5 Mitochondria And Oxidative Phosphorylation

Question 1

Q: Draw an annotated diagram of a mitochondrion.

Answer 1

A: inner mitochondrial membrane folds = cristae

Matrix

Question 2

Q: Which proteins are located on the inner mitochondrial membrane?

Answer 2

A: electron transport chain

Question 3

Q: What are this evolutionary origins of the mitochondria?

Answer 3

A: evolutionary descendant of prokaryote

Consumed by eukaryote and established endosymbiotic relationship

Question 4

Q: What is the evidence supporting the endosymbiosis theory?

Answer 4

A: mitochondria can arise only from preexisting mito and chloro

Possess own genome- circular with no associated histones (resembles prokaryotes)

Question 5

Q: Define the chemiosmotic theory and describe the 2 steps.

Answer 5

A: transfer of electrons down electron transport chain through series of oxidation and reduction reactions that releases energy

1. Movement of protons from within mito matrix into intermembrane space controlled by electron transport chain
2. Pumped protons re enter mito matrix via specific proton channel associated with ATP synthase enzyme

Question 6

Q: What does the movement of protons fro, the mitochondrial matrix to the intermembrane space establish?

Answer 6

A: proton/potential/ pH gradient

Question 7

Q: What is the force that drives the movement of protons back into the mito matrix?

Answer 7

A: proton motive force

Question 8

Q: What does the electron transport chain consist of?

Answer 8

Q: 3 complexes and 2 mobile carriers (act as electron carriers)

Question 9

Q: What are the 3 membrane complexes that make up the ETC?

Answer 9

A: NADH dehydrogenase complex
Cytochrome b-c1 complex
Cytochrome oxidase complex

Question 10

Q: What are the 2 mobile carriers that make up the ETC?

Answer 10

A: coE Q (ubiquinone)

Cytochrome C

Question 11

Q: What occurs as you go along each unit in the ETC and why is this useful?

Answer 11

A: each increases in election affinity which means electron movement can follow a logical order

More positive redox potential

Question 12

Q: As electrons pass along the ETC, what happens to protons?

Answer 12

A: pumped from mito matrix to intermembrane space

Question 13

Q: What is ubiquinone and what does it do?

Answer 13

A: electron carrier

Transfers electrons from NADH dehydrogenase complex to cytochrome b-c1

Question 14

Q: How is ubiquinone bound to the lipid membrane?

Answer 14

A: hydrophobic tail

Question 15

Q: Why is oxygen the ideal terminal electron acceptor?

Answer 15

A: has high affinity for electrons which provides a driving force for oxidative phosphorylation

Question 16

Q: How is water formed at the end of the ETC?

Answer 16

A: cytochrome oxidase being the last membrane complex in the ETC receives 4 electrons from cytochrome C (cycle repeats so 2 each time)
Cytochrome c passes it on to oxygen to form water

Question 17

Q: Draw the electron transport chain.

Answer 17

A: NADH dehydrogenase complex, ubiquinone, cytochrome b-c1 complex, cytochrome C, cytochrome oxidase complex

Question 18

Q: How are electrons transferred in the electron transport chain?

Answer 18

A: by redox and oxidation with NAD+/NADH and FAD/FADH2

Question 19

Q: Do electrons lose or gain energy as they move down the ETC?

Answer 19

A: lose

Question 20

Q: Which unit of the ETC is the entry point for electrons donated by FADH2?

Answer 20

A: ubiquinone

Question 21

Q: Draw a labelled diagram for ATP synthase.

Answer 21

A: f0= a b c
F1= alpha beta gamma

Each have 3 subunits

Question 22

Q: How do protons enter ATP synthase and what happens?

Answer 22

A: pore

Disc of c subunits rotates
Gamma subunit in f1 is fixed to the disc so rotate with it
Alpha and beta subunits in f1 are locked into position by the b subunit meaning alpha and beta can’t rotate
B subunit is anchored into subunit a in membrane

As gamma rotates (asymmetrical axle) the b subunit undergoes structural changes of its catalytic portions which changes its affinity for ATP and ADP

torsional energy flows from the catalytic subunit into the bound ADP and Pi to promote ATP formation

Question 23

Q: How can ATP be hydrolysed?

Answer 23

A: ATP synthase working in opposite direction as protons are pumped out

Question 24

Q: How can mitochondrial respiration be examined experimentally?

Answer 24

A: The Oxygen Electrode measures the oxygen concentration in a solution housed in a small chamber

base of chamber= teflon membrane with two electrodes beneath= Platinum (Pt) cathode and silver (Ag) anode

a small voltage is applied between the anode and cathode

oxygen diffused through the teflon membrane and is reduced to water at the platinum cathode:

O2 + 4H+ + 4e- -> 2H2O

The silver anode is slowly oxidised to AgCl:

4Ag+ 4Cl- -> AgCl + 4e-

The resulting current is proportional to the oxygen concentration in the sample chamber.

We can use the oxygen electrode to dissect various components of the electron transport chain

->first step is to prepare the suspension of mitochondria from tissue and place into chamber