After Midterm Flashcards

Question 1

Q

Carbohydrates include dietary fibre. True or False?

Question 2

Q

What is the dietary goal for carbohydrates?

Answer

A

Dietary goal is to increase the intake of non-digestible CHO.

Question 3

Q

What is the Health Canada recommended CHO intake (%)?

Question 4

Q

What are the two essential fatty acids?

Answer

A

α-linolenic (ω-3) and linoleic (ω-6)

Question 5

Q

What are the functions of lipids?

2

Answer

A

precursors for signalling molecules,
structural role in
membranes, etc.

Question 6

Q

What are the dietary goals for lipids?

2

Answer

A

Goal:

lower the intake of total fat (especially saturated and trans fat)
increase intake of MUFA and ω-3 fats

Question 7

Q

What is the Health Canada recommended fat intake? (%)

Question 8

Q

What is the Health Canada recommended protein intake? (%)

Question 9

Q

The average consumption in North America of protein is ______% of daily calories.

Answer

A

The average consumption in North America of protein is 16% of daily calories.

Question 10

Q

In humans there are _____ proteinogenic AAs (includes selenocysteine).

Answer

A

In humans there are 21 proteinogenic AAs (includes selenocysteine).

Question 11

Q

What is a proteinogenic AA?

Answer

A

A “proteinogenic AA” refers to an AA that can be incorporated into a protein during translation.

Question 12

Q

Do non-proteinogenic AA exist?

Answer

A

Yes. ex. neurotransmitters like GABA

but they are not used to make protein

Question 13

Q

How many essential amino acids are there?

Answer

A

9 essential AAs

Question 14

Q

What are the %s in the average body of:

water, fat/lipid, CHO, proteins, minerals

Answer

A

Water: 60%
Fat/lipid: 20-25%
CHO: 0.2%
Proteins: 15%
Minerals: 2%

Question 15

Q

Between Blood, Connective tissue and Skeletal muscle which has the highest % of protein?

Answer

A

Connective tissue (37%) > Blood (35%) > Skeletal Muscle (20%)

we store a lot of protein in muscle purely because of its mass

Question 16

Q

% protein content of animal-derived foods is generally higher than plants. True or False?

Question 17

Q

Every amino acid has 4 basic building blocks. What are they? Give a brief description of each.

Answer

A

Amino terminal
- Amine Functional Group
Side Chain
-Side chain has a variable composition, which may or may not contain functional group(s)
Carboxyl Terminal
- Carboxylic Acid
Functional Group contains a carbonyl carbon
α-Carbon

Question 18

Q

There are two types of AAs in the body. Standard and non-standard. Give a brief description of each.

Answer

A

Standard Amino Acids:
– 20 AAs are encoded in the genetic code (but not selenocysteine)
– All are used to make protein
Non-Standard Amino Acids:
– Usually formed by post-translational modification of other AAs or as intermediates in the metabolic pathways of standard AAs
(ex. the GABA neurotransmitter is a metabolite of the amino acid glutamate)
– Many exist in the body, but they are rarely used to make
proteins

Question 19

Q

All AAs exist as enantiomers except for _____.

Answer

A

All AAs exist as enantiomers except for GLYCINE.

Question 20

Q

AA are naturally occurring in the ___ form.

L or D enantiomer

Answer

A

AA are naturally occurring in the L form.

Question 21

Q

How are D forms of AAs made?

Answer

A

D form of AAs are made through post-translational modifications.

Question 22

Q

At physiological pH, AAs are ionized. What is this called and how does this affect the amine and carboxyl group?

Answer

A

-This is called a Zwitterion
•Protonated amine group
•Deprotonated carboxyl group

Question 23

Q

Zwitterions decrease polarity by making AAs more water soluble.
True or False?

Answer

A

False.

Zwitterions INCREASE polarity by making AAs more water soluble.

Question 24

Q

What is the name of the bonds that keeps amino acids together?

Answer

A

Peptide bonds (also known as amide bonds) are a type of covalent chemical bond
The carboxyl group of one AA reacts with amino group of another AA, releasing H2O (condensation reaction)

Question 25

Q

What is the difference between a peptide and a protein?

Answer

A

A protein is a biologically active version of a peptide.

Proper peptide folding is very important for protein function.

Question 26

Q

Correct protein folding is assisted by _______ proteins.

Answer

A

Correct protein folding is assisted by CHAPERONE proteins.

Question 27

Q

Name the following:
2 AA=
3AA =
Around 50AA = 
>50 AA =

Answer

A

2 AA= Dipeptide
3AA = Tripeptide
Around 50AA = Oligopeptide
>50 AA = Polypeptide

Question 28

Q

The primary structure of a protein is determined by the _____ _________.

Answer

A

The primary structure of a protein is determined by the DNA SEQUENCE.

Question 29

Q

Counting of AAs always starts from the carboxyl end. True or False?

Answer

A

False.

Counting of AAs always starts from the amino end.

Question 30

Q

Secondary structure of a protein is determined by ______ bonds that create a stable structure.

Answer

A

Secondary structure of a protein is determined by HYDROGEN bonds that create a stable structure.

Question 31

Q

The secondary structure of a protein also involves the side chains.
True or False?

Answer

A

False.

Doesn’t involve side chains, only backbone atoms.

Question 32

Q

There are two types of stabilized secondary structures in proteins. What are they? Give a brief description of each.

Answer

A

α-helix
• An amino group makes a hydrogen bond with a carboxyl group 4 AAs down the chain, creating a helical shape in the polypeptide chain.
β-pleated sheets
• An amino group makes a hydrogen bond with a carboxyl group in the folded back polypeptide chain.
• Can be parallel or anti-parallel.

Question 33

Q

Tertiary structure corresponds to the arrangement of secondary structures.
True or False?

Question 34

Q

What protein structure involves interactions between AA side chains?

Answer

A

Tertiary structure.

Question 35

Q

The folding in protein tertiary structure plays a role in two protein characteristics. What are they?

Answer

A

Binding pockets

2. Hydrophobic regions

Question 36

Q

A disulfide bond is an example of an interaction in a _____ structure protein.
(hint: primary, secondary, tertiary, quaternary)

Answer

A

A disulfide bond is an example of an interaction in a TERTIARY structure protein.

Question 37

Q

A _______ structure corresponds to a combination of 2 or more _______ structures that are required to make a functional protein

Answer

A

A QUATERNARY structure corresponds to a combination of 2 or more TERTIARY structures that are required to make a functional protein

Question 38

Q

When proteins combine in a quaternary structure, what are the individual proteins called?

Answer

A

Subunits.

Question 39

Q

Proteins like insulin and immunoglobulin form multi-subunit complexes.
True or False?

Answer

A

True.

They are quaternary proteins with multiple polypeptides.

Question 40

Q

All proteins have a quaternary structure.

True or False?

Answer

A

False.

NOT all proteins have a quaternary structure.

Question 41

Q

What does the term “native protein” correspond to?

Answer

A

A native protein corresponds to a protein in its normal 3D configuration.

Question 42

Q

What are some examples of ways a protein can be denatured?

Answer

A

heat, salt treatment,

detergents, pH (stomach acid)

Question 43

Q

Explain what happens when a protein is denatured.

Answer

A

When a protein is denatured, it loses its bioactivity.
Denaturation affects 2°, 3°, and 4° structures (but not 1°).

*The peptide chains aren’t affected when denatured, it’s just the structure that is affected, meaning it’s no longer biologically active

Question 44

Q

Compare native and denatured albumin (egg protein).

Hint: Physical appearance

Answer

A

Native albumin –> transparent and liquid

Denatured (cooked) –> opaque and hard

Question 45

Q

What are the three major ways of classifying AAs?

Answer

A

Essential vs. not essential
Basic, acidic, or neutral
Polar versus non-polar

Question 46

Q

Explain the kinds of AA classification concerning essentiality.
(Hint: 3)

Answer

A

Essential AA (Indispensable)
- Not made by the body or can’t be made quickly enough to meet demands
Conditionally Essential
- Not normally required in the diet in a healthy individual, but become essential under specific contexts
(something happens to the individual for the aa to become essential)
Non-Essential (or Completely Dispensable)
- Can be synthesized in the body and are not essential in the diet

Question 47

Q

What are the essential amino acids?

9

Answer

A

9 AAs:

lys, thr, iso, leu, met, phe, trp, val, & his

Question 48

Q

What are the kinds of conditinally essential AAs? Give an example of each and explain.

Answer

A

Born with a genetic problem:
- Phenylketonuria–> an inborn error of metabolism where a person is unable to breakdown Phe into Tyr.
• A build-up of Phe in the body causes mental retardation
• Solution: limit Phe in diet and supplement with Tyr
Develop the problem due to a disease:
- Liver disease (cirrhosis) impairs Phe & Met catabolism
• Tyr and Cys are synthesized from Phe and Met, respectively
• Tyr and Cys become indispensable in this context

Question 49

Q

What are the characteristics of basic AAs?

3

Answer

A

Polar
basic AAs (+ve charge on NH3 group on side chain enables DNA binding)
Important in histone proteins, which bind DNA

Question 50

Q

What are the three basic AAs? Give a brief description of each.

Answer

A

Lysine
- Essential
- Simple straight chain
- Absent from grain products
- Lysine Contingency? (Jurassic Park)
Arginine
-Conditionally Essential
-Preterm infants unable to synthesize arginine
-Non-essential in healthy adults
(as a child grows, it’s no longer essential)
- Plays an important role in urea cycle
Histidine
- Essential
- Ring structure
- Used to produce histamine (inflammation)
- Important in children (they can’t make it on their own, therefore essential)

Question 51

Q

What are the characteristics of Acidic AAs?

2

Answer

A

Acidic AA (-ve charge on side chain carboxyl group)

2. Acidic AAs are very polar

Question 52

Q

What are the 4 acidic AAs? Give a brief description of each.

Answer

A

Asparatate
- Non-essential
- Involved in protein catabolism
- Transaminated to oxaloacetate (Krebs)
- Donates nitrogen to urea cycle
Glutamate
-Non-essential
-Transaminated to α-ketoglutarate (Krebs)
-“Source” of NH3
-Used to produce
GABA (neurotransmitter)
Asparagine
- Non-essential
Glutamine
-Non-essential
-Important in AA
catabolism because it is a carrier of nitrogen (to liver & kidney)
(amino group is toxic –> can’t let it accumulate)

Question 53

Q

What is transamination?

