential nutrients that are proteins/amino acids?
A
valine, isoleucine, leucine, phenylalanine, threonine, tryptophan, methionine, lysine, histidine, arginine
23
Q
what are the 12 essential nutrients that are vitamins?
A
fat soluble: A, K, E
water soluble: niacin, riboflavin, thiamin, pyridoxine, pantothenic acid, biotin, folate, cobalamin, ascorbate
24
Q
what are the 14 essential nutrients that are minerals?
A
macro: Ca, Na, K, Cl, Mg, P
micro: Fe, Cu, Zn, Se, I, F, Mn, Mo
25
what are nutrient requirements?
frequency distributions of nutrient intake needed by individuals within a population to achieve similar end points
26
what is the formula for therapeutic index?
TI = UL/RDA
27
what is EAR?
reflects the median requirements
28
what is RDA?
derived from EAR and meets or exceeds the requirement for 97.5% of the population
29
what is UL?
the highest average daily intake that may not pose risk of adverse effects to most individuals in a population
30
what is AI?
used when EAR and RDA cannot develop due to insufficient evidence
reflects the average intake based on observed/experimental data
31
what is EER?
average dietary intake that is predicted to maintain energy balance in healthy, normal weight individuals of a defines weight, age, gender, height and level of physical activity consistent with good health
32
what is AMDR?
acceptable macronutrient distribution range, intake range for an energy source associated with reduced risk of chronic disease
33
how much of an adults diet should be protein?
10-35%
34
how much of an adults diet should be fat?
20-35%
35
how much of an adults diet should be carbs?
45-65%
36
what is energy expenditure?
resting metabolism + physical activity
37
what should you consume more of; macronutrients or micronutrients?
macronutrients
38
what are the main hormones that drives anabolism?
insulin and growth hormone
39
what are the main hormones that drive catabolism?
glucagon, epinephrine, norepinephrine and glucocorticoid steroids
40
what happens when a meal is consumed?
nutrient intake - influx of nutrient building blocks - excess of ATP
41
what is food composition analysis?
development, application, and study of analytical methods for characterizing food and their constitutes
42
what is nutritional density?
total amount of essential nutrients in 1 serving of food, relative to the energy content
43
what is fibre?
organic matter that is indigestible and is used to add bulk to the feed
44
what is proximate analysis?
basic determination of moisture, crude protein, crude fat, crude fibre, and ash
45
what is Southgate analysis?
fro crude fibre for modern CHO labelling
46
when was proximate analysis developed and for what purpose?
developed in Germany during the 1800s, originally used to analyze animal feeds
47
what is the process of proximate analysis?
1. determine amount of moisture lost
2. ether extract
3. ash
4. crude protein
5. crude fibre
48
what is ether?
a non-polar solvent that will carry out the lipids with it
49
what is the goal for ether extraction?
determine the quantity of lipids in the food sample that have nutritional importance
50
is there a definition of subclasses of lipids with basic ether extraction?
No, further analysis are needed by gas chromatography to quantify the relative amounts of various fatty acids
51
what are insoluble sources of fibre?
cellulose, lignin, hemicelluose
52
what are soluble sources of fibre?
pectins, gums, mucilages
53
how is energy content derived?
total fat, CHO, and protein by 9, 4, and 4 kcal/g
54
how long does gastric emptying take?
2-6 hours
55
what is the breakdown of protein strands initiated by?
enzymes, pepsin, and parapepsin
56
what is chyme acidity neutralized by in the small intestine?
pancreatic bile and duodenal secretions
57
what are digestive enzymes mainly secreted by?
pancreatic juice
58
what does bile do?
brings detergents to emulsify fats
59
what kind of meal with cause more bile secretion?
high fat meals
60
where are most of the decisions about secretion, motility, absorptive processes, blood flow, etc. made?
wishing the nerves of the GIT
61
what do kerckring folds in the small intestine do?
give the inner surface a wrinkly appearance
62
what are the epithelial cells in the villi called?
enterocytes
63
what do glycoproteins act as?
a site for binding of certain digestive enzymes`
64
Describe diffusion
- lipid soluble molecules can diffuse directly through the membrane
- form of passive transport
- unaided its slow
- require concentration gradient
65
describe facilitated diffusion
water soluble molecules use a transporter (protein structures in the bilayer) to diffuse through the membrane
- require concentration gradient
66
describe active transport
ATP expended to maintain a Na gradient (Na higher on the outside)
-drives nutrients into the cell
67
what is the large intestine the site of?
