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Macro Nutrients - Protein


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Protein structure
H2N(amino)-C-COOH (carboxyl)

Avg American consumes how much protein?

median men & women

recommended men & women
80-125 g/day

median (M) 71-101 / (W)55-62

recommended (M) 52-56 / (W)46

Explain the protein source now vs. then.
The amount of protein is about the same, but the composition is very different.

Now 70% animal 17% plant

What % of daily energy comes from protein?

Protein provides how many kcal/gram of energy?

Do you determine protein requirements based on current weight or healthy weight?

How do you calculate the RDA (recommended dietary allowance) for protein per day?
RDA = .8 g/kg/day

Daily allowance = healthy weight X RDA
example 55kg healthy weight X .8 g/kg/day PRO = 44 g PRO per day

Describe Marasmus.
more common than kwashiorkor
↓ protein and energy (glucose)
severe deprivation/absorption of protein, energy, vitamins, minerals
develops slowly (chronic PEM)
severe weight loss, muscle wasting & fat usage for energy
<60% weight for age
no edema
no fatty liver
anxiety, apathy
possible good appetite
hair is sparse, thin, dry
skin is dry, thin, wrinkled
ascites (bloated belly from ↑constipation, GI tract atrophies, ↓peristalsis and digestive enzymes)
↓ body temp & metabolism

Describe Kwashiorkor.
AKA evil spirit that infects young children after next baby is born
1-3 yrs old
↓ PRO with ↑ CHO from starchy weaning foods
rapid onset, acute PEM
some weight loss
some muscle wasting, less fat usage
60-80% weight for age
fatty liver (↓enzymes to break down fat)
apathy, misery, irritability, sadness
hair is dry, brittle, sparse, lighter in color, straight
skin lesions
ascites (bloated belly)

Problems with formula given to very poor populations include watering down formula to make it last longer and using poluted water to mix formula.

can result from glucose IV therapy (no protein in IV)

Protein Classification

Aliphatic - Gly, Ala, Val, Leu, Ile

OH - Ser, Thr

Sulfur - Cys, Met

Acidic - Asp, Asn, Glu, Gln

Basic - Arg, Lys, His

Aromatic - Phe, Tyr, Try

Imino - Pro

Protein Classification
Solubility (chem prop)

Simple - amino acid only

Conjugated - amino acid + other

Examples of Simple proteins
Albumin (egg white)
Globulin (blood)
Prolamine (zein-corn, high Arg)
Histones (nucleohistone in nucleus)
Protamines (salmine & sturine)
albuminoid (scleroprotein, rich in Pro, Gly, Ala)

Examples of Conjugated proteins
Glycoproteins & Mucoproteins (sugar w/N-glycocidic linkage)

Lipoprotein (lipid - apolipoprotein increases atherogenic action)

Nucleoproteins (nucleic acids DNA/RNA - virues)

Phosphoproteins (phosphate - milk casein)

Hemoproteins (iron - hemoglobin)

Metallaproteins (w/metal not iron)

Flavoprotein (coenzyme - FAD, TPP, NAD, CoA-SH)

Which of the 20 amino acids can bind to carbohydrate?
Asparagine (Asn)
Serine (Ser)
Threonine (Thr)
Hydroxylysine (Lys)

Protein Classification

List the 10 essential amino acids.

Histidine (kids only)
Arginine (kids only)

List the conditionally essential amino acids.

List the precursors for the conditionally essential amino acids.
Phenylalanine → Tyrosine (cirrhosis, missing phenylalanine hydroxylase enzyme)

Serine & Methionine → Cysteine (premature babies, kidney disease)

Glutamate → Proline (premature babies)

Glutamine & Glutamate & Aspartate→ Arginine (only in children)

Glutamate & Ammonia → Glutamine (liver disease)

Deficiencies of the following amino acids lead to what reduced end products?
* emphasized in class

Arginine → creatine, nitric oxide

Aspartate → nucleic acid bases

Cysteine → glutathione, taurine

Glutamate → glutathione, nuceic acid bases

*Glycine → glutathione, nuceic acid bases, heme, creatine, methyl group metabolism, bile acids

*Lysine → Carnitine (shuttle for FA transport)

Methionine → Creatine, methyl group metabolism

Serine → methyl group metabolism

Taurine → bile acids

Tryptophan → serotonin, nicotinic acid
Tyrosine → catecholamines, thyroid hormone, melanin

Protein Classification
Nutritive Value

Complete - contain all essential AA (mainly animal products except gelatin)

Incomplete - lacking one or more essential AA

List the common incomplete proteins and name the missing AA(s).
Collagen/Gelatin - tryptophan

Legumes (not beans) - methionine, tryptophan

Corn (zein) - lysine, tryptophan

Wheat - lysine

Beans - methionine

What plants are considered legumes?

Vegan diets typically combine which incomplete proteins?