Answer

A

Transamination = passing an amino group from a donor to an acceptor

Question 54

Q

What is transamination?

Answer

A

Transamination = passing an amino group from a donor to an acceptor

Question 55

Q

What are the characteristics of neutral AAs?

3

Answer

A

Neutral AAs (no charge on side chain)
Non polar
Aliphatic (C & H atoms joined in straight or branched chains)

Question 56

Q

What are the two neutral AAs? Give a brief description of each?

Answer

A

Glycine
- Non-essential
- No enantiomers
- Used primarily to produce porphorin (a component of
the heme protein found in hemoglobin)
Alanine
- Non-essential
- Important in AA
catabolism because it’s a carrier of nitrogen (to liver & kidney)
-Important role in glucose-alanine cycle

Question 57

Q

There is only one AA that does not have enantiomers. What AA is it an why?

Answer

A

Glycine has no enantiomers because it has two hydrogen side chains.

Question 58

Q

What are the characteristics of branched chain AAs?

3

Answer

A

Neutral aliphatic AAs (no charge on side chain)
Non-Polar
All are branched

Question 59

Q

What are the three branched-chain AAs? Give a brief description of them?

Answer

A

Leucine
Isoleucine
Valine

All are essential
Not catabolized in the liver, so high levels found in circulation
-Promotes protein synthesis
-BCAA levels are high in protein supplements
(not metabolized by the liver, so they go directly to the muscle)

Question 60

Q

What are the characteristics of hydroxylated AAs?

2

Answer

A

OH-group on side chain is important for protein phosphorylation
Polar AAs

Question 61

Q

What AA can be classified as both hydroxylated and aromatic?

Answer

A

Tyrosine.

Question 62

Q

What are the two hydroxylated AAs? Give a brief description of each.

Answer

A

Serine
- Non-essential
Threonine
- Essential

Both are important for protein phosphorylation –> allow chemicals to become bioactive

Question 63

Q

What are the characteristics of sulfur-containing AAs?

Answer

A

Contain a sulfur group

- Non-polar

Question 64

Q

What are the two sulfur-containing AAs? Give a brief description of each.

Answer

A

Cysteine
- Non-essential
- Made from methionine
“Spares” methionine when cysteine consumed in the diet
- Used to form disulfide bonds
- Used in glutathione synthesis (oxidant defence system)
- could become conditionally essential
Methionine
- Essential
- 1st step in the synthesis of all proteins
- Methionine is limiting in legumes

Answer 59

A

Contain Aromatic rings

2. Non-polar (except tyrosine because of the OH group in its side chain)

Answer 60

A

Phenylalanine
- Essential
- Used to make Tyr
Tyrosine
- Non-essential
- “Spares” Phe (if tyr is high in diet)
- Used to synthesize neurotransmitters
Tryptophan
- Essential
- Used to make serotonin (mood)
- Used for niacin (Vit B3) synthesis
Proline
- Non-essential
- Important for collagen production (extracellular matrix)
- Aliphatic side chain

Answer 61

A

PTMs take place in polypeptide chains, not free AA.

Answer 62

A

Phosphorylation by kinase enzymes
Hydroxylation
Gamma-carboxylation
Iodination
ADP-ribosyltaion

Answer 63

A

Serine-OH
Threonine-OH
Tyrosine-OH

Phosphorylation is phosphorus dependent.

Answer 64

A

Lysine –> hydroxylysine
- very important in elastin subunits
- copper dependent
- associated with aortic rupture

Proline–> hydroxyproline
very important in collagen subunits (allows the extracellular matrix to be made; gives tissues their structure)
Vit C dependent
associated with scurvy

Answer 65

A

Required for calcium homeostasis and blood clotting
Certain proteins are modified to become Ca2+ binding proteins
Another carboxyl group is added to glutamate
Vitamin K dependent

Answer 66

A

Critical in the formation of thyroid hormones
Crucial for regulation of the metabolic rate
Iodine deficiency in about 2 billion humans
Iodine dependent

Answer 67

A

Adding ADP-ribose to an acceptor protein
Critical for DNA repair and regulation of protein function
Dependent on Vit B3 (niacin)
Niacin used to form NAD+. When NAD+ is broken down in the cell, ADP-ribose
and nicotinamide are the products.

Answer 68

A

Mouth
- No enzymatic digestion
- Mechanical breakdown only
Stomach
- HCl in gastric juice (proteins denatured)
- Pepsin (endopeptidase)
Pancreas
-Pancreatic juice containing zymogens
(inactive digestive proenzymes)
Small Intestine
- Zymogens are activated
- Enzymes break-down peptides
- Absorption of AAs

Answer 69

A

HCl in the stomach is secreted from PARIETAL cells.

Answer 70

A

HCl release is triggered by gastrin, acetylcholine, and histamine.

Answer 71

A

Denatures proteins
- breaks: hydrogen bonds, electrostatic bonds
Activates pepsin

Answer 72

A

HCl denatures pepsinogen (changes the shape) and then the protein becomes active.
(undergoes a proteolytic cleavage)

Answer 73

A

Pepsin is secreted as PEPSINOGEN, which is an inactive zymogen.

Answer 74

A

Pepsin is activated in an ACIDIC pH, and inactive at a NEUTRAL pH.

Answer 75

A

Pepsin is an ENDOPEPTIDASE, i.e., in other words, it cleaves peptide
bonds within the polypeptide chain.

*This generates mostly oligopeptides and some free AAs.

Answer 76

A

False.

Polypeptide cleavage occurs not only at ends, but in the middles as well (different length oligopeptides)

Answer 77

A

Enteropeptidase is located in the brush border.

Enteropeptidase activates trypsinogen to trypsin.

Answer 78

A

Trypsinogen, chymotrypsinogen, proelastase, procaboxypeptidase A & B.

Answer 79

A

Trypsin activates other zymogens:
Chymotrypsinogen –> Chymotrypsin
Proelastase –> Elastase
Procarboxypetidases –> Carboxypeptidase

Answer 80

A

Facilitated diffusion
Active transport (> 60% of AAs are absorbed this way, it is the dominant system)
- sodium-dependent transporters (indirect ATP requirement)

Answer 81

A

False.

ESSENTIAL AAs are absorbed faster than non-essential AAs.

Answer 82

A

FREE AAs have no absorptive advantage (i.e. protein supplements) over AAs in FOOD.

*Important to consider when incorporating protein supplements into diet, because protein supplements often have BCAA

Answer 83

A

FREE AAs have no absorptive advantage (i.e. protein supplements) over AAs in FOOD.

*Important to consider when incorporating protein supplements into diet, because protein supplements often have BCAA

Answer 84

A

energy
synthesis of new protein

*Estimates indicate 30-40% of essential AA are used in the small intestine

Answer 85

A

Generate energy for the cell
Stimulate cell proliferation (to replace shed enterocytes)
Increase synthesis of heat shock proteins (chaperones)
Drive mucus production, which helps to prevent bacterial translocation

Answer 86

A

Liver uses ~20% of the AAs to:

Make new proteins
Make new enzymes
Make albumin and other transport proteins
Make peptide hormones

Liver catabolizes the remaining 80% of AAs, where:

NH3 sent to the urea cycle
Carbon skeleton sent to Kreb’s cycle (for energy) or used for gluconeogenesis or lipogenesis

Answer 87

A

No. BCAAs are not taken up by liver, and instead are anabolic signals for tissues like muscle

Answer 88

A

AA composition
Digestibility
Presence of Toxic factors
Species consuming the protein

Answer 89

A

Any protein that provides all essential AA = “high quality”.
Animal protein > plant protein.
Ex. grains are limiting in lysine, legumes are limiting in sulfur-containing AA (methionine).

Answer 90

A

Some proteins are more digestible than others. More digestible = higher quality.
Animal protein > plant protein.
Ex. Some materials, like hair, have a great amino acid balance but are indigestible.

Answer 91

A

Less toxic factors = higher quality.
Animal protein > plant protein.
Plants contain thousands of phytochemicals.
Ex. soybeans contain
trypsin inhibitors with interfere with trypsin, thus preventing protein digestion.

Answer 92

A

Humans, pigs and chickens have similar protein needs.
Ruminants have bacteria in the rumen that can make all AAs, so none are considered essential (remember that ruminants can use low quality protein sources).

Answer 93

A

PER = Official method in Canada for the evaluation of protein quality

With this method, young rats are fed a diet for 4 weeks. The diet has all nutrients present at adequate levels except for protein, which is included at 10% of the diet
10% protein is marginal for health. If there is anything wrong with the protein source, growth of rats will be impacted
Rats are weighed at the beginning and end of the 4 weeks. Food consumption is carefully monitored

Answer 94

A

PER = gain in body mass (g) / total protein intake (g)

An optimal PER value is 2.0 (2g of rat growth per gram of intake) = whole egg

ex. rat gains 10g and eats 14g, PER= 10g/14g = 0.71

Answer 95

A

Simple
Cheap
Very sensitive to AA balance, digestibility, toxic factors

Answer 96

A

Rats are not humans
Growth, not maintenance
You don’t know WHY a protein is poor quality

Answer 97

A

CS =

the test protein is chemically digested into free AAs
these are then quantified by chromatography, and mathematically compared to the composition of whole egg protein

Answer 98

A

CS = (abundance of first limiting AA in test protein / abundance of same AA in whole egg) x 100

ex. CS of wheat 
% lysine in egg = 7.2
% lysine in wheat = 2.7
(2.7/ 7.2) x 100 = 37
the CS of wheat protein is 37.

Answer 99

A

•Simple and cheap
•Identifies the limiting AA in the food
•Used to optimize feeds by mixing
different sources of protein

Answer 100

A

Doesn’t account for digestibility or toxins (e.g. hair)

* Is whole egg an ideal protein?

Answer 101

A

Nitrogen balance = a measure of N loss (urine, feces, sweat) and N intake (diet)

Nitrogen Balance (NB) = Nitrogen Intake – Nitrogen Loss

Answer 102

A

False.

During growth, pregnancy, and times of tissue repair (NB > 0).

