2.8 (Cell Respiration)

Question 1

What are reasons for cell respiration (3)?

Answer 1

• Organic compounds from the food we eat such as glucose contain stored energy within their covalent bonds
• All living organisms carry out respiration in order to convert stored energy into a form that can be used by the cell
• When organic molecules are broken down, the energy formed is eventually stored in a high energy molecule called ATP

Question 2

Define cell respiration.

Answer 2

The controlled release of energy from organic compounds in cells to produce ATP.

Question 3

What are the main types of cellular processes (3)?

Answer 3

• Synthesising large molecules
• Pumping ions across membranes by active transport
• Moving things around the cell (e.g. vesicles, chromosomes and muscle contraction)

Question 4

How is energy released?

Answer 4

Spitting ATP –> ADP + Pi

Question 5

Outline glycolysis including anaerobic respiration and products (7).

Answer 5

• Glucose (6C) broken down into 2 pyruvate (3C) in the cytoplasm by glycolysis
• Net gain of 2 ATP
• Does not require oxygen
• Anaerobic respiration occurs in cytoplasm
• First stage: glucose to pyruvate, 2 ATP gain
• If no oxgyen is available, pyruvate is converted to lactate or ethanol (depending on organism- lactate in humans)
• No CO2 produced as lactate is a 3 carbon molecule

Question 6

Outline human lactate production in terms of muscle contractions.

Answer 6

• Blood flow to muscles is reduced during high intensity exercise, causing a reduction in oxygen
• In oxygen’s absence, muscle cells use glycolysis to produce ATP.
• Glycolysis generates ATP faster than oxidative phosphorylation, meaning some muscles resort to glycolysis even when oxygen is present
• Consequence: lactic acid accumulated in muscles causes soreness and fatigue

Question 7

Carbon dioxide and the baking industry.

Answer 7

Yeast is used in baking bread. It is mixed into dough before baking. The yeast uses up all the O2 and then produces ethanol and CO2. The CO2 forms bubbles making the dough rise.

Question 8

Ethanol and the brewing industry.

Answer 8

Yeast is cultured in a liquid containing sugar and other nutrients without O2 available. This causes the yeast to use anaerobic respiration for metabolic activities resulting in alcohol.

Question 9

Outline aerobic respiration.

Answer 9

• Begins with glycolysis, producing 2 pyruvate molecules per glucose
• Requires oxygen in the mitochondria
• Much more efficient than anaerobic respiration
• Products created in redox reactions of Krebs cycle plus oxygen will produce large quantities of ATP though oxidative phosphorylation in ETC with water being released
• Glucose + oxygen will produce carbon dioxide and water with 32-34 ATP molecules produced