Respiration

Question 1

What are the two types of respiration?

Answer 1

Aerobic-
Requires oxygen
Produces water and much ATP

Anaerobic- 
Absence of oxygen 
Produces lactate (in animals)
Produces ethanol and CO2 (in plants)
Only a little ATP

Question 2

What are the 4 stages of aerobic respiration?

Answer 2

Glycolysis
Link reaction
Krebs cycle
Electron transport cycle

Question 3

State where in the cell glycolysis occurs.

Answer 3

Cytoplasm of cell

Question 4

Explain the process of glycolysis.

Answer 4

1. Phosphorylation of glucose.
2. So forming phosphorylated glucose.
3. Then splitting into two triose phosphates.
4. For formation of pyruvate/dehydrogenation and formation of reduced NAD.
5. Pyruvate produced.
6. Total production 4 ATP / net production of 2 ATP

Question 5

What is the overall yield of one glucose molecule undergoing glycolysis?

Answer 5

Two molecules of ATP (two were used up in the initial phosphorylation).
Two molecules of reduced NAD more ATP.
Two molecules of pyruvate.

Question 6

Explain the link reaction.

Answer 6

The pyruvate molecules produced in the cytoplasm during glycolysis are actively transported into the matrix of the mitochondria.
The pyruvate is oxidised by removing hydrogen.
This hydrogen is accepted by NAD to form reduced NAD.
The 2 carbon molecule called an acetyl group that is therby formed combines with coenzyme A to produce acetylcoenzyme A.
A CO2 molecule is formed from each pyruvate.

Question 7

What is the equation for the link reaction?

Answer 7

Pyruvate + NAD + CoA -> acetyl CoA + reduced NAD + CO2.

Question 8

Summarise the Krebs cycle.

Answer 8

The 2 carbon acetylcoenzyme A from the link reaction combines with a 4 carbon molecule to produce a 6 carbon molecule.
This 6 carbon molecule loses carbon dioxide and hydrogens to give a 4 carbon molecule and a single molecule of ATP (substrate level phosphorylation).
The 4 carbon molecule can now combine with a new molecule of acetylcoenzyme A to begin the cycle again.

Question 9

For each molecule of pyruvate, the link reaction and the Krebs cycle produce what?

Answer 9

Reduced coenzymes such as NAD and FAD.
One molecule of ATP.
Three molecules of carbon dioxide.

Question 10

Apart from respiration, give three uses of ATP in a liver cell.

Answer 10

Active transport
Phagocytosis
Mitosis
Synthesis of protein

Question 11

Human skeletal muscle can respire both aerobically and anaerobically. Describe what happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is advantageous to human skeletal muscle.

Answer 11

Forms lactate
Use of reduced NAD
Regenerates NAD
NAD can be re-used to oxidise more respiratory substrate
Can still release energy/form ATP
when oxygen in short supply/when no oxygen

Question 12

Other substances are produced in the Krebs cycle in addition to the carbon compounds
shown in the diagram. Name three of these other products.

Answer 12

reduced NAD
reduced FAD
ATP

Question 13

Describe the part played by the inner membrane of a mitochondrion in producing ATP.

Answer 13

Electrons transferred down electron transport chain;
Provide energy to take protons into space between membranes.
Protons/H+ pass back through membrane into matrix
Energy used to combine ADP and phosphate/to produce ATP

Question 14

Give two advantages of ATP as an energy-storage molecule within a cell.

Answer 14

Cannot pass out of cell
Quickly/easily broken down
Stores / releases small amounts of energy

Question 15

In the presence of oxygen, respiration yields more ATP per molecule of glucose than it does in the absence of oxygen. Explain why.

Answer 15

Oxygen as terminal hydrogen/electron acceptor
Operation of electron transport chain
Fate of pyruvate
Krebs cycle
Significance of ATP formed in glycolysis

Question 16

Name one step in which carbon dioxide is produced.

Answer 16

Krebs cycle/link reaction/pyruvate to acetylcoenzyme A;

Question 17

If five molecules of glucose enter the process of glycolysis.

a) How many molecules of pyruvate will be produced?
b) How many molecules of reduced NAD will be produced?
c) What will the net gain of ATP be?

Answer 17

10 (two molecules of pyruvate are made for every molecule of glucose that enters glycolysis).
10 (two molecules of reduced NAD are made for every molecule of glucose that enters glycolysis).
10 (four molecules of ATP are produced for each molecule of glucose however 2 are also used.)

Question 18

How is acetylcoenzyme A prodcued in the link reaction?

Answer 18

Pyruvate is decarboxylated: CO2 is removed.

It is added to CoA to form Acetyl CoA

Question 19

Role of pyruvate in anaerobic respiration allowing continued glycolysis

Answer 19

Red NAD to NAD which is recycled

Question 20

Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why.

Answer 20

1. Oxygen is final/terminal (electron) acceptor /
   oxygen combines with electrons and protons;
2. Oxidative phosphorylation / electron transport
   chain provides ATP;

Question 21

Advantages of using ATP

Answer 21

∙Provides energy in small amounts (1 glucose molecule would produce too much energy for a single process and some would be wasted)
∙Energy in ATP can be released quickly and easily in a specific area

Question 22

Where does the link reaction take place

Answer 22

Matrix of mitochondria

Question 23

Chemiosmosis

Answer 23

Use of electrochemical gradient to synthesise ATP

Question 24

Evidence of chemiosmosis

Answer 24

1. pH gradient across mitochondria/chloroplast membrane → conc of H⁺ ions across membrane
2. As long as there is a pH gradient ATP is still produced, even without electron transport chain
3. Chemicals preventing H⁺ transport across the membrane stop ATP production
4. Mitochondria at pH8 put into pH4 solution produce ATP in presence of ADP and P

Question 25

Aerobic Respiration

Answer 25

Aerobic respiration uses oxygen to break down glucose.
Aerobic respiration can be described as the process of releasing energy
through the oxidation of glucose molecules.