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Biochemistry > Chapter 15 > Flashcards

Chapter 15 Flashcards

1
Q

Lipid asymmetry is maintained by

A

enzymes

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2
Q

Two classes of vitamins

A

lipid-soluble
water-soluble

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3
Q

Function of Vitamin A

A

site of the primary photochemical reaction in vision

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4
Q

Function of Vitamin D

A

regulates calcium metabolism

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5
Q

Function of Vitamin E

A

serves as an antioxidant; necessary for reproduction in rats and may be necessary for reproduction in humans

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6
Q

Function of Vitamin K

A

regulatory function in blood clotting

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7
Q

Two modes of passage across the membrane

A

passive and active

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8
Q

Passive transport

A

does not require energy input
diffuse according to the concentration gradient

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9
Q

Active transport

A

always requires the input of energy
always requires a transporter protein

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10
Q

Two types of passive transport

A

simple diffusion
facilitated diffusion

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11
Q

Simple diffusion

A

solute diffuses through the bilayer or through a static protein channel

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12
Q

Facilitated Diffusion

A

works kind of like an enzyme
1. solute binds to transporter
2. conformational change brings the solute across the membrane
3. Reverse protein conformational change resets the transporter for another round of transport

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13
Q

water specific porin

A

Aquaporin

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14
Q

How does water-specificity of an aquaporin work

A

each subunit contains a small pore
lined with hydrophobic residues except for two asparagine side chains
these asparagine side chains attract water and disrupt hydrogen-bonded chain of water molecules
prevents proton transport across the membrane

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15
Q

Ion channels

A

proteins that provide a hydrophilic route through the greasy bilayer

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16
Q

K+ channel selectivity filter

A

pore narrows and four polypeptide backbones fold so their carbonyl groups project into the pore
carbonyl oxygen atoms arranged with geometry suitable for coordinating desolvated K+ ions
desolvate Na+ is too big

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17
Q

facilitated diffusion

A

passive transport
solute binds to a membrane protein changes shape so that the transported molecule is released on the other side of the membrane

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18
Q

Glucose transporters are what type of diffusion

A

facilitated diffusion

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19
Q

Transporter proteins act like

A

enzymes
- accelerate the rate at which a substance crosses the membrane
- can be saturated by high concentrations of their substrate
- susceptible to competitive and other types of inhibition

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20
Q

GLUT transporter has a

A

glucose binding site that alternately faces the cell exterior and interior

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21
Q

Conformations of GLUT proteins

A

12 membrane-spanning alpha helices arranged in two domains
two conformational states are in equilibrium- can move glucose in either direction

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22
Q

Uniporter

A

transports one substance

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23
Q

Symporter

A

two substances moved in the same direction

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24
Q

Antiporter

A

two substances moved in the opposite direction

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25
Q

what is essential to keep the concentrations of some solutes be different inside and outside cells

A

active transportM

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26
Q

more than or equal to 25% of the cell’s energy is spent to

A

maintain the ionic gradient

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27
Q
A
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28
Q

The inside of the cell is

A

negative

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29
Q

The outside of the cell is

A

positive

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30
Q

The charge difference in the cell is essential for

A

conduction of action potentials in neurons

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31
Q

Reaction cycle of Na, K-ATPase

A
  1. 3 intracellular Na+ ions bind
  2. ATP binds
  3. phosphoryl group transferred from ATP to Asp side chain of the pump. ADP is released
  4. protein conformation changes, exposing the Na+ binding sites to the cell exterior
    5.two extracellular K+ ions bind
    6.aspartyl phosphate group is hydrolyzed
  5. protein conformation changes, exposing K+ binding sites to the cell interior.
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32
Q

Secondary active transport

A

the transporter takes advantage of a gradient already established by another pump

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33
Q

endocytosis

A

cells absorb external material by engulfing it with the cell membrane

34
Q

Na can be found in greater quantities in the

A

outside of the cell

35
Q

K+ ions can be found in greater value in

A

the inside of the cell

36
Q

Action potential

A

depolarization of the membrane potential

37
Q

Myelin sheath do what

A

propagate action potentials rapidly

38
Q

Electron transport is highly _______ and coupled to _______

A

exergonic
phosphorylation of ATP which is highly endergonic

39
Q

Oxidative phosphorylation is the process by which

A

ATP is formed as a result of electrons being transferred from NADH or FADH2 to O2 by a series of electron carriers

40
Q

Electron transport drives

A

the pumping of protons across the inner membrane to the intermembrane space of the mitochondria

41
Q

Electron transport is the result of a

A

proton gradient

42
Q

proton gradient provides

A

the energy for phosphorylating ADP to ATP

43
Q

Electron Transport Chain equation

A

ADP+Pi -> ATP + H2O

44
Q

Goals of the electron transport chain

A

transport protons from the matrix across the inner membrane of the mitochondria

creates a higher concentration of protons outside the matrix and in the intermembrane space

45
Q

Active transport of H+, driven by electron transfer steps from NADH to O2 forms

A

a proton gradient

46
Q

The flow of electrons in the electron transport chain is ______ and involves a series of oxidation-reduction reactions

A

directional

47
Q

How does this directional flow of electrons from one protein complex to the next occur?
What determines the direction of electron flow?

