protein and amino acid metabolism

Question 1

how many different AA are there

Answer 1

21

Question 2

what makes up proteins

Answer 2

chains of AA

Question 3

how is protein digested/absorbed by the body

Answer 3

pepsin breaks down protein in stomach
further broken down in small intestine by pancreatic enzymes like trypsin, chymotrypsin and carboxypeptidase.
short chain AA and single AA can be absorbed by the small intestine

Question 4

what is the dietary protein quality?

Answer 4

reflects how closely the proportion of AA in a protein resemble that of milk or egg proteins
human milk is set as standard

Question 5

what percentage of body weight do proteins make up

Answer 5

16% - hormones, enzymes, structural and muscle

Question 6

which two molecules make up an AA

Answer 6

amino group and carboxyl group

Question 7

amino acids are amphoteric, what does this mean

Answer 7

AA posses the qualities of both acid and base

Question 8

what is an essential AA

Answer 8

an AA that cannot be synthesised by the metabolism and must be taking in through the diet

Question 9

what is a non-essential AA

Answer 9

an AA that can be synthesised by the body

Question 10

how are AA bonded together in chains

Answer 10

by peptide bonding

Question 11

what are the two types of peptide bonding

Answer 11

cis-peptide bonding and trans-peptide bonding

Question 12

explain the difference between cis and trans peptide bonding

Answer 12

in cis peptide bonding the two functional carbons appear on the same side of the double bond
in trans peptide bonding the two function carbons appear on different sides of the double bond

Question 13

what happens after deamination of AA

Answer 13

carbon skeletons of AA degrade into intermediates of glycolysis, TCA cycle or fatty acid metabolism

Question 14

what are AA degraded into

Answer 14

glucogenic - degraded to intermediates then to glucose
ketogenic - degraded to acetyl CoA
some AA are able to do both

Question 15

describe the process of protein synthesis

Answer 15

dna transcription, mRNA production and exported from nucleus, mRNA and ribosomes initiate translational complex, mRNA used as a template for peptide synthesis, leading to a synthesised polypeptide chain

Question 16

what are the four protein structures

Answer 16

primary, secondary, tertiary, Quaternary

Question 17

describe the primary structure

Answer 17

AA sequence in protein

Question 18

describe the secondary structure

Answer 18

alpha helix / beta sheet

Question 19

describe the tertiary and quaternary structure

Answer 19

3D shape

globular/fibrous

Question 20

what factors affect the rate of protein synthesis

Answer 20

rate of synthesis of mRNA coding for a particular protein is increased
rate of synthesis of the polypeptide chain by the ribosomal mRNA complex is increased
increased production of ribosomal and translational cofactors
rate of degradation of mRNA is decreased
rate of degradation is decreased

Question 21

describe the process of protein degradation

Answer 21

different from protein digestion/absorption

requires cleavage of peptide bonds by proteases and peptidases

Question 22

how is intracellular protein degradation different from digestion of protein

Answer 22

digestion of protein is a crude and unselective process, using a low pH to denature proteins and pancreatic enzymes to cleave peptide bonds to allow for AA and small AA chains to be absorbed through the small intestine
intracellular protein breakdown is a strictly controlled process to prevent degradation of the entire cell, proteasomes are used