UNIT 1 : Processes

Question 1

The electron transport chain (ETC) is a series of protein complexes embedded in the inner mitochondrial membrane that transfer electrons from

Answer 1

NADH and FADH2 to molecular oxygen, generating a proton gradient across the membrane. This gradient is then used to drive ATP synthesis.

Question 2

glycolisis: what happens to pyruvate if oxygen is present?

Answer 2

oxidative phosphorylation to generate lots of ATP

Question 3

glycolisis: what happens to pyruvate if oxygen is not present?

Answer 3

fermentation, regenerates NAD+ so the cells can further metabolize glucose and produce small amounts of ATP (yeast, muscle cells under stress, tumour cells)

Question 4

Each pyruvate that enters the mitochondrion generates:

Answer 4

4 NADH (3 from the TCA cycle, 1 from production of Acetyl-CoA) 1 FADH2
1 GTP

Question 5

Each pyruvate that enters the mitochondrion generates:
4 NADH (3 from the TCA cycle, 1 from production of Acetyl-CoA) 1 FADH2
1 GTP
So, including glycolysis, after the TCA cycle there is a TOTAL of:

Answer 5

10 NADH
2 FADH2
2 ATP
2 GTP

Question 6

During oxidative phosphorylation, it is estimated that each NADH molecule generates

Answer 6

~2.5 ATP molecules

Question 7

the overall yield of ATP molecules from a single glucose molecule

Answer 7

30

Question 8

each FADH2 molecule generates

Answer 8

~1.5 ATP molecules

Question 9

complexes of the electron transport chain: complex 1:

Answer 9

NADH dehydrogenase

Question 10

Complex 3:

Answer 10

cytochrome BC1

Question 11

Complex 2:

Answer 11

succinate dehydrogenase

Question 12

complex 4

Answer 12

cytochrome c oxidase

Question 13

Step 1 electron transport chain:

Answer 13

Electrons derived from either NADH (via complex I or NADH dehydrogenase) or FADH2 (complex II or succinate dehydrogenase) are passed to ubiquinone (Q or UQ), a lipid-soluble molecule

Question 14

Step 2 electron transport chain:

Answer 14

The electrons are then passed from coenzyme Q (a.k.a. ubiquinone) to complex III (or the cytochrome b-c1 complex)

Question 15

Step 3 electron transport chain:

Answer 15

Electrons are then transferred to cytochrome c, a peripheral membrane protein, which carriers electrons to complex IV (or cytochrome oxidase)

Question 16

Step 4 electron transport chain:

Answer 16

Complex IV transfers electrons to molecular oxygen to form H2O within the matrix

Question 17

Step 5 electron transport chain:

Answer 17

The electron transfers in complexes I, III and IV generate energy, which is used to pump protons from the matrix to the intermembrane space, establishing a proton gradient across the inner membrane. The energy stored in the proton gradient is then used to drive ATP synthesis as the protons flow back to the matrix through complex V (or ATP synthase)

Question 18

ATP can be blocked by:

Answer 18

metabolic poisons such as cyanide, sodium azide and carbon monoxide – bind to catalytic sites of complex IV.

Question 19

Electron transport can be “uncoupled” from ATP synthesis by

Answer 19

endogenous proteins (uncoupling proteins) such as UCP1 in brown adipose tissue. UCP1 dissipates the H+ gradient and the energy of electron transfer is released as heat rather than a high- energy ATP molecule.

Question 20

Chemicals (e.g. 2,4-dinitrophenol (or DNP)) also

Answer 20

dissipate the proton gradient and prevent ATP production.

Question 21

Reduced [ATP] causes the cell to

Answer 21

oxidize stores of fat to replenish the [ATP]. Therefore, burn fat resulting in weight loss (in theory).