Which type of AAs are typically high and/or low?
legume + grain

High lysine, methionine, cysteine

Low sulfur

What is the vegan dietary formula for protein sources?
60% PRO from grain
35% PRO from legume
5% PRO from leafy greens

What are the plant protein percentages for protein in diet....US & World?
US 32%
World 65%

Protein Classification

Glucogenic AAs - produce a net amoun of pyruvate or Krebs cycle intermediates via deamination or transamination

Ketogenic - produce only acetylCoA or acetoacetylCoA to supply fatty acid synthesis pathways

Which amino acids are only ketogenic?

Which amino acids can be both glucogenic and/or ketogenic?

& all aromatic AAs:

Describe deamination.
Removal of amino group without transfering it to another compound.

threonine → a-ketobutyrate + NH4
{loses H2O & uses PLP (B6)}

Describe transamination.
removed amino group & transfers it to another compound to form a nonessential AA

alanine → pyruvate
a-ketoglutarate → glutamate
{uses ALT (alanine AA transferase) & PLP (B6)

aspartate → oxaloacetate
a-ketoglutarate → glutamate
{uses AST (aspartate AA transferase) & PLP (B6)

Asparaginase is used for what medical purpose?

What is it made from?

What does it do?

What are the side effects?
chemo for ALL (acute lymphoblastic leukaemia)

Erwinia crysanthemi

It is an enzyme that breaks down extracellular asparagine into aspartic acid and ammonia. Cells need asparaginine to build protein. Normal cells can sythesize, but these malignant cancer cells cannot. Starving the cancer cells of asparaginine slows rapid growth by intefering with the DNA/RNA sythesis, targets G1 phase of cell division, and results in apoptosis. Within a few days of IV or intramuscular injection the extracellular asparaginine falls to undetectable levels and decrease in leukocytes are seen

feel sick, nose bleeds, fever/chills, decreased appetite, loss of fertility, impact on liver

Carbon skeletons are created by what process?

What factors determine the type of products generated by metabolizing AA?

Carbon skeletons can produce what products?

Making glucose for energy from AA is

The pathway used depends on the type of AA being deaminated and the nutritional state of the body (AA used when energy intake is inadequate).

AA → pyruvate (glucogenic)
AA → acetyl CoA (ketogenic)
AA → products to enter Krebs Cycle directly (glucogenic or ketogenic)

gluconeogenesis (primarily in liver)


1. Can all AA be fully oxidixed to generate energy? Can all AA generate glucose?

2. What happens if you do not eat CHO, but eat lots of fat and/or protein?

3. Which body
1. All AA can be completely oxidized to generate energy, but not all can form glucose.

2. The body still needs CHO for glucose and will break down protein tissue for glucose. Some of the FAT & PRO consumed can be converted to glucose, but most of it will form acetyl CoA, which cannot be converted to glucose.

3. RBC, retina-eye, CNS

4. stored as fat

5. Leucine forms HMG-CoA & HMB (also taken as a muscle building supplement). Both are cholesterol percursers.
The liver uses Acetyl CoA to synthesize cholesterol.

Urea Metabolism

What produces the ammonia?

How is it detoxified?

Where does it go next?

What is needed to excrete it?

Name the diseases associated with high ammonia or urea?
deamination of AAs in liver
AA → NH3+CO2 → Urea

ammonia is combined with carbon dioxide to detoxify and form urea before releasing it into the blood

the blood containing the urea eventually reaches the kidneys

urea must be combined with water (to keep it in solution and maintain normal blood levels of urea) before excreting it into the urine

liver disease = high ammonia
kidney disease = high urea

Too much protein intake means excess sulfur containing AA. Sulfur causes calcium loss in the urine and can lead to stones if too little H2O is consumed.

1. What are the Institute of Medicine's established ranges for % of callories for adults: CHO, FAT and PRO?

2. What % of calories for PRO is appropriate for young and older children?

3. Very low FAT and high CHO
1. CHO 45-65%
FAT 20-35%
PRO 10-35%

2. Young children 5-20%
Older children 10-30%

3. lowers

4. under 50 (M)=38g (W)=25
over 50 (M)=30g (W)=21g

1. What does EAR stand for and what are the units?

2. What does RDA stand for and what are the units? How are they determined?

3. Does the RDA for protein provide all of the essential amino acid requirement
1. estimated average requirement (g/kg/day)

2. recommended dietary allowance
(g, mg, micrograms, etc)
They are based on the EARs for a nutrient and then are applied to the nutrient needs for 97% of a healthy group based on age and gender.

3. For people that consume mostly plant products, the RDA for protein may not provide adequate lysine.

List the EAR protein requirements for the groups below....

infants (0-6m)
older infants (7-12m)
children (1-3y)
adolescent (4-13y)
older adolescent (14-18y)
adult (19+y)
infants (0-12m)
1.52 g/kg/day

children (1-3y)
1.10 g/kg/day

adolescent (4-13y)
0.95 g/kg/day

older adolescent (14-18y)
0.85 g/kg/day

adult (19+ y)
0.80 g/kg/day

1.10 g/kg/day

PKU Process

Describe the process for breaking down phenylananine the liver and in the kidneys.

