MCQs

Question 1

Which type of bond makes acetyl CoA an energy carrier molecule?

Answer 1

thioester

Question 2

The standard free energy change for the following reaction
malate + NAD+ → oxaloacetate + NADH + H+
was calculated in the lecture as ΔG°’ = + 28 kJ/mol, yet the reaction proceeds in this direction in the TCA cycle, because oxaloacetate is rapidly removed by conversion to

Answer 2

citrate

Question 3

The equation that relates E°’ to the equilibrium constant for a reaction was not provided in the lecture, but you can work out that it is:

Answer 3

ΔEo’ = RT ln Keq
————-
nF

Question 4

what does NADH released when oxidised

Answer 4

2 electrons and 1 proton

Question 5

between complex I and complex II:

only one is an enzyme in the TCA cycle. True or false?

Answer 5

True

Complex II is succinate dehydrogenase and links TCA to ETC

Question 6

between complex I and complex II: true or false?

both feed electrons into different rounds of the Q cycle

Answer 6

False

QH2 from I and II are functionally equivalent and so Complex III cannot distinguish between them

Question 7

between complex I and complex II: true or false?

only one complex pumps protons across the IMM

Answer 7

true

I does
II doesn’t

Question 8

between complex I and complex II: true or false?

One reduces FADH2 and the other NADH

Answer 8

True

I reduces NADH
II reduces FADH2

Question 9

What is the fate of semi-quinone form of ubiquinone produced during round 1 of Q cycle?

Answer 9

It is fully reduced to GH2

Question 10

symbol for semi quinone and when is it produced

Answer 10

Q-

produced during round one of Q cycle

Question 11

where is the F1 subunit of ATPsynthase located

Answer 11

matrix

Question 12

where is cytochrome C located in mitochondria

Answer 12

IMS

Question 13

where is Complex II located

Answer 13

matrix

Question 14

True or false:

The complex reducing FADH2 sometimes gains enough energy from that reaction to pump protons across the IMM.

Answer 14

False

redox potential of FADH2 oxidation never provides enough energy to pump protons

Question 15

True or false:

The complex reducing NADH always gains enough energy from that reaction to pump protons across the IMM.

Answer 15

FALSE –

while redox potential of NADH oxidation can provide enough energy to pump protons, once the proton gradient is large enough, the ΔG of NADH oxidation is insufficient to pump protons

Question 16

True or false:

ComplexesI, III and IV all pump protons through a transmembrane protein complex

Answer 16

FALSE –

Complex III uses the Q cycle rather than pumping protons through the complex.

Question 17

True or false:

In addition to pumping protons directly across the membrane, complex IV also removes protons from the matrix

Answer 17

True:

2 protons are removed from the matrix and combined with O2 and electrons to produce water

Question 18

what is the site of O2 reduction in mitochondria

Answer 18

Complex IV

formation of water

Question 19

In the absence of oxygen, cells can still produce small amounts of ATP through substrate-level phosphorylation during glycolysis. Why must lactate be produced to allow this process to continue

Answer 19

To oxidise NADH

Cells can run glycolysis in the absence of O2, but soon run out of NAD+ which is required for glycolsysis.
Conversion of pyruvate to lactate oxidises NADH to NAD+ allowing glycolysis to continue

Question 20

what is required for the F0 domain of ATP synthase to rotate

Answer 20

• proton gradient
• Pi
• ADP

Question 21

is NADH required for the F0 domain of ATP synthase to rotate

Answer 21

nope

Question 22

why can’t the F0 domain of ATP synthase to rotate without ADP

Answer 22

Because this allows respiration to be regulated by ADP/ATP ratio – ie cellular energy status

Question 23

True or false:

Mutations in the mitochondrial genome affect all the mitochondria in a cell

Answer 23

false

Proportion of mutant and normal DNA vary between mitochondria meaning some mitochondria or some tissues may be unaffected by the mutation

Question 24

Dynamin-related protein 1 (Drp1) is involved in which process

Answer 24

mitochondrial fission:

• Cytosolic Dynamin-related protein (Drp)1 is phosphorylated
• Drp1 recruited to mitochondria and binds receptors
• Forms cuff around mitochondrion which constricts the organelle
• Constriction severs both membranes
• Generates new mitochondria

Question 25

effect of TTFA on ETC

Answer 25

binds at quinone reduction site of Complex II, preventing formation of ubiquinone

• use of succinate as fuel will be low, bc Complex II is where TCA joins ETC
• use of pyruvate high

Question 26

effect of rotenone on ETC

Answer 26

Complex I

• inhibits transfer of electrons from Fe-S in Complex I to ubiquinone
• this interferes with NADH
• use of pyruvate as fuel low
• use of succinate as fuel high

Question 27

effect of antimycin on ETC

Answer 27

Complex III

• binds to Qi, inhibiting oxidation of ubiquinone
• disrupted Q-cycle

Question 28

effect of cyanide of ETC

Answer 28

complex IV

• binds to Fe atoms and inhibits transfer of electrons to oxygen

prevents cells from reducing oxygen to water

Question 29

effect of oligomycin on ETF

Answer 29

an antibiotic

• inhibits ATP synthase
• blocks proton channel of F0 subunit
• stops ETC

Question 30

is DNP weak or strong acid

Answer 30

weak

HA H+ + A-

Question 31

which tissue expresses large amounts of UCP-1

Answer 31

brown adipose tissue

Question 32

why does brown adipose tissue express lots of UCP-1

Answer 32

allows for controlled uncoupling of mitochondria to produce heat

Question 33

example of another mitochondrial uncoupler

Answer 33

DNP

it is a weak acid and is membrane impermeable

Question 34

what do beta islets produce

Answer 34

insulin

Question 35

what do alpha islets produce

Answer 35

glucagon

Question 36

what do delta islets produce

Answer 36

somatostatin

Question 37

what secondary hormone does insulin induce

Answer 37

PIP3

Question 38

what secondary hormone does glucagon induce

Answer 38

cAMP

Question 39

what secondary hormone does adrenaline induce

Answer 39

cAMP

Question 40

what are the main substances, from other tissues, that are used by the liver for gluconeogenesis

Answer 40

lactate
alanine
glycerol

Question 41

how is the rate of kexokinase active affects across physiological blood glucose levels?

(Km = 0.1mM)

Answer 41

it will not significantly change during physiological ranges

Question 42

if glucokinase has a Km of 10mM, will it saturated at 20mM

Answer 42

NO

Question 43

how does GLUT2 compare to GLUT4 in terms of affinity

Answer 43

GLUT2 has lower affinity than GLUT4

Question 44

what directly triggers insulin vesicles to fuse with plasma membrane and release insulin?

Answer 44

increased intracellular Ca2+ concentration

Question 45

is glycogen transported from muscle to liver

Answer 45

nope