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biochem > ch 15 part 2 > Flashcards

ch 15 part 2 Flashcards

1
Q

what amino acids can be phosphorylated

A

Ser Thr and Tyr

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2
Q

at normal blood ph 7.4, what charge does a phosphorylated AA have?

A

-1 charge

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3
Q

at normal blood ph 2.1, what charge does a phosphorylated AA have?

A

-2 charge

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4
Q

what kind of enzyme is glycogen phosphorylase

A

a hydrolase enzyme

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5
Q

how does glycogen phosphorylase get activated

A

by adding a phosphate group to it

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6
Q

what does glycogen phosphorylase do

A

it cleaves branches pieces of glucose on glycogen through hydrolysis

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7
Q

what does glycogen synthase do

A

it creates more glycogen

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8
Q

how is glycogen synthase activated

A

by removing a phosphate group

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9
Q

step one of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. hormones (epinephrine or glucagon) will bind to a membrane receptor and this will release a G protein that binds and activates adenylate cyclase which is a transmembrane enzyme.
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10
Q

what hormones start the pathway for glycogen phosphorylase

A

epinephrine or glucagon

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11
Q

step two of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. adenylate cyclase will catalyze the cyclization of ATP to cyclic AMP or cAMP
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12
Q

step three of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. cAMP binds to the regulatory units in Protein kinase A making PKA active
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13
Q

step four of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. PKA activates a kinase by phosphorylation
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14
Q

step five of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. active kinase activates glycogen phosphorylase also by phosphorylation
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15
Q

step six of the pathway in which enzymes/proteins result the phosphorylation of glycogen phosphorylase

A
  1. glycogen phosphorylase catalyzes the hydrolysis of glycogen to glucose
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16
Q

what enzyme makes cAMP

A

adenylate cyclase

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17
Q

Protein kinase A regulates what two enzymes

A

GP and GS

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18
Q

how does PKA make phosphorylase kinase active

A

adding phosphate group

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19
Q

how does PKA make GS inactive

A

adding phosphate group

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20
Q

what occurs when you phosphorylate both GS and GP

A

GS becomes inactive and GP becomes active to cleave glucose units

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21
Q

why does PKA phosphorylate both GS and GP

A

GS is phosphorylated to become inactive and GP comes active after adding the phosphate group. this occurs so that GS doesnt make more glycogen when GP is trying to break it down to use it for energy.

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22
Q

what hormone activates GP

A

glucagon or epinephrine

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23
Q

what hormone activates GS

A

insulin

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24
Q

what is mechanism of action for GP and GS

A

MOA is phosphorylation of GP and dephosphorylation of GS

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25
Q

how does insulin activate GS

A

it activates phosphatases which deactivates GP by removing group and activates GS by this form

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26
Q

predict if these alterations would increase/decrease/ not change the amount of glycogen in the liver:
mutation of ser to ala in GP

A

decrease because we can only phosphorylate -OH groups and Ala is neutral and doesnt have -OH group

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27
Q

predict if these alterations would increase/decrease/ not change the amount of glycogen in the liver:
addition of epinephrine

A

increase because this is the starting hormone for this pathway

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28
Q

predict if these alterations would increase/decrease/ not change the amount of glycogen in the liver:
mutation that causes adenyl cyclase to always be active

A

increase because it no longer need hormones to start it so its active all the time

29
Q

predict if these alterations would increase/decrease/ not change the amount of glycogen in the liver:
serine to Thr in GP

A

no change because both have -OH group

30
Q

what are the two inhibitors of GP

A

insulin, increase ATP, and increase glucose 6 phosphate are all negative heterotropic effectors deactivating GP

31
Q

what is an activator for GP

A

Amp is a positive heterotropic effector of GP because it uses AMP not ATP

32
Q

what are the 3 main characteristics of myoglobin

A
  1. stores oxygen at the tissue level 2. its a single peptide chain 3. obeys michaelis menten kinetics
33
Q

what are the 5 main characteristics of hemoglobin

A
  1. its job is to bind to O2 at the lungs 2. transports O2 3. 4 polypeptide chains 4. allosteric enzyme 5. has cooperativity
34
Q

what do inhibitors do to hemoglobin

A

it forces the hemoglobin to release oxygen to the tissues

35
Q

what are inhibitors to hemoglobin

A

CO2 and low PH causing high acidity

36
Q

what are the five atoms (molecule/ligand) coordinated with the iron in the heme group in deoxygenated hemoglobin

A

-4 nitrogens on pyrrole rings -nitrogen on the proximal histidine

37
Q

what are the six atoms (molecule/ligand) coordinated with the iron in the heme group in oxygenated hemoglobin

A

-4 nitrogens on pyrrole rings - 1 nitrogen on the proximal histidine -O2 when oxygenated

38
Q

true or false: Hemoglobin is a tetramer while myoglobin is a monomer

A

True

39
Q

true or false: hemoglobin exhibits a sigmoidal (S curve) while myoglobin exhibits a hyperbolic curve

A

True

40
Q

true or false: hemoglobin exhibits O2 binding cooperativity while myoglobin does not

A

True

41
Q

true or false: hemoglobin exhibits lower degree of O2 saturation at all physiologically relevent partial pressures of O2 than does myoglobin does

A

True

42
Q

from a physical standpoint, how does binding of one O2 ligand impacts the interactions between Hb subunits resulting in positive cooperativity

A

O2 (the sixth ligand) binds, then pulls on the Fe2+, which causes the heme to flatten, which then causes the proximal His to be pulled, this changes the shape of the subunits all around

43
Q

explain from a thermodynamic standpoint, the nature of + cooperativity of O2 binding to hemoglobin (why does the binding affinity increase when one or more O2 molecules are already bound.