What is the result of these processes?
phenylalanine → phenylalanine hydroxylase (this enzyme is deficient in PKU) →
tyrosine (deficient due to deficient enzyme)

phenylalanine (accumulates because liver can't process very well due to lack of enzyme) →
phenylpyruvic acid →
other phenyl acids accumulate (kidneys are processing too much of the burden)

both the excess phenyl acid accumulation and the deficiency of tyrosine lead to mental retardation

HMB (beta-hydroxy beta-methybutyrate) is a __________ metabolite and precursor for ________.

What did the research study about supplementation conclude?
leucine, cholesterol

lowered total cholesterol and LDL, decreased systolic blood pressure, decreased risk for heart attack and stroke, the supplement is safe

Sports Physiologists

1. Protein most concerned with?

2. Why is it important and how does it work?

3. Does it enhance athletic performance?
1. Creatine

2. Creatine is used to form phosphocreatine. Phosphocreatine is a storehouse for high energy phosphate and is used to relenish ATP in rapidly contracting muscle tissue. This delays the use of glycogen stores in muscles during and postpones fatigue. It also works as an acid-base buffer.

3. It can increase performance by 1-4%, but may have more of a positive effect on short burts of activity like sprinters vs. long-distance runners.

Virologists & Immunologists

How is protein related to viruses?

How is the immune system effected by deficient protein intake?
Viruses are wrapped in protein.

Antibodies are made of protein.


Describe how yeast, algae, and spirulina are grown and their benefits.

Describe algae and its benefits.
microbial byproduct of sugar refining-grown on molasses, also grown on petroleum, harvested and dried, has a meaty flavor

aquatic plants including seaweed, they use sunlight and carbon dioxide for growth, ex. Chlorella has a high yield per acre of protein and tastes like fishy spinach

is a mircoalgae, is a safe variety of wild blue-green algae, grows in salty lakes, can be dried into cookies, 60% digestible plant protein, highest in beta carotene of all foods, contains GLA an EFA, rich in iron, magnessium, and trace minerals, B12, B complex, and many phytonutrients


What is the syndrome associated with tryptophan contamination?

What is free tryptophan used for?
Eosinophilia-myalgia syndrome
blood disorder caused by contaminated L-tryptophan, results in muscle pain, fatigue, weakness, headaches, fever and death

it is used a drug or food additive in infant formulas, also used to induce sleep


Describe what happens if an intact protein from the GI tract is absorbed into the blood.
The body sees the intact protein as a foreign protein and produces antibodies to ensure they do not circulate in the blood.

This system may break down if the gut has increased permeability (examples: paracitic infection or infant with underdeveloped GI tract)


How is this connected to two different concerns related to protein consumption?
High protein diets create an acidic environment, which is then buffered by stored calcium.

5.8 mg of calcium is needed to compensate for calcium lost for each gram of protein consumed.

Protein rich foods generally contain phosporus. Phosporus is linked to osteoporosis.

Renal Function

How is high animal protein consumption related to kidney stones?

Restriction of dietary protein is known to ______ the symptoms of chronic renal insufficiency.
The acidic environment from high protein consumption leads to calcium buffering and excretion in the urine. If adequate water is not consumed the calcium oxalate and calcium phosphate come out of solution and become kidney stones.


AA Imbalance

ratios of EAAs = amt of each EAA

Food processing tends to destroy the _____content of food.

Deficiency in this AA has been related to what medical conditions? How?

(1)herpes simplex infections
It prevents the recurrence of infections. Studies on supplementation were equal to the amt that should be found in the diet.
(2) Lysinuric protein intollerance
genetic disorder that leads to lysine being lost in urine and childhood osteoporosis. Suggests that lysine deficiency could have an effect on bone health making food processing even more damaging.


How does PEM (protein-energy malnutrition)affect brain development?

How are neurotransmitters affected by AA deficiencies?
PEM causes decreased # and size of neurons, and decreased neurotransmitters

Tryptophan → 5-HTP → serotonin (5-hydroxytryptamine)

Tryptophan and 5-HTP cross the BBB w/ot assistance, but serotonin cannot

3-5% of tryptophan becomes niacin (B3), but requires riboflavin (B2) and PLP (B6)

Why does a high CHO meal make you sleepier than a high PRO meal?

List the LNAAs
High PRO meals contain many AAs. The large neutral AAs (LNAAs) compete for one carrier into neurons and decrease the amount of tryptophan (doesn't need a carrier) able to cross the BBB.

High CHO and low PRO meals lead to more tryptophan crossing even if the meal doesn't contain tryptophan (less competition).
High CHO → high insulin → transport of LNAAs into muscle.

LNAAs: valine, leucine, tyrosine, phenylalanine

How are SAD (seasonal-affective disorders), CHO (carb-craving obesity), and PMS (pre-mentrual syndrome) related to high CHO intake?
High CHO intake causes peaks and valleys in serotonin, which effects mood stability.

Blocking the reuptake of serotonin with d-fenfluramine (REDUX)(an SSRI similar to Prozac) prolongs its effects and normalizes serotonin levels. Supresses CHO snackingand eases depression.

