Module 5

Question 1

what is a ligand?

Answer 1

a molecule reversibly bound by the protein

Question 2

what are the 2 ligands of hemoglobin?

Answer 2

1. oxygen
2. 2,3 BPG

Question 3

what is an induced fit?

Answer 3

changes in protein confirmation caused by ligand binding

Question 4

what are the advantages and disadvantages of transition metals?

Answer 4

1. they can bind oxygen
2. but they produce free radicals

Question 5

is o2 soluble in aqueous solutions?

Answer 5

very little

Question 6

what amount of oxygen that can be delivered within the organism can limit…

Answer 6

its size

Question 7

what is myoglobin

Answer 7

monomeric molecule that facilitates oxygen storage in peripheral tissue

Question 8

where is myoglobin found?

Answer 8

in muscles

Question 9

myoglobin tertiary structure

Answer 9

binds 1 o2 with high affinity

Question 10

is myoglobin’s curve closer to y or x axis

Answer 10

y axis bc it has higher affinity

Question 11

what is hemoglobin?

Answer 11

tetrametic protein that transports O2 from lungs to the periphery

Question 12

where is hemoglobin found?

Answer 12

in red blood cells

Question 13

what structure does hemoglobin represent?

Answer 13

quaternary structure that transports O2 with lower affinity

Question 14

how many O2 molecules can hemoglobin bind to?

Answer 14

4

Question 15

what shape of curve does hemoglobin represent?

Answer 15

sigmoidal (S shaped)

Question 16

what is a heme group?

Answer 16

cellular iron that makes it less reactive

Question 17

what does a heme group consist of?

Answer 17

protoporphyrin ring system bound to a single iron atom

Question 18

what do both myglobin and hemoglobin use to enable O2 binding?

Answer 18

a heme group

Question 19

what is the 6th position in heme group?

Answer 19

position for O2 binding

Question 20

what does distal histidine do?

Answer 20

provides a stabilizing interaction for bound O2

Question 21

what is the myoglobin structure?

Answer 21

small globular protein consisting of single polypeptide and a heme group

Question 22

what is the equation for fraction saturation?

Answer 22

[PO2] / [PO2] + [P50]

Question 23

what value is PO2 in the lungs?

Answer 23

100 torr

Question 24

what is the value of PO2 in the periphery?

Answer 24

20 torr

Question 25

what is an allosteric protein?

Answer 25

can adopt 2 different conformations

Question 26

what 2 confirmations can allosteric proteins form?

Answer 26

T & R states

Question 27

what is the T state of an allosteric protein?

Answer 27

inactive state (deoxyhemoglobin)

Question 28

what is the R state of an allosteric protein?

Answer 28

active state, always increasing hemoglobin's affinity for O2

Question 29

what are allosteric modulators?

Answer 29

small molecules that can bind to a proton and influence the equilibrium between T & R states

Question 30

what do allosteric activators do?

Answer 30

stabilize the R state & speed things up

Question 31

what do allosteric inhibitors do?

Answer 31

stabilize the T state & slow things down

Question 32

what does homotropic mean?

Answer 32

when ligand & modulator are the same

Question 33

what does heterotropic mean?

Answer 33

when ligand and modulator are different

Question 34

what 2 things does O2 serve as?

Answer 34

1. ligand 2. allosteric molecule

Question 35

how are the binding & release of O2 regulated?

Answer 35

allosterically

Question 36

what is the position of the iron atom at the T state?

Answer 36

outside heme ring

Question 37

what is the position of the iron atom in the R state?

Answer 37

inside heme ring

Question 38

what is the purpose of 2,3 BPG?

Answer 38

to decrease hemoglobin's affinity for O2

Question 39

how many units of negative charge does 2,3 BPG have?

Answer 39

5

Question 40

true or false: fetal hemoglobin has a higher affinity for O2than maternal hemoglobin

Answer 40

true because bc of less positive charge

Question 41

what is the 1 amino acid difference between fetal and maternal hemoglobin?

Answer 41

HIS 143 is replaced by SER

Question 42

what does affinity mean?

Answer 42

attraction

Question 43

what is the Bohr effect?

Answer 43

lower pH= decreased hemoglobin affinity for O2

Question 44

what is the purpose of the Bohr effect?

Answer 44

to coordinate increased release of O2 to tissues

Question 45

what occurs in mechanism 1?

Answer 45

CO2 is taken up into red blood cells & converted to bicarbonate

Question 46

what enzyme is used in mechanism 1?

Answer 46

carbonic anhydrase

Question 47

what occurs in mechanism 2?

Answer 47

CO2 can form a covalent linkage to the N terminus to form carbaminohemoglobin

Question 48

does carbamino hemoglobin or hemoglobin have a lower O2 affinity?

Answer 48

carbamino

Question 49

what is sickle cell anemia?

Answer 49

disease of hemoglobin that causes red blood cells to sickle

Question 50

what happens in the T state of sickle cell anemia?

Answer 50

hemoglobins link together

Question 51

what causes red blood cells to sickle?

Answer 51

the fibers

Question 52

where is sickle cell anemia higher?

Answer 52

in areas where malaria is present

Question 53

why is sickle cell anemia increased in areas with malaria?

Answer 53

bc infection decreases red blood cell pH

Question 54

what is hemocyanin?

Answer 54

uses copper rather than iron to transport oxygen

Question 55

is there a heme group in hemocyanin?

Answer 55

no

Question 56

how many copper atoms bind to 1 O2 molecule in hemocyanin?

Answer 56

2

Question 57

Hemoglobin weighs ( ) times as much as myoglobin

Answer 57

4

Question 58

O2 serves as a ( ) for hemoglobin

Answer 58

homotropic allosteric activator

Question 59

2,3 BPG acts as a ( ) for hemoglobin

Answer 59

heterotropic allosteric inhibitor