Lecture 6

Question 1

Do all eukaryotic cells contain mitochondria?

Answer 1

No, most.

Question 2

How do eukaryotic cells without mitochondria obtain ATP?

Answer 2

Glycolytic fermentation.

Question 3

How many mitochondria do most cells contain?

How many mitochondria do liver cells contain?

Answer 3

Most cells several hundred.

Liver cells about 2,500.

Question 4

What are the two parts of a mitochondrial membrane?

Answer 4

Inner and outer membrane.

Question 5

What is the inner membrane of the mitochondrial folded into?

Answer 5

Cristae.

Question 6

What are the two compartments in the mitochondria?

Answer 6

The matrix inside the inner membrane,

Intermembrinal space.

Question 7

What moves mitochondria around the cells and whereabouts are they usually found in the cell?

Answer 7

Microtubules of the cytoskeleton.

Regions of high ATP consumption, e.g. myofibrils of muscle cells.

Question 8

What protein comprises the majority of the outer membrane of mitochondria and what does it form?

Answer 8

Porin.

Large non-specific aqueous channels through the outer membrane.

Question 9

What benefit do cristae offer the mitochondria?

Answer 9

Increases surface area.

Question 10

What is the inner membrane of the mitochondria?

Answer 10

Energy transducing membrane.

Question 11

What is the inner membrane of the mitochondria impermeable to and why?

Answer 11

Impermeable to most small ions due to cardiolipin.

Question 12

Three types of membrane complex found in the inner membrane of the mitochondria?

Answer 12

Components of the electron transport chain,
ATP synthase,
Specific transporters moving metabolites between mitochondrial matrix.

Question 13

Which cell type has the greatest variety of metabolite transporters and why?

Answer 13

Liver mitochondria.

Involved in the initial reactions of several anabolic pathways.

Question 14

What does the mitochondrial matrix contain?

Answer 14

Enzymes that catalyse the Krebs cycle and fatty acid oxidation. Also contains ribosomes and mitochondrial DNA.

Question 15

Where does glycolysis take place?
How much energy is released, and how?
What product is formed?

Answer 15

Cell cytosol.
About a quarter of the energy of glucose, through substrate level phosphorylation.
Pyruvate.

Question 16

After glycolysis what happens to pyruvate?

Answer 16

Enters mitochondria and converted to acetyl CoA with the loss of CO2.

Question 17

What electron carriers carry electrons from the Krebs cycle?

Also where do they transport them to?

Answer 17

NAD and FAD.

Electron transport chain on the inner membrane of the mitochondria.

Question 18

What does the election transport chain do?

Answer 18

Pumps H+ ions across the inner membrane creating an ion gradient used by ATP synthase to generate ATP.

Question 19

Where does the Krebs cycle take place?

Answer 19

In mitochondrial matrix.

Question 20

What is the majority of the energy in the Krebs cycle proceed from?

Answer 20

Transfer of electrons to NAD and FAD.

Only a small amount of ATP generated due to substrate level phosphorylation.

Question 21

How does the ETC generate energy?

Answer 21

Via redox reactions.

Question 22

What does the ETC consist of?

Answer 22

Collection of molecules (mostly proteins with prosthetic groups) embedded in the inner membrane of the mitochondria.

Question 23

What is the first molecule in the electron transport chain and why has it been given its name?

Answer 23

Flavoprotien.

Because prosthetic group = flavin mononucleotide.

Question 24

What does the last cytochrome in the ETC pass its electrons onto? What does this molecule do?

Answer 24

Oxygen.

Picks up a pair of H+ ions forming water.

Question 25

What is the name for the indirect generation of ATP from the electron transport chain?

Answer 25

Chemiosmosis.

Question 26

What is the overall energy drop from NADH to O2?

Answer 26

53 kcal/mol.

Question 27

What is the ion gradient which drives ATP synthesis?

Answer 27

H+ gradient.

Question 28

Why is cyanide the fastest poison?

Answer 28

Prevents the passage of electrons from one of the cytochromes, halting the electron transport chain.

Question 29

What does DNP do?

Answer 29

Makes the inner membrane leaky to hydrogen ions so a gradient cannot be generated. ETC still works, but just releases energy as heat instead of ATP.

Question 30

What is brown fat, and what is the function of the mitochondria in brown fat?

Answer 30

Specialised type of adipose tissue in many mammals.

Produce heat.

Question 31

In what type of human is brown fat found in large quantities? And why?

Answer 31

New-born babies, important to generate heat to maintain body temperature.

Question 32

What is unique about the structure of mitochondria in brown fat, and what does it mean?

Answer 32

Have a special protein on their inner membrane functioning as an H+ channel through the membrane (thermogenin).
Means H+ ions pumped across membrane by ETC leak back without passing through ATP synthase molecule, so doesn’t generate ATP.

Question 33

Is brown fat present in healthy human adults?

Answer 33

Yes.

Question 34

What type of technique has just been conceived to prevent passing on faulty mitochondria?

Answer 34

IVF technique.

Question 35

What is MERRF? And what is it caused by?

Answer 35

Myoclonic epilepsy and ragged-red fiber disease.

Caused by mutation in mitochondrially encoded tRNA Lys gene.

Question 36

What type of disease is MERRF?

Answer 36

Multisystem, affecting mainly muscles but also causing epilepsy and general weakness.