Natural Anti-Depressants

1. Which foods are rich in tryptophan?

2. When serotonin levels are low it is tempting to consume CHO rich foods. Does this help or hinder?
1. turkey, chicken, fish, cottage cheese, bananas, eggs, nuts, wheat germ, avacados, milk, cheese, legumes(beans, peas, pulses, saya), plus small amounts in bread, cereals, potatoes, and rice

2. Hinder by perpetuating the cravings cycle instead of normalizing serotonin levels.

Natural Anti-depressants

Describe 3 supplements.
St John's Wort - prevents the breakdown of serotonin to keep levels constant (SSRI-selective serotonin re-uptake inhibitor), more effective than Prozac (not for severe depression) without side effects

Griffonia simplicifolia - a natural source, easily absorbable form of 5-HTP (precursor for serotonin)

Rhodiola - inhibits the monoamine oxidase (MAO)that breaks down serotonin and improves brain levels by 30%, used by cosmonauts to cope with long spells of weightlessness in a small place under high stress

Bone health & Protein (soy vs. animal)

Explain how soy protein consumption can protect against osteoporosis.
Aminal protein is high in sulfur-containing AAs that lead to acidity and calcium loss due to its use for buffering.

Soy protein has phytoestrogens to help with menopause and less sulfur-containing AAs. It is not a complete protein and would need to be combined with a grain.

1 - 3 of Protein Functions

List and give examples.
1. Growth & Development - AAs needed to build proteins of new tissues

2. Enzymes -
HYDROLASES (add water to cleave bond between carbon and other)
ISOMERASES (catalyze the conversion of different isomers[forms of the same molecule])
LIGASES (break bonds between carbon and other by using ATP)
TRANSFERASES (move functional groups)

3. Hormones - not all are made of protein

GROWTH HORMONE → promotes growth
INSULIN & GLUCAGON → regulate blood sugar
CALCITONIN & PARATHYROID HORMONE → regulate blood calcium
ANTIDIURETIC HORMONE → regulate fluid and electrolyte balance
TYROSINE → catecholamines (dopamine & NorEpi)
TRYPTOPHAN → melatonin

4-6 Protein Functions

List and give examples.
4. Antibodies - in response to antigens and dependent of adequate protein intake

5. Fluid Balance - protein concentration effects osmotic pressure in cells and blood

6. Acid-Base Balance - some buffering proteins lose or gain hydrogen in response to change in pH

7-10 Protein Functions

List and give examples.
7. Transport Proteins - some move molecules in/out of cells other from place to place in blood (ex. albumin carries calcium, zinc, and B6 in blood)

8. Protein as Energy - AA used for energy of inadequate CHO intake

9. Proteins as Lubricants - mucoproteins found in musous is a conjucated protein containing hexosamine, protein surrounds joints for ease of movement

10. Others - blood clotting (fibrin), vision (opsin)

The Fed State

1. Name 2 cell types that burn glucose directly?

2. Which organ receives the glucose first and what does it do with it?

3. Where does the rest of the glucose go?

4. What happe
1. CNS cells and RBC because they cannot store glucose and exclusively burn glucose.

2. The liver replenishes the glycogen stores.

3. Some glucose bypasses the liver and gets absorbed by the small intestine. This enters circulation to supply the CNS and blood.

4. Excess glucose gets converted to fatty acids if energy intake exceeds energy expenditure.

5. The Krebs cycle is used for all except the RBC (convert glucose to lactate because the do not have a mitochondria).

6. 3 hours after ingestion of a meal

Postabsorptive/Early Fasting State

1. How long does this state last?

2. What metabolic pathways are used?

3. What is used for energy?
1. 3-12 hours after ingestion of a meal

2. Glycogenolysis (breaking down of glycogen) and gluconeogenesis (making new glucose)

3. glycogen is released, new glucose is formed, branched chain amino acids, other AAs are released froom muscle (these AAs are used to support the Glucose-Alanine cycle-needs an alpha amino acid to donate amino group in order to generate an alpha keto acid

Explain the glucose-alanine cycle
Muscles use this to eliminate nitrogen and replenish energy.

glucose → pyruvate → lactate
glucose → pyruvate → alanine (via transamination w/PLP & ALT)

Alanine → Pyruvate (deamination produces NH3 → urea) → glucose (transamination in gluconeogenesis pathway)

The Fasting State

1. When does it begin and how long does it last?

2. What is used for energy?

3. Which AAs produce ketones and which tissues begin to use them for energy?

4. What triggers t
1. If Postabsorptive state lasts 48 hours, the fasting state begins and can last up to 2 days additional days (no food intake)

2. AAs from muscle used for gluconeogenesis, glycerol from lypolosis, lactate from anaerobic use of glucose

3. Leucine & Lysine are ketogenic, heart, brain, and skeletal muscle begin using ketones for energy

4. Glucagon & glucocorticoid hormones increase in response to low glucose

5. Large loss of urinary nitrogen due to gluconeogenesis from AAs

The Starvation State

1. How long does this state last?

2. What metabolic shift happens in this state?

3. What form of energy is now used by the major tissues?

4. What happens to the liver af
1. Starvation can last several weeks with little or no food. If fat stores are significant before this state a person can survive for months or up to a year if ketosis doesn't cause death