Answer 103

A

The problem is worsened with poor protein quality because body proteins are used as a source of essential AA
(in other words, body proteins are broken down to “free up” essential AA, ultimately leading to a loss of function)
– NB < 0 is seen in people with serious tissue injuries, wasting diseases like sarcopenia, and long-term fasting

Answer 104

A

True.

This is commonly observed in developed countries like USA.

Answer 105

A

True.

People are generally in balance.

Answer 106

A

Protein requirements are higher during infancy, childhood, teenagers, and during pregnancy & lactation.

Answer 107

A

True.
Plant sources may be less digestible due to differences in the nature of protein and other components (fibre). If recommendations used plant sources of protein, the values would be higher.

Answer 108

A

High protein diets (Atkins, South Beach)

2. Protein Supplementation

Answer 109

A

Deficient in both protein quantity and energy (overall malnutrition)
Deficient in only protein quantity

Answer 110

A

Atkins Diet (most criticized) (C:F:P = 3:64:33)
- Different phases where macronutrient content varies.
- CHO intake very low, while fat and protein intake very high (~30% protein).
- Criticized because no attention to type of CHO or fat consumed.
South Beach diet (C:F:P = 30:40:30)
- Different phases where macronutrient content varies.
- For CHO intake there is an emphasis on low GI foods.
- Protein is consistent throughout the various phases (~30%)
The Zone Diet
- Not really a high protein diet, rather a balanced diet.

Answer 111

A

False.
All high protein diets NOT created equal
– Huge differences in macronutrient content and the types of CHO/fats consumed, so it’s hard to compare outcomes.

Answer 112

A

short term weight loss is comparable to other diet approaches.
Some studies show improved insulin sensitivity with high protein as compared to high CHO diets
(probably due to reduced burden on the pancreas to generate insulin).
Conflicting results with respect to effect on cardiovascular disease. A moderate increase in protein appears to be cardioprotective, but high protein may be a concern in the long-term.
People with kidney diseases should avoid high-protein diets.

Answer 113

A

True.

HOWEVER, this would be the same if a person ate a high quality protein (eggs, meat, fish).

Answer 114

A

Most protein supplements deliver high levels of BCAAs, are rapidly absorbed and delivered to the muscle.

Answer 115

A

Anabolic response of the muscle to a protein meal gradually diminishes after 40 years of age.

*this can be improved with BCAA supplements

Answer 116

A

MARASMUS is a protein and energy deficiency.

Answer 117

A

Very low intake of a balanced diet with around 8-10% protein (so just a bit below what is needed).
Because everything is in balance, the body
switches to starvation mode.
Well organized utilization of body fuel stores allows survival, eventually leading to a complete loss of body fat which causes a wrinkled appearance to the skin

Characterized by: complete loss of body fat and muscle, peeling skin, uneven pigmentation

Answer 118

A

KWASHIORKOR is a protein deficiency.

Answer 119

A

Diet has sufficient Calories, but is deficient in protein
(Only 1-2% protein in the diet)
Typically seen in developing countries where agriculture is key
High CHO foods (e.g., tuber cassava)
– When child is weaned from mother’s breast milk (very balanced source of nutrients) to cassava porridge (no protein or fat)
– Lots of CHO, but no protein to metabolize or transport nutrients

Characterized by: enlarged abdomen, ‘burns’ on the skin and diarrhea

Answer 120

A

Decreased plasma proteins causes an osmotic imbalance in the gut (edema); leads to a swelling of the gut
Liver is enlarged due to the inability to export fat from the liver (can’t make VLDL)

Answer 121

A

Variable protein/energy restriction:
When the dietary challenge fluctuates over time (i.e., feast and famine).
-People typically survive these challenges, but can be quite ill for several months of the year.
Acute protein/energy restriction:
When a severe dietary challenge sets in.
-If there is no change, then this would cause death after 1-2 months.

Answer 122

A

False.

BOTH Marasmus & Kwashiorkor lead to immune dysfunction.

Answer 123

A

True.

Lect. 11, slide 2

Answer 124

A

Most AAs derived from protein breakdown are reused to make new protein, while a little is catabolized.
(made from carbon skeleton or ammonia)

Answer 125

A

Fasted state involves the formation of both glutamine and alanine, while the fed state is primarily glutamine.
Fed state involves both the liver and kidneys.
Fed state involves the excretion of NH4
+ as urea, whereas the fasted state involves the excretion of ammonium (NH4
+) directly.

Answer 126

A

The liver converts the amino group to urea in a process that uses HCO3-
Metabolism of Sulfur-containing AA produces a bit of sulphuric acid to neutralize pH

Answer 127

A

The liver converts the amino group to urea in a process that uses HCO3-
Metabolism of Sulfur-containing AA produces a bit of sulphuric acid to neutralize pH

Answer 128

A

minor amounts of protein are catabolized to release glucogenic amino acids (for gluconeogenesis)
- however the primary source of energy is fat (TAG)
The breakdown of TAG leads to the production of acidic ketone bodies

*The brain will start to use ketone bodies instead of glucose, but there is production of a slightly acidic molecule

Answer 129

A

Long-term fasting encourages a slight ACIDOSIS (pH can DROP to 7.0). This is also known as nutritional KETOSIS.

Answer 130

A

Products of TAG breakdown (long hydrocarbon chains) are not very water soluble.
The liver converts these long hydrocarbons into small soluble ketone bodies (which the brain can uses for energy during starvation).

Answer 131

A

When AAs are catabolized in the fasted state, the amino group is brought directly to the kidney (thus bypassing the urea cycle where HCO3- is used up.) This means that HCO3- produced in the Kreb’s cycle can be used to neutralize the weak acidosis state caused by ketones.

Answer 132

A

When AAs are catabolized in the fasted state, the amino group is brought directly to the kidney (thus bypassing the urea cycle where HCO3- is used up.) This means that HCO3- produced in the Kreb’s cycle can be used to neutralize the weak acidosis state caused by ketones.

Answer 133

A

Glutamate
Aspartate
Alanine
Glutamine

Answer 134

A

Incredibly important in AA catabolism
It is a common end product of transamination reactions
- α-ketoacid for glutamate is alpha-ketoglutarate

Answer 135

A

Donates an amino group in the urea cycle

- α-ketoacid for asparatate is oxaloacetate

Answer 136

A

Inter-organ nitrogen carrier (goes to liver)

- α-ketoacid for alanine is pyruvate

Answer 137

A

Most abundant AA in the body
Inter-organ nitrogen carrier (goes to liver & kidney)
Can donate a NH3 group to other reactions

Answer 138

A

Transamination
Oxidative deamination
3a. Glutamine production
3b. Glutamate Regeneration
Urea cycle

Answer 139

A

Transamination
Oxidative deamination
3a. Glutamine production
3b. Glutamate Regeneration
Urea cycle

Answer 140

A

Transamination = transfer of an amino group to an AA carbon skeleton
(i.e., α-ketoacid) –> catalyzed by “aminotransferases”

Answer 141

A

most AA undergo transamination (except lysine, proline, and threonine)

Answer 142

A

PYRIDOXAL PHOSPHATE (active form of Vit B6) is the coenzyme that holds the NH3 group during transamination.

Answer 143

A

Bi-directional reactions
Active in all tissues
Always produces an AA (usually glutamate) and α-ketoacid
At least 1 transaminase exists for each AA, with each using glutamate/ alpha-ketoglutarate as one of the pairings

Answer 144

A

Glutamate pyruvate transaminase (GPT) (also known as ALT)

Alpha-ketoglutarate + alanine –> Glutamate + Pyruvate

Glutamate oxaloacetate transaminase (GOT) (also known as AST)

Alpha-ketoglutarate + Aspartate –> Glutamate + Oxaloacetate

Answer 145

A

Glutamate is the main AA to undergo oxidative deamination.

Because glutamate is the main product of transamination.

Answer 146

A

NH3 is released from the glutamate backbone
Reaction favours the formation of alpha-ketoglutarate
A process that is very active in all tissues in the body

*This is a point in the pathway –> how to get the amino group out of glutamate

Answer 147

A

Extrahepatic tissue (EHT)–> the
NH4+ is used in the synthesis of
glutamine
Liver–> NH4+ is used for urea synthesis
Kidneys–>NH4+ is excreted directly as is into urine

Answer 148

A

Formation of glutamine (primary inter-organ nitrogen carrier)
Muscles are the main producer of glutamine (produces ~90% of the glutamine found in the body)

Answer 149

A

Glutamine synthetase.

Answer 150

A

Fed state –> travels to liver

Fasted state –> travels to kidney

Answer 151

A

Opposite reaction to glutamine production; however, a different enzyme is required
Releases NH3 (NH4+) from the glutamine side chain (i.e., deamination)
Active in liver in the fed state (NH3 used for urea synthesis)
Active in the kidney during fasting (NH3 secreted as NH4+)

Answer 152

A

Glutamate regeneration.

Answer 153

A

Glutaminase.

Answer 154

A

Toxic NH4+ is converted to less toxic urea in the liver

2. Urea transported to kidney for excretion

Answer 155

A

Fasted state:
80-90% of urinary N will be in the form of NH4+.

Fed state:
80-90% of urinary N will be in the form of UREA.

Answer 156

A

Oxidative deamination

2. Glutamate regeneration from glutamine

Answer 157

A

In the urea cycle, aspartate condenses with CITRULLINE and DONATES an amino group.

Answer 158

A

The urea cycle uses HCO3-, thereby preventing ALKALOSIS.

Answer 159

A

Defects lead to developmental neurotoxicity due to a build-up of NH4+ in the body.

Answer 160

A

Cahill cycle.

Answer 161

A

For every glucose, you get 2 alanine.

1 glucose = 2 pyruvates; each pyruvate undergoes transamination to alanine

Answer 162

A

Fed state:

non-liver protein catabolism leads to glutamine formation (from glutamate).
Glutamine is transported to the liver, where it delivers an amino group for urea production.
Urea is then transported to the kidney and excreted in urine.

Answer 163

A

Fasted state:

non-liver protein catabolism leads to glutamine formation (from glutamate) and alanine (from pyruvate).
Glutamine is transported directly to the kidney, while alanine is sent to the liver (for gluconeogenesis).
In the kidney, glutamine is converted to glutamate and the removed amino group is excreted in urine as NH4+.

