Unit 1 KA7 - Cellular respiration

Question 1

What are the final products when one molecule of glucose is passed along the glycolytic pathway?

Answer 1

Two molecules of pyruvate, two molecules of ATP, and two hydrogen ions on carrier molecules (as NADH).

Question 2

what is cellular respiration?

Answer 2

a series of metabolic pathways that brings about the releases of energy from a foodstuff and the regeneration of the high-energy compound adenosine triphosphate (ATP).

Question 3

what are the three stages of cellular respiration?

Answer 3

glycolysis, citric acid cycle and electron transport chain.

Question 4

what does ATP stand for and what is it made of?

Answer 4

adenosine triphosphate is made of adenosine and three inorganic phosphate groups.

Question 5

ATP is synthesised in a ………….. reaction from …….. and …… (…………. and …………..)

Answer 5

reversible, ADP, Pi, adenosine diphosphate, phosphate.

Question 6

the …………… of ATP to ADP and ………… …………….. energy.

Answer 6

breakdown, phosphate, releases.

Question 7

the ……….. of ATP from ADP and ………. uses the energy released from ……….. …………..

Answer 7

regeneration, phosphate, cellular respiration.

Question 8

what is phosphorylation?

Answer 8

an enzyme-controlled process in which a phosphate group is added to a molecule.

Question 9

give an example of phosphorylation.

Answer 9

ADP + Pi to produce ATP.

Question 10

why is phosphorylation important?

Answer 10

often, a step in a pathway can only occur if a reactant is phosphorylated and energised.

Question 11

name the two stages of glycolysis.

Answer 11

energy investment stage and energy pay off stage.

Question 12

where do the three stages of cellular respiration take place?

Answer 12

glycolysis - cytoplasm.
citric acid cycle - matrix of the mitochondria.
electron transport chain - inner mitochondrial membrane.

Question 13

describe glycolysis.

Answer 13

involves the breakdown of glucose to pyruvate.

it occurs in the cytoplasm and no oxygen is required.

Question 14

describe the energy investment stage of glycolysis.

Answer 14

2 ATP are used to phosphorylate glucose and intermediates.
1st phosphorylation produces an intermediate which can move to other integrated metabolic pathways.
2nd phosphorylation is an irreversible reaction that can only lead to glycolysis pathway.

Question 15

describe the energy pay off stage of glycolysis.

Answer 15

4 ATP are produced causing a net gain of 2 ATP per molecule of glucose.
hydrogen ions and electrons are released from intermediates.
H+ ions and electrons are passed onto the co enzyme NAD to form NADH.

Question 16

describe the citric acid cycle.

Answer 16

occurs in the matrix of the mitochondria in the presence of oxygen.
1. pyruvate is broken down to an acetyl group.
carbon dioxide is released as well as h+ ions and electrons which bind to NAD to form NADH.
2. acetyl group combines with coenzyme A to form acetyl coenzyme A.
3. acetyl coenzyme A combines with oxaloacetate to form citrate.
coenzyme A leaves to find another acetyl group.
4. several enzyme controlled steps of the citric acid cycle regenerate oxaloacetate while;
- ATP is regenerated from ADP and Pi
- coenzyme and NAD is reduced to NADH as dehydrogenase enzymes remove Hydrogen ions and electrons from intermediates.
- carbon dioxide is released.

Question 17

describe the electron transport chain.

Answer 17

occurs in the inner mitochondrial membrane.

1. NADH releases the electrons to the electron transport chain where they cascade down the chain, releasing energy.
2. the energy is used to pump H+ ions across the inner mitochondrial membrane.
3. the return flow of H+ ions drives ATP synthase and produces the bulk of the ATP generated by cellular respiration.
4. the final electron acceptor is oxygen, which then combines with hydrogen ions and electrons to form water.

Question 18

what is fermentation and where does it occur??

Answer 18

the breakdown of glucose in the absence of oxygen, occurs in the cytoplasm.

Question 19

describe fermentation.

Answer 19

glycolysis occurs as normal, and in the absence of oxygen, the pyruvate undergoes fermentation, becoming lactate.

Question 20

what is ATP synthase and where is it found?

Answer 20

the enzyme that catalyses the synthesis of ATP from ADP and phosphate, found in membranes in the cell.

Question 21

what is the role of dehydrogenase enzymes?

Answer 21

remove hydrogen ions and electrons and passes them to the coenzyme NAD, forming NADH.
used in both glycolysis and citric acid cycle.

Question 22

what is the role of ATP?

Answer 22

used to transfer energy to cellular processes which require energy.