topic 5 - organotrophy - ETC

Question 1

what/where are the 2 e- taxis in the ETC

Answer 1

ubiquinone - in IMM
cytochrome C - in IMS

transfer e- from NADH and FADH2 to O2

Question 2

is ATP synthase a part of the ETC

Answer 2

no

Question 3

what is the final e- acceptor in the ETC

Answer 3

O2

Question 4

why do e- flow through the ETC

Answer 4

chain organised based on free energy relative to O2

redox driven

e- flow to increasingly more e-n prosthetic groups until they reach O2

with each e- transfer, the e- moves closer to the atomic nucleus of the next group and the free energy that is released is used to do work (pump H+)

Question 5

what are prosthetic groups

Answer 5

associated with a protein but not made up of amino acids (made of other organic molecules or metal ions)

each complex has one or more prosthetic groups (accepts e- and passes them onto the next group)

Question 6

what is e- flow coupled to

Answer 6

coupled to pumping H+ from the matrix to othe IMS to generate electrochem gradient

creates PE

Question 7

what happens at complex I

Answer 7

NADH (matrix) donates an e- to complex I (reduces)

H+ are pumped from teh matric to IMS by complex I

Question 8

what happens at complex II

Answer 8

FADH2 transfers e- to complex II (reduces)

FADH2 doesn’t have enough energy to transfer to complex I

Question 9

what is ubiquinone

Answer 9

hydrophobic e- taxi

can diffuse within the phospholipid bilayer (behaves similar to phospholipid)

Question 10

what does ubiquinone (UQ) do

Answer 10

• taxis e- from complex I to complex III
• taxis e- from complex II to complex III

when reduced (gain e-) it takes up a proton from the matrix and when it is oxidised (passes e- on to complex III) it releases the proton in the IMS

Question 11

what happens at complex III

Answer 11

e- flow from complex II, through complex III to the next e- taxi (cytochrome C)

Question 12

what is cytochrome C and what does it do

Answer 12

hydrophilic peripheral membrane protein in the IMS that moves e- from complex III to complex IV

Question 13

what happens at complex IV

Answer 13

e- flow through complex IV to O2 which combines with 2 protons to be reduced to water

complex IV works to pump protons from the matrix to the IMS

Question 14

how does the ETC generate an electrochemical gradient

Answer 14

H+ concen is lowered in the matrix when they are
- pumped across the membrane
- when O2 is reduced to water (takes up protons from the matrix)

H+ electrochemical gradient = PMF
- taken energy in high energy e- and transformed it to PMF

Question 15

what is the difference in pH between the IMS and matrix

Answer 15

IMS = pH 5 (more H+)
matrix = pH 7 (less H+)

Question 16

what is PMF (proton motive force)

Answer 16

force that promotes mvmt of protons across membranes down the electrochemical potential

ratio of protons on one side of the membrane to the other side

Question 17

what is chemiosmosis

Answer 17

ATP synthase catalyses ATP synthesis (make ATP from ADP and Pi) using energy from the H+ gradient across the membrane

Question 18

what is oxidative phosphorylation

Answer 18

energy in PMF generated by the ETC is used to make ATP

synthesis of a proton gradient across a membrane that drives ATP synthesis

Question 19

how does ATP synthase work

Answer 19

H+ flow through the channel in ATP synthase, the C ring rotates and the energy is used to drive the catalytic part (held stationary)

rotation triggers a change in change of the catalytic subunits
have an active site where they will bind to ADP and Pi to create ATP

Question 20

is ATP synthesis exer or endergonic

Answer 20

endergonic (positive change in free energy)
- couple the synthesis of ATP with an exergonic process (flow of H+ from IMS to matrix) - to create a negative total change in free energy (exergonic)

Question 21

what is the total ATP and CO2 made in aerobic resp

Answer 21

~32 ATP (can be as high as 38)
6 CO2

Question 22

why is there variation in ATP production

Answer 22

some PMF used for other purposes
NADH and FADH2 can be used in other reactions

Question 23

hwo many ATP are made in oxidative phosphorylation

Answer 23

28 ATP

10 NADH x 2.5 = 25
2 FADH2 x 1.5 = 3 ATP

Question 24

why does FADH2 make less ATP than NADH

Answer 24

joins ETC later - get fewer protons pumped therefore less ATP pumped per FADH2 compared to NADH