- fermentation via colonic bacteria
| - water and electrolyte absorption/reabsorption
68
how many species of colonic bacteria have been identified so far?
over 500
| predominantly anaerobic
69
what does fermentation produce?
lactate and VFA in the colon
70
where does the functional caecum join?
with the upper colon
71
what does the caecum do?
has a large bacterial population that ferments soluble and insoluble fibres and produces VFAs
72
what is the caecum a great adaption for?
fringe environments
| - little nutrient dense food available
73
what is coprophagy?
consuming their own faces to get enough nutrients
74
what does too much starch in a horses diet lead to?
lactic acidosis leading to colic
75
what is the order of the path food takes in the cows stomach?
reticulum
rumen
omasum
abomasum
76
what does the reticulum and rumen do?
ferments food
| helps select between more and less chewed food
77
what does the omasum do?
removes excess water
78
what does the abomasum do?
has essential nutrients absorbed and digested
79
where is 60-80% of the cows energy requirements absorbed in the form of VFAs?
the rumen
80
what is eructation?
the emission of fermentation gases
81
where does foregut fermentation take place in cows?
the rumen
82
describe the total collection method
* Allow the animal or person to adapt to the diet in question for 7-21 days;
* Measure intake over a 3-10-day period;
* Collect and weigh all feces, with minimal contamination by urine;
* Analyze homogenized sample of food and feces for the nutrient of interest.
83
what does the apparent digestibility coefficient (ADC) equal in the total collection method?
ADC= (total intake - total feces) / total intake
84
what are the characteristics of a good indicator?
* It should be non-absorbable and move through the GIT uniformly;
* It must not alter GIT function;
* It must mix well with the other food/feed components;
* It must be easily and accurately measured in feed and fecal samples
85
what are the steps to follow in the indicator method?
1. Adapt animal to test diet (includes marker): The animals are given time to adapt to the diet in question, as in the previous method.
2. Collect feed and fecal samples, dry and weight them.
3. Analyze feed and fecal samples for relative amounts of the marker and the nutrient of interest.
86
What does ADC equal in the indicator method?
```
ADC= (A-B) / A
A = ratio of nutrient/marker in feed
B = ratio of nutrient/marker in feces.
```
87
What does true digestibility take into account that apparent does not?
the endogenous contribution of nutrients into fecal sample
88
What does the Trade digestibility coefficient equal?
A-(B-C) / A
| C = residual ratio of the nutrient to the marker
89
how does feed intake influence digestion?
If intake is limited, animals may digest more when food is restricted to make the most of the least. A larger meal may reduce digestion efficiency
90
how does particle size influence digestion?
The smaller the particle size, the faster it travels through the GI tract, allowing less time for digestion.
91
how does chemical composition influence digestion?
: Different feeds are chemically distinct and may trigger a different response in the GI tract
92
how does geography influence digestion?
Digestibility is higher at higher altitudes, possibly due to a greater retention time.
93
how does age influence digestion?
mature animals digesting certain nutrients such as fibre or minerals, better than the young
Digestibility may diminish with aging.
94
what is energy metabolism?
the sum of all chemical reactions involved in obtaining and utilizing food energy
95
what do we need to understand to quantify energy intake?
caloric values of the different macronutrients found in our diet, and the obligatory losses that occur as we move these substrates into metabolism
96
what do we need to understand to quantify energy expenditure?
the physiology of heat production, and how it can be measured directly or estimated by measuring oxygen consumption and carbon dioxide release.
97
what is energy?
the capacity to do metabolic or physical work
98
what is the predominant source of energy at the cellular level?
ATP
99
what are cellular ATP pools supported by?
dietary macronutrient intake
100
what are macronutrients eventually oxidized to?
carbon dioxide and produce energy
101
what are dietary proteins a source of?
amino acids
102
what are dietary fats used for?
make membranes
store triglycerides
cholesterol
103
what are dietary carbohydrates used for?
make glycogen, glycoproteins, and glycolipids
104
what does hydrolysis of ATP release?
energy captured in chemical bonds, driving forward metabolic reactions and physical movement, releasing heat
105
what is a calorie a measure of?
the amount of energy required to raise the temperature of 1g (or 1mL) of water by 1°C.
106
what is energy balance?
the difference between energy intake and energy expenditure
107
when is the body in a positive energy balance?
When dietary energy intake is greater than energy expenditure
108
when does negative energy balance occur?
during weight loss and infection, and as the body degrades protein faster as it tries to support immune functions.
