Protein Biochemistry 1

Question 1

What amino acid repeats are found in collagen?

Answer 1

4-hydroxyproline and 5-hydroxylysine

Question 2

Three individual units of _________ come together to form a supercoil.

Answer 2

collagen

Question 3

While the importance of 4-hydroxyproline is disputed in the interactions of collagen fibers, __________ is undeniably important because it forms covalent connections.

Answer 3

5-hydroxylysine

Question 4

Lysyl oxidase has been implicated in ______________.

Answer 4

breast cancer

Question 5

Two enzymes are needed to create the modified amino acids in collagen: ______________.

Answer 5

prolyl hydroxylase and lysyl hydroxylase

Question 6

What process does gamma-carboxylation allow?

Answer 6

Calcium chelation, in which calcium binds to two strands of protein

Question 7

____________ uses ten of its gamma-carboxy groups to fold around calcium and expose non-polar groups that then anchor into membranes.

Answer 7

Prothrombin

Question 8

__________ is ATP-dependent.

Answer 8

Ubiquination

Question 9

Pepsin is a ___________ protease that cleaves _____________.

Answer 9

aspartic; N-terminal of aromatic residues

Question 10

Trypsin and chymotrypsin are both __________ proteases that attack the ________, but chymotrypsin cleaves __________ amino acids while trypsin cleaves ___________ amino acids.

Answer 10

serine; C-terminus; aromatic and nonpolar; basic

Question 11

Aminotransferases require the cofactor __________.

Answer 11

pyridoxine, which “holds” the amino group during transfer (note: it is a phosphorylated version); even in a rested state, PLP forms a Schiff base with the aminotransferases

Question 12

The aminotransferase reaction is directed by ____________.

Answer 12

concentration of substrates (because the reaction is reversible)

Question 13

Ammonia is converted to a less toxic molecule: _________.

Answer 13

urea

Question 14

Vitamin C is a cofactor in the enzyme ______________.

Answer 14

lysyl hydroxylase and prolyl hydroxylase

Question 15

The ___________ protein degradation pathway is ATP independent.

Answer 15

lysosomal

Question 16

Nitrogen can enter the urea cycle as __________ or _____________.

Answer 16

aspartate; ammonia

Question 17

Which two amino acids are purely ketogenic?

Answer 17

Leucine

Lysine

Question 18

Which four amino acids are both ketogenic and glucogenic?

Answer 18

Tryptophan
Isoleucine
Tyrosine
Phenylalanine

Question 19

What two residues crosslink in collagen?

Answer 19

Lysine and hydroxylysine

Question 20

PLP (a derivative of B6) is a cofactor for what reaction?

Answer 20

The aminotransferase reaction

Question 21

Ammonia and bicarb join with ATP to form _______________.

Answer 21

carbamoyl phosphate