Protein Structure

Question 1

Peptide bond

Answer 1

Amide bond between carboxyl of one acid and amino of another. Side chain and peptide bond alternate together. Rigid because of resonance

Question 2

Amino acid sequence

Answer 2

Dictates protein structure

Question 3

Only single unit enzyme with sigmoid kinetics

Answer 3

Glucokinase

Question 4

Primary structure

Answer 4

Arise from covalent bonds. Sequence, disulfide bonds, cleavage, modifications.

Question 5

Secondary structure

Answer 5

Alpha helix, beta sheet, beta turn

Question 6

Tertiary structure

Answer 6

Association into 3D structure. Stabilized non covalently. Hydrophobic interior.

Question 7

Quaternary structure.

Answer 7

Non covalent association of multiple protein subunits. Homo or heteromeric. Allows allosterism.

Question 8

Disulfide bonds

Answer 8

Formed by oxred reactions

Question 9

Post translational modification

Answer 9

Phosphorylation, ubiquitination, glycosylation, acetylation

Question 10

Prohibited peptide configuration

Answer 10

Cis prohibited

Question 11

Limited carbon bond rotation in secondary structure

Answer 11

Steric hindrance.

Question 12

Alpha helix

Answer 12

Side chains away from axis I+4 rule for hydrogen bonds. Right handed helix, 5.4 A with 3.4 aminos per turn. 1.5 aminos per A.

Question 13

Beta sheets

Answer 13

Side chains above and below plane. H bonds always between different strands.

Question 14

Beta turn

Answer 14

I+3 rule for H bonds.

Question 15

Amino acids preferred structures

Answer 15

Not much. Alpha for Glu. Val and Ile for B sheet. Gly and Pro for turns.

Question 16

Globular proteins

Answer 16

Tertiary. Non structural. Enzymes

Question 17

Fibrous

Answer 17

Elongated and for big physical structures. Can be in coiled coil.

Question 18

Collagen

Answer 18

Rich in glycine and proline.makes triple helix

Question 19

Domains

Answer 19

Made of tandem globular regions.

Question 20

Isoelectric point.

Answer 20

pH at which net charge is zero. Most proteins have pI below 7. Least soluble then.

Question 21

Denaturation

Answer 21

Physical- heat, freeze.

Chemical- pH, solvents.

Question 22

Protein folding

Answer 22

Concerted and sequential. Occurs cooperatively, with intermediates.

Question 23

Size fractionation

Answer 23

SDS-page, gel filtration

Question 24

Charge fractionation

Answer 24

Gel electrophoresis, ion exchange chromatography.

Question 25

pI fractionation

Answer 25

Isoelectric focusing

Question 26

Binding activity fractionation

Answer 26

Affinity chromatography