2.8 Respiration

Question 1

Cellular respiration

Answer 1

The gradual and controlled release of energy by breaking down organic compounds (primarily glucose) to produce ATP (Adenosine Tri Phosphate)

Question 2

What is energy used for in organisms?

Answer 2

• Active transport
• Anabolic reactions
• Movement
• Maintaining body temperature

Question 3

ATP production

Answer 3

ATP: a high energy molecule that functions as an imediate source of power for cell processes
- One molecule of ATP contains three covalently linked phosphate groups – which store potential energy in their bonds
- When ATP is hydrolysed (to form ADP + P) the energy stored in the phophate bond is released to be used by the cell
- Cell respiration uses energy stored in organic molecules to regenerate ATP from ADP + P (via oxidation)

Question 4

Anaerobic respiration

Answer 4

• Cellular respiration that takesplace without oxygen
• Releases a small yield of energy in the form of ATP
• Takes place in the cytoplasm

Glucose is broken down into 2 pyruvate molecules and 2 ATP molecules

Question 5

Alcoholic fermentation

Anaerobic respiration in yeast

Answer 5

Glucose is broken down into pyruvate
Pyruvate –> ethanol + carbon dioxide + 2 ATP molecules

Question 6

Lactic acid fermentation

Anaerobic respiration in muscle cells

Answer 6

• When exercising at high intensity, the cells’ energy demands will exceed what the available levels of oxygen can supply aerobically
• Hence the body will begin breaking down glucose anaerobically to maximise ATP production

The glucose is broken down into pyruvate
Pyruvate –> lactate (lactic acid) + 2 ATP molecules
- This will result in an increase in the production of lactic acid, which leads to muscle fatigue

Question 7

What happens to lactic acid after exercise?

Answer 7

Its transported away from the muscles as it is toxic, and into the liver where oxygen is used to break it down into carbon dioxide and water to make glucose.
- This means that the athlete will have to continue to breathe heavily to obtain the extra oxygen.

Question 8

Oxygen debt

Answer 8

• Whenever lactate is produced by anaerobic respiration, an oxygen debt is being built up.
• This debt is paid back at the end of the exercise by breathing more deeply than you would normally need to at rest.
• Oxygen is used to convert lactate to pyuvarate and then glucose

Question 9

Aerobic cell respiration

Answer 9

• Cellular respiration that requires oxygen
• Produces a large yield of energy in the form of ATP
• Takes place in the cytoplasm and the mitochondria
  Glucose + oxygen = carbon dioxide + water + energy
  C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP

Question 10

Respirometer

Answer 10

• An apparatus that measures the rate of respiration
• A substance that absorbes carbon dioxide (usually soda lime) is placed in a test tube along with a living organism that respires (like germinating seeds)
• As the living organism respires, oxygen is used and carbon dioxide is released but absorbed by the soda lime.
• This results in a lower volume of gas in the tube which lowers the pressure and sucks the water/ink towards the organism.

Question 11

Why keep the temperature constant?

Respirometer

Answer 11

• A higher tempereture would increase the pressure
• A lower temperature would decrease the pressure

Question 12

Where does respiration happen?

Answer 12

In the mitochondria.

Question 13

Is ATP from cell respiration is immediately available as a source of energy in the cell?

Answer 13

Yes