Answer 164

A

When body’s energy sources are low, protein is broken down. AA catabolism releases (1) AMINO GROUP (NH3), and (2) α-KETOACID.

Answer 165

A

Deamination –> removal of amino group from AA. The carbon skeleton that remains is the α-ketoacid (mostly seen with glutamate).
Transamination –> transfer of an amino group from an AA to an α-ketoacid. In the process, the “donating” AA becomes an α-ketoacid and the “receiving” α-ketoacid becomes an AA.

Answer 166

A

α-ketoacids contain KETONE and CARBOXYLIC ACID functional groups.

Answer 167

A

Ketogenic –> a degraded AA that can be converted into Acetyl CoA

Answer 168

A

Glucogenic –> a degraded AA that can be converted into Glucose.

Answer 169

A

Acetyl CoA (leucine)
Acetoacetyl CoA (lysine)

(lecutre 11 slide 19)

Answer 170

A

Pyruvate
α-ketoglutarate
Succinyl-CoA
Fumarate
Oxaloacetate

Answer 171

A

Intermediates with 3 to 6 carbons can be used to make glucose.

Answer 172

A

Because Acetyl CoO is purely ketogenic.

Answer 173

A

To burn fat, you must have an active Kreb’s cycle, which depends on availability of oxaloacetate (a CHO).

*Doesn’t matter how much fat you have, if you don’t have oxaloacetate there won’t be any energy production.

Answer 174

A

False.

Burning fat is NOT a problem when glycogen is present (have oxaloacetate).

Answer 175

A

When glycogen is depleted, you have GLUCONEOGENESIS to maintain blood glucose.

(from glycogenic AA catabolism)

Answer 176

A

Oxaloacetate is a gluconeogenic precursor, so if something ELSE isn’t doing this job, oxaloacetate will be used to make glucose and the Kreb’s cycle slows and can’t burn fat.

Answer 177

A

24 hours.

Answer 178

A

Blood glucose: between 60-100mg/dL (<60mg/dL you develop a coma and die)
Blood pH: near neutrality (related to amino group handling)

Answer 179

A

always required by RBC as energy substrate (no mitochondria)
required by central nervous system (brain)0 (although gradual adaptation to ketones is possible)
maintaining an active Kreb’s cycle

Answer 180

A

Fed
-Dietary CHO (if high carbohydrate diet)
-Dietary protein (if high protein diet)
(any leftover AAs are used)
Post-absorptive (no food left in GIT)
- Glycogen from liver (direct) and muscle (indirect)
Fasting (no glycogen) (after 24 hours)
- Gluconeogenesis from protein catabolism (only in liver)
Starvation (several days, have biochemical adaptations)
-Gluconeogenesis from glycerol produced by TAG
breakdown; some protein catabolism

Answer 181

A

Macronutrient flux –> the way our body is using carbs, fats, proteins

Answer 182

A

Macronutrient flux is regulated by multiple TISSUES and numerous HORMONES.

Answer 183

A

Short-term = (minutes to hours) i.e., between meals

Tissue crosstalk:

Hormones move throughout the body and activate signalling pathways in their target tissues
(e. g. insulin, glucagon, epinephrine, etc.)
Hormones usually affect protein function
(e. g. phosphorylation or de-phosphorylation of enzymes)
This occurs rapidly because protein is already made and waiting for modification

Answer 184

A

Long-term = (several hours to days) i.e., fasting, starvation

– Affects gene expression

*Cell says “i need to start making different proteins that will allow me to respond in different ways”; it needs to make rna, translate, etc. this takes a lot of time

Answer 185

A

Insulin
- Anabolic
- Pancreas (β-cells )
Glucagon
- Catabolic
- Pancreas (β-cells )
Corticosteroids (cortisol)
- Catabolic
- Adrenal Cortex
Catecholamines (epinephrine)
- Catabolic
- Adrenal medulla

Answer 186

A

↑ glucose and AA uptake in muscle and liver
↑ glycogen and protein synthesis in muscle
and liver; ↑ fat synthesis and storage

Answer 187

A

↑ breakdown of glycogen, protein & fat

↑ gluconeogenesis from AAs and glycerol

Answer 188

A

↑ Muscle protein catabolism

↑ gluconeogenesis from AAs

Answer 189

A

↑ glycogenolysis and lipolysis

at the level of adipose tissue

Answer 190

A

The brain has a high requirement for OXIDATIVE METABOLISM to support its continuous electrical activity.

Answer 191

A

100-120g of glucose per day

Answer 192

A

Fatty acids can’t cross the blood-brain barrier enough to provide sufficient energy
(ketone bodies CAN cross but it requires adaptation)

Answer 193

A

Brain consumes about half of this.

Answer 194

A

False.

The liver DOES regulate blood glucose levels.

Answer 195

A

Extra carbs get converted into Fatty Acids.
Insulin sends glucose to acetyl coA, acetyl CoA is turned into FA.

Glucose –> pyruvate –> acetyl coA –(ACC) –> Malonyl CoA –> Fatty Acid

Answer 196

A

Fatty acids (FAs) from diet and de novo lipogenesis

2. Only tissue to produce ketone bodies (*critical during starvation)

Answer 197

A

False.
Adipose tissue has a LOW energy requirement, therefore NOT A LOT of oxidative fuel consumption.

*doesn’t need a lot of energy to perform its function of storing fat

Answer 198

A

For TAG synthesis

2. Provides energy for fatty acid uptake (via LPL)

Answer 199

A

•Releases non-esterified fatty acids (NEFA) into circulation (from lipolysis)

Depending on circumstances, NEFA can be a major metabolic fuel for the body
NEFA are the same thing as “free fatty acids”

*Notice that lipolysis occurs in adipose tissue.

Answer 200

A

Skeletal muscle represents around 40% of body weight.

Answer 201

A

Nutritional status

2. Exercise

Answer 202

A

Slow-twitch
- Used for long duration activity, slow contraction
- Predominant source of energy = Fatty acids
(i. e., NEFA from adipose tissue)
Fast twitch
- Used for short duration activity, quick contraction
- “Local” glycogen stores = energy source

Answer 203

A

(e.g. weight-lifting and sprinting)
• hormones are too slow to act
• signal = Ca2+ release
• energy released from:
- muscle glycogen stores
- muscle creatine phosphate

Answer 204

A

(e.g. jogging)
• diffusion of substrates & O2 from blood
• slow process
• energy released from complete oxidation of glucose and fatty acids

Answer 205

A

low-to-moderate intensity exercise–> fatty acids are the primary source of energy
high intensity exercise–> glucose is the primary source of energy

Answer 206

A

False.
The Gastrointestinal tract has a HIGH rate of cell turn-over, so energy is needed to allow for protein synthesis and production of DNA/RNA to make new cells.

Answer 207

A

In the small intestine: Glutamine (AA) is the main source of energy (converted to α-ketoglutarate, an intermediate in the Kreb’s cycle)

Answer 208

A

In the large intestine:
SCFA from bacterial fermentation are also used for energy
(Particularly butyrate)

Answer 209

A

“Precious” glucose is used quickly
Glycogen reserves last for 24 hrs, and are then depleted
Protein breakdown occurs initially, releasing glucogenic amino acids
- This slows down to preserve protein function, but continues to provide what is needed to maintain Kreb’s cycle activity
Fatty acid breakdown occurs to “spare protein”; eventually used to make ketone bodies

Answer 210

A

High blood glucose
Insulin secreted from pancreas
Glucose uptake and glycogen formation promoted in liver and muscle

Answer 211

A

AA are catabolized by liver
- BCAA go directly to the muscle and promote protein synthesis
Glutamine carries nitrogen to the liver from every tissue in the body that is catabolizing AAs
- Urea is produced, thus preventing alkalosis conditions
(use up HCO3-)

Answer 212

A

Lipid uptake into adipose tissue

Answer 213

A

Blood glucose maintained by glucagon, which increases hepatic glycogen breakdown
Liver secretes glucose
Necessary to maintain blood glucose for RBC and brain
Blood glucose supports Kreb’s cycle in all tissues

Answer 214

A

Muscle secretes alanine, which goes to the liver (glucose-alanine cycle)

Answer 215

A

Fat not yet used as a source of energy

Answer 216

A

Glycogen pools are empty
RBC and brain still require glucose for energy
Blood glucose supports Kreb’s cycle in all tissues
Glucose-alanine cycle active (liver secretes glucose)

Answer 217

A

Corticosteroids secreted from adrenal gland promote more
protein catabolism
- Mostly in muscle, but also gut
Glucogenic AAs are used to make glucose in liver (Glucose-alanine cycle active)
Alanine and glutamine carry nitrogen (i.e., amino group)
- ~50/50 mix between urea and ammonia (kidney)

Answer 218

A

Fat starts to be used for energy

Answer 219

A

Liver produces ketones, which promotes a slight acidosis

2. Glucose-alanine cycle active

Answer 220

A

Liver produces ketones, which promotes a slight acidosis
Still have to maintain Kreb’s cycle with protein catabolism (i.e., glucogenic amino acids)
Glutamine carries nitrogen directly to kidney (allows HCO3- to be used to buffer against acidic ketone bodies)
Glucose-alanine cycle active

Answer 221

A

Body switches primarily to fat usage
for energy
Glucagon and catecholamines regulate adipose tissue lipolysis
Fat is predominantly ketogenic (only the glycerol backbone is glucogenic)
Tissue metabolism adapts to “spare”
protein loss

Answer 222

A

Long term starvation leads to MARASMUS.

Answer 223

A

Exhaustion is due to loss of glycogen pools; this leads to a drop in blood glucose or failure of tissue Kreb’s cycle activity (drop in oxaloacetate)

Answer 224

A

Carbohydrate loading while resting
- Can double muscle glycogen reserve
- Delays failure of the Kreb’s cycle
Fasting for 3hr prior to start
- Avoid insulin secretion–> higher glucagon
Consume supplementary CHO during the event
- Ex. someone running the Ironman requires around 5000 kcal during the event
Caffeine (ergogenic aid)
- Stimulates an early release of epinephrine, which activates HSL to promote adipose tissue lipolysis

Answer 225

A

No. It depends on genotype. People with CC genes (slow breakdown) may actually do worse when given caffeine than without.

