Lecture 6: Myoglobin and hemoglobin

Question 1

O2 has ____ solubility in water

Answer 1

O2 has limited solubility in water

Question 2

heme allows _____ which _____ and _____

Answer 2

heme allows Fe2+ to bind O2 which prevents reduction of O2 and keeps Fe2+ soluble

Question 3

function of myoglobin

Answer 3

O2 storage in muscle

Question 4

myoglobin holds onto O2 until ____

Answer 4

myoglobin holds onto O2 until P(O2) becomes low

Question 5

function of hemoglobin

Answer 5

O2 transport from lungs to tissues

Question 6

structure of myoglobin (2)

Answer 6

• helical [primarily alpha helix]

- single polypeptide chain; 8 alpha-helices (a-h) connected by loops

Question 7

the hydrogen bond in heme is between ____ and ___; it stabilizes ____

Answer 7

the hydrogen bond in heme is between the distal His64 and the bound O2; it stabilizes coordination of oxygen

Question 8

Θ = ?

Answer 8

= fractional saturation; % of mb bound to oxygen

Question 9

P(O2) = ?

Answer 9

~ concentration of O2

Question 10

P50 = ?

Answer 10

= P(O2) value where you have 1/2 saturation

Question 11

Mb binds O2 (non/ effectively)

Answer 11

= Mb binds O2 effectively

Question 12

a larger P50 value means (weaker/ stronger) binding

Answer 12

a larger P50 value means weaker binding

Question 13

a hyperbolic curve is when a transport protein is _____ but ____ or vise versa

Answer 13

a hyperbolic curve is when a transport protein is efficient in binding but inefficient in unloading

Question 14

a sigmoidal binding curve is when a transport protein is ____ because ____

Answer 14

a sigmoidal binding curve is when a transport protein is efficient in both binding and unloading because is can switch between higher and lower affinity states

Question 15

cooperative binding

Answer 15

apparent change in a proteins affinity for its ligand as a function of ligand concentration

Question 16

Hb has ___ different O2 binding sites

Answer 16

Hb has 4 different O2 binding sites

Question 17

slope of the hill plot gives ____ ?

Answer 17

slope of the hill plot gives the index of cooperativity

Question 18

nH > 1 = ?

nH < 1 = ?

Answer 18

nH > 1 = + cooperativity

nH < 1 = - cooperativity

Question 19

nH = ?

Answer 19

nH = slope of transition state

Question 20

of binding sites always (< / >) nH

Answer 20

of binding sites always > nH

Question 21

Goldilocks interactions in hemoglobin

Answer 21

alpha 1 - beta 2 or alpha 2 - beta 1