Respiration

Question 1

where does glycolysis occur?

Answer 1

in the cytoplasm of cells

Question 2

what are the two stages in glycolysis?

Answer 2

phosphorylation and oxidation

Question 3

what happens in glycolysis?

Answer 3

2 phosphates are added to the glucose molecule which then splits into triose phosphate. The triose phosphate loses 2H+ forming pyruvate.

Question 4

where does the pyruvate go after glycolysis?

Answer 4

actively transported into the matrix of the mitochondria

Question 5

what happens in the link reaction?

Answer 5

pyruvate loses one carbon to CO2, this is oxidised to form acetate then combines with CoenzymeA.

Question 6

what happens in the Kreb’s cycle?

Answer 6

acetyl coconzyme A combines with a 4-carbon molecule, loses 2 carbons to CO2 and 4H+ to NAD and FAD.

Question 7

what happens in oxidative phosphorylation?

Answer 7

Hydrogen atoms from NAD and FAD are released and split into H+ and e-. These are passed along an electron transport chain releasing energy which pumps protons into the intermembrane space producing an electrochemical gradient. The protons move down the gradient through ATP synthase channels producing ATP.

Question 8

What does aerobic respiration produce?

Answer 8

CO2, water and ATP

Question 9

What does anaerobic respiration produce?

Answer 9

Lactate, CO2 and a little ATP

Question 10

What is the energy yield from glycolysis?

Answer 10

2 molecules of ATP
2 molecules reduced NAD
2 molecules of pyruvate

Question 11

where are the enzymes for the glycotic pathway found?

Answer 11

In the cytoplasm of cells and so glycolysis does not require any organelle or membrane

Question 12

Why does the pyruvate need to be converted into lactate or ethanol during anaerobic respiration?

Answer 12

To re-oxidise the NAD so that glycolysis can continue and prevent the redNAD building up.

Question 13

What is the overall equation for the link reaction?

Answer 13

pyruvate + NAD + CoA –> acetyl CoA + redNAD + CO2

Question 14

What are the four important roles the Kreb’s cycle has in organisms?

Answer 14

• Breaks down macromolecules into smaller ones,
• Produces hydrogen atoms that are carried by NAD to the electron transfer chain, providing energy for oxidative phosphorylation,
• It regenerates the 4-carbon molecule,
  It is a source of intermediate compounds used by cells in the manufacture of other important substances such as fatty acids.

Question 15

What would happen without oxygen?

Answer 15

The hydrogen ions and electrons would ‘back-up’ along the chain and the process of respiration would come to a halt.

Question 16

Why are the electrons passed down an electron transfer chain?

Answer 16

Allows the energy to be released gradually, minimising heat loss.

Question 17

What is substrate level phosphorylation?

Answer 17

The direct transfer of phosphate from a respiratory intermediate to ADP to produce ATP.

Question 18

What is oxidative phosphorylation?

Answer 18

the indirect linking of energy from phosphate to ADP to produce ATP involving energy from the hydrogen atoms that are carried on NAD and FAD.

Question 19

Explain why converting pyruvate to lactate allows ATP to be produced.

Answer 19

Regenerates NAD from reduced NAD

So it can continue to be used in glycolysis.