Answer 226

A

Exogenous supply is required (can’t make on our own)
Needed in small amounts
Distinct from sugars, fats and proteins in regard to structure and function
Perform at least one essential biochemical function in the body
When lacking in the diet, a characteristic
deficiency disease develops
Vitamins are organic
- Primary distinction from minerals (which are inorganic)

Answer 227

A

The functional groupings allow us to talk a little bit more about the bioactivity of vitamins and minerals.

Answer 228

A

Group I:
Micronutrients that control type II steroid hormone receptors and have major global health implications
ex. Iodine, Vit A, Vit D, Calcium, Vit K, Phosphorus and Fluoride
Group II:
Micronutrients that work together in oxidant defense
ex. Vit E, Selenium, Vit C, Niacin, Riboflavin, Copper, Zinc, Manganese
Group III:
Micronutrients that act as enzyme cofactors
ex. Thiamin, Niacin, Riboflavin, Vit B6, Folate, Vit B12, Biotin, Pantothenic
acid
Group IV:
Iron, copper, and zinc-related divalent cations

Answer 229

A

These micronutrients control cellular function through type II steroid receptors.

Answer 230

A

True.
Only the bioactive forms of Vit A, Vit D, and iodine act directly on steroid hormone receptors

(But we can’t talk about Vit D without talking about calcium, phosphorus, and Vit K since they are all involved in bone metabolism)

Answer 231

A

Iodine used to make T3 hormone, which regulates synthesis of proteins that control a person’s basal metabolic rate

Answer 232

A

Vit A precursors are converted to retinoids, which regulate night vision, epithelial differentiation, and gene expression

Answer 233

A

Vit D precursors are converted to calcitriol, which regulates
calcium levels in the body

Answer 234

A

Steroid Hormone Receptors –>
intracellular protein receptors
They need to bind a ligand to become a functional (active) transcription factor

Answer 235

A

Type 1 Receptors: Cytosolic
- Respond to steroid hormones like estrogen, testosterone, progesterone, glucocorticoids, and mineralcorticoids
(We won’t discuss this type)

Type 2 Receptors: Nuclear
- Respond to steroid & non-steroid
ligands, like thyroid hormone, retinoic acid, and calcitrol

Answer 236

A

False.

NOT all ligands are derived from steroids.

Answer 237

A

Iodine is an INORGANIC mineral that is highly WATER soluble.

Answer 238

A

True.

Seafood has high concentrations of iodine (especially sea greens)

Answer 239

A

In North America, most of the iodine consumed comes through “salt fortified with potassium iodine”
- Iodized salt contains 0.03mg iodine per g of salt

Answer 240

A

False.

Dietary iodine can be bound to amino acids or found free.

Answer 241

A

In our gastrointestinal tract, iodine (I) is rapidly converted to iodide (I- , its ionic form) and absorbed
- Most is absorbed in the stomach, and a bit in small intestine

Answer 242

A

In the blood, free I- circulates and can enter all tissues; however, most accumulates in the thyroid gland
(70-80% of the iodine in our body is in the thyroid gland)

Answer 243

A

Uptake of I- in the thyroid gland is mediated by an ACTIVE transport system known as the Na+/I- SYMPORTER (NIS).

Answer 244

A

False.

• All tissues depend on thyroid hormones (T3 and T4) rather than iodide itself

Answer 245

A

• Once T3 and T4 are made, they are released into blood and transported by specific carrier proteins (albumin, transthyretin, etc.)

Answer 246

A

50× more T4 in blood compared to T3.

Answer 247

A

T3 is 100× more potent.

Answer 248

A

T3 half-life < T4.

Answer 249

A

T3 interacts with thyroid hormone receptor (THR).

Answer 250

A

T3 and T4 production is regulated by TSH (thyroid stimulating hormone).

Answer 251

A

When T3 blood levels are low, the HYPOTHALAMUS signals to the pituitary to release TSH.

Answer 252

A

Iodide radical attacks the TYROSINE residue of the thyroglobulin.

*This causes the cross-linking between tyrosine residues

Answer 253

A

The colloid (lumen) of the thyroid cell.

Answer 254

A

Thyroid cell proteases hydrolyze THYROGLOBULIN, releasing fragments that correspond to T3 and T4 hormones.

Answer 255

A

Thyroid hormones influence how your body stores and uses energy (i.e., affects metabolism).

Answer 256

A

Breathing
Heart function
Nervous system function
Body temperature
Cholesterol level
Energy balance
Brain development
Moisture in the skin
Menstruation

Answer 257

A

True.

This means they can easily cross plasma membranes.

Answer 258

A

True.

This mainly occurs in the liver (but can occur in other tissues too).

Answer 259

A

T3 + THR (thyroid hormone receptor) –> bind to response element in the promoter region of DNA –> activate gene expression (mRNA)

*Note: THR is already in the nucleus

Answer 260

A

ATPases (pump Na+ and Ca2+ out of cells), which increases metabolic rate
- Na+ (muscle contraction, neuron
firing)
- Ca2+ (signaling events)
Growth hormone (anabolic effects)

Answer 261

A

Adipose Tissue --> lipolysis
Muscle --> contraction
Bone --> promotes making bone
Heart --> Increases heart rate
GIT --> stimulates nutrient digestion

Answer 262

A

When T3 levels are LOW, the pituitary gland releases TSH (thyroid stimulating hormone).

Answer 263

A

Hyperplasia (↑ cell #)
Hypertrophy (↑ cell size)

*Protein is still being produced, which grows the cell.

Answer 264

A

Goiter (in adults) –> thyroid enlargement
- Can be treated with iodine supplements
- If left untreated, becomes thyroid cancer
Cretinism –> when iodine levels are low in mother, the fetus doesn’t develop properly
- Growth & developmental abnormalities
- Irreversible
- 50 million people have some degree of mental impairment caused by IDD (WHO).

Answer 265

A

They measure it through urine (iodine is water soluble).

Answer 266

A

Through fortification.

ex. salt

Answer 267

A

It helps with thyroid gland support.

Answer 268

A

Vitamin A supports night vision, eyesight, and skin health.

Answer 269

A

Ancient Egyptians and Greeks realized that LIVER could cure night blindness.

*egyptians squeezed it into their eyes, greeks ate it

Answer 270

A

Originally named fat soluble A because egg yolk contains a fat soluble material that is necessary for life.

Answer 271

A

Vitamin A is a general term used to refer to a group of compounds known as RETINOIDS.

Answer 272

A

Major forms of Vitamin A in the body are:

retinol, retinal, retinoic acid, & retinyl ester

Answer 273

A

The alcohol form, RETINOL, was first identified and then CAROTENE were recognized as the plant form of Vitamin A.

Answer 274

A

False.

In plants, carotenes are pro-vitamins used for pigmentation. In animals, vitamin A is bioactive.

Answer 275

A

Carotenes (provitamin A) are PRECURSORS for Vitamin A.

Answer 276

A

They are pigments produced in plants (e.g. β-carotene, α-carotene, etc.)

Answer 277

A

Milk, eggs.

Answer 278

A

RETINYL ESTER = retinol + fatty acid

Answer 279

A

For absorption, a RETINYL ESTERASE must cleave the fatty acid from retinol (in a retinyl ester)

Answer 280

A

Essentially nothing. β-carotene can be absorbed just like that.

Answer 281

A

Both retinol and β-carotenes are LIPOPHILIC compounds, therefore incorporated into mixed micelles.

Answer 282

A

Both are absorbed by passive diffusion.

Answer 283

A

Converted into a retinyl ester in the intestinal cell then incorporated into chylomicrons
Incorporated “as is” into chylomicrons

Answer 284

A

β-carotene can be packaged into VLDL and sent for storage in adipose tissue.
Retinyl esters (e.g., retinyl palmitate) are stored in hepatic stellate cells until needed

When needed, liver retinyl esterase removes FA, releases retinol to bind to RBP and secreted into blood

Answer 285

A

Low levels of retinol-RBP stimulate the liver to release retinyl esterase.

Answer 286

A

β-carotene comes from plants, which have higher fiber levels than animal products. Fiber reduces the rate of absorption.

Answer 287

A

In the intestine, β-carotene can be broken down into TRANS RETINAL (aldehyde) by the enzyme 15,15’-CAROTENOID DIOXYGENASE.

Answer 288

A

All trans retinal can be converted to trans retinol by RETINOL DEHYDROGENASE.

Answer 289

A

False.
The retinol acts like a detergent, which is UNSAFE for a cell. So retinol is converted into a retinyl ester (safer for the cell).

Answer 290

A

Nothing. Retinyl esters have no direct function in the body.

Answer 291

A

All trans retinal can be converted into TRANS RETINOL or RETINOIC ACID (directly).

Answer 292

A

Night vision.

Answer 293

A

Rod cells use rhodopsin to absorb light (greyish purple colour)
Opsin + 11-cis retinal combine to become rhodopsin, which is light-sensitive
(night sensitivity causes neuron signalling = vision)
When light hits rhodopsin, it reforms all trans retinol

Answer 294

A

Isomerase introduces a KINK to all-trans retinal when it converts it to 11-cis retinal.

Answer 295

A

In the cytosol, retinol is converted into retinoic acid.

Answer 296

A

RA –> into nucleus –> binds to and activates RAR & RXR transcription factors –> complexes homo- & hetero-dimerize with other NHR –> creates a large number of possible TF combinations –> allows regulation of gene expression

*RAR –> retinoic acid receptor
RXR –> retinoid X receptor
NHR –> nuclear hormone receptors

Answer 297

A

Night blindness (lack of rhodopsin)
- Reversible, one of the first signs of Vit A deficiency
- Associated with Bitot’s spots, a buildup of keratin debris in the conjunctiva of the eye
Impaired epithelial cell differentiation
- Can cause permanent blindness and life threatening infections
Impaired growth (growth hormone not produced)
- Impacts bone development, tooth decay, etc.
Impaired fertility
- Decreased sperm formation, fetal resorption (early death of embryo)
Fetal development defects
- Birth defects due to loss of control of differentiation
- Can occur with too little OR too much Vit A

Answer 298

A

Night blindness (lack of rhodopsin)
- Reversible, one of the first signs of Vit A deficiency
- Associated with Bitot’s spots, a buildup of keratin debris in the conjunctiva of the eye
Impaired epithelial cell differentiation
- Can cause permanent blindness and life threatening infections
Impaired growth (growth hormone not produced)
- Impacts bone development, tooth decay, etc.
Impaired fertility
- Decreased sperm formation, fetal resorption (early death of embryo)
Fetal development defects
- Birth defects due to loss of control of differentiation
- Can occur with too little OR too much Vit A

Answer 299

A

RAE = Retinol Activity Equivalents
RAE accounts for differences in the biological
activity of carotenoids

1 RAE = 1 μg dietary retinol = 12 μg dietary β-carotene = 24 μg other carotenes

Answer 300

A

Men –> 900 μg/d RAE

Women –> 700 μg/d RAE

Answer 301

A

UL = 3000 μg/d RAE

Answer 302

A

Carotenoids prevent deficiency, but don’t cause toxicity.
15,15’-carotenoid dioxygenase regulated by Vit A status. If you have enough Vit A, carotenoids aren’t converted to retinol, but are stored “as is”.

