cell integrity

Question 1

• Why does re-oxidation of FADH2 mean that less ATP is produced compared to oxidation of NADH?

Answer 1

Because Complex I is bypassed, so fewer H+ are pumped into Intermembrane space, so less ATP is produced

Question 2

• What does it mean if a redox couple has a negative redox potential?

Answer 2

Redox couple has a tendency to donate electrons, so it has more of a reducing power than hydrogen

Question 3

• What are the two parts of ATP Synthase called?

- How does ATP Synthase allow the production of ATP?

Answer 3

F0 is part bound to membrane
F1 is part suspended in matrix

H+ moves from the intermembranal space to the matrix
as a result, f0 rotates and absorbs this potential energy
causing F1 to synthesise ATP

Question 4

• Why does ATP production vary in the ATP Synthase?

Answer 4

Rotation of enzyme drives the transitional states with altering affinities for ATP and ADP

The directional flow of protons through ATP Synthase decides whether ATP synthesis or hydrolysis occurs

If there is a higher concentration of H+ in intermembrane space and lower concentration of ATP in matrix, then the conditions are more favourable towards ATP Synthesis

Question 5

• How can we use the Oxygen Electrode to measure changes in ETC?
• what is the structure of an oxygen electrode?

Answer 5

By placing suspension of mitochondria into chamber, we can see effects of various substrates and inhibitors on ETC through changes in [O2]

teflon membrane is base of chamber- oxygen permeable
above membrane is two electrodes- platinum cathode and silver anode

oxygen diffuses through teflon membrane and reduced to water at platinum cathode
ag is oxidised to AgCl due to KCL electrolyte
resulting current is proportional to oxygen conc in chmaber

Question 6

• How does rotenone reduce oxygen consumption in the electron transport chain?

Answer 6

It inhibits electron transfer from Complex I to Coenzyme Q
which also inhibits production of NADH by citrate metabolism and ultimately oxygen consumption
but ultimately only slows electron transport as a whole because complex 2 can still be used

Question 7

• How does Complex II reduce the effects of rotonone?

Answer 7

Complex II passes electrons directly from FADH2 to Coenzyme Q

This bypasses Complex I and therefore the effects of rotonone

Question 8

• How do CN- and N3- act as metabolic poisons?

Answer 8

They bind with high affinity to Fe3+ form of haem group

in cytochrome oxidase complex (IV)

blocking final step of ETC

Question 9

• How does Malonate act as a metabolic poison?

Answer 9

Resembles succinate and acts as competitive inhibitor of succinate dehydrogenase (complex II)

inhibiting oxidation of succinate to fumarate

slowing the flow of electrons from succinate to ubiquinone

Question 10

• How does Oligomycin act as a metabolic poison?

Answer 10

It is an antibiotic produced by Streptomyces that inhibits oxidative phosphorylation by binding to F0 of ATP Synthase and blocking the flow of H+ through the enzyme

Question 11

• How does DNP induce weight loss?

Answer 11

By transporting protons across the mitochondrial membrane

Thereby uncoupling oxidative phosphorylation from ATP production 

markedly increasing the metabolic rate and body temperature

This is because of the compensatory effect to increase metabolic rate to produce the energy needed to maintain the body

energy used to pump H+ dissipates as heat hence inc body temp

Question 12

• Why did people taking DNP die?

- How does substrate level phosphorylation differ from oxidative phosphorylation?

Answer 12

The margin between the slimming dose and that required to poison or kill is slight

Oxidative phosphorylation ultilises an electron transport chain to drive ATP production

substrate level phosphorylation is the direct transfer of high energy phosphate to ADP

Question 13

• Explain as to how the electron transport chain works?

Answer 13

NADH comes from cytoplasm through malate-aspartate shuttle and FADH2 comes from cytoplasm through glycerol-3-phosphate shuttle

NADH donates electron to complex I → NAD+ and a H+

FADH2 donates electron to complex II- another proton released

Electrons from either complex flow into coenzyme Q which passes electrons to complex III

Complex III uses its cytochromes to pass the electrons to cytochrome C which then transports these to complex IV

Complex IV then gives electrons to Oxygen to make it electronegative enough to bind to hydrogen which forms water

At same time as transporting electrons energy is released and so Complexes I, III and IV transport H+ from matrix to IMS

This creates an electrochemical gradient, as there is now a higher conc of H+ in the IMS than in matrix and so H+ is transported by a membrane transporter protein called F0 which is bound to F1 (ATP synthase)

As a H+ passes through the F0 into the matrix, ATP is synthesised

Question 14

where does oxidative phosphorylation take place?

where does krebs cycle take place

Answer 14

inner membrane

mitochondrial matrix

Question 15

what is respiratory control?

Answer 15

uptake of oxygen is controlled by the components of ATP synthesis (ADP and phosphate)
allows body to adapt oxygen consumption to energy requirements

Question 16

if the post mortem of someone who took DNP has …

• lack of fat and adipose tissue
• large amounts of red marrow
• faster rigor mortis

explain why for each finding

Answer 16

inc respiration, fuelled by triglycerides and fatty acid withing adipose, depleted

body was in a state of hypoxia as oxygen used too quickly, stimulates erythropoiesis

relaxing muscles fibres requires ADP to be displaced by incoming ATP, as ATP concentration is very low due to DNP, muscle is left contracted

Question 17

what is non shivering thermogenesis?

when does regulated uncoupling of Ox Phos occur?

How does this happen?

Answer 17

uncoupling of oxidative phosphorylation from ATP production
energy to pump H+ dissipates as heat

animals, newborn babies coming out of hibernation, rodents in temperate climates

UCP-1 aka thermogenin, activated in a response to drop in core temperature
allows protons to bypass ATP synthase, releasing heat from dissipation of proton gradient

Question 18

What is respiratory control

Answer 18

when the uptake of oxygen is controlled by the components of ATP synthesis (ADP and phosphate)

allows the body to adapt to 02 consumption with energy requirements