Fibrous proteins

Question 1

What defines a fibrous protein in terms of secondary structure?

Answer 1

They usually only have one or the other. Either alpha or beta

Question 2

What is the function of fibrous proteins?

Answer 2

Structural roles: strength, support, and flexibility

Question 3

What is a globular protein?

Answer 3

A more compactly folded protein that various elements of secondary structure, are much more structurally and functionally diverse

Question 4

What is an example of an alpha helical fibrous protein?

Answer 4

Alpha keratin

Question 5

Which amino acids is alpha keratin rich in?

Answer 5

A, V, L, I, M, F, C

Question 6

What is the supersecondary structure of alpha keratin?

Answer 6

Coiled coil. Two alpha helices twist around each other

Question 7

What is the handedness of the individual helices and the coiled coil in alpha keratin?

Answer 7

Each helix is a right handed turn, but the coiled coil has a left handed supertwist

Question 8

What holds the two helices together in alpha keratin?

Answer 8

Interactions between the hydrophobic amino acids and disulfide bonds

Question 9

What is an example of a fibrous protein made of beta sheets?

Answer 9

Silk fibroin

Question 10

Which amino acids is silk fibroin rich in?

Answer 10

A and G

Question 11

What is the supersecondary structure of silk fibroin?

Answer 11

Stacked anti parallel beta sheets packed very closely together

Question 12

Why can’t silk fibroin be stretched?

Answer 12

The polypeptide chain is completely extended and no helices are present, so the protein has no stretchiness

Question 13

Why is spidroin both strong and stretchy?

Answer 13

Has regions of strong crystalline beta sheets that are interspersed with stretchy amorphous regions

Question 14

What is the supersecondary structure of collagen?

Answer 14

Left-handed triple helix

Question 15

What is the characteristic amino acid sequence of collagen?

Answer 15

Gly Pro Hyp (hydroxyproline)

Question 16

Which of the 3 amino acids in collagen is absolutely critical to its function and can’t be substituted?

Answer 16

Glycine

Question 17

Why is the glycine so critical to the structure of collagen?

Answer 17

It is inside the helix and the entire structure gets disrupted if there’s anything larger there

Question 18

What is the enzyme that adds the hydroxyl to the second proline in collagen?

Answer 18

Prolyl hydroxylase

Question 19

Which vitamin is required for prolyl hydroxylase to work?

Answer 19

Vitamin C

Question 20

What is the handedness of each helix in collagen?

Answer 20

Left handed

Question 21

What holds the 3 collagen strands together?

Answer 21

H bonds

Question 22

How are collagen triple helices assembled into a fibril?

Answer 22

Cross linking between the helices

Question 23

Which amino acids are involved in cross linking the collagen triple helices together?

Answer 23

Lysine and hydroxylysine

Question 24

Which enzyme modifies lysine to be able to form cross links with other collagen triple helices?

Answer 24

Lysyl oxidase. Converts lysine into an aldehyde: allysine