2: Cell Respiration

Question 1

What do all living cells need?

Answer 1

a continual supply of energy

Question 2

What is energy used by cells used for? Where does this energy come from (chemically)?

Answer 2

• a wide range of processes including active transport and protein synthesis
• energy in form of ATP (adenosine triphosphate)

Question 3

How do cells get ATP?

Answer 3

• produce it themselves through cell respiration:
• carbon compounds e.g. glucose or fat are carefully broken down and the energy released by doing this is used to make ATP

Question 4

Define ‘cell respiration’.

Answer 4

controlled release of energy from organic compounds to produce ATP

Question 5

Is ATP a good source of energy?

Answer 5

yeaa boi - immediately available as an energy source:

- it can diffuse to any part of the cell and release its energy within a fraction of a second

Question 6

Contrast aerobic cell respiration and anaerobic cell respiration.

Answer 6

1. oxygen used?
   - aerobic: yes
   - anaerobic: no
2. substrate:
   - aerobic: glucose or lipids
   - anaerobic: glucose only
3. yield of ATP per glucose
   - aerobic: large
   - anaerobic: small
4. products:
   - aerobic: CO2 and water
   - anaerobic:
   humans: lactate
   yeast: CO2 and ethanol

Question 7

Draw a flow diagram of aerobic cell respiration. (p32)

Answer 7

pyruvate -> large amount of ATP + water + CO2

Question 8

Draw a flow diagram of anaerobic cell respiration. (p32)

Answer 8

glucose -> pyruvate + small amount of ATP

Question 9

State an advantage of anaerobic respiration over aerobic respiration when providing energy for muscles. When is anaerobic respiration often used?

Answer 9

• although anaerobic makes less ATP per glucose, it can supply ATP at a more rapid overall rate than aerobic (for a short time - about 2 mins)
• during very vigorous exercise e.g. sprinting or weight lifting

Question 10

Why can we only anaerobically respire for a very short time?

Answer 10

• lactate (lactic acid) and hydrogen ions are produced by anaerobic respiration
• hydrogen ions lower the pH of blood
• after ~2mins, concentration of hydrogen ions is too high, making blood too acidic, so aerobic cell respiration must be used

Question 11

What are the two products of anaerobic respiration in yeast?

Answer 11

ethanol and CO2

Question 12

How is CO2 (produced by anaerobic respiration of yeast) used?

Answer 12

In baking industry:

• yeast mixed into dough before baking
• rapidly uses up all oxygen present and then produces ethanol and CO2
• CO2 forms bubbles making bread rise, and less dense (leavened)
• when baked, ethanol evaporates

Question 13

How is ethanol (produced by anaerobic respiration of yeast) used?

Answer 13

in brewing and biofuel industries:

• yeast cultured in liquid containing sugar and other nutrients, but not oxygen (therefore anaerobic respiration)
• ethanol concentration rises, at 15% ethanol -
• fermentation ends before ethanol conc becomes toxic to yeast
• CO2 bubbles into atmosphere