Cell Integrity

Question 1

What is substrate level phosphorylation?

Answer 1

Production of ATP by the direct transfer of a high-energy phosphate group from an intermediate substrate to ADP

Question 2

What is oxidative phosphorylation?

Answer 2

ATP is produced using energy derived from I the transfer of e- in an electron transport chain

Question 3

Where does oxidative phosphorylation occur?

Answer 3

Inner mitochondrial membrane

Question 4

What are the overall reactions for the oxidation of NADH and FADH2 by oxygen in the mitochondria?

Answer 4

NADH + H+ +1/2O2 —> NAD+ + H2O

FADH2 + H+ + 1/2O2 —> FAD + H2O

Question 5

What are the 4 membrane proteins in the ETC?

Answer 5

4 membrane proteins:
- complex I (NADH dehydrogenase)
- complex II (succinate dehydrogenase)
- complex III ( Q-cytochrome C oxidoreductase)
- complex IV (cytochrome c oxidase)

Question 6

What re the two mobile carriers in the ETC?

Answer 6

Co-enzyme Q (ubiquinone)

Cytochrome C

Question 7

How does the ETC work?

Answer 7

Complexes I, III and IV accept e- from the oxidation of NADH and FADH2 —> passed through the chain

As they pass they lose energy which is used to pump H+ into the intermembrane space

Question 8

What happens in complex I?

Answer 8

NADH is oxidised (gives e- to the complex) and a H+ is pumped out

Question 9

What happens in complex II?

Answer 9

FADH2 is oxidised and the complex takes an e- and passes it to coenzyme Q which picks up two protons and forms QH2

Question 10

Why does NADH form 3ATP and FADH2 only 2ATP

Answer 10

FADH2 bypasses complex I so fewer protons are pumped into the intermembrane space

So fewer protons flowing through ATP synthase so less ATP generated

Question 11

What is ATP synthase?

Answer 11

A sub unit protein that consistes of a F0 and F1 part

Question 12

Where is F0 and F1 located?

Answer 12

F0 —> membrane bound

F1 —> projecting into the matrix space

Question 13

How does ATP synthase work?

Answer 13

Protons flow into matrix —> drives rotational movement of F1

Altering affinities for ATP, ADP and Pi
—> conformational energy flows from the catalytic subunit into bound ADP+Pi to from ATP

Direction of proton flow dictates whether ATP is generated or consumed

Question 14

What does an oxygen electrode do?

Answer 14

Measures O2 consumption

Question 15

How does the oxygen electrode work?

Answer 15

O2 diffuses through the Teflon membrane and reduces water at the platinum electrode

Silver anode slowly oxidised to silver chloride by the KCl electrolyte

Resulting current is directly proportional to O2 conc. in sample chamber

Question 16

How cane we analyse mitochondrial respiration with an oxygen electrode?

Answer 16

Place suspension of mitochondria in the chamber and start recording

Measure baseline respiration over a minute

Add ADP which will cause a lot of the O2 to be used up

Find the ratio of the amount of ADP phosphorylated to the amount of O2 consumption —> ADP-Oxygen index

After all ADP is used up —> restored basal respiration rate and O2 continuous to decrease until all used up

Question 17

What is respiratory control?

Answer 17

Allows body to adapt O2 consumption to the actual energy requirements

Question 18

What is a metabolic poison?

Answer 18

Molecule that interferes with either:
-floe of e- along the ETC
-flow of protons through ATP synthase

Question 19

What do Cyanide and azide do?

Answer 19

Bind with high affinity to the ferric form of the haem group in the cytochrome oxidase complex
—> block flow of e- through the final step of the ETC

Question 20

What does malonate do?

Answer 20

Closely resembles succinate —> competitive inhibitor

Slows down flow of e- from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate

Question 21

What does dinitrophenol do?

Answer 21

Transports H+ across inner mitochondrial membrane
—> bypasses ATP synthase —> uncouples ATP production from proton pumping
—> increase metabolic rate and body temp
—> induces weight loss

Question 22

What is non-shivering thermogenesis?

Answer 22

UCP-1 is activated in response to drop in core body temp
—> ATP synthase bypassed
—> much energy within the H+ gradient dissipated as heat

Question 23

What does Rotenone do?

Answer 23

Inhibits transfer of e- from complex I or ubiquinone

Question 24

What d’oies Oligomycin do?

Answer 24

Antibiotic

Binds to the stalk of ATP synthase
—> blocks flow of e- through the enzyme