Respiration

Question 1

What 3 main things do you need to remember about respiration?

Answer 1

1. 2 types aerobic and anaerobic (without O2).
2. Anaerobic respiration produces less ATP.
3. Both start with glycolysis.

Question 2

What are the four stages of respiration?

Answer 2

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. ETC

Question 3

Where do the 4 stages of respiration occur?

Answer 3

Glycolysis: cytoplasm

Link reaction: matrix

Krebs cycle: matrix

ETC: Cristae

Question 4

Outline the stages of glycolysis..

Answer 4

1. Glucose phosphorylated to glucose phosphate by 2xATP
2. Glucose phosphate splits into 2x triose phosphate
3. 2xTP are oxidised to 2xpyruvate
4. Net gain of 2x reduced NAD

(NAD collects the H ions lost from TP when it is oxidised to form pyruvate - it is reduced to reduced NAD)

(4 ATP produced, but 2 were used in the first stage of glycolysis).

Question 5

Flowchart of glycolysis.

Answer 5

Question 6

How does pyruvate from glycolysis enter the mitochondria?

Answer 6

Via active transport

Question 7

Describe the link reaction.

Answer 7

1. Pyruvate is decarboxylated (1C is removed in the form of CO2).
2. Pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD.
3. Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A (ACoA).

No ATP produced.

Question 8

Diagram of the link reaction.

Answer 8

Question 9

Outline the Krebs cycle with a diagram.

Answer 9

Question 10

For every glucose molecule, what is produced?

Answer 10

2 pyruvate molecules are made for every glucose molecule that enters glycolysis

So, the link reaction happens twice for every glucose molecule.

So for every glucose molecule:

2 ACoA → krebs cycle
2 CO2 → released as waste product
2 reduced NAD → ETC

Question 11

Products of anaerobic respiration in different organisms?

Answer 11

In anaerobic respiration, pyruvate is converted into:

Ethanol - in plants and yeast
Lactate - in animals and some bacteria

Question 12

How is ethanol produced by anaerobic respiration.

Answer 12

• In plants/yeast
• by alcoholic fermentation

Question 13

How is lactate produced in anaerobic respiration.

Answer 13

• in animals and some bacteria
• by lactate fermentation

Question 14

How can ATP still be produced by anaerobic respiration?

Answer 14

The production of ethanol or lactate regenerates oxidised NAD.
This means glycolysis can continue even when there isn’t any oxygen.
A small amount of ATP can still be produced.

Question 15

Describe the ETC (1)

Answer 15

1) Hydrogen atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD. The H atoms split into protons (H+) and electrons (e-).

2) The electrons move down the electron transport chain (made up of electron carriers), losing energy at each carrier.

3) This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space.

4) The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix.
- this forms an electrochemical gradient.

Question 16

Describe the ETC (2)

Answer 16

5) Protons then move down the electrochemical gradient, back across the inner mitochondrial membranev- the cristae and into the matrix, via ATP synthase (which is embedded in the cristae). This movement drives the synthesis of ATP from ADP and inorganic phosphate (Pi).

6) This process of ATP production driven by the movement of protons across a membrane is called chemiosmosis.

7) In the matrix, at the end of the transport chain, the protons, electrons and O2 (from the blood) combine to form water.
Oxygen is the final electron acceptor in the ETC.