A

Reduction potentials

48
Q

Reference point for reduction potentials is the

A

hydrogen electrode

49
Q

overview of mitochondrial electron transport

A

NADH -> NAD+
complex 1
Q
Complex III
Cytochrome c
Complex IV
O2 and H2O

50
Q

Complex I transfers electrons from

A

NADH to ubiquinone
four protons from the matrix to the intermembrane space via a proton wire

51
Q

Flavin mononucleotide (FMN) does waht

A

picks up the first two electrons donated by NADH near the far end of the complex I arm
then they are transferred one at a time to an iron-sulfur cluster

52
Q

Iron in the iron-sulfur clusters is ____ when it gins an electron

A

reduced to Fe2+

53
Q

Iron in the iron-sulfur clusters is _____ when it loses an electron

A

oxidized to Fe3+

54
Q

Iron-sulfur clusters carry how many electrons

A

one at a time

55
Q

Electrons are passed from iron-sulfur complex to

A

coenzyme Q

56
Q

Overall net reaction for complex I

A

NADH + H+ + CoQ -> NAD+ + CoQH2
extremely exergonic

57
Q

Complex II is

A

succinate dehydrogenase

58
Q

Complex III passes electrons from the

A

ubiquinol pool to cytochrome c and pumps protons across the membrane

59
Q

The Q cycle- ubiquinol to cytochrome c

A
  1. QH2 donates one electron to the iron-sulfur protein- electron travels to cytochrome C1 and then cytochrome c
  2. QH2 donates other electron to cytochrome b- two protons are released
  3. oxidized ubiquinone diffuses to another quinone binding site- accepts electron from cytochrome b- half reduced semiquinone
    SECOND ROUND
  4. second QH2 surrenders its two electrons to complex III and two protons to the intermediate space- one electron goes to cytochrome c
  5. other electron goes to cytochrome b and then to the waiting semiquinone produced in the first part of the cycle- regenerates QH2
60
Q

Net result of the Q cycle

A

two electrons from QH2 reduced two molecules of cytochrome c
four protons are translocated to intermembrane space- two from QH2 in the first round of the Q cycle and two from QH2 in the second round

61
Q

Cytochrome oxidase- Complex IV contains

A

two copper atoms which are involved in electron transport

62
Q

Complex IV does what

A

transfers electrons from cytochrome c to oxygen

63
Q

The last step of Complex I involves electrons being

A

passed to coenzyme Q
also called ubiquinone when oxidized and ubiquinol when reduced

64
Q

How is the proton gradient used to make ATP?

A

energizes the membrane with two forms of potential energy- electrical and chemical

65
Q

Chemiosmotic coupling

A

coupling of oxidation and phosphorylation that converts the electrochemical potential to the chemical energy of ATP

66
Q

ATP synthase is known as the

A

F0-F1 complex

67
Q

ATP is functionally

A

separate from the electron transport complexes (I-IV)

68
Q

F0 part of the ATP synthase functions as

A

a transmembrane channel that permits H+ to flow back into the matrix following its gradient

69
Q

F1 part of ATP synthase does what

A

catalyzes the reaction
ADP+Pi -> ATP+H2O

70
Q

Proton transport through ATP synthase requires

A

rotation of the c ring past the stationary a subunit

71
Q

ATP Synthase uses what to form what chemical bond

A

mechanical energy (rotation)
the attachment of a phosphoryl group to ADP

72
Q

Three possible conformations for the sites for substrate on ATP synthase

A

Open
Loose binding
tight binding

73
Q

Open

A

a low affinity for substrate

74
Q

loose binding

A

loosely binds ADP and Pi

75
Q

Tight binding

A

catalytically active, binds ATP

76
Q

Proton flux converts Loose to _____, which ____

A

tight
produces ATP

77
Q

Proton flux converts Tight to ____, which ____

A

open
releases ATP

78
Q

NADH is oxidized to produce a P/O ratio of

A

2.5

79
Q

FADH2 is oxidized to form a P/O ratio of

A

1.5

80
Q

Why does NADH produce a higher ratio than FADH2

A

oxidation of NADH exports more protons from the matrix than FADH2 and a bigger contribution to the proton gradient

81
Q

Yield of ATP per glucose oxidation

A

Glucose + 6O2 -> 6H2O + 6CO2 + 30 (32) ATP

Biochemistry (14 decks)

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