Unit 2 KA2

Question 1

Oxygen

Answer 1

The final hydrogen acceptor at the end of the electron transport chain.

Combines with hydrogen ions and electrons to make water.

This keeps the citric acid cycle and electron transport chain running.

Question 2

Ethanol

Answer 2

Produced along with carbon dioxide by the fermentation of pyruvate in the cytoplasm of plant and yeast cells.

Used to remove pyruvate and hydrogen to keep glycolysis running.

Question 3

Lactate

Answer 3

Produced in the cytoplasm as a result of the fermentation of pyruvate in the cytoplasm of animal cells.

Used to remove pyruvate and hydrogen to keep glycolysis running.

Question 4

Fermentation

Answer 4

Anaerobic respiration (without oxygen),

Glucose is partially broken down in the cytoplasm creating 2 ATP only - the net gain from glycolysis.

Question 5

Respiration

Answer 5

A series of vital metabolic pathways which are responsible for the production of ATP in cells.

Question 6

ATP

Answer 6

Adenosine triphosphate (adenosine + 3 phosphate groups)

The 3rd phosphate is attached with a high energy bond that can be broken easily to release large amount of energy when required.

Acts as an energy storage and transfer molecule in cells, linking catabolic and anabolic reactions.

Question 7

ADP

Answer 7

Produced when the 3rd phosphate is removed from ATP, which breaks the high energy bond and releases energy rapidly.

ATP —————-> ADP + Pi

This reaction can be reversed when energy is released from glucose during respiration and is used to restore the high energy bond.

ADP + Pi ————–> ATP

Question 8

Phosphorylation

Answer 8

Addition of a phosphate

eg. ADP + Pi —-> ATP

(Also the phosphorylation of glucose in glycolysis)

Question 9

Glycolysis

Answer 9

Occurs in the cytoplasm.

Results in the breakdown of glucose into 2 x molecules of pyruvate, with a net gain of 2 ATP.

It is enzyme controlled and does not require oxygen.

Question 10

Energy investment phase

Answer 10

2 ATP are used to phosphorylate glucose, making it more reactive.

Question 11

Energy payoff phase

Answer 11

Phosphorylated glucose splits to form 2 molecules of pyruvate, which generates 4 ATP.

Net ATP gain from glycolysis = 2ATP

Question 12

Dehydrogenase enzymes

Answer 12

Remove hydrogen (H+ and e-) and use them to reduce coenzyme NAD to NADH.

Happens in glycolysis and the citric acid cycle.

Question 13

NAD

Answer 13

A coenzyme molecule that is reduced when it combines with hydrogen to become NADH.

Carries hydrogen ions and high energy electrons to the electron transport chain.

Question 14

Matrix (mitochondrion)

Answer 14

The central jelly-like part of the mitochondrion.

The citric acid cycle happens here.

Question 15

Acetyl coenzyme A

Answer 15

Pyruvate loses carbon (as carbon dioxide) to become acetyl, which combines with coenzyme A so that it can enter the citric acid cycle.

This is known as the link reaction.

It happens in the mitochondrion.

Question 16

Citric acid cycle

Answer 16

One of the metabolic pathways of respiration which occurs in the matrix of the mitochondrion.

The acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate, which is gradually converted back to oxaloacetate in a series of enzyme controlled steps.

Carbon dioxide and ATP are generated, and hydrogen ions and electrons are removed by dehydrogenase enzymes creating NADH.

Question 17

Electron transport chain

Answer 17

A group of protein molecules in the inner mitochondrial membrane, which act as electron acceptors and carriers.

They work with the enzyme ATP synthase in a metabolic pathway which generates large quantities of ATP.

Hydrogen ions and high energy electrons are unloaded from NADH.

The high energy electrons pass along the electron transport chain and drive the pumping of protons across the membrane, into the intermembrane space.

Question 18

ATP synthase

Answer 18

A complex of protein molecules in the inner mitochondrial membrane, which rotates to generate ATP from ADP + Pi.

It is driven by the return flow of protons from the intermembrane space back to the matrix of the mitochondrion.

Question 19

Concentration gradient

Answer 19

A difference in concentration between 2 areas.

A high concentration of protons is maintained by pumping them into the intermembrane space, resulting in a return flow of protons back to an area of low concentration through ATP synthase.