2. Protein sparing so antibodies, enzymes, hemoglobin etc can sustain life. Shift to lipolysis and fat stores become primary source of energy

3. Brain uses glucose (from glycerol for gluconeogenesis), all else uses fatty acids

4. Ketone bodies build up (ketosis) in the liver and reduces the need for glucose/gluconeogenesis, which spares the use of AA (protein sparing)

Malnutrition & Protein

1. Which hormones/proteins decrease during malnutrition?

2. What increases during malnutrition?

3. What's the difference between stunting and wasting?
1. ↓insulin, growth hormone (unless recovering then higher), thyroid hormone, albumin concentration, oxidation of AA (less synthesis and degradation)


stunting (shorter for age)
wasting (weigh less for height)

Injury/Disease & Protein

trauma, cancer, HIV, infections = loss of protein

1. How is this similar/different than starvation?

2. What happens to basal metabolic rate (BMR) in starvation vs. cancer,
1. adaptation to preserve lean body mass does not occurr as in starvation

↑demand for making new proteins to fight medical condition won't allow for protein sparing effect

2. BMR increases during a cancer, HIV, trauma, or infection. BMR decreases in starvation.

3. The body does not switch over to depend on ketones for main energy source when glucose is scarce. This means it continually uses AAs for gluconeogenesis and wastes protein throughout the disease/illness state all while preserving the body fat, cachexia (weight loss, wasting of muscle, loss of appetite, and general debility that can occur during a chronic disease)

1. What amino acid can be used to screen for muscle protein degradation?

2. What is it?

3. What test is used to measure it?
1. 3-methyl histidine

2. It's an amino acid found in the actin & myosin of skeletal muscle.

3. 3-methyl histidine is measured in urine because it is not used to make new proteins. It's excreted in urine when skeletal muscle is broken down.

Protein digestion in stomach

1. _____ begins the digestion process. It is released and stimulated by the release of ____, ____, and ______. It _____proteins and activates _________.

2. Which stomach cells produce
1. HCL, gastrin, gastric releasing peptide (GRP), neurotransmitter ACh, denatures, pepsin.

2. Parietal cells - HCL & intrinsic factor
Chief cells - pepsinogen
Endocrine cells - gastrin

3. Pepsin (activated from pepsinogen by HCL), inhibits pepsinogen synthesis, endo peptidase (cleaves inner peptide bonds), ones next to the carboxy end of Leucine, Methionine, or an Aromatic AA

Protein digestion in the SI

1. When acidic chyme reaches the duodenum, which digestive enzymes are triggered by which cells?

2. What are the end products of digestion in SI?
1. SI endocrine mucosal cells release CCK and secretin. CCK signals the pancreas to release zymogen digestive enzymes and the gall bladder to release bile. Secretin (CCK strengthens the Secretin signal) signals pancreas to release bicarbonate.

2. dipeptides, tripeptides, free AAs - able to be absorbed across the brush border

SI Zymogens

1. Which zymogens are secreted by the pancreas? What is needed to activate? What are the activated forms called?

2. Name the peptidases secreted by the brush border.
trypsinogen → enteropeptidase (brush border secretes in response to CCK & secretin) → trypsin

chemotrypsinogen→ trypsin → chymotrypsin

procarboxypeptidase A (or) B → trypsin → carboxypeptidases

proelastase → trypsin → elastase


Where on the protein do these enzymes cleave peptide bonds? Are they endo or exopeptidases?

1. Trypsin
2. Chymotrypsin
3. Carboxypeptidase A
4. Carbxypeptidase B
5. Aminopeptidase
6. Dipeptidylamin
1. next to lysine and arginine (endopeptidase)

2. next to phenylalanine, methionine, tyrosine, tryptophan, and histidine (endopeptidase)

3. cleave aromatic or brached chain AAs from carboxyl end (Phe, Tyr, Try, Ile, Leu) (endopeptidase)

4. cleave arginine, lysine from carboxyl end (exopeptidase)

5. cleave AAs from the amino end of small polypeptides (exopeptidase)

6. cleave AAs from the amino ends of dipeptides (exopeptidase)

What coenzymes are needed for these enzymes to work properly?

