Electron transport chain

Question 1

What are the electron carriers involved in the ETC?

Answer 1

1) Coenzyme Q (ubiquinone)
2) Cytochromes
3) Fe-S proteins

Question 2

What is a distinguishing characteristic of coenzyme Q?

Answer 2

Long lipid soluble aliphatic tail

Question 3

Can ubiquinone accept or donate electrons?

Answer 3

Both

Question 4

Which cytochrome is not an integral membrane protein?

Answer 4

Cytochrome c

Question 5

What causes cytochromes to be different?

Answer 5

• Different amino acid sequences

- Different binding to iron-containing hemes

Question 6

What type of protein is cytochrome c?

Answer 6

Peripheral membrane protein

Question 7

What does cytochrome c bind and how?

Answer 7

Binds heme C covalently via cys residues

Question 8

What is standard reduction potential?

Answer 8

A measure of the free energy of the electron

Question 9

Why are the electron carriers arranged in the way they are?

Answer 9

So that a given carrier can accept electrons from one carrier only and pass them to one carrier only

Question 10

Carriers with high ___ reduction potentials pass electrons to carriers with high ____ reduction potentials

Answer 10

• Negative

- Positive

Question 11

What is the net reaction that occurs are complex 1?

Answer 11

NADH + H+ + UQ -> NAD+ + UQH2

Question 12

What happens to UQH2 in complex 1?

Answer 12

It diffuses through the membrane to complex 3

Question 13

How many hydrogens are pumped across the membrane in complex 1?

Answer 13

4

Question 14

What is the name of complex 1?

Answer 14

NADH dehydrogenase

Question 15

What is the name of complex 2?

Answer 15

Succinate dehydrogenase

Question 16

What is the only membrane-bound enzyme of the TCA cycle?

Answer 16

Complex 2/succinate dehydrogenase

Question 17

What is the net reaction that occurs in complex 2?

Answer 17

FADH2 + UQ -> FAD + UQH2

Question 18

What is the name of complex 3?

Answer 18

UQ-cyt c oxidoreductase

Question 19

What happens to cytochrome c in complex 3?

Answer 19

It dissociates from complex 3 and carries 1 electron at a time to complex 4

Question 20

What is the net reaction that occurs in complex 3?

Answer 20

UQH2 + 2Cyt c-Fe3+ -> UQ + 2Cyt c-Fe2+

Question 21

How many hydrogens are pumped across the membrane by complex 3?

Answer 21

4

Question 22

What is the name of complex 4?

Answer 22

Cytochrome oxidase

Question 23

What is the net reaction that occurs at complex 4?

Answer 23

2Cyt c-Fe2+ + 1/2O2 + 2H+ -> 2 Cyt c-Fe3+ + H2O

Question 24

What do 2 electrons pass through in complex 4 and where do these electrons come from?

Answer 24

• Pass from cyt c to 1/2 O2

- Come from 1 NADH

Question 25

How many hydrogens are pumped across the membrane in complex 4?

Answer 25

2

Question 26

How is energy stored during electron transport?

Answer 26

In the form of a proton concentration gradient

Question 27

Electrons in ____ have high G

Answer 27

NADH

Question 28

Electrons in _____ have low G

Answer 28

Water

Question 29

How much free energy is needed to make 1 ATP from ADP and Pi?

Answer 29

30.5 kJ/mol

Question 30

How many ATPs are formed when electrons are transferred from NADH to O2?

Answer 30

2.5

Question 31

How many ATPs are formed from succinate oxidation?

Answer 31

1.5

Question 32

How is free energy of electron flow converted into ATP synthesis?

Answer 32

During transport of 2 e- down the ETC from NADH, complexes 1, 3, and 4 transport 10 H+ from the matrix into the space between the inner and outer membranes, using the free energy

Question 33

Where is OH- found?

Answer 33

In the matrix

Question 34

Where is H+ found?

Answer 34

In the space

Question 35

How many hydrogens are moved for every 2 electrons passing down the chain from NADH?

Answer 35

- 4 are pumped by complex 1 - 4 are pumped by complex 3 - 2 are pumped by complex 4

Question 36

How many hydrogens are moved for every 2 electrons passing down the chain from FADH2?

Answer 36

- 4 are pumped by complex 3 | - 2 are pumped by complex 4

Question 37

How is the H+ gradient coupled to ATP synthesis?

Answer 37

FoF1 ATP synthase

Question 38

What is generated as H+ flows through Fo?

Answer 38

A torque that is transmitted to F1 via the gamma-shaft

Question 39

Do Fo and F1 subunits rotate in the same or opposite directions and what is this rotation energy used for?

Answer 39

- Opposite | - To release ATP from its binding site

Question 40

What is electron transport tightly coupled to?

Answer 40

Oxidative phosphorylation

Question 41

What regulates oxidative phosphorylation?

Answer 41

The supply of ADP and phosphate

Question 42

What is the function of the enzyme ATP/ADP translocase?

Answer 42

To move ATP into the cytoplasm and ADP into the mitochondrion

Question 43

How many ATPs are produced from glycolysis and by what processes?

Answer 43

- 5 from 2 NADH + H+ in the ETC | - 2 from substrate level phosphorylation

Question 44

How many ATPs are produced from the conversion of pyruvate to acetyl CoA and where?

Answer 44

5 from 2 NADH + H+ in the ETC

Question 45

How many ATPs are produced from the citric acid cycle and by what processes?

Answer 45

- 2 from 2 GTP from substrate level phosphorylation - 3 from 2 FADH2 in the ETC - 15 from 6 NADH + H+ in the ETC