109
what are molecules extracted from food oxidized by to produce metabolized energy?
glycolysis and TCA cycle
110
how much energy is lost as heat in metabolism?
~60%
111
what is bomb calorimetry?
a measurement of heat production when a food sample is completely combusted in a high oxygen environment.
112
what does measuring heat allow for in bomb calorimetry?
allows estimation of the potential energy that was present in the food.
113
what does gross energy represent?
represents the maximum amount of energy which could be obtained when food is completely oxidized metabolically or by chemical combustion.
114
what does digestible energy (DE) equal?
DE = GE - energy lost in feces
115
what does metabolized energy (ME) equal?
ME = DE - energy lost in urine
116
what is the GE for fats?
9.40
117
what is the GE for protein?
5.65
118
what is the GE for CHO?
4.15
119
what is the DE for fats?
9
120
what is the DE for protein?
5.25
121
what is the DE for CHO?
4
122
what is the ME for fat?
9
123
what is the ME for protein?
4
124
what is the ME for CHO?
4
125
order from highest to lowest GE value:
| fat, CHO, proteins
Fats, protein, CHO
126
why do fats provide more kcal/g?
low level of inherent oxidation of the molecules.
In fats, there are FEWER oxygen atoms per carbon than in CHO, so there is more potential energy remaining in fats to generate energy
127
how can stearic acid be represented?
18:0
128
what is the GE of stearic acid?
9.53 kcal/g
129
how much of the chain of butyric acid can yield metabolized energy?
75%
130
what is the GE of butyric acid?
5.35 kcal/g
131
what does the Heat Increment of Feeding (HIF) include?
* Energy expended in in digestion, absorption, distribution and storage of dietary nutrients
* Further metabolism of nutrients required to maintain homeostasis
132
what does net energy (NE) equal?
NE = ME - HIF
133
when is the peak in energy expenditure?
about 2 hours after a meal is ingested
134
which macronutrient has the largest HIF?P
protein > CHO > lipids
135
what are the 3 components to energy expenditure other than HIF? In order of most to least energy
1. Basal metabolic rate (BMR);
2. Physical Activity;
3. Thermoregulation.
136
what is the BMR the measure of?
energy spent by a subject under the following conditions:
• shortly after wakening;
• in a post-absorptive state or fasting (for 12hrs) to avoid HIF expenditure;
• lying down and relaxed, but not asleep;
• in a room that is at a comfortable temperature so there is no energy spent in thermoregulation.
137
when would BMR drop?
during periods of malnutrition or starvation
138
whose metabolic rate is less variable; men or women?
women
139
how does genetics affect BMR?
Inheritance of a fast or slow BMR
140
how does age affect BMR?
Young people tend towards higher BMR, in part because of greater % lean mass.
141
how does gender affect BMR?
Men tend towards higher BMR, in part because of greater % lean mass.
142
how does physical activity affect BMR?
higher amounts can increase BMR, in part because of greater lean mass %;
143
how does temperature activity affect BMR?
in the environment which stress the maintenance of thermoregulation: Higher thermoregulation needs can lead to increased BMR
144
how is energy expenditure measured?
by direct or indirect calorimetry
145
what does direct calorimetry measure?
change in heat, change in water temperature
146
what does indirect calorimetry measure?
amount of oxygen taken in, amount of CO2 produced, amount of urinary nitrogen produced
147
what does pure fat generate a RQ of?
0.7
148
what does pure CHO generate a RQ of?
1.0
149
what does respiratory Quotient (RQ) equal?
CO2 produces (L) / O2 produced (L)
150
what can RQ be used to estimate?
* Energy expenditure;
| * Proportion of macronutrient substrates being oxidized
151
what is the average RQ for protein?
0.82
152
what is glycogenesis?
the production of glycogen granules from glucose
153
what is glycogenolysis?
the breakdown of stored glycogen to release glucose molecules
154
what is glycolysis?
the oxidation of glucose to pyruvate or lactate in hypoxic conditions
155
what is Gluconeogenesis?
the production of glucose using various substrates
156
what is Gluconeogenesis critical for?
the maintenance of blood glucose during exercise and fasting
157
what does the Hexose Monophosphate Shunt (or pentose phosphate pathway) do?
uses glucose to form NADPH and ribose sugars
158
what is the main role of the TCA cycle?
oxidize acetyl CoA to CO2 and capture energy in the form of electrons in NADH
159
What does the TCA cycle participate in?
gluconeogenesis
160
Where do NADH and FADH2 from the TCA cycle donate their electrons?
different components of the ETC
| potential energy used to pump protons out of the mitocondria
161
where does oxygen accept electrons?
at the end of the ETC
162
why would glucose enter glycogenesis?
for energy storage
163
what happens when glucose enters glycogenesis?
converted to glucose-6-phosphate (G-6-P), then to glucose-1-phosphate (G-1-P) and be processed into glycogen
164
what happens when glucose enters glycolysis?
energy production via substrate level phosphorylation.
