Cell integrity

Question 1

What is substrate level phosphorylation?

Answer 1

Formation of ATP or ATP equivalent such as GTP

Question 2

How is the bulk of ATP formed?

Answer 2

By oxidative phosphorylation

Question 3

Where does oxidative phosphorylation occur?

Answer 3

Inner membrane of mitochondria

Many folds of cristae increase S.A. where oxidative phosphorylation takes place

Question 4

What happens to NADH and FADH2?

Answer 4

Reoxidised by molecular oxygen:

NADH + H+ + 1/2 O2 -> NAD+ +H2O

FADH + H+ + 1/2 O2 -> FAD + H2O

Question 5

What is the free energy (delta G) of the reaction of NADH and FADH2?

Answer 5

-223 and -170 KJ/mol respectively

Question 6

What are the different membrane proteins in the electron transport chain?

Answer 6

Complex I (aka NADH-Q oxidoreductase or NADH dehydrogenase)

Complex II (aka. succinate- Q reductase or succinate dehydrogenase)

Complex III (aka. Q- Cytochrome C oxidoreductase)

Complex IV (aka. cytochrome C oxidase)

Question 7

What are mobile carriers in the ETC?

Answer 7

Coenzyme Q (ubiquinone)
Cytochrome C

Question 8

Which complexes accept electrons and protons from aqueous solution?

Answer 8

I, II, IV

Question 9

What happens as electrons pass through each complex?

Answer 9

A proton is passed to the intermembranous space

Question 10

What is succinate dehydrogenase?

Answer 10

Complex II

An enzyme that enters the TCA cycle and sits in the inner mitochondrial membrane

Uses FAD as a cofactor and can communicate directly with ubiquinone (Coenzyme Q)

As electrons are passed from FADH2 to coenzyme Q, it picks up a pair of protons- this regenerated FAD. and makes QH2

Its a bypass of complex I

Question 11

How is ATP regenerated?

Answer 11

Protons flowing back into matrix via ATP synthase are used to regenerate ATP

Question 12

What is a redox reaction?

Answer 12

Electron transfer reaction involving a reduced substrate and an oxidised substrate

Question 13

What is a redox couple?

Answer 13

A substrate which exists in both oxidised and reduced forms

Question 14

What is the redox potential?

Answer 14

The ability of a redox couple to accept or donate electrons

Question 15

How can you measure standard redox potential (E0)?

Answer 15

Use a hydrogen electrode

Positive E0 implies tendency to accept electrons so more oxidant power so more likely to be reduced

Negative E0 implies tendency to donate electrons so more reduction power so more likely to be oxidised

Question 16

What is ATP synthase?

Answer 16

Makes ATP
Is a multimeric enzyme
Has a membrane bound part (F0) and F1 part which projects into matrix space

Question 17

What dictates ATP synthesis vs ATP hydrolysis?

Answer 17

direction of H+ flow

Question 18

What does the oxygen electrode measure?

Answer 18

Measure O2 conc. in a solution housed in a small chamber

Question 19

What is the base of the sample chamber made of ?

Answer 19

Base of chamber formed by teflon membrane

Underneath membrane is a compartment containing platinum cathode and silver anode

Question 20

How is oxygen conc. measured?

Answer 20

1. Small voltage of 0.6V applies between cathode and anode
2. Oxygen diffuses through teflon membrane and is reduced to water at Pt cathode
3. Circuit is completed at silver anode which is slowly oxidised to AgCl by KCl electrolyte
4. Resulting current is proportionate to O2 conc.

Question 21

Whats the most common cause of failed oxidative phosphorylation?

Answer 21

Hypoxia and anoxia

Question 22

What are metabolic poisons?

Answer 22

Molecules that interfere with flow of electrons along ETC or flow of protons through ATP synthase which interrupt ATP synthesis
They’re highly toxic

Question 23

Name 6 metabolic poisons?

Answer 23

Cyanide + Azide
Malonate
Rotenone
Oligomyocin
Dinitrophenol (DNP)

Question 24

How does cyanide and azide act as a metabolic poison?

Answer 24

Bind with high affinity ferric haem group in cytochrome oxidase (complex IV) blocking final step of ETC

Question 25

How does malonate act as a metabolic poison?

Answer 25

Closely resembles succinate and acts as a competitive inhibitor of succinate dehydrogenase (Complex II)

Slows down flow of electrons from succinate to ubiquinone

Question 26

How does rotenone act as a metabolic poison?

Answer 26

An isoflurane found in roots and seeds of some plants. Inhibits transfer of electrons from complex I to ubiquinone

Question 27

How does oligomycin act as a metabolic poison?

Answer 27

Antibiotic produced by streptomycin

Inhibits OP by binding to stalk of ATP synthase and blocking flow of protons through enzyme

Question 28

How does DNP act as a metabolic poison?

Answer 28

Proton ionophore which can shuttle protons across inner mitochondrial membranes

Question 29

How can dinotrophenol induce weight loss?

Answer 29

Uncouples OP from ATP production and increases metabolic rate and body temp.

Used as anti-fat medication but difference between slimming dose and that required for metabolic poisoning is close

Its now used for pesticides and food dye but is illegal to sell for human consumption