ATP production

Question 1

What are the functions of mitochondria?

Answer 1

1. Outer membrane limits size of organelle
2. Inner membrane with folds that project inwards called Cristal
3. Reactions of oxidative phosphorylation take place in inner membrane
4. Krebs cycle in matrix
5. Folds in cristae increase surface area upon which oxidative phosphorylation can take place
6. Co-enzymes NADH and FADH2 are re-oxidised

Question 2

What is some evidence that mitochondria where evolutionary decedents of prokaryotes?

Answer 2

1. Mitochondria can only arise from pre-existing mitochondria (or chloroplasts in the case of plants).
2. Mitochondria possess their own genome, resembling that of prokaryotes, being a single circular molecule of DNA, with no associated histones.
3. Mitochondria have their own protein-synthesizing machinery, which again resembles that of prokaryotes not that of eukaryotes.
4. The first amino acid of mitochondrial transcripts is a formylated methionine residue (fMet) as is the case in bacteria and not methionine (Met) as in eukaryotic proteins.
5. A number of antibiotics (e.g., streptomycin) that act by blocking bactarial protein synthesis also block protein synthesis within mitochondria. They do not interfere with protein synthesis in the cytoplasm of the eukaryotes

Question 3

What are the enzymes in the ETC?

Answer 3

NADH Dehydrogenase complex
Cytochrome b-c1 complex
Cytochrome oxides complex

Question 4

What are the carrier in the ETC?

Answer 4

Ubiquinone (aka Co-enzyme Q)

Cytochrome C

Question 5

What happens to proteins in ETC?

Answer 5

• Proteins accept electrons and H+ from aq solution

- As electrons pass through each complex, a proton is passed into inter membrane space

Question 6

What does succinate dehydrogenase do?

Answer 6

1. Succinate dehydrogenase an integral membrane protein, attached to inner surface of inner mitochondrial membrane
2. Communicate directly with ubiquinone - therefore one less proton pumped to intermembrane space cf NADH and so less ATP produced

Question 7

What is a redox couple and some examples of them?

Answer 7

• A substrate that can exist in both oxidised and reduced forms is known as a redox couple
  e. g. NAD+/ NADH; FAD / FADH2; Fe3+/Fe2+; ½ O2/H2O.
• Ability of redox couple to accept or donate electrons can be determined experimentally known as redox potential

Question 8

Describe the structure of ATP synthase

Answer 8

1. Multimeric enzyme, membrane bound part (F0) andF1 part projects into matrix space
2. Rotation of enzyme drives transitions states with altering affinities for ATP and ADP.
3. Therefore conformational energy flows from the catalytic subunit into the bound ADP and pi to promote formation of ATP
   - Depending on direction of flow of protons through ATP synthase, complex either generate ATP or consumes it.

Question 9

What is respiratory control?

Answer 9

1. Uptake of oxygen by mitochondria is controlled by the components of ATP production (inorganic phosphate (pi) and ADP)
2. This is known as respiratory control and allows the body to adapt oxygen conduction to its actual energy requirements

Question 10

What is a metabolic poison?

Answer 10

-Molecules that interfere with either the flow of electrons along ETC or flow of protons through ATP synthase, interrupt ATP synthesis and so are highly toxic and termed metabolic poisons

Question 11

How is cyanide and azide metabolic poisons?

Answer 11

Cyanide (CN-) and azide (N3-) bind with high affinity to ferric (Fe3+) from of the ahem group in cytochrome oxidase complex, blocking final step of ETC

Question 12

How is malonate a metabolic poison?

Answer 12

Malonate, resembles succinate and acts as competitive inhibiter of succinate dehydrogenase and slow down the flow of electrons from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate

Question 13

How is rotenone a metabolic poison?

Answer 13

Rotenone is isoflavone found in roots and seeds of some plants and it insist the transfer of electrons from complex 1 to ubiquinone

Question 14

How is oligomycin a metabolic poison?

Answer 14

Oligomycin is an antibiotic produced by streptomycin that inhibits oxidative phosphorylation by binding to the stark of ATP synthase and blocking the flow of protons thought the enzyme

Question 15

How is DNP a metabolic poison?

Answer 15

Dinitrophenol (DNP) is a proton ionophore which can shuttle protons across the inner mitochondrial membranes