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Dental Biochemistry Exam 1 > Hemoglobin/Myglobin, O2 and Enzyme Regulation > Flashcards

Hemoglobin/Myglobin, O2 and Enzyme Regulation Flashcards

hemoglobin, myoglobin and enzyme regulation

1
Q

What are the main functions of myoglobin?

A
  • carry oxygen in muscle cells
  • store oxygen in muscle cells
  • deleiver oxygen to mitochondria
  • binds oxygen at LOW levels
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2
Q

What are the main functions of hemoglobin?

A
  • carry oxygen in the blood
  • binds oxygen in the lungs
  • releases oxygen to the tissues
  • sensitive to small changes in oxygen levels
  • carries CO2 from the tissues to the lungs
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3
Q

Oxygen binds to the _______ of myoglobin and hemoglobin

A

heme group

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4
Q

The heme prosthetic group contains one _______ atom in the center

A

iron (Fe)

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5
Q

oxygen only binds the ________ in the heme

A

reduced iron (Fe2+)

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6
Q

myoglobin has ______ oxygen binding sites

A

one

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7
Q

hemoglobin has _____ oxygen binding sites

A

four

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8
Q

hemoglobin contains ______ polypeptide chains each with a heme capable of binding one O2

A

four

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9
Q

Positive cooperation

A

a form of allostery……once one ligand binds it makes it easier for other ligands to bind

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10
Q

The T state of hemoglobin has a _______ affinity for oxygen

A

LOW

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11
Q

The R state or relaxed state has a _________ affinity for oxygen

A

HIGH

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12
Q

there are ______ salt bridges in the T state than there are in the R state

A

more

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13
Q

hemeoglobin consists of ___ alpha dimers and _____ beta dimers

A

two, two

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14
Q

In the absense of oxygen ______ is out of the heme plane

A

Fe

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15
Q

myoglobin oxygen binding is _________ which means its hill coefficient is =1

A

non-cooperative

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16
Q

hemoglobin oxygen binding is _______ which means its hill coefficient is greater than 1

A

positive-cooperation

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17
Q

homotropic allosteric modifier

A

when an activator or inhibitor molecule binds to the active site

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18
Q

what is an example of a homotropic allosteric modifier?

A

oxygen binding to hemoglobin

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19
Q

heterotrophic allosteric modifiers

A

when an activator or inhibitor molecule DOES NOT bind to the active site…..ligand binding at one site influences ligand binding at a different site

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20
Q

heterotrophic inhibitors stabilize the _____ state of the active site

A

T (low affinity)

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21
Q

heterotrophic activators stabilize the ______ state of the active site

A

R (high affinity)

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22
Q

What are the 3 heterotrophic allosteric modifiers of Hemoglobin?

A

H+, CO2, and 2,3-BPG (they all inhibit O2 binding)

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23
Q

H+ decreases oxygen binding to hemoglobin by stabilizing the hemoglobin ____________ state

A

low affinity T

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24
Q

CO2 decreases oxygen binding to hemoglobin by stabilizing the hemoglobin ____________ state

A

low affinity T

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25
Q

What is the Bohr effect?

A

the effect of pH and CO2 on binding and release of O2 by hemoglobin

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26
Q

2,3-BPG decreases O2 binding to hemoglobin by stabilizing the hemoglobin ____________ state

A

low affinity T

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27
Q

BPG binds at a site _____ from the O2 binding site

A

distant

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28
Q

BPG weakens O2 binding to hemoglobin allowing more ______ to be released to the tissues

A

oxygen

29
Q

Carbon monoxide at the hemoglobin active site has ________ and _______ effects

A

non allosteric and allosteric

30
Q

How does carbon monoxide have non-allosteric effects

A

carbon dioxide competes with oxygen binding at the active site

31
Q

How does carbon monoxide have allosteric effects

A

carbon monoxide bound at the active site increases oxygen binding at the other active site

32
Q

what are the main types of hemoglobin in adults?

