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Biochem Exam 1 > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

nitric acid (NO)

A

signaling molecule, helps in delivery of oxygen. also causes vasodilation, inhibition of platelet aggression

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2
Q

myoglobin + hemoglobin

A

approx. 10% of total proteins in the body

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3
Q

myoglobin

A

storage of oxygen in the cytosol, mainly in muscle (gives muscle red color) but also in brown fat

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4
Q

hematocrit

A

40-50% blood volume is red blood cells

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5
Q

hemoglobin

A

contained in red blood cells, transports oxygen from the lungs/gills

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6
Q

oxygen transport and storage

A

hemoglobin transports oxygen from the lungs, delivered to tissues, myoglobin stores it for metabolism by mitochondria, CO2 carried back to lungs and expired

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7
Q

nitroglycerin

A

breaks down release nitric oxide, causes vasodilation of vessels and gets rid of chest pain (angina)

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8
Q

bond types in hemoglobin

A

NOT COVALENT BONDS, forces holding bonds together are ionic, hydrophobic interactions, Van der Waals forces

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9
Q

histidine in hemoglobin

A

crucial for F8 and E7 helices

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10
Q

physical characteristics of myoglobin

A

-extremely compact, 70% of the main chain is alpha helical
-8 major helical segments, all right handed, denoted A-H
- interior consists almost entirely of hydrophobic residues such as leucine, valine, methionine, phenylalanine
- the only charged residues inside Mb are two histidines, critical function at the oxygen binding site
- outside of the protein has both polar and non-polar residues

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11
Q

heme

A

prosthetic portion of myoglobin and hemoglobin

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12
Q

ferric iron

A

when ferrous iron becomes oxidized by dissolved oxygen, can no longer bind more oxygen groups once oxidized

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13
Q

ferrous becomes ferric:

A

Hb becomes methemoglobin
Mb becomes metmyoglobin

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14
Q

distal histidine

A

acts as blocker to oxygen, safely allows oxygen to bind weakly and irreversibly so that ferrous iron is not oxygenated

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15
Q

E7 of histidine

A

blocking role; allows oxygen to bind weakly to ferrous iron preventing oxidation

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16
Q

oxygen binding curve for myoglobin

A

has hyperbolic shape, Mb has one oxygen binding site per molecule, O2 pressure at 50% of Mb= 2mmHg

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17
Q

hemoglobin

A
  • 4 polypeptide chains
  • weak non-covalent attractions: electrostatic (ionic), hydrogen bonding, hydrophobic, Van der Waals
  • in concentrated urea solutions, dissociates into alpha-beta dimers, suggesting strongest contacts are between alpha and beta chains
  • adult hemoglobin (HbA1) consists of two alpha chains and two beta chains
    -four oxygen binding sites act in cooperative manner
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17
Q

attractions in hemoglobin

A

electrostatic (ionic), hydrogen bonding, hydrophobic, van der Waals (NO COVALENT)

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18
Q

HbA1

A

adult hemoglobin, consists of two alpha chains and two beta chains

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19
Q

each chain contains a ___ group and a ___ oxygen binding site

A

heme, single

20
Q

amount of oxygen binding sites on hemoglobin

A

four

21
Q

deoxy conformation

A

tense or T conformational state

22
Q

oxy conformation

A

higher O2 affinity, relaxed or R conformational state

23
Q

hemoglobin binding curve

A

sigmoidal due to cooperative nature
- enables hemoglobin to release more oxygen to the tissues that are in more dire need of oxygen

24
Q

percentage of oxygen tissues get from bound hemoglobin at rest

A

21

25
Q

percentage of oxygen tissues get from bound hemoglobin during exercise

A

45

26
Q

binding of the first oxygen molecule to deoxyHb enhances binding of the second molecule by factor of ___

A

3

27
Q

when 3 oxygen molecules are bound to Hb, the remaining oxygen binding site has an affinity for oxygen ___ times that of the fully deoxygenated Hb

A

20

28
Q

progressive loss of oxygen molecules from a fully oxygenated Hb ____ the binding of the remaining molecules of bound oxygen

A

weakens

29
Q

degree of rotation as hemoglobin is oxygenated

A

15 degrees

30
Q

allosteric effect

A

uptake of one ligand by a protein influencing the affinities of remaining unfilled binding sites

31
Q

lowers binding affinity of oxygen

A

hydrogen ions (pH drop), carbon dioxide

32
Q

effects of carbon dioxide on hemoglobin

A

promote the release of oxygen bound to Hb

33
Q

2,3-diphosphoglycerate

A

stabilizes deoxy (T) form of Hb and weakens the affinity of Hb for oxygen in red blood cells

34
Q

bohr effect

A
  • facilitates the delivery of oxygen to rapidly metabolizing tissues where carbon dioxide and lactic acid decrease pH
  • less oxygen a tissue has, the more acidic it becomes. acidity of the tissue allows increase release of oxygen, allowing tissues to receive more oxygen and become less acidic to return to normal state
35
Q

oxygen binding curves for Hb

A

shift to the RIGHT as pH drops

36
Q

haldane effect

A

deoxygenated blood can carry more carbon dioxide

37
Q

bisphosphoglycerate (diphosphoglycerate)

A

-5 charge at pH of 7.4
helps to stabilize deoxy state

38
Q

DPG is ___ when hemoglobin is oxygenated

A

expelled

39
Q

hemoglobin affinity with 2,3-BPG

A
  • hemoglobin in red blood cells lowers the affinity, favors unloading of oxygen to tissues for respiration, leading to the increase of oxygen delivery from 8% (without) to 66%
40
Q

hemoglobin A1

A

principal hemoglobin in adults, consists of two alpha chains and two beta chains

41
Q

hemoglobin F

A

the principal hemoglobin in fetuses, consists of two alpha chains and two gamma chains

42
Q

hemoglobin A2

A

minor hemoblogin at 2% of total = alpha 2 delta 2

43
Q

fetal Hb vs maternal Hb

A
  • fetal Hb has higher affinity for oxygen than maternal Hb
  • fetal hemoglobin is able to take up more oxygen
  • replacement of histidine with serine raies the affinity of fetal hemoglobin, shifting it to the left which favors oxygen loading allowing more oxygen to be delivered to the lungs
44
Q

presence of DPG in fetal Hb

A

oxygen of fetal Hb is higher than that of maternal hemoglobin

45
Q

cooperativity

A

loss of oxygen molecules from fully oxygenated R conformation of Hb, destabilizes the R configuration

46
Q

allosteric effectors

A

H+ (Bohr effect), CO2 (Bohr effect) and DPG act to strengthen the deoxy T conformation (shift curve to the right)

47
Q

strengthening of deoxy conformation (T) shifts binding curve to the right

A

high CO2, high H+, high T degree, low pH, high DPG

48
Q

strengthening of oxy conformation (R) in remaining oxygen binding sites shifts binding curve to the left

A

loss of 2 positive charges on fetal Hb (His to Ser), CO binding Fe2+, Fe2+ to Fe3+ methemoglobin at one site

Biochem Exam 1 (7 decks)

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