165
what does acetyl CoA do?
fuel the TCA cycle or provide building units for fatty acid production and storage as triglycerides.
166
what happens when glucose enters the hexose monophosphate shunt?
G-6-P flows through 6-phosphogluconate (6-PG) to form NADPH and pentose phosphates (5-carbon monosaccharides).
167
which is the main pathway in the cell for reducing NADP+ to NADPH?
hexose monophosphate shunt
168
which pathway generates precursors important in biogenesis?
hexose monophosphate shunt
169
where are the hormones glucagon and insulin made?
in specialized cells in the islets of the pancreas
170
where is glucagon released from and why?
released from alpha cells in response to low blood glucose
171
where is insulin released from and why?
is released from beta cells in response to high blood glucose
172
what are the 2 main tissues that make glycogen?
liver and the muscles
173
how much of the body's glycogen reserve is stored in the muscles?
75%
174
how can you increase muscle glycogen?
carbohydrate loading
175
what is glycogen synthesis triggered by?
the presence of G-6-P
176
what happens when hexokinase in the muscle is allosterically inhibited by high G-6-P?
the glycogen pool in the muscle fills up, then the muscle enzyme will stop phosphorylating glucose and free glucose will be built up inside muscle cells. This will stop the transport of glucose into in the muscle from the blood stream.
177
is glucokinase in the liver inhibited by accumulation of G-6-P?
no, the liver cells continue to phosphorylate free glucose, and thus continue to take glucose up from the blood stream
178
what happens once the glycogen pools in liver are full?
further G-6-P will be processed to acetyl CoA (via glycolysis), which will fuel the de novo synthesis of fatty acids and triglycerides (TG). These will be assembled into VLDL particles and exported in the blood stream
179
what does circulating insulin favour?
the formation of glycogen
180
how many high energy phosphates are expended per glucose to be stored as glycogen?
2
181
what is the hormone that drives glycogen synthesis?
insulin
182
what protein does glycogen synthesis start on?
glycogenin
183
can muscles directly release glucose into the bloodstream?
no, only the liver can
184
why can the liver release glucose directly into the bloodstream?
has the enzyme glucose-6-phosphatase, located in the smooth endoplasmic reticulum. This enzyme clips the phosphate off the G6P and passes the glucose into the interior of the envelope of the smooth endoplasmic reticulum, which is attached to a pore in the plasma membrane, passing the glucose to the blood stream
185
what happens to G-6-P in the muscle?
enters glycolysis, and is either fully oxidized to CO2, or may pass into the blood stream as lactate
186
describe the enzymes in the liver and muscles regarding glycogenolysis
Liver and muscle both have glycogen phosphorylase and debranching enzymes, but only the liver expresses gluocose-6-phosphatase.
187
what does increased glucagon drive?
glycogenolysis
188
how are linear chains of glycogen cleaved?
by glycogen phosphorylase
189
what can G-6-P be converted in the liver?
free glucose and leave the cell with the help of glucose-6-phosphatase
190
what are the 2 ways to generate ATP in a cell?
substrate-level and oxidative phosphorylation.
191
when does substrate level phosphorylation occur?
when we have a high energy bond in the substrate which can be linked with the formation of ATP from ADP.
192
what does substrate level phosphorylation produce?
a small amount of ATP per glucose molecule, but it is very important under low oxygen conditions.
193
where does substrate level phosphorylation occur?
in both the mitochondria matrix (TCA cycle) and the cytosol (Glycolysis).
194
what is oxidative phosphorylation?
is where ATP is synthesised from ADP and inorganic phosphate (Pi) by the protein F1ATPase.
195
what does oxidative phosphorylation require?
the presence of reducing equivalents (NADH/FADH2) and oxygen.
196
what happens as electrons are donated by NADH and FADH2?
they move through the protein components of the ETC, moving down a gradient of electronegativity. Some of this energy is captured and used to pump protons from inside the mitochondria to the intermembrane space
197
what is the proton gradient the driving force of?
