Chapter 20: ETC and Chapter 21: Proton-Motive Force

Question 1

Oxidative phosphorylation takes place in _______ and is the major source of _______.

Answer 1

Mitochondria

Energy for aerobic organisms

Question 2

How much ATP is generated from oxidative phosphorylation?

Answer 2

26 ATP

Question 3

Electrons flow from NADH and FADH₂ to O₂ in the ________.

Answer 3

Electron-transport chain or respiratory chain

Question 4

The electron flow generates a…

Answer 4

Proton gradient that powers ATP synthesis

Question 5

Collectively, the citric acid cycle and oxidative phosphorylation are called…

Answer 5

Cellular respiration

Question 6

Outer mitochondrial membrane is ______ while inner mitochondrial membrane is ______.

Answer 6

Outer - permeable

Inner - impermeable

Question 7

A negative redox potential means that a molecule has…

Answer 7

Lower affinity for electrons compared to H2

Question 8

A positive redox potential means, the molecule has…

Answer 8

A higher affinity for electrons

Question 9

A measure of a molecule’s tendency to donate or accept electrons

Answer 9

Redox potential

Question 10

Only 3 of the 4 protein complexes pump protons. They are…

Answer 10

• NADH-Q oxidoreductase (Complex I)
• Q-cytochrome c oxidoreductase (Complex III)
• Cytochrome c oxidase (Complex IV)

Question 11

The complex that is not a proton pump is called:

Answer 11

Succinate Q-reductase (Complex II)

Question 12

These complexes appear to be associated with one another in what is called the _______.

Answer 12

Respirasome

Question 13

What are the 2 mobile electron carriers?

Answer 13

• Ubiquinone (coenzyme Q or Q)
• Cytocrome C

Question 14

How many protons are simultaneously pumped out of the mitochondria by Complex I?

Answer 14

Four

Question 15

Complex III electron transfer is coupled to the pumping of ______.

Answer 15

Two protons from the matrix

Question 16

Cytochrome c oxidase pumps _______ from matrix to cytoplasmic side

Answer 16

Four protons

(This reaction requires oxygen)

Question 17

The cytochrome c oxidase complex catalyzes the reduction of molecular oxygen. During this catalysis small amounts of superoxide anions and hydrogen peroxide are released. These are called…

Answer 17

• Reactive oxygen species or ROS.
• ROS are harmful for cells.
• The cells developed mechanisms to deal with ROS .

Question 18

What % of oxygen molecules consumed by mitochondria are converted into superoxide ions?

Answer 18

2-4%

Question 19

What two enzymes protect against ROS damage?

Answer 19

Superoxide dismutase and catalase

Question 20

_________ converts superoxide radicals to hydrogen peroxide and water.

Answer 20

Superoxide dismutase

Question 21

______ converts hydrogen peroxide into water and oxygen

Answer 21

Catalase

Question 22

What is the chemiosmotic theory?

Answer 22

Electron transport and ATP synthesis are coupled by a proton gradient across the inner mitochondrial membrane

*ATP synthesis is powered by the proton-motive force

Question 23

Proton-motive force consists of what two gradients?

Answer 23

1. Chemical gradient
2. Charge gradient

Question 24

The chemical gradient of the proton-motive force…

Answer 24

is generated by the difference in pH inside and outside the matrix (outside has more protons and is more acidic than matrix)

Question 25

The charge gradient of the proton-motive force

Answer 25

is generated by the charge difference inside and outside the matrix (outside has more protons, which is more positive and matrix has less protons and is more negative). ## Footnote

Question 26

The structure of ATP synthase. ## Footnote

Answer 26

It consists of 2 units 1. F_o= proton-conducting unit –contains the proton channel. 2. F1= ATP-synthesizing unit, contains the catalytic activity (beta-subunit).

Question 27

How many protons must flow into the matrix for each ATP formed and released by the b subunit?

Answer 27

Three protons

Question 28

The __________ accounts for the synthesis of ATP by the b subunit in response to proton flow.

Answer 28

Binding change mechanism

Question 29

T or F: Cytoplasmic NADH cannot enter the mitochondria.

Answer 29

True

Question 30

Electrons from cytoplasmic NADH are carried across the mitochondrial membrane by two major mitochondrial shuttles: ## Footnote

Answer 30

* Glycerol 3-phosphate shuttle (muscle) * Malate-aspartate shuttle (heart and liver)

Question 31

In muscle, electrons from cytoplasmic NADH enter the electron-transport chain via the \_\_\_\_\_\_\_\_.

Answer 31

Glycerol 3-phosphate shuttle Yields 1.5 ATP

Question 32

In heart and liver, electrons from cytoplasmic NADH are used to generate mitochondrial NADH in \_\_\_\_\_\_\_\_.

Answer 32

Malate-aspartate shuttle Yield 2.5 ATP \*No energy loss

Question 33

The synthesis of 1 ATP requires ______ (\_\_\_\_ in ATP synthesis and ____ for ATP transport)

Answer 33

**4 H+ ** 3 in synthesis 1 in transport

Question 34

\_\_\_\_ protons are translocated per NADH and ____ protons per FADH₂.

Answer 34

10 protons per NADH 6 protons per FADH₂

Question 35

P/O for NADH

Answer 35

P/O = (10 H+/ 4 H+) = 2.5 ATP/O

Question 36

P/O for FADH₂

Answer 36

P/O = (6 H+/ 4 H+) = 1.5 ATP/O (FADH₂ does not pass through complex I)

Question 37

The\_\_\_\_\_\_\_\_ is the most important factor in determining the rate of oxidative phosphorylation. This regulation is called \_\_\_\_\_\_\_\_\_\_.

Answer 37

* Levels of ADP * Respiratory control or acceptor control

Question 38

\_\_\_\_\_\_\_ carry protons across the inner mitochondrial membrane. The electron-transport chain functions, but ATP synthesis does not because the proton gradient can never form.

Answer 38

Uncouplers

Question 39

Rotenone (fish/insect poison) and amytal (barbiturate sedative)...

Answer 39

Block the electron transfer in NADH-Q oxidoreductase

Question 40

Antimycin A...

Answer 40

Blocks the electron flow in Q-cytochrome c oxidoreductase

Question 41

CN-, N₃ and CO...

Answer 41

block the electron transfer in cytochrome c oxidase

Question 42

Oligomycin and dicyclohexylcarbodiimide (DCCD, antifungal agent) inhibits the ATP synthase by...

Answer 42

Preventing the influx of protons.

Question 43

\_\_\_\_\_\_\_\_\_ uncouples electron transport from phosphorylation in mitochondria by carrying the protons across the inner mitochondrial membrane. It stops ATP synthesis without affecting electron transport from NADH to O2

Answer 43

2,4-Dinitrophenol (DNP)

Question 44

NADH is a strong ________ agent and has a ________ redox potential (E0).

Answer 44

Reducing agent Negative redox potential

Question 45

In an experiment, oxidative phosphorylation is inhibited by Antimycin A. Which one of the following molecules will be in the reduced state (received electrons)?

Answer 45

Ubiquinone Q

Question 46

Cyctochrome c, a small soluble protein, shuttles electrons from Q-cytochrome c oxidoreductase to:

Answer 46

Cytochrome C oxidase

Question 47

In oxidative phosphorylation, the transfer of electrons from NADH to O2 leads to pumping of _________ protons (H+) from the mitochondrial matrix to the intermembrane space.

Answer 47

10

Question 48

T or F: The electron transport chain generates a proton gradient that is required for NADH production.

Answer 48

False

Question 49

The F1 subunit of the ATP synthase is also known as...

Answer 49

ATP synthesizing unit