Chapter 6

Question 1

what are proteins?

Answer 1

repeating structural units of amino acids
- Carbon (C), Hydrogen (H), & Oxygen (O)
** primary source of N in diet **

Question 2

what are complex organic molecules?

Answer 2

proteins are complex organic molecules
- contractile proteins (muscles)
- blood (hemoglobin)
- hormones, enzymes, & antibodies

Question 3

what is the structure of proteins?

Answer 3

central carbon atom surrounded by 4 groups
1. amine group (nitrogen-containing)
2. acid group
3. hydrogen atom
4. side chain (unique to each amino acid)

Question 4

how many amino acids?

Answer 4

20 different amino acids
- all can produce a protein

Question 5

essential amino acids

Answer 5

these amino acids must be consumed in the diet b/c the body does not make them
histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

Question 6

non-essential amino acids

Answer 6

these amino acids can be manufactured by the body
alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine

Question 7

protein synthesis

Answer 7

the body synthesizes proteins by grouping together amino acids from the diet

Question 8

what dictates the sequence of amino acids

Answer 8

genetic material (DNA) determines the sequence of amino acids

Question 9

Proteins

Answer 9

long chains of amino acids joined by peptide bonds

Question 10

dipeptide

Answer 10

2 amino acids joined together

Question 11

tripeptide

Answer 11

3 amino acids joined together

Question 12

olgiopeptide

Answer 12

4-9 amino acids joined together

Question 13

polypeptide

Answer 13

> 10 amino acids joined together

Question 14

Dehydration synthesis

Answer 14

two amino acids are joined together using water to create a dipeptide

Question 15

polypeptide chains

Answer 15

as polypeptides grow longer the structure begins to change

Question 16

what are the four levels of protein structure?

Answer 16

1. primary structure
2. secondary structure
3. tertiary structure
4. quaternary structure

Question 17

Primary Structure

Answer 17

• linear sequence of amino acids
• genetic code determines sequence

Question 18

secondary structure

Answer 18

primary structure twists due to amino acid characteristics
(size, charge, hydrophobic etc)

Question 19

tertiary structure

Answer 19

the secondary structure folds into 3-D structure
- this shape determines function

Question 20

quaternary structure

Answer 20

often two or more polypeptide chains joined together

Question 21

what is transamination?

Answer 21

inability to convert essential amino acid from a non-essential (transfer the amine group)

** conditionally essential amino acid **

Question 22

phenylketonuria (PKU)

Answer 22

inherited disorder
- cannot metabolize phenylalanine into non-essential amino acid such as tyrosine

Question 23

Missing amino acids

Answer 23

some foods are missing essential amino acids
- limits protein synthesis and effects quality of protein

Question 24

complete protein

Answer 24

contains all 9 essential amino acids
- most complete sources are from animal proteins
- Soy is only complete source of vegetable protein

Question 25

incomplete proteins

Answer 25

do not contain all essential amino acids - not sufficient to support growth and health

Question 26

mutual supplementation

Answer 26

- combining incomplete proteins to make complete protein

Question 27

complementary foods

Answer 27

when combined - foods provide complementary proteins

Question 28

what determines protein quality?

Answer 28

1. presence/absence of amino acids 2. protein digestibility

Question 29

presence/absence of amino acids

Answer 29

- the higher the quantity of essential amino acids the higher the quality - - complete proteins are ‘high quality’

Question 30

protein digestibility

Answer 30

how complete our bodies can digest the protein Animal foods - highly digestible (90%) Soy foods - highly digestible (~80%) plant-based foods (grains & vegetable protein) - less digestible (60-90%)

Question 31

Protein Digestion Oral Cavity

Answer 31

Proteins are crushed/moistened - No enzymatic digestion of proteins occurs in the mouth

Question 32

Protein Digestion Stomach

Answer 32

smell/taste/chewing - triggers the Vagus Nerve to release stimuli (Ach) - Ach trigger G-cells (enteroendocrine cells) of stomach/duodenum - produce gastrin (peptide hormone)

Question 33

Role of gastrin in protein digestion

Answer 33

gastrin stimulates parietal cells to secrete gastric acid (HCL) and serotonin (aids in GI movement)

Question 34

Role of HCL

Answer 34

- HCL denature the 2 and 3 degree strands - HCL converts inactive pepsinogen into active pepsin

Question 35

role of pepsin

Answer 35

works in the acidic environment - breaks proteins into short polypeptides (>10 a.a.) & single a.a

Question 36

Protein digestion Small Intestine

Answer 36

utilizes: chyme proteases intestinal enzymes produce peptidases

Question 37

chyme

Answer 37

- end product of stomach - shorter polypeptides & single a.a. - Pepsin is inactivated by the neutral pH of small intestine

Question 38

proteases

Answer 38

produced by the pancreas (proteolytic enzymes) - hydrolyze peptide bonds polypeptides > oligopeptides, tripeptides, dipeptides & some free a.a.

Question 39

intestinal enzymes

Answer 39

produce peptidases oligopeptides, tripeptides & dipeptides → single a.a. for absorption

Question 40

protein absorption small intestine

Answer 40

- uptake of fluid/substances by tissues of body - Amino acids, dipeptides & tripeptides transported into epithelial cell via primary active transport - Transport of amino acid into bloodstream is via passive transport - Then to liver and on to cells in need!

Question 41

benefit of proteins

Answer 41

1. serve as energy source 2. function as enzymes 3. function as hormones 4. help with fluid balance

Question 42

proteins as energy source

Answer 42

- proteins are not stored (carbs and fats are) If needed for energy ... - proteins pulled from blood & tissues - excess amino acids consumed leads to deamination (removal of amino group and converted to ammonia)

Question 43

function as enzymes

Answer 43

- specialized proteins speed up chemical reactions

Question 44

function as hormones

Answer 44

Substances that act as chemical messengers in the body * Insulin is protein with a sequence of 51 amino acids * Glucagon is a linear protein having 29 amino acids

Question 45

help with fluid

Answer 45

- proteins attract fluids - low protein intake leads to edema

Question 46

how much proteins should we eat?

Answer 46

Adults : RDA 0.8 gm/kg (0.35 gm/lbs) AMDR 10%-35% ** higher during growth/development (children, pregnant/lactating women) **

Question 47

high protein diets can be harmful

Answer 47

associated with high cholesterol may contribute to bone loss

Question 48

high cholesterol

Answer 48

Saturated fats in animal products - increase blood cholesterol - increase risk of heart disease. Vegetarians - greatly reduced rate of heart disease (Frase 1999).

Question 49

contribute to bone loss

Answer 49

animal products contain more sulphur-containing amino acids (methionine and cysteine) - increases blood acidity when metabolized...Ca+ pulled from bone as a buffer.