Topic 3

Question 1

conformation

Answer 1

spatial arrangement of proteins

Question 2

3D structure of a protein determined by?

Answer 2

amino acid sequence

Question 3

stabilization of protein structure

Answer 3

non-covalent interactions

Question 4

protein functions

Answer 4

enzyme catalysis
protein-protein/carb/lipid interaction
transport
structural support
buffer
signal transduction

Question 5

non-covalent interactions

Answer 5

hydrogen bonds
ionic bonds
hydrophobic interactions

Question 6

structural protein classification

Answer 6

fibrous
globular
intergral

Question 7

fibrous proteins

Answer 7

insoluble
supports structure
e.g. collagen, keratin

Question 8

globular proteins

Answer 8

water soluble

e.g. myoglobin, hemoglobin

Question 9

integral membrane proteins

Answer 9

embedded in membrane
supports structure and/or function or both
e.g. membrane bound enzymes, receptors, ion channels

Question 10

amino acid polymerization

Answer 10

condensation reaction to form peptide bond

water released

Question 11

protein configuration

Answer 11

carbonyl & amino groups have trans configuration d/t partial double bonds
exception: proline has cis configuration (6%)

Question 12

primary structure

Answer 12

amino acid sequence of its poly peptide chains
derived by covalent peptide bond formation; disulfide linkage
change can alter biologic activity

Question 13

secondary structure

Answer 13

3D structure w/o regard to the conformation of side chains
2 types: α-helix, β-sheet
hydrogen bonds cause bends/folds

Question 14

α-helix

Answer 14

spiral configuration
side chains directed outward
stabilized by hydrogen bonds
right-handed more thermodynamically stable

Question 15

β-sheet

Answer 15

laterally stacked chains extended not condensed
proline must be present
glycine often found w/in 4 positions of proline

Question 16

antiparallel β-sheet

Answer 16

strands that extend in opposite directions

most stable

Question 17

parallel β-sheet

Answer 17

strands that extend in the same direction

less stable d/t distorted H-bonding

Question 18

mixed β-sheet

Answer 18

common, consisting of both parallel and antiparallel sheets

Question 19

tertiary structure

Answer 19

overall 3D structure

helices and sheets combined to form motifs

Question 20

quaternary structure

Answer 20

3D arrangement composed of multi polypeptides
subunits joined by non covalent interactions
disulfide linkages sometimes formed
e.g. hemoglobin, insulin, collagen, immunoglobulins

Question 21

native proteins

Answer 21

proteins in their functional and folded conformations

marginally stable at physiologic conditions

Question 22

function of structure in native proteins

Answer 22

specific structural stability
specific functions
solubility
fluctuating flexibility of conformation allowing diffusion of small molecules

Question 23

denaturation

Answer 23

loss of native structure

Question 24

denaturation factors

Answer 24

heat
pH
certain reagents (detergent/bile salt, urea, alcohols, weak bless, some non-enzymatic modifications)

Question 25

polypeptide folding

Answer 25

fold rapidly in a systematic stepwide manner
some undergo assisted folding
defective folding results in diseases

Question 26

renature

Answer 26

under proper conditions, unfolded proteins can refold spontaneously

Question 27

permanent denaturation

Answer 27

extreme pH

heat (>100C)

Question 28

myoglobin

Answer 28

monomer (single polypeptide)
muscle tissue
oxygen STORAGE
Fe2+ can bind one O2
higher affinity for O2
releases O2 when tissue becomes hypoxic
hyperbolic O2 saturation curve

Question 29

heme

Answer 29

present in myoglobin, hemoglobin, and other proteins

oxygen can bind to a heme prothetic group

Question 30

metmyoglobin

Answer 30

oxidized myoglobin

cannot bind oxygen

Question 31

hemoglobin

Answer 31

tetramer
RBCs
oxygen TRANSPORT
binds 4-O2 molecules (allosteric, cooperative binding)
high affinity O2 in lungs, low affinity O2 in tissue
sigmoidal O2 saturation curve

Question 32

right shift Bohr effect

Answer 32

decrease pH
increase PCO2
increase temp
increase 2,3-BPG
reversed in lungs

Question 33

effect of pH

Answer 33

decrease in pH promotes release of O2

Question 34

effect of 2,3-biphosphoglycerate

Answer 34

product of glycolysis
binds to deoxyhemoglobin
decreases O2 binding affinity of Hb

Question 35

left shift Bohr effect

Answer 35

increase pH
decrease PCO2
decrease temp
decrease 2,3-BPG

Question 36

fetal hemoglobin (HbF)

Answer 36

tetramer of α2γ2
does not bind 2,3-BPG
higher affinity for O2 than HbA

Question 37

sickle cell hemoglobin (HbS)

Answer 37

tetramer of α2β2
one nucleotide change in the β-change:
glutamate –> valine at position 6
β-chain of HbS has very low affinity for O2