Chapter 18: Electron Transport Chain and Oxidative Phosphorylation

Question 1

Free energy via a proton gradient drives the synthesis of ATP from ADP and Pi via:

a) Oxidative phosphorylation
b) Substrate level phosphorylation

Answer 1

a.

Question 2

T/F the inner mitochondria membrane separating the matrix from the intermembrane space is impermeable to almost everything, including protons and OH.

Answer 2

True.

Question 3

T/F outermembrane of the mitochondria is permeable to many things, excluding items such as acetyl coA, oxaloacetate or NADH and large proteins

Answer 3

True.

Question 4

the ETC ____ NADH and FADH2 to ____ O2 into H2O. The redox energy is used to ____ out of the ____ and into the ____, forming an electrochemical gradient.

Answer 4

the ETC OXIDIZES NADH and FADH2 to REDUCE O2 into H2O. The redox energy is used to PUMP PROTONS out of the MATRIX and into the INTERMEMBRANE SPACE, forming an electrochemical gradient.

Question 5

What’re the 2 main shuttle systems of NADH?

Answer 5

1) the malate aspartate shuttle

2) the glycerophosphate shuttle.

Question 6

the malate-aspartate shuttle pushes ____ from the inner membrane space, past the impermeable inner mitochondrial membrane into the _____

Answer 6

the malate-aspartate shuttle pushes NADH (in the form of malate) from the inner membrane space, past the impermeable inner mitochondrial membrane into the MATRIX

Question 7

Draw the Malate Aspartate shuttle

Answer 7

refer to notes

Question 8

What’re the 2 transporters of the Malate Aspartate shuttle

Answer 8

malate-alphaketoglutarate transporter, and the glutamate-aspartate transporter

Question 9

in the malate-aspartate shuttle, malate crosses from the ____ to the ___ of the mitochondria, and aspartate is created in the ____ and is transported to the _____.

Answer 9

in the malate-aspartate shuttle, malate crosses from the INNER MEMBRANE to the MATRIX of the mitochondria, and aspartate is created in the MATRIXand is transported to the INNER MEMBRANE.

Question 10

T/F: Cells that use the glycerophosphate Shuttle as a method of transporting NADH across the inner membrane of the mitochondria get one less ATP per glucose than cells using the malate-aspartate shuttle. Why or Why not?

Answer 10

True. Because the glycerophosphate shuttle creates FADH2 in the matrix, instead of NADH. FADH2 is less energetic than NADH, in the sense that FADH2 is worth 1.5 ATP, and NADH is worth 2.5 ATP, THUS 1 ATP LESS.

Question 11

Draw the glycerophosphate shuttle system

Answer 11

refer to notes

Question 12

the more positive the reduction potential, the _____ the liklihood of the compound having a higher affinity for electrons.

Answer 12

the more positive the reduction potential, the higher the likelihood of the compound having a higher affinity for electrons.
the more positive the potential, the greater the species’ affinity for electrons and tendency to be reduced.

Question 13

FAD+ had a redox potential of -0.219V, and NAD+ has a redox potential of -0.315 V(more negative). Is NADH of FADH2 a stronger reducing agent? Why?

Answer 13

the standard reduction potential for FAD is less negative than for NAD+ (-0.219 vs. -0.315 V). This means that NADH has a more positive oxidation potential (+0.315) and hence is a better reducing agent (will donate more electrons) than FADH2, thus yields more energy when it coughs up its electrons, resulting in greater ATP production.

Question 14

A solution with a higher (more positive) reduction potential than the new species will have a tendency to _____ electrons from the new species (i.e. to be reduced by oxidizing the new species) and a solution with a lower (more negative) reduction potential will have a tendency to ____ electrons to the new species (i.e. to be oxidized by reducing the new species).

Answer 14

A solution with a higher (more positive) reduction potential than the new species will have a tendency to GAIN electrons from the new species (i.e. to be reduced by oxidizing the new species) and a solution with a lower (more negative) reduction potential will have a tendency to LOSE electrons to the new species (i.e. to be oxidized by reducing the new species).

Question 15

What is the adenine nucleotide translocase antiporter (ANT). How is it facilitated? What 3 transporters are involved?