(Carotenoids are stored in the inactive form and are converted when needed, but retinol is always in the active form and can cause toxicity.)

Answer 303

A

Most severe consequence is liver cell death.

Answer 304

A

Retinyl esters are stored in the stellate cells of the liver and with excess Vit A intake, the cells get full to capacity.
Raw Vit A spills out and the local hepatocytes become damaged and die.

Answer 305

A

Excessive intake of β-carotene can cause hypercarotenosis (skin turns yellow-orange).

Answer 306

A

It was shown to cause birth defects in women in the early months of pregnancy.

Answer 307

A

It was shown to cause birth defects in women in the early months of pregnancy.

Answer 308

A

You would have Vit A toxicity.

Human liver has ~170 RAE/g
Polar bear liver has ~10,000 RAE/g

Answer 309

A

Supports a healthy immune system and bone health.

Answer 310

A

Although Vit A and Iodine deficiencies are prevalent in the developing world, VITAMIN D is the most prevalent micronutrient deficiency in the developed world.

Answer 311

A

Made in one tissue (kidney) and acts on other tissues

2. Works with other hormones such as parathyroid and calcitonin

Answer 312

A

Rediscovered the use of cod liver oil to prevent bone diseases.

Answer 313

A

This indicated that fat soluble Vit D can also be synthesized in the body.

Answer 314

A

Natural Plant Sources (Provitamin D2)
Natural Animal Sources (Provitamin D3)
Sunlight
Supplementation
Fortification

Answer 315

A

Natural Plant Sources (Provitamin D2)
Natural Animal Sources (Provitamin D3)
Sunlight
Supplementation
Fortification

Answer 316

A

Shitake mushrooms
It’s not very active in plants, so not a great source of Vit D

*Ergocaliferol is less bioactive than cholecalciferol

Answer 317

A

After irridation, ergosterol (provitamin D2) turns into ERGOCALCIFEROL (vitamin d2).

Answer 318

A

Fish, fish liver oils

Answer 319

A

• 7-dehydrocholesterol (7-D) is converted to CHOLECALCIFEROL (Vit D3) by sunlight (UVB and infrared)

This occurs in sebaceous glands of skin.

Answer 320

A

False.

This occurs as soon as you go out in the sun.

Answer 321

A

Vit D3 binds to the Vitamin D binding protein.

Answer 322

A

These molecules are inactive, and are eventually lost as we shed skin.

*Note: Luminesterol and tachysterol can also be converted back into 7D.

Answer 323

A

MELANIN in the epidermis absorbs UV rays, which can limit Vit D3 production.

*This was part of the problem for population deficiencies over time (migrating populations).

Answer 324

A

We should use Vit D3 (cholecalciferol).

This is especially important for someone who spends lots of time indoors.

Answer 325

A

No.

It is insufficient for health if this is a person’s only source of Vit D3.

Answer 326

A

No.

It is insufficient for health if this is a person’s only source of Vit D3.

Answer 327

A

There is no risk.

Answer 328

A

It can go to:
• Liver (conversion)
• Adipose (storage)

Answer 329

A

Vitamin D3 is absorbed PASSIVELY in the ileum, but this is not very efficient.

Answer 330

A

There is no difference. It is the same molecule.

Answer 331

A

In the liver, Vit D3 is HYDROXYLATED to form 25-OH D3 via 25-HYDROXYLASE (a cytochrome p450 enzyme).

Answer 332

A

25-OH D3 is secreted into blood bound to DBP.

*This corresponds to the largest pool of 25-OH D3 in body.

Answer 333

A

Low 25-OH D3 in the blood is the key sign of Vit D deficiency.

Answer 334

A

When CALCIUM levels are low in the body, 25-OH D3 will be converted into an active molecule.

Answer 335

A

False.

High gradient of blood to intracellular Ca2+ is essential.

Answer 336

A

Low blood Ca2+ is sensed by the PARATHYROID GLAND.

Answer 337

A

When the parathyroid gland senses low blood Ca2+, it releases PTH (parathyroid hormone).

PTH promotes uptake of 25-OH D3/ DBP complex into the kidney.

Answer 338

A

In the kidney, 1-hydroxylase converts inactive 25-OH D3 into active 1,25-(OH)2 D3.

Answer 339

A

The active form of Vitamin D3 (1,25-(OH)2 D3) is known as CALCITRIOL.

Answer 340

A

Genomic

2. Non-genomic

Answer 341

A

Vit D receptor (VDR) = nuclear hormone receptor
Transcription factor that promotes calcium binding protein synthesis
Calcium-binding proteins are activated by Vitamin K dependent post-translational modifications (γ-carboxylation)

Answer 342

A

Binds cell surface receptors, like MARRS
(membrane associated
rapid response
steroid-binding protein)
Activates intracellular signalling cascades
Very fast, no dependence on Vit K

Answer 343

A

VDR is activated and turns on the expression of genes coding for calcium binding proteins
(require Vitamin K dependent γ-carboxylation to become fully functional)
Membrane transporters are activated (e.g., MARRS)

Answer 344

A

Elevated calcitriol and PTH work together to stimulate resorption of Ca2+ and Phorphorus from bone
Calcitriol causes an increase in the expression of RANK ligand (RANKL), a cytokine
RANKL activates osteoclasts to increase their activity
Osteoclasts secrete factors that degrade the bone matrix to release Ca2+ and P into the blood

(high calcitriol (and pth) –> high RANKL –> high osteoclast activity)

Answer 345

A

Primary function is to increase absorption and reabsorption of Ca2+
Calcitriol turns on the expression of genes coding calcium binding proteins

Answer 346

A

Absorption (small intestine)
Reabsorption (kidney)
Resorption (bone)

Answer 347

A

Minerals need transporters to be absorbed by intestinal cells and enter into portal circulation
Proper absorption of Ca2+ depends on the expression of Ca2+ binding proteins in enterocytes

Answer 348

A

Small molecules like Ca2+ circulate in blood and eventually reach the kidney, where they pass through the filter and can end up in the urine (unless reabsorbed)
Reabsorption removes the molecules from the filtrate and gets them back into the blood

Answer 349

A

Dissolving bone structure to release Ca2+ into the blood
(Osteoclasts resorb bone, osteoblasts build bone)
Balance between break-down and synthesis allows for bone maintenance, remodeling and repair

Answer 350

A

Serves to INCREASE blood calcium (1st response):

Promotes the production of calcitriol in kidney by activating 1-hydroxylase enyzme
Stimulates resorption of bone by activating osteoclasts
Maximizes tubular reabsorption of calcium in kidney
No direct effect on small intestinal absorption

Answer 351

A

Serves to INCREASE blood calcium:

Stimulates Ca2+ resorption from bone
Helps to increase absorption of Ca2+ from intestine
Maximizes tubular reabsorption of Ca2+ in kidney

Answer 352

A

Secreted by parafollicular cells in the thyroid
Serves to DECREASE blood Ca2+ (e.g. in response to Ca2+ rebound):
- Suppresses tubular reabsorption of Ca2+ in kidney
- Inhibits bone resorption and facilitates remineralization

Answer 353

A

The composition of normal bone is a mixture of SOLID (outer) and SPONGY (inner) parts.

Answer 354

A

Solid part is 60% mineral (Ca2+, P) and 40% organic (collagen)

Answer 355

A

False.

In babies, bones start as COLLAGEN and gradually become infused with MINERALS.

Answer 356

A

Vit D deficiency concerns only the SOLID part of bones, as it changes the ratio of mineral to collagen in the bone matrix.

Answer 357

A

Vit D deficiency in Infants = Rickets (poor mineralization)

Bones don’t mineralize properly and can’t support the body’s weight when they start walking (permanent and reversible only with surgery)
Was seen in Britain during the industrial revolution

Answer 358

A

Vit D deficiency in Adolescents to Adult = Osteomalacia
–-Bones become demineralized (can be reversed with supplementation)
- Bone fractures can occur more easily

Answer 359

A

Vit D deficiency in Middle-Aged to Elderly = Osteoporosis

Normal part of aging (loss of both mineral and organic parts of bone)
Diagnosed with bone density scans
Difficult to reverse due to erosion of bone (holes in bone form)

Answer 360

A

UV treatment and cod oil.

Answer 361

A

Osteoporosis –> Bone loss associated with aging

Answer 362

A

False.
Men have higher peak bone mass between 20-30 yrs
and LOWER bone loss

Answer 363

A

Treatments include supplementation or drugs that affect bone formation/ resorption.

Answer 364

A

Menopause.

Answer 365

A

The RDA for Vit D intake for adults is 600 IU (international units).
1μg Vit D = 40 IU…so this means 15 μg of Vit D / day.

Answer 366

A

In 2010, the RDA was 200 IU. Health Canada tripled the RDA based on overwhelming scientific evidence
(Used input from research, stakeholders, and scientists)

Statscan found that a lot of canadians were deficient.

Answer 367

A

False.

Production of Vit D3 is limited by amounts of 7-D present in the skin
– Sunglight also produces the inactive lumisterol and tachysterol metabolites with prolonged sun exposure, which have no bioactivity

Answer 368

A

Very high dietary levels of Vitamin D can cause HYPERCALCEMIA, leading to a possible calcification of soft tissues.

Answer 369

A

They claim it supports a healthy immune system and bone health

Answer 370

A

Vitamin K is most important for bone FORMATION and blood COAGULATION.

