Proteins

Question 1

Protein

Answer 1

Accounts for 20% of adult weight

Involved in most of the body’s functions and life processes

Make up of chains of amino acids
- sequence of amino acids is determined by DNA

Question 2

Amino acid

Answer 2

Basic building blocks of protein

Composed of carbon, hydrogen, oxygen and nitrogen atoms

Twenty common amino acids

• 9 essential
• 11 essential

Question 3

Functions of protein

Answer 3

◦ Major structural and functional component of every living cell

◦ Body structure and framework

◦ Enzymes

◦ Other body secretions and fluids

◦ Acid–base balance

◦ Transport molecules

Question 4

Essential amino acids

Answer 4

Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine 
Tryptophan
Valine

Question 5

Nonessential amino acids

Answer 5

Alanine
Arginine
Asparagine 
Aspartic acid
Cystine (cysteine)
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine

Question 6

Structure of the protein

Answer 6

Primary structure

Secondary structure

Tertiary structure

Quaternary structure

Question 7

Denaturing

Answer 7

Alteration of the protein’s shape and this functions through the use of:

• Heat
• Acids
• Bases
• Salts
• Mechanical agitation

Question 8

Digestion of proteins

Answer 8

Hydrochloric acid denatures protein and activates pepsinogen form the active enzyme pepsin

Pepsin breaks the polypeptide chain into smaller polypeptides

Enzymes from pancreases continue to break down peptide bonds resulting in dipeptides, tripeptides and single amino acids

Tripeptides and dipeptidases on the surface of the small intestinal cells finish digestion to yield single amino acids

Question 9

Absorption of proteins

Answer 9

Amino acids, and sometimes a few dipeptides or larger peptides, are absorbed through the mucosa of the small intestine

These are transported to the liver vita portal vein

Question 10

Liver metabolism

Answer 10

Retains amino acids to make liver cells, nonessential amino acids and plasma proteins such as heparin, prothrombin and albumin

Regulates the release of amino acids into the bloodstream

Removes the nitrogen from amino acids

Converts protein to fatty acids which form triglycerides

Forms urea from nitrogenous wastes of protein

Question 11

Gluconeogenesis

Answer 11

Amino acids can be used to make glucose when glucose is limited

Question 12

Energy production

Answer 12

Amino acids can be used for energy when the diet is deficient in kilocalories

Question 13

Fat cells

Answer 13

Amino acids can be converted to fatty acids and stored as a triglyceride in adipose tissue when kilocalorie intake is sufficient

Question 14

Protein turnover

Answer 14

Proteins are constantly made and broken down, releasing their amino acids into the amino acid pool or are used for protein synthesis

Question 15

Metabolic pool

Answer 15

Contains a supply of each amino acid

Consists of recycled amino acids from body proteins that have broken down and also amino acids from food

In a constant state of flux

Question 16

Nitrogen balance

Answer 16

Reflects the state of balance between protein breakdown and protein synthesis

Determined by comparing the amount of nitrogen intake with the nitrogen output.

Healthy adults are in neural nitrogen balance

Question 17

Positive nitrogen balance

Answer 17

Protein synthesis exceeds protein breakdown

• Pregnant
• Growing children and adolescents
• Athletes

Question 18

Negative nitrogen

Answer 18

An undesirable state that occurs when protein breakdown exceeds protein synthesis

• Experiencing a medical trauma
• Not eating a health diet

Question 19

Mary is a 25 year old woman who was admitted to the hospital with multiple fractures and traumatic injuries from a car accident. A nutritional intake study indicated a 24-hours protein of 64 g. A 24-hour urinary urea nitrogen (UUN) collection result 19,8g. Calculate nitrogen balance

Answer 19

Determine nitrogen intake by dividing protein intake by 6.25
- 64 g / 6,25 = 10.24 g of nitrogen

Determine total nitrogen output by adding a coefficient of 4 of the UUN
- 19.8 g / 4 = 23.8g of nitrogen

Calculate nitrogen balance by subtracting nitrogen output from nitrogen output from nitrogen intake
- 10.24 g - 23.8g = -13.56g in 24 hours

Interpret the results
- A negative number indicates that protein breakdown is exceeding protein synthesis. Mary is in a catabolic state.

Question 20

Complete proteins

Answer 20

High biologic value

Provide adequate amounts and proportions of all essential amino acids needed for protein synthesis necessary to support tissue growth and repair

Animal proteins and soy protein are complete proteins

Question 21

Incomplete proteins

Answer 21

Lack of adequate amounts of one or more essential amino acids

Except for soy protein, all plants are sources of incomplete proteins

Gelatin is also an incomplete protein

Question 22

Complementary proteins

Answer 22

Two proteins that when combined provide adequate amounts and proportions of all essential amino acids needed to support protein synthesis

Question 23

Recommended Dietary Allowance (RDA)

Answer 23

Healthy adults is 0.8 g/kg

Question 24

Acceptable Macronutrient Distribution Range for protein

Answer 24

10% to 35%

Question 25

Kwashiorkor

Answer 25

Severe protein deficiency

Aggressive nutritional support is used to restore metabolic balance as quickly as possible

Question 26

Marasmus

Answer 26

Results from a severe deficiency in kilocalories

Occurs secondary to chronic diseases

Nutritional therapy is started slowly and advanced gradually

Question 27

Too little protein

Answer 27

◦ Cells lining the GI tract are not sufficiently replaced as they slough off

◦ Digestive function is inhibited

◦ Absorption of food is reduced

◦ Intestinal bacteria gets into the blood and causes septicemia

◦ Immune system is compromised due to malnutrition and cannot fight infection

Question 27

Too little protein

Answer 27

◦ Cells lining the GI tract are not sufficiently replaced as they slough off

◦ Digestive function is inhibited

◦ Absorption of food is reduced

◦ Intestinal bacteria gets into the blood and causes septicemia

◦ Immune system is compromised due to malnutrition and cannot fight infection

Question 28

Symptoms of Kwashiorkor

Answer 28

◦ Edema in legs, feet, and stomach

◦ Muscle tone and strength diminish

◦ Hair is brittle and easy to pull out

◦ Appear pale, sad, and apathetic

◦ Prone to infection, rapid heart rate, excess fluid in lungs, pneumonia, septicemia, and water and
electrolyte imbalances

Question 29

Symptoms of Marasmus

Answer 29

◦ Frail, emaciated appearance

◦ Weakened and appear apathetic

◦ Many cannot stand without support

◦ Look old

◦ Hair is thin, dry, and lacks sheen

◦ Body temperature and blood pressure are low

◦ Prone to dehydration, infections, and unnecessary blood clotting

Question 30

Symptoms of Marasmic Kwashiorkor

Answer 30

Chronic deficiency in kilocalories and protein

◦ Have edema in legs and arms

◦ Have a “skin and bones” appearance

◦ With treatment the edema subsides and appearance becomes more like someone with marasmus

Question 31

Best sources of protein

Answer 31

Proteins are abundant in
◦ Dairy foods
◦ Meats
◦ Poultry
◦ Meat alternatives such as dried beans, peanut butter, nuts, and soy

Question 32

3 oz serving of cooked meat, poultry, or fish provide

Answer 32

◦ Provides 21–25 grams of protein
◦ About 7 g/oz
◦ About the size of a deck of cards
◦ Adequate amount for one meal