1. Carboxypeptidases A & B

2. Dipeptidylaminopeptidase
1. zinc and vitamin A

2. magnesium

What happens to the tri & dipeptides once they are in the SI (7 steps)?
1. the tripeptides & dipeptides are broken down into AA and absorbed into the blood

2. the AAs are all sent to the liver for distrubution

3. some are used to synthesize albumin, liver proteins, or other proteins for export in the blood

4. excess AAs are catabolized by the liver (carbon skeleton is broken down to either glucose or fatty acid for storage as either glycogen or FA, the amino group (NH2) is converted to urea

5. the rest are distributed to all of the tissues that need AAs

6. muscle, pancreas, epithelial cels etc. take up the AAs

7. nitrogen from NH2 amino group is excreted

1. The liver is the main site for AA catabolism except for which type of AAs? Where is this type catabolized?

2. Synthesis of muscle protein and liver enzymes is related to what? What hormone is involved?
1. branched chain AAs, muscle

2. eating patterns, insulin

What are the four types of nutrient absorption?

facilitated diffusion (carrier)

active transport (carrier, ATP, Na+)

pinocytosis (similar to endocytosis)

1. How is the pancreas protected from inappropriate zymogen activation?

2. What is the condition called if these protections fail?

3. What causes heriditary pancreatitis?

4. What foods contain trypsin
1. Trypsin inhibitors (located in the pacreatic acinar cells) are released if zymogens become activated while still in the pancreas, lysosomal hydrolases degrade zymogens if trypsin gets activated while still in the pancreas as backup protection in case the acinar cells are not working properly

2. "acute pancreatitis" leads to tissue damage resulting from proteolysis by trypsin and chymotrypsin

3. Genetic mutations in the way trypsinogen is formed seem to have caused autoactivation problems that result in autodigestion by activated enzymes in the pancreas.

4. pulses (peas, beans, and lentils), cereals (wheat, buckweat, rice bran)

5. They can be inactivated by wet heating or processing techniquies that concentrate and/isolate proteins (soy processing)

6. They can lower the nutritional quality of other dietary proteins by decreasing digestibility.

7. They do show promise in the treatment of panceatitis by controlling tissue damage.


1. definition
2. enzyme involved
3. symptoms
4. treatment
5. diagnosis
1. disorder of tyrosime metabolism, homgenitate cannot be broken down and leads to a build up of homogentisate acid and its oxidative products

(phenylalanine → tyrosine → p-hydroxyphenylpyruvate → homogentisate → {broken here} maleyacetoacetate → fumarylacetoacetate → fumurate & acetyl CoA)

2. homogentistic acid oxidase

3. homogentisate acid build up is released into the urine, the urine becomes dark brown/black when exposed to air because homogentisate oxidation, this also can happen to other areas exposed to air like the mouth and eyes, benign in childhood, later in life it manifests as ochronosis (bluish gray discoloration of ears & nose from build up & presents >40 yrs), arthritis, and brown pigmentation of skin in areas of perspiration, pigments also effect the cornea

4. no effective treatment, antioxidants may prevent pigment deposition, low Phe/Tyr diet may prevent the progression of ochronosis and arthritis

5. if ochronosis is not visible, it's not uncommon to go undiagnosed

Maple Syrup Urine Disease (MSUD)

1. definition
2. enzyme involved
3. symptoms
4. complications & treatment
5. diagnosis
1. Branched chain AAs (valine, leucine, isoleucine) are not metabolized because of a missing enzyme, transamination occurs normally and forms keto acids, but the keto acids cannot be broken down by oxidative decarboxylation.

2. alpha-keto acid dehydrogenase

EARLY: By 5th or 6th day of life, urine, skin, and perspiration smell and look like maple syrup. Irritability, refusal to feed,↓ weight gain, rapid loss of reflexes, and irregular jerky respiration

LATE: alternating hyper & hypotonicity, convulsion, seizures, opisthotonos (rigid posturing of back with head back), coma, respiratory disturbances, death

4. untreated infants die within 20 days, secondary infections are often life treatening

1st: remove all isoleucine, leucine, and valine from diet
2nd: supplement isoleucine and valine once they return to normal (happens before leucine)
3rd: supplement leucine

Note: patients need some BCAAs to prevent nitrogen loss, they just can't process a normal amount

5. Alloisoleucine is formed from the excess isoleucine and is used for diagnosis

Hereditary Tyrosemia Type I

1. definition
2. enzyme involved
3. symptoms
4. treatment
5. diagnosis
1. An autosomal recessive condition of tyrosine metabolism that leads to buildup of fumarylacetonacetase and succinylacetone. Liver damage causes secondary inhibition of p-hydroxyphenylpyruvic acid oxidase.

(phenylalanine → tyrosine → p-hydroxyphenylpyruvate → homogentisate → maleyacetoacetate → fumarylacetoacetate → {broken here} fumurate & acetyl CoA)

2. fumarylacetoacetate hydrolase enzyme

3. EARLY: vomitting, diarrhea, failure to thrive, abdominal distention
LATE: enlarged spleen & liver, ascites (excessive fluid in peritoneal cavity), edema, bilateral cataracts, uncontrolable eye movements, severe dry eye, hyperactivity, mental retardation, small head size, corneal erosion, Vitamin D resistant rickets, ↓ phosporus in blood, ↑phosporus in kidneys, cabbage-like odor, liver is worst symptom, NO MENTAL RETARDATION, HT 1 is most severe and most common

4. Tyrosine restrictd diet does not prevent hepatic deterioration, liver transplant, no sucessful medical treatment

5. prenatal (mid-trimester) amniotic fluid - check for elevated succinylacetone

Hereditary Tyrosemia Type 2

1. definition
2. enzyme involved
3. symptoms
4. treatment
5. diagnosis
1. Tyrosine cannot be broken down due to lack of an enzyme. Tyrosine levels rise and crystalize in cells and tissues.

