Cellular Respiration and Oxidative Phosphorylation

Question 1

The Steps of Cellular Respiration (and location)

Answer 1

1. Glycolysis: glucose -> pyruvate; occurs in cytosol
2. Pyruvate Dehydrogenase Complex: pyruvate -> acetyl CoA; occurs in mitochondria
3. TCA Cycle: acetyl CoA -> CO2; occurs in mitochondria
   - —- energy captured as NADH or FADH2 —-
4. Oxidative Phosphorylation: coupling of electron transport to ATP synthesis; occurs in mitochondria
   - ETC: OXIDATIVE step; electrons captured as NADH and FADH2 in the preceding pathways are used to reduce oxygen to water
   - ATP Synthesis: PHOSPHORYLATION step; energy captured in ETC is used to ADP -> ATP

Question 2

Reduced form

Answer 2

H

Question 3

FADH2 transfers e- directly to

Answer 3

CoQ; misses first H+ transfer step, no pumping H+=less energy made per FADH2

Question 4

Oxidative Phosphorylation results in

Answer 4

O2->H2O

Question 5

1ATP = __ H+?

Answer 5

3H+ = 1 ATP

Question 6

ETC and ATP Synthesis is

Answer 6

COUPLED! a decrease in one results in an decrease in all

Question 7

H+ gradient is referred to as

Answer 7

proton-motive force

Question 8

Prerequisites for Oxidative Phosphorylation

Answer 8

• reduced forms of NADH and FADH2
• O2
• low ATP (high ADP)
• sufficient quantity of mitochondria

Question 9

If the ETC were deficient, what would happen?

Answer 9

Pyruvate levels would decrease, and lactate levels would increase

Question 10

Anaerobic Glycolysis

Answer 10

in cytoplasm; net yield of 2 mol ATP

Question 11

2 ways to interfere with OxPhos

Answer 11

Inhibitors of the Respiratory Chain
-bind to one of the complexes in the ETC and stop oxidation-reduction reactions and electron transfer

Uncouplers
- break link between the rate of ET and synthesis of ATP

Question 12

Atractyloside

Answer 12

• binds and inhibits ATP/ADP antiporter, preventing transport and availability of ADP in matrix for ATP synthesis
• in turn slows down ETC

Question 13

Inhibitors that Disrupt Respiratory Chain

• Rotenone
• Antimycin
• CO
• Cyanide
• Oligiomycin

Answer 13

• Rotenone: (I)
• Antimycin: (III)
• CO: (IV)
• Cyanide: (IV)
• Oligiomycin: V

Question 14

Rotenone

Answer 14

• potent inhibitor of NADH dehydrogenase (Complex I) of ETC
• ** WILL NOT COMPLETELY INHIBIT ETC ** No NADH will be able to be used, however FADH2 will still be able to be used as it enters at Complex II
  ^ significantly decreases proton gradient and amount of ATP produced

Question 15

Antimycin

Answer 15

• inhibitor of Complex III

- electron carriers before III become fully reduced, and after III are completely oxidized

Question 16

Cyanide (CN) Poisoning

Answer 16

• inhibitor of Complex IV; binds tightly to ferric iron Fe3+ state of cyt a3 (IV)
• NO NET ATP PRODUCTION: a3 gives e- to O2
• CN Antidote: Nitrite followed by thosulfate treatment (converts ferrous to ferric and allows for transport to hemoglobin rather than having in ETC)

Question 17

CN distinct odor

Answer 17

bitter almonds

Question 18

Carbon Monoxide

Answer 18

• inhibits Complex IV

Question 19

Oligomycin

Answer 19

• binds to F0 portion of ATP synthase
• prevents transport of protons
• no ATP can be made

Question 20

Uncouplers

Answer 20

molecules that allow protons to reenter the mitochondrial matrix from the intermembrane space INDEPENDENT of the proton-channeling function of ATP synthase

• allow ETC to proceed but ATP synthesis does not occur because no proton gradient established
• energy linked with the transport of electrons is dissipated as heat
• ** OXYGEN CONSUMPTION CONTINUES but NOT ATP IS PRODUCED **

Question 21

2,4-dinitrophenol (DNP)

Answer 21

• Uncoupler
• Starves cells of ATP
  (like high dose asprin)

Question 22

Thermogenesis: Heat Production and Maintenance

Answer 22

1. Shivering: uses ATP and generates heat
2. Non-shivering Thermogenesis: use uncoupling to generate heat
   - Thermogenin found in brown fat generates heat and maintains body temp (found in babies and bears)

Question 23

Cyanide poison result

Answer 23

O2 will not be consumed, and no ATP will be generated

Question 24

Oligomycin poison

Answer 24

O2 will not be consumed and no ATP will be produced

- blocking ATP synthase also inhibits the consumption of O2

Question 25

DNP posion

Answer 25

DNP = uncoupler ( H+ “smuggler”)

- O2 will be consumed by no ATP will be produced

Question 26

Malate-Aspartate Shuttle

Answer 26

transports cytoplasmic NADH into mitochondrial matrix in order to participate in OxPhos

• ** COMPLEX I ** 1 NADH = 3 ATP **
• NADH cytosol -> mitochondria
• reversible
• no ATP loss (Malate -> OAA conversion “pumps” NADH in)
• only works if [NADH]/[NAD+] is higher in cytoplasm than in matrix
• operates in liver, heart, and kidneys

Question 27

Glycerol Phosphate Shuttle

Answer 27

transports cytoplasmic NADH into mitochondrial matrix in order to participate in OxPhos

• ** COMPLEX 3 ** BYPASS RXN ** 1NADH = 2 ATP ***
• irreversible
• NADH -> FADH2 exchange (NADH cytosol -> FADH2 mitochondria)
• yields 1 less ATP
• operates in brain and skeletal muscle: where you need energy fast!
• Faster than malate-aspartate