Electron Transport

Question 1

Electrons are carried to the electron transport system in the mitochondria by:

Answer 1

NADH and FADH2

Question 2

The site of electron transport and oxidative phosphorylation:
-Both of these processes are what?

Answer 2

Mitochondria cristae

-interdependent

Question 3

Where do electrons entering complex I come from?

Answer 3

NADH

Question 4

Where do electrons entering complex II come from?

Answer 4

FADH2

Question 5

What is the job of Coenzyme Q?

Answer 5

Accepts a pair of electrons from complex I or complex II and passes electrons singly to complex III. Acts as a “traffic cop” for electrons.

Question 6

Sequence of electrons passing from coenzyme Q- (5 passing points)

Answer 6

• Coenzyme Q
• Complex III
• Cytochrome C
• Complex IV
• oxygen (to form water)

Question 7

The terminal electron acceptor and is a limiting compound during periods of heavy exercise:

Answer 7

Oxygen

Question 8

During passage of electrons through them, complexes I, III, and IV do what? (complex II with FADH2 does not do this)

Answer 8

Pump protons out of the mitochondrial matrix and into the intermembrane space.

Question 9

this electron carrier would not be present without oxygen:

Answer 9

NAD, because NADH would never donate its proton since oxygen is not present to pull the reaction forward.

Question 10

This complex in the electron transport chain contains iron-sulfur proteins and flavins for transferring electrons:

Answer 10

Complex I

Question 11

These two complexes contain heme groups known as cytochromes:

Answer 11

Complex III and IV.

Question 12

What do heme groups contain and what are the two forms>

Answer 12

contains iron that can exist as Fe+2 and Fe+3, the difference being one electron

Question 13

This complex contains copper atoms bound either by the sulfurs of cysteine (CuA) or by histidine (CuB):

Answer 13

Complex IV

Question 14

What are the two ways the Cu can exist?

Answer 14

Cu+1 or Cu+2

Question 15

If oxygen is not available what happens? What is this a part of?

Answer 15

Electrons will NOT pass through the electron transport system and NADH and FADH2 will not be reoxidized.
-part of metabolic control

Question 16

Rotenone (insecticide) and amytal are compounds that block what?

Answer 16

All action of Complex I

Question 17

Antimycin A blocks what?

Answer 17

All action of Complex III

Question 18

Cyanide, Azide, and carbon monoxide block what?

Answer 18

All action of Complex IV

Question 19

Movement of electrons through Complex III is known as:

Answer 19

The Q cycle

Question 20

How does the Q cycle begin? How many electrons and protons are present?

Answer 20

The binding of two molecules of CoQ (QH2 and Q) to Complex III. QH2 has two electrons and two protons. Q has neither.

Question 21

What is the first half of the Q cycle after Q and QH2 bind?

Answer 21

• QH2 sends one electron to Q, creating Q-, and one electron to cytochrome C.
• The two protons QH2 was carrying are sent to intermembrane space, converting QH2 to Q.
• Both cytochrome C and Q leave the complex, but Q- remains behind.

Question 22

What is the second half of the Q cycle?

Answer 22

• Another QH2 and another cytochrome C binds to Complex III.
• QH2 sends one electron to Q-, creating Q-2 and one electron to cytochrome C. It also sends two protons to the intermembrane space and becomes Q.
• Then Q-2 extracts two protons from the matrix and becomes QH2.

Question 23

What happens at the end of the Q-cycle?

Answer 23

-Last, cytochrome C, QH2, and Q all leave the complex.

Question 24

Electron Transfer through complex IV occurs via how many electrons at a time and why?

Answer 24

One electron at a time because this is how they arrive from cytochrome C after the Q cycle.

Question 25

Interruption of electron flow can result in:

Answer 25

production of reactive oxygen species

Question 26

Cellular enzymes, such as superoxide dismutase and catalase help to deactivate what?

Answer 26

superoxides

Question 27

During electron movement through Complex IV, how many protons are taken from the matrix? What are they combined with and what do they make?

Answer 27

4 protons taken from matrix and combined with oxygen to make two water molecules.

Question 28

Complex IV also pumps how many protons where in the mitochondria?

Answer 28

Pumps 4 protons outside the mitochondial matrix.

Question 29

What is the overall consequence (relating to protons) of electron movement through Complex IV? What is the net difference?

Answer 29

proton numbers in matrix decrease by 8 during the process. While the protons outside the mitochondrian increase by 4. Net difference is 12 protons for movement through complex IV.

Question 30

What is used to deactivate superoxides ,which are reactive oxygen species (O2-) due to seperation of electrons incorrectly?

Answer 30

Superoxide dismutase (SOD)

Question 31

What is the two step fashion that superoxide dismutase (SOD) acts in (it uses a ping pong mechanism)?

Answer 31

• The oxidized form of SOD accepts an electron from O2-, creating molecular oxygen and a reduced SOD.
• The reduced SOD combines its extra electron with that of another O2- and two protons to create hydrogen peroxide and the oxidized form of SOD.

Question 32

How is hydrogen peroxide (H2O2) dealt with in the body?

Answer 32

It is converted to oxygen and water by the enzyme catalase.