Answer 371

A

Vitamin K is found in leafy greens as PHYLLOQUINONE, and made by gut bacteria in the form of MENAQUINONE.

Answer 372

A

There is little Vit K in mother’s milk and babies aren’t eating leafy plants yet
Babies also haven’t developed their colonic (gut) bacteria, so no menaquinone
Babies given Vit K via a heel prick at birth

Answer 373

A

False.

Deficiency is very rare in adults due to bacterial production

Answer 374

A

Phylloquinone requires no digestion

Incorporated into micelles and absorbed in the small intestine
Absorbed via NPC1L1 apical transporter (also involved in cholesterol absorption)

Answer 375

A

Menaquinones produced by bacteria in the large intestine

– Passive absorption

Answer 376

A

Vit K can be stored in cell membranes in lungs, kidneys, adrenal glands, bone, etc.

Answer 377

A

Phylloquinone in PLANTS (Vit K1): Saturated side chain

Menaquinone by BACTERIA (Vit K2): Unsaturated side chain

Answer 378

A

γ-CARBOXYLATION is the post-translation modification that Vit K is responsible/ essential for.

Answer 379

A

WARFARIN= (anti-coagulant drug) rat poison that functions by inhibiting epoxide reductase, keeps vitamin k in inactive form and prevents the pathway from taking place.

Answer 380

A

Gla residues on blood clotting proteins bind Ca2+. Ca2+ allows Gla-containing proteins to bind to phospholipids on membranes of blood platelets and endothelial cells.

Answer 381

A

Newborn infants (injected with phylloquinone at birth)
- Little Vit K in breast milk
- Vit K can’t cross the placenta for delivery to the developing fetus
- Gut bacteria population not established
People who take antibiotics chronically
- Antibiotics destroy the gut bacterial community
(can no longer produce menoquinone)
People with malabsorptive illnesses (IBD, Crohn’s, pancreatitis)

Answer 382

A

Impaired blood clotting
- Possible hemorrhagic syndrome (mostly seen in newborns)
Impaired activation of calcium binding proteins
- Accelerate development of osteoporosis (mostly seen in elderly adults)

Answer 383

A

Helps to prevent osteoporosis and develop strong bones.

Answer 384

A

Calcium represents 40% of the body’s mineral mass.

*1,000 – 1,400 mg in human body

Answer 385

A

99% –> Bones and teeth contain

1% –> critically important for signalling pathways

Answer 386

A

Parathyroid hormones.

Answer 387

A

Predominantly obtained from dairy products, but also high in sardines, salmon, and some green leafy vegetables

*Present in these foods as an insoluble salt
– Stomach acid creates soluble Ca2+

Answer 388

A

Small intestine.

Answer 389

A

Primary uptake: Saturable, carrier-mediated, active transport
• Absorption regulated by calcitriol; Most calcium absorbed this way

Secondary pathway uptake: Diffusion via paracellular route is

Answer 390

A

~40% bound to albumin
~10% found complexed with sulfate, phosphate, etc
~50% found in free (ionized) form

Answer 391

A

BONE Calcium (99%)
- Minerals (calcium, phosphorus, fluoride, magnesium, potassium,
etc) make up hydroxyapatite (a crystal like structure)
(This is ~60% of solid bone mass)

Answer 392

A

INTRA- and EXTRACELLULAR Calcium (1%)
Ionized calcium is active and used for:
- Blood clotting (formation of “Gla” residues on coagulation proteins)
- Skeletal muscle contraction (release of calcium stores)
- Nerve potential (acting through ion channels)
Intracellular signalling pathways
(e.g., Ca2+ activates PLA2, which cleaves arachidonic acid from
phospholipids to produce eicosanoids)

Answer 393

A

Bone is sacrificed in this case.

Answer 394

A

Most is stored in mitochondria and ER
Released from stores in response to an extracellular signal (e.g. receptor binding) to ultimately promote an intracellular response (e.g., gene expression, neurotransmission, etc.)
(leads to depolarization of the cell, and very rapid changes)

Answer 395

A

-Maintained at a very constant level; ~10,000x the concentration of intracellular calcium***
(when something happens within the cell that needs the response of calcium, there is a very favourable gradient that allows calcium to rush into the cell and come into effect)
– Nearly identical to the concentration of phosphorus
(detected by parathyroid hormone)

Answer 396

A

The majority (around 99%) of the calcium in the body is in the bone and teeth
In bone, 99% is in mineral phase (hydroxyapatite), and 1% is in a pool that can exchange with extracellular calcium

Answer 397

A

↑ UL in children
↓ UL in adults (51-70 yrs)
↓ UL in >70yrs to prevent developing kidney stones

Answer 398

A

↑ UL in children (help mineralization and formation of bones)
↓ UL in adults (51-70 yrs) (due to kidney stones)
↓ UL in >70yrs to prevent developing kidney stones

Answer 399

A

Caffeine ↓
Some fibres ↓
Magnesium &amp; Zinc ↓
PTH (Vit D) ↑
Pregnancy &amp; lactation ↑ (this is why RDA for calcium remains the same during pregnancy)

Answer 400

A

*Profoundly affects bone and muscle

Bone
• Inadequate mineralization in bone
– Rickets in children (commonly associated with Vit D deficiency)
– Osteomalacia in adults (and increases risk of developing Osteoporosis)
Muscle
• Tetany
– A condition characterized by involuntary muscle contractions
Evidence for association with hypertension
Evidence for association with colon cancer (current research supports association in high risk populations)

Answer 401

A

Constipation, bloating, and/or gas
Hypercalcemia (calcification of soft tissues)
– Kidney stones

Answer 402

A

Phosphorus.

Answer 403

A

Phospphorys is widely distributed in foods.

Answer 404

A

Phosphorus is found in animal products as PHOSPHORUS and in grains as PHYTIC ACID.

Answer 405

A

Most phosphorus is absorbed in the small intestine in its ionic form

Passive diffusion (primary method)
Saturable, carrier-mediated, active transport (NaPi cotransporter) (could also be with ATP active transport)

50-70% of the phosphorus in foods is absorbed.

Answer 406

A

Absorption inhibited by magnesium, aluminum, & calcium (these are called phosphate binders).

Answer 407

A

Absorption inhibited by magnesium, aluminum, & calcium (these are called phosphate binders).

Answer 408

A

Phosphorus is primarily transported in the blood as ORGANIC PHOSPHATE (it is incorporated into PHOSPHOLIPIDS).

Answer 409

A

Phosphorus is found largely in bone (HYDROXYAPATITE), but also in molecules key for metabolism like ATP, DNA, RNA, cAMP, etc.

Answer 410

A

Phosphorus plays a key role in protein PHOSPHORYLATION, a common PTM in proteins.

Answer 411

A

No.

Fluoride is present in the body in trace amounts.

Answer 412

A

Community water fluoridated (with ~1 ppm or ~1mg/L) for the past 60 years

Answer 413

A

Absorption in stomach by passive diffusion (nearly 100% efficiency)

Answer 414

A

Transported in the body as ionic fluoride or bound to plasma proteins.

Answer 415

A

Increases resistance of enamel to acid demineralization by forming fluoroapatite (protective layer)

Answer 416

A

Increased incidence of tooth decay

Answer 417

A

Fluorosis (mottling of the teeth)

-Tolerable upper limit in adults is 10mg/day

Answer 418

A

Fluorosis (mottling of the teeth)

-Tolerable upper limit in adults is 10mg/day

Answer 419

A

Group II micronutrients are involved in REDOX reactions.

Answer 420

A

Involves the transfer of electrons between two substrates (donor and acceptor)
Many biochemical reactions are essentially electron transfers

Answer 421

A

•
The primary electron carriers in the body are NADH and FADH2

They are important for the creation of ATP.

Answer 422

A

Glycolysis
Lactic Acid Production
Pyruvate Dehydrogenation
Kreb’s Cycle
Gluconeogenesis
β-oxidation

Answer 423

A

The primary electron carriers in the body are NADH (niacin) and FADH2 (riboflavin)

They are important for the creation of ATP.

Answer 424

A

Glycolysis
Lactic Acid Production
Pyruvate Dehydrogenation
Kreb’s Cycle
Gluconeogenesis
β-oxidation

Answer 425

A

Reactive Oxygen Species (ROS).

-ROS produced as a by product of the ETC when proper electron flow fails (~1% “leakage”)

Occurs in a O2 rich environment, where oxygen can react with electrons
(causes oxygen radicals with free electrons that are very reactive)

Answer 426

A

Mutations in SOD cause Lou Gehrig’s.

Answer 427

A

H2O2 is converted to H2O by GLUTATHIONE PEROXIDASE and CATALASE (selenium dependent enzymes).

Answer 428

A

T3 and T4 production

Answer 429

A

H2O2.

Glutathione perosidase converts H2O2 to 2 H2O, but if H2O2 reacts with a free electron, there is a Fenton reaction, creating a hydroxyl radical.

Answer 430

A

H2O2.

Glutathione perosidase converts H2O2 to 2 H2O, but if H2O2 reacts with a free electron, there is a Fenton reaction, creating a hydroxyl radical.

Answer 431

A

Mixed tacopherol antioxidant support

Answer 432

A

Vitamin E is a general term that describes 8 structurally-related compounds known as VITAMERS.

Answer 433

A

4 tocopherols
- Have saturated side chains with 16 carbons
4 tocotrienols
- Have unsaturated side chains with 16 carbons

Vitamers in both classes ( α , β , γ , δ)

*Although they are all similar, the differences are big enough at the molecular level that they have different transport proteins (especially tocopherol)

Answer 434

A

Only α-tocopherol has significant activity in the body

Answer 435

A

There is no inter conversion of vitamers in animals

Ex., β-tocotrienol cannot be converted into α-tocopherol

Answer 436

A

Tocopherols

Answer 437

A

The tocopherol nomenclature is used to describe the # and position of RING METHYL (CH3) groups.

Answer 438

A

The HYDROXYL group is the antioxidant site of vitamers.

Answer 439

A

α isoform has the most methylated ring.

Answer 440

A

Transport mediated uptake in the small intestine (e.g., NPC1L1)

Answer 441

A

The “R” and “S” of vitamers refers to CHIRAL CARBON configuration of methyl groups on side chain.

