Topic 4

Question 1

function of protein determined by…

Answer 1

primary structure

Question 2

myoglobin is a ….

Answer 2

monomer, no quaternary structure

Question 3

Hemoglobin is a …..

Answer 3

oligomer, has quaternary

Question 4

function of hemoglobin

Answer 4

binds O2 in the lungs and then releases in tissues

Question 5

function myoglobin

Answer 5

binds O2 in muscle cells as ligand

local reserve of O2 during intense exercise

Question 6

function of proteins depends on….

Answer 6

binds ligands reversibly

Question 7

Kd is ____ if _____ is greater

Answer 7

smaller, affinity

Question 8

the greater the affinity , the concentration is

Answer 8

higher

Question 9

Structure of myoglobin

Answer 9

monomer, single polypeptide, hydrophobic pocket between helix E and F

Question 10

Structure of Heme

Answer 10

• prosthetic group
• circular and planar
• large aromatic
• polar surface exposed, hydrophobic core

Question 11

Porphyrin ring

Answer 11

Fe 2+ ion surrounded gy 4

Question 12

Porphyrin ring

Answer 12

Fe 2+ ion surrounded by 4 N and 2 other bonds

Question 13

5th coordination

Answer 13

His binds to Heme

Question 14

6th coordination

Answer 14

attracts O2 by H-bonds

Question 15

proximal histidine (F8)

Answer 15

binds heme in heme pocket, prevents oxidation of iron atom, 5th coordination

Question 16

distal histidine (E7)

Answer 16

increases O2 binding affinity, lowers affinity for other molecules, increased specificity for O2, 6th coordination

Question 17

O2 binding to myoglobin is a ____ plot and the reaction is ____

Answer 17

hyperbolic, reversible

Question 18

Hemoglobin is a ____ (quaternary structure)

Answer 18

heterotetramer (2a and 2b)

Question 19

3 polypeptides with 8 a-helices

Answer 19

alpha globin, beta globin, myoglobin

Question 20

when proteins are homologous

Answer 20

they have the same ancestor, similar structure, similar function

Question 21

how many O2 bind to Hb

Answer 21

4

Question 22

how many O2 bind to Mb

Answer 22

1

Question 23

Conservative substitutions

Answer 23

minor effects on structure and function

Question 24

critical substitutions

Answer 24

change structure and function

Question 25

Hyperbolic curve

Answer 25

constant affinity (Mb)

Question 26

Sigmoidal curve

Answer 26

cooperative binding affinity (Hb)

Question 27

Cooperatvie binding affinity

Answer 27

affinity changes as more ligand bind

Question 28

Mb vs Hb

Answer 28

similar functions, Mb within tissue,Hb lungs and tissue

Question 29

Tense state

Answer 29

low O2 affinity, deoxy Hb, large central cavity, His between Thr and Pro

Question 30

Relaxed state

Answer 30

high O2 affinity, oxygen Hb, smaller central cavity, His between 2 Thr

Question 31

Effector

Answer 31

alter affinity at other binding sites upon binding

Question 32

Homoallosteric

Answer 32

binding of same compound effects itself

Question 33

Heteroallosteric

Answer 33

binding of different compound affects itself

Question 34

Activator , +

Answer 34

increase binding affinity

Question 35

Inhibitor , -

Answer 35

decrease binding affinity

Question 36

O2 is a ____ activator of Hb

Answer 36

homoallosteric

Question 37

BPG is a ___

Answer 37

heteroallosteric inhibitor

Question 38

H+

Answer 38

heteroallosteric inhibitor

Question 39

Bohr Effect

Answer 39

changes pH to diminish H2O binding | metabolism generates H+ > lowers pH > Side chains protonate > BPG binding enhances

Question 40

Increased BPG =

Answer 40

decreased O2 binding

Question 41

BPG binds in (state)

Answer 41

T-state

Question 42

high pH =

Answer 42

high BPG, low O2

Question 43

why is this important

Answer 43

pH of lungs is low so O2 binding high, pH of tissue is high so O2 released

Question 44

Sickle cell anemia

Answer 44

Glu replaced with Val, critical sub

Question 45

Fetal Hb

Answer 45

higher O2 affinity

Question 46

4 His in central cavity

Answer 46

BPG binding