protein structure

Question 1

What is the central carbon in an amino acid called?

Answer 1

Alpha carbon

Question 2

Which functional groups are attached to the alpha carbon in an amino acid?

Answer 2

Amino group, carboxyl group, hydrogen, and side chain (R group)

Question 3

What gives amino acids their unique properties?

Answer 3

The side chain (R group)

Question 4

How many amino acids are encoded by DNA?

Answer 4

20

Question 5

Which amino acids are not directly encoded by DNA?

Answer 5

Hydroxyproline, Selenocysteine, Homocysteine

Question 6

What is the nature of the peptide bond?

Answer 6

Planar, rigid, partial double bond character, polar

Question 7

What role do peptide bond atoms play in protein secondary structure?

Answer 7

Peptide bond atoms (C=O and N-H) can form hydrogen bonds with other backbone groups

Question 8

What is primary protein structure?

Answer 8

The linear sequence of amino acids

Question 9

How is an alpha-helix stabilized?

Answer 9

By hydrogen bonds between backbone atoms every 4th residue

Question 10

What is the handedness and turn of the alpha-helix?

Answer 10

Right-handed, 3.6 residues per turn

Question 11

Where do R-groups point in an alpha-helix?

Answer 11

Outward from the helix

Question 12

What are the features of beta-pleated sheets?

Answer 12

Hydrogen bonds between strands, R-groups alternate above and below

Question 13

What are the two types of beta-sheets?

Answer 13

Parallel and antiparallel

Question 14

What stabilizes tertiary protein structure?

Answer 14

Hydrogen bonds, ionic interactions, van der Waals forces, hydrophobic interactions, disulphide bonds

Question 15

What defines quaternary structure?

Answer 15

Association of multiple polypeptides into a functional unit

Question 16

What covalent interaction stabilizes protein structure?

Answer 16

Disulphide bonds between cysteines

Question 17

Name four non-covalent interactions in proteins.

Answer 17

Hydrogen bonds, ionic interactions, van der Waals forces, hydrophobic effect

Question 18

What determines protein folding?

Answer 18

The primary amino acid sequence

Question 19

What assists folding in cells?

Answer 19

Chaperone proteins

Question 20

Why are proteins marginally stable?

Answer 20

They are stabilized by a small amount of energy (~12 kJ/mol)

Question 21

What can denature proteins?

Answer 21

pH, temperature, ionic strength, detergents

Question 22

Which disease is associated with amyloid-β plaques?

Answer 22

Alzheimer’s disease

Question 23

What causes prion diseases?

Answer 23

Infectious misfolded proteins

Question 24

What mutation causes PKU?

Answer 24

Defective phenylalanine hydroxylase

Question 25

Which enzyme is defective in one form of albinism?

Answer 25

Tyrosinase

Question 26

What is the structure of collagen?

Answer 26

Triple helix of three left-handed chains forming a right-handed supercoil

Question 27

What is the repeating sequence in collagen?

Answer 27

Gly–X–Y, where X = proline and Y = hydroxyproline

Question 28

What post-translational modification is needed for collagen stability?

Answer 28

Hydroxylation of proline

Question 29

What cofactor is required for hydroxylation of proline?

Answer 29

Vitamin C

Question 30

What residues form disulphide bonds?

Answer 30

Cysteine

Question 31

What are the types of glycosylation?

Answer 31

O-linked (Ser/Thr) and N-linked (Asn)

Question 32

Which amino acid forms disulphide bonds?

Answer 32

Cysteine

Question 33

Which amino acid is smallest and most flexible?

Answer 33

Glycine

Question 34

Which amino acid disrupts alpha helices?

Answer 34

Proline

Question 35

Which amino acids can be phosphorylated?

Answer 35

Serine and Threonine

Question 36

Which amino acid can buffer at physiological pH?

Answer 36

Histidine

Question 37

Which amino acids are negatively charged at pH 7.4?

Answer 37

Aspartate and Glutamate

Question 38

Which amino acids are positively charged at pH 7.4?

Answer 38

Lysine and Arginine