Answer 442

A

Natural α-tocopherol is RRR

Fits into the binding pocket of the Tocopherol Transfer Protein (TTP)
It is the only one that fits into TTP properly

Answer 443

A

Tocotrienols.

Answer 444

A

Transport mediated uptake in the small intestine (e.g., NPC1L1)

Answer 445

A

Tocotrienols are only not converted to α-tocopherol or able to fit in the TTP binding pocket.

Answer 446

A

Food sources: nuts, seeds, vegetable oils, avocado

- Mostly obtained from plants because stored in adipose tissue in animals (and we don’t normally eat the fat).

Answer 447

A

Yes. (Sensitive to food preparation & storage (e.g. roasting nuts ↓ Vit E levels)

Answer 448

A

True.

Adults (15 mg = 22.4 IU) of α-tocopherol per day
- The RDA is increased for pregnant women compared to age matched non pregnant women (due to oxidative damage that can occur to the fetus)

Answer 449

A

Estimated with tests to examine the hemolysis (breakdown) of red blood cells in the presence of dilute H2O2

(put RBC in dilute H2O2 and see what happens; lack of vitamin E = hemolysis)
- (>20% RBC hemolysis means there is a Vit E deficiency)

Answer 450

A

UL = 1,000 mg / day (above this amount will cause increased bleeding)
- However, gastrointestinal problems can be seen at lower levels than the UL

*Note: UL changes from person to person, some people have GI problems at 600mg or lower

Answer 451

A

Pre-mature infants (kept in oxygen rich incubators, which increases oxidative stress)
People with fat malabsorption disorders or gallbladders removed
People with genetic defects in lipoproteins or TTP (need to be monitored as they have problems transporting vitamin e across the body)

Answer 452

A

Requires bile acids for emulsification & incorporation into micelles
Absorbed in small intestine by transporters (e.g., NPC1L1)
Packaged into chylomicrons
Chylomicron remnants, containing Vit E, are taken up by the liver
Liver makes TTP, which is needed to get α tocopherol packaged into VLDL
(Other vitamers can help a bit with anti-oxidant activity in the liver only, but are quickly degraded)
No specific “storage” organ for Vit E, but most of it goes into lipid droplets in adipose tissue

Answer 453

A

Lines of Defense:

GSH peroxidase
Vitamin E
FA peroxidase

Answer 454

A

Super Antioxidant support

Answer 455

A

Plants incorporate selenium from the soil into methionine and cysteine AAs instead of sulfur

Therefore, selenium content in food is determined by selenium levels in the soil

*Note: selenocysteine makes certain proteins function, selenomethionine makes them not functional.

Answer 456

A

SelenoAA are absorbed in the small intestine by amino acid transporters and travel freely in the blood

Answer 457

A

The body uses selenocysteine

–~30 specific selenocysteine containing proteins in body that are involved in thyroid hormone metabolism, DNA synthesis and protection from oxidative damage

Answer 458

A

China and Africa (low Se in soil)
Keshan disease
(cardiomyopathy from cell damage by free radicals)

Answer 459

A

Selenosis –> chronic consumption of lots of brazil nuts which are rich in selenium can lead to hair and nail loss (most common symptoms)

Answer 460

A

Glutathione peroxidase = 1st line of defence against lipid peroxidation
Fatty acid peroxidase = 3rd line of defence against lipid peroxidation

Answer 461

A

Both selenoproteins use GLUTATHIONE (GSH) as a substrate, which helps to protect cells against oxidative damage (it acts as the reducing agent).

Answer 462

A

The structure of glutathione is crucial as GLUTAMATE and CYSTEINE linked through a gamma-carbon. This gamma peptide bond is resistant to cellular PROTEASES.

*Note: glutathione itself does not have selenium in its structure.

Answer 463

A

Selenium gets incorporated into the enzymes, not into the glutathione itself. It is however within the peroxidase enzyme.

Glutathione is a SINGLE electron donor (1 electron per glutathione) and it is a reducing agent.

Glutathione will donate an electron from its thiol group, but it keeps its structure thanks to the bond between cysteine and glutamate
- glutamate is attached to cysteine via its side chain (gamma carbon)
this gamma-peptide bond gives stability –> resistant to cellular proteases
it allows glutathione to function as a good reducing agent within the cell

Answer 464

A

2 GSH.

GSH is oxidized and reacts with another GSH to form GSSG.

Answer 465

A

High cellular
levels of GSSG
indicative of
high oxidative
stress.

Answer 466

A

High cellular levels of GSSG indicative of high oxidative stress.

Answer 467

A

False.

Oral GSH supplements not very effective because they are poorly absorbed.

Answer 468

A

The pentose phosphate pathway (HEXOSE MONOPHOSPHATE SHUNT) regenerates NADPH (which requires niacin).

Answer 469

A

Jamison claims vitamin c has antioxidant support.

A better description would be support the immune system.

Answer 470

A

Vitamin C is ASCORBIC acid; at physiological pH is it known as ASCORBATE.

Answer 471

A

The L isomer is biologically active in humans.

Answer 472

A

This is because we lack the specific enzyme gulonolactone oxidase.

Glucose (or galactose) –> gulonolactone –(gulonolactone oxidase) –> ascorbic acid

Answer 473

A

Fruits and vegetables.

Answer 474

A

Vitamin C doesn’t require digestion prior to absorption.

Answer 475

A

Uptake via sodium dependent vitamin C (SVCT) 1 and 2 transporters in the small intestine (feedback mechanism exists)

70 90% dietary Vit C is absorbed
There appears to be a maximum amount of Vit C that can be absorbed (this is what feedback mechanism means)

Answer 476

A

Found in circulation primarily in “free form” (i.e., not bound to a protein)

Answer 477

A

Found in circulation primarily in “free form” (i.e., not bound to a protein)

Answer 478

A

Reduced: Ascorbic acid
Oxidized: Dehydroascorbic acid

*Foods contain mostly ascorbic acid, but can have small amounts of the oxidized form (dehydroascorbic acid).

Answer 479

A

Vit C concentrations are high in WHITE blood cells, as well as in many tissues.

Answer 480

A

Collagen synthesis.

Answer 481

A

True.

“2 electron donor”

Answer 482

A

Proline-OH.

Answer 483

A

Electron donated from Vit C is used to form proline OH.

Answer 484

A

Collagen is what gives tissues their structure.

Answer 485

A

Each ascorbic acid reactivates 2 prolyl hydroxylases.

Answer 486

A

This evidence suggests that Vitamin C has a role in oxidant defense.

Answer 487

A

This evidence suggests that Vitamin C has a role in oxidant defense.

Answer 488

A

RDA goal: to maximize tissue concentrations and minimize urinary excretion.

Answer 489

A

RDA is increased in pregnant and lactating women to support mother and infant.

*Collagen plays a huge role in the development of the fetus –> bone (cartilage), tissue, organs

Answer 490

A

Above this amount increases risk for digestive problems (diarrhea) and kidney stones.

Answer 491

A

Scurvy (plasma Vit C levels < 0.2 mg/ dL
(If you consume 10 mg Vit C per day, signs of scurvy develop in 1 month)
Increased risk of hemorrhages (skin, follicles, gums)
Increased hair loss, loose teeth
Swollen joints, poor wound healing
- due to problems producing
hydroxyproline (i.e.

Answer 492

A

The gums.

Since they have such a high turnover rate, if there was a problem making collagen, that’s where we would see it first.

Answer 493

A

limey’s = term to describe british sailors
- early physicians realized that british soldiers that didn’t have any citrus fruit had scurvy, and to prevent that they started bringing limes with them

Answer 494

A

•
False.
-Meta analyses suggest that Vit C does not prevent colds (except in people performing intense physical activity (e.g. marathon running))
- Some evidence suggesting Vit C shortens the duration of a cold

Answer 495

A

Vitamin E: scavenges PUFA peroxy radicals within the cell.

Answer 496

A

Selenium: Essential for the proper functioning of selenoproteins.
– Glutathione Peroxidase (reduces hydroxyl radicals by converting H 2 O 2 into water)
– FA Peroxidase (converts PUFA hydroperoxides into PUFA alcohols)

Answer 497

A

Vitamin C: major blood reducing agent, but it’s role in oxidant defence remains debatable.

However, Vit C is critical for the production of hydroxylated prolines.

Answer 498

A

Sulfur AA (cysteine): is necessary for the synthesis of glutathione (GSH).

Answer 499

A

Niacin: is required to make NADPH (which is needed to regenerate GSH by glutathione reductase)

Answer 500

A

Riboflavin: also required by glutathione reductase as a coenzyme

Answer 501

A

Zn2+ and Cu+: are enzyme cofactors that donate electrons to convert superoxide into H2O2.

Answer 502

A

Free Fe2+ in the cell in the presence of H2O2 increases risk for making hydroxyl radicals.

Answer 503

A

Free Fe2+ in the cell in the presence of H2O2 increases risk for making hydroxyl radicals.

Answer 504

A

Group III:
Micronutrients that act as enzyme cofactors
ex. Thiamin, Niacin, Riboflavin, Vit B6, Folate, Vit B12, Biotin, Pantothenic
acid

Answer 505

A

Converts carbs, proteins, fats to energy.

*It plays an important role in biochemical pathways used to produce energy.

Answer 506

A

Niacin is also called Vitamin B3.

Answer 507

A

Discovered through the condition pellagra in humans and a similar condition, called black tongue, in dogs
-Niacin was considered the “anti black tongue” factor

High incidence in areas where corn is the main dietary staple (because niacin is attached to indigestible carbohydrates in corn, therefore it is poorly absorbed)
pellagra began when explorers came to america and started eating corn; you can’t digest the niacin in corn well, and so the indigenous people had a special way of preparing it to “release” the niacin, however the explorers did not do that.

Answer 508

A

Most fish, meats, breads and cereals, coffee and tea.

*In coffee, trigonelline is converted to niacin by heat (ie ., coffee bean roasting)

Answer 509

A

Nicotinamide
Nicotinamide adenine dinucleotide (NAD)
Nicotinamide adenine dinucleotide phosphate (NADP)

Answer 510

A

In plant foods, Vitamin B3 is predominantly found as NICOTINIC ACID, which is considered a provitamin.

Answer 511

A

No.
Only about 1/60 th of Trp is converted into niacin.

*Note: Although the conversion is very small it is still taken into account by government when creating RDA values.

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