Proteins

Question 1

Protein structure

Answer 1

carboxyl group, amino group, hydrogen group, R group

Question 2

levels of protein structure

Answer 2

primary, secondary, tertiary, quaternary

Question 3

primary structure of a protein

Answer 3

sequence of amino acids

Question 4

secondary structure of a protein

Answer 4

alpha helices and beta sheets; stabilized by hydrogen bonds and disulfide bonds

Question 5

tertiary structure of a protein

Answer 5

3D shape which determines protein function; altered by denaturation

Question 6

denaturation

Answer 6

affects 3D structure of protein; change in protein function

Question 7

quaternary structure of a protein

Answer 7

2 or more protein units joined together to form a larger protein

Question 8

list of essential amino acids

Answer 8

isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, histidine

Question 9

list of nonessential amino acids

Answer 9

alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine

Question 10

essential amino acids

Answer 10

cannot be synthesized; bodies can’t make carbon skeleton, cannot attach amino group to skeleton, or are not fast enough to meet needs.

Question 11

conditionally essential amino acids

Answer 11

amino acids that become essential in certain conditions: infancy, disease, trauma, infection, phenylketonuria, etc.

Question 12

Protein functions

Answer 12

growth and maintenance of tissues, essential metabolic compounds, transport of nutrients, regulation of water balance, maintenance of pH, defense and detoxification, energy (4 kcal/g)

Question 13

protein examples

Answer 13

enzymes, hormones, hemoglobin/myoglobin, apoproteins, transferrin/ferritin, antibodies, thrombin/fibrinogen/fibrin, collagen,

Question 14

complete proteins

Answer 14

food that contains all essential amino acids in sufficient quantities to support growth

Question 15

first limiting amino acid

Answer 15

essential amino acid in smallest supply in a food in relation to body needs; limits the amount of protein the body can synthesize from this food

Question 16

protein quality

Answer 16

spectrum of amino acids in food; quality may be more important than quantity in some situations

Question 17

proteases

Answer 17

enzymes that break down proteins by hydrolysis of the peptide bonds

Question 18

protein digestion in stomach

Answer 18

HCl denatures protein, increasing access by enzymes; pepsin

Question 19

pepsin

Answer 19

released in stomach as pepsinogen; release controlled by gastrin; optimum pH 1.6-3.2; activated by HCl

Question 20

protein digestion in small intestine

Answer 20

partially digested food in duodenum causes release of cholecystokinin, which stimulates release of proteolytic enzymes from pancreas; most secreted as proenzymes and have selective activity; smaller peptides digested further by enzymes secreted by intestinal mucosa

Question 21

absorption of proteins

Answer 21

occurs by active transport;

Question 22

protein synthesis

Answer 22

requires adequate amounts of all amino acids; Transcription, Translation; results in primary structure

Question 23

DNA

Answer 23

instructions for protein synthesis; genetic info located in nucleus of all cells

Question 24

Transcription

Answer 24

DNA “copied” to mRNA and transferred from nucleus to cytoplasm

Question 25

Translation

Answer 25

mRNA “decoded” into a polypeptide by ribosome in cytoplasm

Question 26

tRNA

Answer 26

needed to deliver each amino acid as needed in translational process

Question 27

amino acid catabolism

Answer 27

deamination to yield C-skeleton and ammonia (NH4); yields 4 kcal/g; fates: glucogenic or ketogenic; nitrogen disposed of

Question 28

urea cycle overview

Answer 28

disposal of nitrogen waste product from protein metabolism