A

it makes the other parts of the protein go into the R state making it more readily available to bind with other O2 molecules

44
Q

why would a person with CO poisoning be places in an oxygen tent

A

CO is a competitive inhibitor of Oxygen so you need to overpower its high affinity with substrate concentration to outcompete the CO.

45
Q

given that small amounts of CO will kill a person, which has a lower P50 CO or O2

A

CO has a lower KM due to it having a higher affinity to hemoglobin

46
Q

considering R to T equilibrium, how does the equilibrium shift when O2 binds to Hb

A

moves to R<—T

47
Q

considering R to T equilibrium, how does the equilibrium shift when H+ hinds to Hb

A

moves to T<—R because remember low pH means high acidity which is an inhibitor

48
Q

how does the binding of H+ affect the release of O2 by HB

A

the distal His pulls on the O2 more strongly so that the O2 pops out and is no longer a ligand

49
Q

what effect does alkalemia (ph increase) due to hyperventilation have on the oxygen binding affinity of hemoglobin

A

P50 decreases and oxygen affinity increases

50
Q

what is 2,3 BPG

A

allosteric inhibitor of Hemoglobin, lowers O2 affinity

51
Q

where does 2,3 BPG bind in HB? How does the binding occur?

A

allosteric site is the central cavity and the binding occurs by the (-) part of the 2,3 BPG attraction to the (+) nitrogen of His and Lys

52
Q

what increases the production of 2,3 BPG

A

low PH acidic conditions

53
Q

what is a short term adaption to high altitude and low O2 conc? long term?

A

increase the inhibitor to release O2. long term: more red blood cells

54
Q

what happens if a mutation changes Lys to val in the allosteric site

A

2,3 BPG will not bind at the allosteric site as tightly due to difference in charge which causes the release of O2

55
Q

what is different between fetal Hb and adult Hb

A

fetal Hb has Ser instead of Lys which causes it to have a higher affinity of O2

56
Q

O2 is what kind of effector

A

positive homotropic effector

57
Q

Co2, H+, and 2,3 BPG are what kind of effector

A

negative heterotropic effectors

58
Q

what disease causes children to not be able to turn their fetal hemoglobin to adult hemoglobin

A

thalassemia (Hb binding to O2 TOO tighetly)

59
Q

in adults, fetal hemoglobin production can be reactivated pharmacologically which is useful in what disease?

A

sickle cell anemia, O2 doesnt bind well to Hb here

60
Q

explain why Hb S molecules aggregate into long chainlike polymeric structures

A

a single AA substitution in the B chains of HB causes sickle cell anemia (Glu is replaced by val which protrudes and fits into the EF pocket of another Hb S molecule. The val side chain acts like a hook as it protrudes out and causes the red blood cells to be sticky as well.

61
Q

the oxygen dissociation curve for hemoglobin reflects allosteric effects that result from the interaction of Hemoglobin with O2, Co2, H+, and 2,3 BPG. all of the following structural changes occur in the hemoglobin molecules when O2, CO2, H+, and 2,3-BPG bind except: T or F
The binding of O2 pulls the iron into the plane of the heme and causes a change in the interaction of all four globin subunits, mediated through His F8

A

True

62
Q

the oxygen dissociation curve for hemoglobin reflects allosteric effects that result from the interaction of Hemoglobin with O2, Co2, H+, and 2,3 BPG. all of the following structural changes occur in the hemoglobin molecules when O2, CO2, H+, and 2,3-BPG bind except:
2,3-BPG binds at a single site between the four globin subunits in deoxyhemoglobin and
stabilizes the deoxyhemoglobin form by cross-linking the beta subunits.

A

True

63
Q

the oxygen dissociation curve for hemoglobin reflects allosteric effects that result from the interaction of Hemoglobin with O2, Co2, H+, and 2,3 BPG. all of the following structural changes occur in the hemoglobin molecules when O2, CO2, H+, and 2,3-BPG bind except:
The deoxy form of hemoglobin has a greater affinity for H+ because the molecular environment of His and the alpha-NH2 groups of the chains changes, rendering these groups less
acidic when O2 is released

A

True

64
Q

The oxygen dissociation curve for hemoglobin reflects allosteric effects that result from the interaction of hemoglobin with O2, CO2, H+, and 2,3-BPG. All of the following structural changes
occur in the hemoglobin molecules when O2, CO2, H+, and 2,3-BPG bind except:
the binding of CO2 stabilizes the oxy form of hemoglobin

A

False

65
Q

adult hemoglobin has what charge residue

A

positive charge

66
Q

hemoglobin inhibitor has what charge residue

A

negative charge

67
Q

fetal hemoglobin has what charge

A

neutral

68
Q

why is it so hard for an inhibitor to make fetal hemoglobin release oxygen to tissues

A

because the inhibitor is negative and the fetal Hb is neutral so theres no attraction like adult Hb that has a positive charge

69
Q

what amino acid does HbA have? HbF?

A

HbA has His and HbF has Serine

biochem (9 decks)

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