Chapter 4 - Proteins

Question 1

protein conformation

Answer 1

spatial arrangement of atoms in a protein

Question 2

native protein

Answer 2

proteins in any of their functional, folded conformations

Question 3

protein stability

Answer 3

tendency of a protein to maintain a native conformation

Question 4

apoprotein

Answer 4

protein part of a complete, catalytically active enzyme together with its bound coenzyme/metal ions

Question 5

secondary structure

Answer 5

describes any chosen segment of a polypeptide chain and the local spatial arrangement of its main-chain atoms without regard to the conformation of its side chains or its relationship to other segments

Question 6

prosthetic group

Answer 6

non-amino acid part of a conjugated protein

Question 7

domains

Answer 7

a part of the polypeptide chain that is independently stable or could undergo movements as a single entity with respect to the entire protein

Question 8

denaturation

Answer 8

loss of three-dimensional structure sufficient to cause loss of function

Question 9

molecular chaperones

Answer 9

proteins that interact with partially folded or improperly folded polypeptides, facilitating correct folding pathways or providing microenvironments in which folding can occur.

Question 10

chaperonins

Answer 10

class of chaperones; elaborate protein complexes required for the folding of some cellular proteins that do not fold spontaneously

Question 11

examples of prosthetic groups

Answer 11

lipids (lipoproteins), sugar groups (glycoproteins), metals (metalloproteins)

Question 12

alpha helix

Answer 12

polypeptide backbone tightly wound around an imaginary axis; R groups protrude outward; stabilized by a hydrogen bond between the hydrogen atom attached to the electronegative nitrogen atom of a peptide linkage and the electronegative carbonyl oxygen of the fourth amino acid; Ala and Leu likely to form; Pro and Gly unlikely

Question 13

beta sheet

Answer 13

backbone of polypeptide chain extended into a zigzag structure; may connect distant regions of the polypeptide chain; when two layered close together in protein, R groups must be small (Ala and Gly residues)

Question 14

beta turn

Answer 14

connect the two ends of two adjacent segments of an antiparallel beta sheet; 180° turn involving four amino acids where carbonyl oxygen of the first residue forms a hydrogen bond with the amino-group hydrogen of the fourth; Gly and Pro residues often occur; often found near the surface of a protein

Question 15

parallel beta sheet

Answer 15

amino-terminal and carboxyl-terminal orientations of adjacent chains are the same; 180° hydrogen bond angles

Question 16

antiparallel beta sheet

Answer 16

amino-terminal and carboxyl-terminal oritentations of adjacent chains are opposite, less than 180° hydrogen bond angles

Question 17

collagen

Answer 17

three left handed alpha chains form right-handed superhelix; primary structure is repeating tripeptide unit Gly-X-Y (X = Pro, Y = 4-Hyp)