Answer 15

a shuttle in the inner mitochondrial membrane that transports ATP OUT OF THE MATRIX, while bringing ADP INTO THE MATRIX. It’s run by using the mitochondrial electrochemical gradient.

1) adenine nucleotide translocase antiporter
2) ATP synthase
3) phosphate translocase symporter

Question 16

Draw the Adenine Nucleotide Translocase Antiporter system

Answer 16

refer to notes

Question 17

T/F the protein complexes in the electron transport chains have higher and higher affinities for e-.

Answer 17

True.

Recall; FADH2 does not release its electrons as well as NADH and has a lower energy level. This means that the it needs to drop off its electrons at further points of the ETC where the proteins have such high electron affinities (want to be reduced) that the FADH2 can give its electrons (oxidize).

Question 18

electrons from NADH are carried from complex 1 to complex 3 by ____

Answer 18

coenzyme Q

Question 19

electrons are carried from Complex 3 to complex 4 by ____

Answer 19

cytochrome c

Question 20

Ubiquinone can carry ____ electrons, where as cytochrome c carries ___ electrons

Answer 20

Ubiquinone can carry 2 electrons, where as cytochrome c carries 1 electron.

Question 21

Complex 2 accepts electrons from ____, as is getting converted into _____

Answer 21

Complex 2 accepts electrons from succinate, as it gets converted into fumarate.

Question 22

Where is ubiquinone located?

Answer 22

in the intermembrane bilayer

Question 23

Where is cytochrome c located

Answer 23

in the intermembrane space.

Question 24

complex 1 pumps out ___ protons into the inner membrane space

Answer 24

pumps 4 protons

Question 25

T/F: CoQ acts as a “collection point for all electrons” and collects electrons from both NADH or succinate

Answer 25

True. collects electrons from both protein 1 and protein 2

Question 26

in terms of proton pumping, why is FADH2 worth less electrons than NADH?

Answer 26

no proton pumping occurs in complex 2 and there is less of a contribution to redox energy (less of a difference in redox potentials). This makes FADH2 worth less ATP.

The electron transport chain is made of carrier molecules assembled into 3 protein complexes, and the passage of an electron through each complex generates enough energy to make roughly 1 ATP per complex. NADH enters the cycle at the first complex, so NADH produces 3 ATP. FADH2 enters the cycle at the 2nd complex, thus generating 2 ATP. (because less protons are pumped across since it bypasses the first complex)

(recall; roughly 3 atps needed to make 1 atp).

Question 27

how many oxidations of cytochrome c is needed in order to reduce O2 into H2O

Answer 27

4 cycles of cytochrome c oxidations, because cytochrome c carries 1 electron at a time.

Question 28

under standard conditions, what is the expected concentrations of all products and reactants?

Answer 28

1 molar, therefore, Q =1

Question 29

Which is the irreversible step of the electron transport chain?

Answer 29

when complex 4 uses the electrons donated by cytochrome C in order to reduce oxygen into O2.

Question 30

Define the chemiosmotic theory

Answer 30

when free energy from electron transport is conserved by pumping hydrogen from the mitchondrial matrix to the intermembrane space to create an electrochemical proton gradient across the inner mitochondrial membrane. The electrochemical potential of this gradient is harnessed to synthesize ATP.

Question 31

How does brown adipose tissue create heat?

Answer 31

has a transporter to allow H+ back into the mitochondria without coupling it to ATP synthesis.
Energy held in the proton concentration gradient made by the NADH, FADH2 etc. becomes heat instead and is used to warm the organism.

Question 32

What step in complex 1 provides the most energy?

Answer 32

the second step, when Q gets reduced to QH2, which pumps 4 protons out of the matrix, resulting in energy being created via a proton concentration gradient.

Question 33

in the glycerophosphate system, NADH gets ___ in the cytosol by DHAP.

Answer 33

NADH gets oxidized by DHAP, which turns into glycerol 3 phosphate. the electrons are then given to FAD+ in the mito membrane, turning into FADH2.

Question 34

draw the krebs cycle

Answer 34

refer to notes

Question 35

Which of the following compounds can not cross the inner mitochondrial membrane (without first being converted into something else)?

a. pyruvate
b. malate
c. citrate
d. oxaloacetate
e. aspartate

Answer 35

d) oxaloacetate. the others can cross the membrane because there are transporters for them.