F1ATPase, which phophorylates ADP to ATP as protons flow back into the mitochondria.
198
where does glycolysis take place?
the cytosol
199
what is the end point of glycolysis?
2 ATP, 2 NADH, 2 pyruvate
200
what happens in hypoxic conditions regarding glycolysis?
the ETC and TCA cycle become dysfunctional, and glycolysis ending in pyruvate will also be unsustainable, as NADH accumulates, and NAD+ is lacking
- cells use NADH to reduce pyruvate to lactate, allowing another cycle of glycolysis to proceed. Under these conditions, only 2 ATP are generated per glucose metabolized, and lactate starts to accumulate, leading to a tendency towards acidosis
201
how can lactate be converted back to glucose?
in the liver glucose via gluconeogenesis (Cori Cycle)
202
in anaerobic conditions, what can yeast do?
break down pyruvate into CO2 and ethanol, which regenerates NAD+.
203
where does the Cori cycle occur?
in the muscle, especially under conditions of low oxygen
204
what does the cori cycle lead to?
production of lactate
205
how much ATP is needed to form glucose with 2 molecules of lactate?
6
206
where does the hexose monophosphate shunt take place?
place in the cytosol using G6P as substrate.
207
what does the hexose monophosphate shunt produce?
NADPH (in the oxidative phase) and pentoses (in both oxidative and non-oxidative phases).
208
what is The pairing of NADP+/NADPH is referred to as?
a redox couple
209
what ratio does a healthy cell keep The pairing of NADP+/NADPH in?
a reduced state, about 10-fold more NADPH than NADP+
210
where can pyruvate go after glycolysis?
* Conversion to oxaloacetate to replenish the core molecules of the TCA cycle;
* Transamination to become the amino acid, alanine;
* Conversion to acetyl CoA, to allow for energy production in the TCA Cycle, or the synthesis of fatty acids or cholesterol.
211
what do The enzymes and cofactors of the pyruvate dehydrogenase complex, located in the mitochondrial matrix, act as?
the gatekeeper into Kreb’s cycle
212
what 4 vitamins are required for the activity of the pyruvate dehydrogenase complex?
* Pantothenic acid, as coenzyme A (CoA);
* Thiamine, as thiamine pyrophosphate (TPP);
* Niacin, as NAD+;
* Riboflavin, as FAD
213
where is over 90% of the potential energy in food is released ?
the TCA cycle and the ETC
214
what does The TCA cycle/ETC do?
completely oxidize acetyl CoA, producing CO2 and water, as well as capturing energy as ATP, by both substrate-level phosphorylation (TCA) and oxidative phosphorylation (ETC).
215
what are the 2 TCA cycle inputs?
acetyl CoA and oxaloacetate
216
what do acetyl CoA and oxaloacetate form?
citrate
217
what does the oxidation of acetyl CoA do?
generated reducing agents in the form of NADH and FADH2, plus substrate level phosphorylation of GTP (that can be transferred to ATP).
218
what is Gluconeogenesis unregulated by?
glucagon secretion and it is critical to the prevention of hypoglycemia.
219
what happens if your blood glucose drops below a certain point?
you will lose cognitive and motor function, followed by loss of consciousness, and death will occur if blood glucose is not corrected.
220
where does Gluconeogenesis occur primarily?
in the liver, starting in the mitochondria and ending in the cytosol.
221
what can contribute to Gluconeogenesis during starvation?
the kidneys
222
what initiates Gluconeogenesis?
Malate the TCA intermediate that leaves the mitochondria
223
what are carbohydrates composed of?
carbon, hydrogen, and oxygen
224
what are carbohydrates?
a major source of fuel or energy in the body
225
do carbohydrates contain any essential nutrient?
no
226
what 2 groups can CHO be divided into?
simple and complex sugars
227
what are monosaccharides?
the simplest forms of CHO molecules.
228
how are disaccharides formed?
through the glycosidic linking of two monosaccharides
229
what is an oligosaccharide?
short chains of monosaccharides (typically 3-9), joined together by glycosidic bonds.
230
what are polysaccharides?
longer chains of 6 or more monosaccharides, which often have hundreds or thousands of units.
231
what is amylose?
is a soluble digestible starch
232
what is cellulose?
an insoluble, poorly fermented, fibre
233
where is an aldehyde present?
at the end of the chain of carbons
234
where is a ketone present?
found somewhere within the chain.
