Citric Acid Cycle

Question 1

Where does the citric acid cycle occur?

Answer 1

matrix of the mitochondrion

Question 2

What is the function of the citric acid cycle?

Answer 2

to produce NADH and FADH2 to be used to make energy

feed in system for any molecule that can be converted to an acetyl group

Question 3

What does the citric acid cycle do specifically?

Answer 3

removes electrons and passes them onto NADH and FADH2

Question 4

How is acetyl CoA made?

Answer 4

from pyruvate through the action of pyruvate dehydrogenase

Question 5

What 2 products is acetyl CoA oxidised to?

Answer 5

CO2 and H20

Question 6

How is pyruvate dehydrogenase regulated?

Answer 6

by its immediate products

by the end point of cellular respiration - ATP

Question 7

What is the difference between utilisation of glycogen in liver and in skeletal muscle tissue?

Answer 7

liver glycogen—-G-6-P—glucose-6-phosphatase—–glucose in blood
skeletal muscle glycogen—G-6-P—–glycolysis—-lactate

Question 8

Where is the site of terminal respiration?

Answer 8

mitochondrion

Question 9

Where is the majority of NADH and FADH2 formed? Where is the rest of it formed?

Answer 9

majority in citric acid cycle

rest in cytosol

Question 10

What is the glycerol phosphate shuttle?

Answer 10

mechanism by which cytosolic NADH passes its electrons onto glycerol-3-phosphate and then to FADH2 for use in the electron transport chain

Question 11

What is the disadvantage of using cytosolic NADH?

Answer 11

FADH2 generates less energy per mole than oxidation of NADH itself

Question 12

There are 4 protein complexes involved in the electron transport chain. What does complex 1 do?

Answer 12

oxidises NADH and passes high energy electrons onto ubiquinone to form ubiquinol
pumps H+ ions into the inter membrane space

Question 13

What does complex 2 do?

Answer 13

oxidises FADH2 and passes high energy electrons onto ubiquinone to form ubiquinol

Question 14

What does complex 3 do?

Answer 14

takes electrons from ubiquinol and passes them onto cytochrome c
oxidation of one ubiquinol yields 2 reduced cytochrome c molecules
pumps protons into intermembrane space

Question 15

What does complex 4 do?

Answer 15

takes electrons from cytochrome c and passes them onto oxygen
pumps protons into inter membrane space

Question 16

How is the energy saved up in the H+ gradient used?

Answer 16

1. proton motive force

2. ATP synthase ‘turbine’ evolved to harness energy from proton gradient

Question 17

What is chemiosmosis?

Answer 17

the process by which protons are pumped into the inter membrane space as electrons are passed along the transport chain

Question 18

What is a proton motive force?

Answer 18

when the protons are allowed to flow back down their gradient and release energy in the process

Question 19

How is ATP synthesised?

Answer 19

protons move by proton motive force back down their gradient back into the matrix of the mitochondrion——– this only happens at certain areas on the membrane and at these sites there is often ATP synthase—– as the protons flow through the ATP synthase, the energy stored in the gradient is used to convert ADP + Pi to ATP

Question 20

ATP synthase has two parts. Name them and describe what they do.

Answer 20

F0- membrane bound proton conducting unit

F1- protrudes into the mitochondrial matrix and acts as a catalyst for ATP synthesis

Question 21

How much ATP is produced per H+?

Answer 21

3H+ moved across the membrane by ATP synthase + 1 ATP

Question 22

What are the end products of terminal respiration?

Answer 22

CO2, H2O and ATP

Question 23

Explain the concept of coupling in relation to oxidative phosphorylation?

Answer 23

electron transport is said to be ‘coupled’ to ATP synthesis
this is because, if the inner mitochondrial membrane becomes permeable to protons, the proton gradient cannot be generated, but the electrons can still be passed along their carriers
therefore O2 still reduced to O2 but no ATP made

Question 24

What does it mean for the processes to be uncoupled?

Answer 24

when the inner mitochondrial membrane becomes permeable to the H+ ions and the proton gradient cannot be generated therefore ATP synthesis doesn’t occur but electron transport chain still occurs
energy from ETC is released as heat

Question 25

What is malignant hyperthermia?

Answer 25

a disease caused by ‘leaky’ mitochondrial membranes that uncouple ETC and ATP synthesis

Question 26

what can cause malignant hyperthermia?

Answer 26

exposure to halothane or halothane-type drugs

Question 27

When does intentional uncoupling occur?

Answer 27

in brown fat in infants
brown fat cells have lots of mitochondria
if baby becomes cold, nor-epinephrine triggers the opening of a channel in a protein called thermogenic
thermogenin is on inner mitochondrial membrane of brown fat cells