A

major adult form (Hb A), Hb F, Hb S (sickle cell)

33
Q

what is sickle cell anemia?

A

a missense mutation in the beta globin gene…..mutation at position 6…… glu to transfer to val which causes abnormally shaped RBC

34
Q

What is the underlying reason sickle cell anemia happenss?

A

in the T conformation, valine 6 on the Hb surface exposes a hydrophobic patch…. forms insoluble fibers on deoxygenation

35
Q

reversible reactions are controlled by changes in ________

A

[substrate]

36
Q

irreversible reactions are _______ regulated

A

enzyme

37
Q

flux is defined as the rate at which the ______ material is converted to the ______ of the pathway

A

starting, products

38
Q

flux through a pathway is ______ faster than the slowest step

A

NEVER

39
Q

The rate limiting step is the _____ step in the pathway

A

slowest

40
Q

enzyme regulated steps are usually ______

A

irreversible

41
Q

feedback regulation is defined as the

A

product of the pathway contrrols its synthesis

42
Q

what is the effect of substrate concentration on enzyme reaction rate?

A
  • when [s] is greater than km, the reaction velocity does NOT change with differences in [s]
  • when [s] is smaller than km, the reaction velocity changes in proportion to [s]
43
Q

Product inhibition occurs when the product of an enzyme is an ______ of that enzyme

A

inhibitor

44
Q

feedback inhibition occurs when the product of a metabolic pathway ________

A

influences its productions

45
Q

Hexokinase has a _____ km and is inhibited by ______

A

LOW, its product glucose-6-phosphatase

46
Q

glucokinase has a ______ km which means that its activity is regulated by the ________

A

high, concentration of glucose

47
Q

glucokinase is a _____

A

glucose sensor

48
Q

What is allostery

A

the process by whichc biological macromolecules transmit the effect of binding at one site to another…… also requires a change in conformation

49
Q

allostery can either result in ________ or _________

A

activation, inhibition

50
Q

cooperativity is defined as

A

binding of a substrate to one active site alters the affinity for substrate at the other active site

51
Q

positive cooperativity is when substrate binding at one active site ______ affinity for substrate at the other active site

A

increases

52
Q

negative cooperativity is when substrate binding at one active site ______ affinity for substrate at the other active site

A

decreases

53
Q

homotropic allosteric modifiers

A

substrates for the active site

54
Q

heterotrophic allosteric modifiers

A

DO NOT bind at the active sites, they are NOT substrates

55
Q

phosphofructokinase-1 incorporates phosphate from ATP into _________ to form ___________

A

fructose-6-phosphate, fructose-1-6-bisphosphate

56
Q

PFK-1 is an _________ modifier

A

allosteric

57
Q

fructose-6-phosphate is an homotropic allosteric activator of _______

A

PFK-1

58
Q

ATP is a substrate and ________ inhibitor of PFK-1

A

heterotropic

59
Q

PFK-1 has two ATP binding sites, one is at the _________ and the other is not at the _________ which stabilizes the low affinity T state for F6P

A

active site

60
Q

Fructose-2,6-bisphosphate activates _______

A

PFK-1

61
Q

F26BP is a heterotrophic _______

A

activator

62
Q

phosphorylation/dephosphorylation of serine, threonine or tyrosine residues is caused by the enzymes called ________

A

kinases

63
Q

Proteolysis that activate a precursor, called _______, by enzymes called proteases

A

zymogen or proenzyme

64
Q

Phosphorylation uses ATP and a protein _______ to transfer a phosphate to the amino acid

A

kinases

65
Q

dephosphorylation uses ADP and a protein _________ to add a phosphate to the amino acid

A

phosphatase

66
Q

AMP is a heterotropic allosteric _______ of glycogen phosphorylase

A

activator

67
Q

The blood clotting cascade is controlled by proteolytic activation of __________

A

inactive proteases (zymogens)

68
Q

prothrombin is an inactive protease that is converted to _______ an active protease by factor XA

A

thrombin

Dental Biochemistry Exam 1 (10 decks)

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