235
what are sugars with an aldehyde group called?
aldoses
236
what are sugars with a ketone group called?
ketoses
237
what is stereoisomerism?
the characteristic shared by molecules that can be mirror images of each other.
238
can a carbon participating in a double bond be chiral?
no
239
what are enantiomers?
pairs of mirror images
240
what are diastereomers?
are not a mirror images with many variations
241
what kind of sugar is fructose?
ketone
242
what is sucrose composed of?
glucose and fructose
243
what is lactose composed of?
glucose and galactose
244
what is maltose composed of?
2 glucose
245
what kind of sugar are both lactose and maltose considered to be?
reducing sugars
246
why is sucrose a nonreducing sugar?
the anomeric carbons on both monosaccharides participates in forming the glycosidic bond, so no hemiacetal is left to act as a reducing agent
247
which type of sugar is less chemically reactive
non reducing
248
what is the metabolic advantage of branching of polysaccharides?
it allows rapid addition and release of glucose units from many ends in a molecule, due to enzymes being able to target several sites and cleave glucose when energy is required.
249
what 2 basic chemical structures to plants produce starches in?
amylose and amylopectin
250
what is amylopectin?
When alpha (1→6) branched points are added
251
what do higher amylose contents in starch lead to?
makes the structure more dense, less soluble, and less digestible
252
what do higher amylopectin contents in starch lead to?
makes looser starch granules which are more soluble and more digestible.
253
what kind of carbohydrates are fibres?
complex carbohydrates (except lignin, but it is an indigestible plant cell wall component)
254
what does adsorptive mean?
the ability of a fibre to hold other molecules on their surface, through various forms of binding.
255
what kind of fibre can lower the Glycemic Index (GI) of foods by slowing the appearance of glucose in the blood stream.
soluble
256
what kind of bonds are in cellulose?
beta
257
what are hemicelluloses?
a diverse family of heteropolysaccharides present along with cellulose in almost all plant cell walls.
258
what is pectin?
present in the cell walls of land plants, abundant in citrus fruits and important in food science as a gelling agent used in jams and jellies.
259
where are natural gums found?
in trees, beans, grains, and seaweeds
260
describe resistant starches
contains the same glycosidic bonds as digestible starch, but it resists digestion in the small intestine, and is fermented by bacteria in the colon.
261
what does saliva contain to combat CHO?
α-amylase, capable of hydrolyzing α-1,4 glycosidic bonds.
262
where does majority of carbohydrate digestion take place?
small intestine
263
what does the glycocalix do?
enhances the functional surface area of the brush border by attaching enzymes in it, while allowing nutrients to diffuse in and be cleaved to absorbable units in close proximity to the membrane.
264
what do Carbohydrate polymers that are not targeted by digestive enzymes become?
fibre components
265
what is isomaltose?
and the disaccharide α-1-6 glucose
266
what is isomaltose targeted by?
an enzyme called isomaltase
267
what does isomaltase do?
cleaves the 1-6 linkage to release two new glucose molecules.
268
where does carbohydrate absorption trajectory originate?
the lumen then to brush border, then lipid bilayer of microvilli
269
what is the Glycocalyx region?
The lipid bilayer surface exposed to the lumen is covered in a mesh of mucopolysaccharides and glycoproteins called the glycocalyx
270
what happens to monosaccharide absorption as the concentration gradient in the lumen diminishes?
absorption must occur via active transport
271
when are sugars and amino acids absorbed via passive diffusion?
at the early points of digestion in the upper duodenum
272
what is glucose and galactose absorption controlled by?
SGLT-1.
273
What is GLUT-5?
a facilitative transporter, primarily of fructose.
274
what is GLUT-2?
the transporter for all sugars located in the basolateral side of the enterocyte
275
what does the apical side of the enterocyte face?
the lumen
276
what does the basolateral side of the enterocyte face?
the capillary leading to the hepatic portal vein.
277
what is blood glucose homeostaically controlled between?
~4-7mM
278
why is fructose absorption easy?
the liver does all the work
| - does not have a homeostatic level to be maintained in the blood stream
279
what is most dietary CHO converted into?
glucose
280
what will happen when not enough carbohydrates are consumed?
experience muscle breakdown to supply glucose to their systems
281
what is the primary source of exogenous glucose?
dietary CHO
282
what is glucose essential for?
proper functioning of red blood cells and tissues of the central nervous system
NUTR 3210
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