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Biochemistry > Chapter 15 > Flashcards

Chapter 15 Flashcards

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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
what is essential to keep the concentrations of some solutes be different inside and outside cells
active transportM
26
more than or equal to 25% of the cell's energy is spent to
maintain the ionic gradient
27
28
The inside of the cell is
negative
29
The outside of the cell is
positive
30
The charge difference in the cell is essential for
conduction of action potentials in neurons
31
Reaction cycle of Na, K-ATPase
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 7. protein conformation changes, exposing K+ binding sites to the cell interior.
32
Secondary active transport
the transporter takes advantage of a gradient already established by another pump
33
endocytosis
cells absorb external material by engulfing it with the cell membrane
34
Na can be found in greater quantities in the
outside of the cell
35
K+ ions can be found in greater value in
the inside of the cell
36
Action potential
depolarization of the membrane potential
37
Myelin sheath do what
propagate action potentials rapidly
38
Electron transport is highly _______ and coupled to _______
exergonic phosphorylation of ATP which is highly endergonic
39
Oxidative phosphorylation is the process by which
ATP is formed as a result of electrons being transferred from NADH or FADH2 to O2 by a series of electron carriers
40
Electron transport drives
the pumping of protons across the inner membrane to the intermembrane space of the mitochondria
41
Electron transport is the result of a
proton gradient
42
proton gradient provides
the energy for phosphorylating ADP to ATP
43
Electron Transport Chain equation
ADP+Pi -> ATP + H2O
44
Goals of the electron transport chain
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
Active transport of H+, driven by electron transfer steps from NADH to O2 forms
a proton gradient
46
The flow of electrons in the electron transport chain is ______ and involves a series of oxidation-reduction reactions
directional
47
How does this directional flow of electrons from one protein complex to the next occur? What determines the direction of electron flow?
Reduction potentials
48
Reference point for reduction potentials is the
hydrogen electrode
49
overview of mitochondrial electron transport
NADH -> NAD+ complex 1 Q Complex III Cytochrome c Complex IV O2 and H2O
50
Complex I transfers electrons from
NADH to ubiquinone four protons from the matrix to the intermembrane space via a proton wire
51
Flavin mononucleotide (FMN) does waht
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
Iron in the iron-sulfur clusters is ____ when it gins an electron
reduced to Fe2+
53
Iron in the iron-sulfur clusters is _____ when it loses an electron
oxidized to Fe3+
54
Iron-sulfur clusters carry how many electrons
one at a time
55
Electrons are passed from iron-sulfur complex to
coenzyme Q
56
Overall net reaction for complex I
NADH + H+ + CoQ -> NAD+ + CoQH2 extremely exergonic
57
Complex II is
succinate dehydrogenase
58
Complex III passes electrons from the
ubiquinol pool to cytochrome c and pumps protons across the membrane
59
The Q cycle- ubiquinol to cytochrome c
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
Net result of the Q cycle
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
Cytochrome oxidase- Complex IV contains
two copper atoms which are involved in electron transport
62
Complex IV does what
transfers electrons from cytochrome c to oxygen
63
The last step of Complex I involves electrons being
passed to coenzyme Q also called ubiquinone when oxidized and ubiquinol when reduced
64
How is the proton gradient used to make ATP?
energizes the membrane with two forms of potential energy- electrical and chemical
65
Chemiosmotic coupling
coupling of oxidation and phosphorylation that converts the electrochemical potential to the chemical energy of ATP
66
ATP synthase is known as the
F0-F1 complex
67
ATP is functionally
separate from the electron transport complexes (I-IV)
68
F0 part of the ATP synthase functions as
a transmembrane channel that permits H+ to flow back into the matrix following its gradient
69
F1 part of ATP synthase does what
catalyzes the reaction ADP+Pi -> ATP+H2O
70
Proton transport through ATP synthase requires
rotation of the c ring past the stationary a subunit
71
ATP Synthase uses what to form what chemical bond
mechanical energy (rotation) the attachment of a phosphoryl group to ADP
72
Three possible conformations for the sites for substrate on ATP synthase
Open Loose binding tight binding
73
Open
a low affinity for substrate
74
loose binding
loosely binds ADP and Pi
75
Tight binding
catalytically active, binds ATP
76
Proton flux converts Loose to _____, which ____
tight produces ATP
77
Proton flux converts Tight to ____, which ____
open releases ATP
78
NADH is oxidized to produce a P/O ratio of
2.5
79
FADH2 is oxidized to form a P/O ratio of
1.5
80
Why does NADH produce a higher ratio than FADH2
oxidation of NADH exports more protons from the matrix than FADH2 and a bigger contribution to the proton gradient
81
Yield of ATP per glucose oxidation
Glucose + 6O2 -> 6H2O + 6CO2 + 30 (32) ATP

Biochemistry (14 decks)

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