(phenylalanine → tyrosine {broken here} → p-hydroxyphenylpyruvate → homogentisate → maleyacetoacetate → fumarylacetoacetate → fumurate & acetyl CoA)

2. Tyrosine Aminotransferase

3. Corneal ulcers and painful hyperkeratotic plaques on the palms and soles. Mental retardation may be present in a minority of patients.

4. tyrosine restricted diet provides dramatic relief of skin lesions and cerebral function

5. check for elevated tyrosine levels

Transient Neonatal Tyrosemia Type 3

1. definition
2. enzyme involved
3. symptoms
4. treatment
5. diagnosis
1. inability to metabolize p-hydroxyphenylpyruvate due to immaturity of the liver & lack of enzyme, occurs in premature infants fed high protein formula with inadequate Vitamin C

(phenylalanine → tyrosine → p-hydroxyphenylpyruvate {broken here}→ homogentisate → maleyacetoacetate → fumarylacetoacetate → fumurate & acetyl CoA)

2. p-hydroxyphenylpyruvic oxidase (pHPPA)enzyme

3. neurologic problems, mental retardation and ataxia (uncoordinated movement)

4. benefit from reducing the protein level in formula and usually do well on breast milk, tyrosine normalization assisted by vit C supplementation, TNT resolves once liver matures

5. 4-hydroxyphenylpyruvic and 4-hydroxyphenyllactic acids in their urine, pHPPA (AKA 4HPPD) enzyme activity is measured in liver.

Phenylketonuria (PKU)

1. definition
2. enzyme
3. symptoms
4. treatment
5. diagnosis
1. an autosomal recessive trait (both parents) affecting phenylalanine metabolism due to a missing enzyme
(phenylalanine {broken here} → tyrosine → p-hydroxyphenylpyruvate → homogentisate → maleyacetoacetate → fumarylacetoacetate → fumurate & acetyl CoA)

2. phenylalanine hydroxylase

3. Because phenylalanine cannot be converted to tyrosine, it gets converted through other pathways. In the kidneys, elevated phenylalanine leads to production of phenylpyruvic acid (ketone), which is then converted to phenylacetic acid. These 2 metabolites and the excessive phenylalanine cause brain damage.

4. Dietary control (near elimination) must happen very early in life to avoid brain damage. Tyrosine supplementation is necessary because it becomes a conditionally essential AA.

5. blood test for phenylalanine levels


1. definition
2. enzymes involved
3. symptoms
4. treatment
5. diagnosis
1. malfunction in metabolism of methionine due to lack of B6, folate, or B12 that leads to excessive hoocysteine and risk for vascular damage

a) 5,10-methylene THF → 5-methyl THF (requires methylene THF reductase)
b) methylcobalamin → cobalamin (requires methionine synthase)
c) homocysteine → cystathioine (requires serine, PLP/B6, & cystathionine B sythase)

3. nervous, cardiovascular, musculo-skeletal, and hematopoetic systems can be affected, mental retardation in children but not common in adulthood

4. comsume adequate B6, B12, and folate to correct the imbalance, reduce animal protein consumption (methionine), ↑exercise, ↓smoking, ↑ 0.5 mmol/L homocysteine → ↑ 20 mg cholesterol

5. blood test for homocysteine

Explain how homocysteine leads to vascular damage and the activates foam cells.
When excess homocysteine (tHcy) cannot be remethylated to methionine or transulfurated to form cysteine, it is auto-oxidized in plasma and forms homocysteine thiolactone and reactive oxygen species (ROS).

tHcy thiolactone modifies proteins especially lysine - called homocysteinylation, which can lead to denaturing of many body proteins including vascular endothelial tissue.

The ROS also damage the vascular endothelial tissue and activate the migration of macrophages carrying the LDL-tHcy aggregates (formed from tHcy thiolactone)and stimulates thrombogenesis to repair the tissue damage.

ROS lead to oxidation of LDL, which triggers production of foam cells. The foam cell release lipids, cholesterol, and more tHcy thiolactone (causing hyperplasia and fibrosis of smooth muscle) into the fibrolipid plaques of vascular endothelial tissue.

Describe Remethylation of Homocysteine
5,10-methylene THF → 5-methyl THF (requires methylene THF reductase)

The folate passes the methyl to B12.

cobalamin → methycobalamin (requires methionine sythase)

B12 passes the methyl to homocysteine to form methionine

homocysteine → methionine (requires homocysteine methy-transferase)

Describe the process of turning methionine into homocysteine.
methionine → SAM (requires ATP & methionine adenosyl transferase)

SAM → SAH (requires an acceptor or methyl group)

SAH → homocysteine (requires H2O to form adenosine byproduct)

Describe the process of transulfuration.
homocysteine → cystathionine (requires cystathionine B synthase, B6, and serine)

cystathionine → cysteine → misc steps lead to sulfur excretion

Describe the steps involved in treating a child with marasmus or kwashiorkor.

