Lecture 11 - Objectives

Question 1

How does an electron transport chain release redox energy?

Answer 1

as electrons pass around they go down in energy level

Question 2

What electron carriers carry only electrons?

Answer 2

1. Heme
2. Iron sulfur protein

Question 3

What electron carries electrons and hydrogen?

Answer 3

1. NADH
2. FADH2
3. Quinol (from quinone)

Question 4

Sketch the mitochondrial electron transport chain in a membrane

Answer 4

1. Complex 1 accepts electron from NADH
2. pass e- to Coenzyme Q
3. pass e- to Complex III
4. Cytochrome C
5. Complex IV
   ATP synthase is on the side

Question 5

How does alternating between electron carrier types pump H+ across the membrane?

Answer 5

When carriers that carry H+ and electrons are reduced they pick up protons from the matrix, as they are oxidized they release protons into the intermembrane space.

Question 6

How does PMF generate ATP using chemiosmosis?

Answer 6

uses ATP synthetase enzyme

movement of hydrogen ions down concentration gradient causes rotation of an enzyme which uses this to make ATP from ADP and P

Question 7

What are 4 differences between bacterial and mitochondrial ETC?

Answer 7

1. Bacteria can use different transport complex
2. can use different terminal electron acceptors
3. can pump variable numbers of H+
4. can use more than one transport chain at a time (branched)

Question 8

What are 3 alternate terminal electron acceptors?

Answer 8

not O2
1. DMSO reductase
2. fumarate reductase
3. nitrate reductase

Question 9

What is the oxidase test?

Answer 9

tests if bacteria has cytochrome c oxidase

Question 10

Given a table (slide 16) predict whether an electron donor and acceptor pair could be used by bacteria to provide energy

Answer 10

electron donor has to be at a higher energy level than electron acceptor (delta G < 0)

Question 11

Sketch Z-schem of oxygenic photosynthesis

Answer 11

a. start with photon hitting PSII
b. pass to plastoquinone
c. pass to cytochrome
d. pass to plastocyanin
e. pass to PSI
d. photon hits PSI
f. pass to ferredoxin
g. make NADPH

PSII makes H from water, plastoquinone transport H

Question 12

Explain where ATP and NADPH are formed in oxygenic photosynthesis

Answer 12

ATP is formed in ATP synthase using PMF
NADPH is made when electrons pass from PSI

Question 13

How is water able to serve as an electron donor in oxygenic photosynthesis

Answer 13

it donates its electrons at PSII (forming O2)

Question 14

Compare photosynthetic and respiratory ETC

Question 15

Photosynthesis in purple bacteria

Answer 15

a. photons hit chlorphyll, excite e-
b. pass to cytochrome B complex
c. produce PMF
d. use PMF to excite e- to make NADH
e. use electron donor

Question 16

Photosynthesis in green bacteria

Answer 16

a. photons hit chlorophylll, excite e-
b. pass to ferredoxin
c. make NADH
d. PMF is used to make ATP in separate path

Question 17

Why do purple sulfur bacteria need reverse electron transport?

Answer 17

They need to use PMF to drive electrons to a higher level so that they can reduce NADP+

Question 18

Why do green sulfur bacteria not need reverse electron transport?

Answer 18

Ferredoxin is already at a high enough energy level to reduce NADP+

Question 19

Cyclic vs non-cyclic photosynthesis

Answer 19

cyclical photosynthesis: electrons are passed back to the chlorophyll, it is non-oxygenic