What is the prognosis?
1. correct dehydration, ↑nutrients, ↑body temp, treat infections

2. introduce mixed foods including milk to gradually increase calories and protein per kg of weight, include potassium, magnesium, and zinc

3. 3 weeks to stabilize and ↑appetite, many more weeks to catch up on weight and growth for age

up to 40% can die from electrolyte imbalance, infection, hypothermia, or heart failure in the first days of treatment. Retardation is likely depending on the duration of malnutrition and age of onset.

What causes "blue-diaper syndrome"?
excessive amounts of unabsorbed tryptophan reach the large intestine, gut bacteria convert it to indigo blue

tryptophan → indole → indican → indigo blue

Describe Hartnup disease.
A defective transporter in the intestines and kidneys leads to poor absorption of tryptophan.

Tryptophan is the percursor for nicotinamine (B3 or niacin), which then produces NAD+ and NADP (essential coenzymes involved in many other pathways).

↓ NAD+ and NADP result in decreased absorption of many other AAs causing high values in urine/feces & low values in blood.

1. Define the AA Score (chemical score) of proteins.

2. How is it calculated?

3. Limitations.
1. A complete protein (contains all EAAs) with an AA score of 100 is used as a reference (ex. egg). The EAA present in the lowest quantity of the test protein is compared to the EAA content in the reference protein.

2. Lysine example:
(2.5% in test food/5.5% in egg as reference)*100 = 45%

The higher the % indicates better protein quality

3. does not take into account digestibility

1. Define the Biological Value (BV) of proteins.

2. Limitations.
1. BV = nitrogen retained from food for maintenance & growth / nitrogen absorbed from protein

2. only considers digestibility of protein

1. Define Protein Efficiency Ratio (PER).

2. Limitations.

3. PER is for what patient population?
1. PER = gain in body weight / protein consumed

2. can't tell if weight gain was from water or lean muscle, doesn't take into account type of protein consumed

3. used for infants (PER is outdated for other groups)

1. Define Protein Digestibility - Corrected AA Score (PDCAAS).

2. Limitations.

3. PDCAAS is used for what patient population?
1. PDCAAS = (mg of limiting AA in test protein * true digestibility %) / mg of AA in reference protein

2. PDCAAS scores have only been calculated for lysine, SAA, threonine, and tryptophan because they are the most common limiting AAs in protein.

3. most commonly used for all groups - provides most complete picture

1. Describe (+) nitrogen balance

2. Describe (-) nitrogen balance

3. Describe nitrogen equilibrium

4. What factor is important in nitrogen balance?

5. How is nitrogen balance assessed?
1. + means storing, consuming more than losing
ex. growth, preganacy, burns, severe illness

2. (-) means losing more than consuming, leads to loss of body protein
ex. restrictive weight loss <800 calories/day, anorexia, cancer

3. (=) consume same amount as losing, not storing or losing body protein
ex. balanced diet, healthy non-pregnant, non-lactating, fully grown adult

4. total calorie intake

5. urine collection and diet records for a 24 hour period

Describe the 4 types of damage Food Processing can cause.
1) mild heating can lead to loss of lysine when it interacts with lactose, called browning reaction, major problem with milk processing

2) severe heating can make proteins resistant to digestion ↓ protein quality of food

3) severe treatment with alkali causes the lysine and alanine to react, which forms a toxic substance called "lysinoalanine"

4) oxidation of food using sulfur dioxide leads to loss of methionine in the protein

Describe 3 complications of excessive AA intake.
1) AA toxicity
methionine & tyrosine are most toxic
threonine can lead to ↓ growth rate

2) AA antagonism
↑ in one AA can ↓ delivery of other AAs
ex. BCAA fight for a similar carrier

3) AA imbalance
the most limiting EAA will determine use of other AAs, supplementing the limited EAA will make all AAs available

Protein Synthesis

1. What are nulceic acids?

2. What are they made of?

3. List the 5 nucleotides/bases and identify which ones are purines and pyrimidines.

4. Which bases pair in DNA & R
1. DNA & RNA are nucleic acids

a) nucleosides (nitrogenous core of purine or pyrimidine
& pentose sugar [RNA=ribose, DNA=dioxyribose])
b) phosphate

adenine & guanine = purines (2 rings)

cytosine, thymine, & uracil = pyrimidines (1 ring)
DNA: A - T, C - G
RNA: A - U, C - G

1. Describe the following: replication, transcription, & translation

2. Describe the 2 different types of RNA.

3. Describe how the genetic code is read from the mRNA.

4. Describe the steps used to
replication = DNA→DNA
transcription = DNA→RNA
translation = RNA→protein

mRNA = DNA template
tRNA = collect AAs & delivers to mRNA for assembly of protein strand

3. 5' (N-terminal/amino end)→ 3' (C-terminal/carboxyl end)

DNA coding strand 5'-3' = TGC
Template 3'-5' = ACG
mRNA 5'-3' = UGC
find UGC with the table = Cysteine

5. Areas of a protein consisting of cysteine and histidine residues that can bind zinc and behave like fingers.

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