Combined Biology - B4 Bioenergetics

Question 1

Write the word and symbol equations for photosynthesis.

Answer 1

carbon dioxide + water → glucose + oxygen

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 2

Why is photosynthesis described as an endothermic reaction?

Answer 2

Energy is transferred from the environment to the chloroplasts, by light.

Question 3

Name four factors that affect the rate of photosynthesis.

Answer 3

• Temperature
• Light intensity
• Carbon dioxide concentration
• Amount of chlorophyll

Question 4

List the 5 ways that plants use the glucose produced in photosynthesis.

Answer 4

• Respiration
• Converted into insoluble starch for storage
• Used to produce fat or oil for storage
• Used to produce cellulose, which strengthens the cell wall
• Used to produce amino acids for protein synthesis

Question 5

As well as glucose, what else do plants need to produce proteins?

Answer 5

Nitrates (that they absorb from the soil)

Question 6

Is respiration an endothermic or exothermic reaction?

Answer 6

Exothermic reaction

Question 7

Q. Which type of respiration releases most energy?

Q. Which type of respiration requires oxygen?

Answer 7

• Aerobic Respiration
• Aerobic Respiration

Question 8

List three things that organisms need the energy from respiration for.

Answer 8

• Chemical reactions to build larger molecules
• Movement
• Keeping Warm

Question 9

Write the word and symbol equations for aerobic respiration.

Answer 9

glucose + oxygen → carbon dioxide + water

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Question 10

Write the word equation for anaerobic respiration in muscles.

Answer 10

glucose → lactic acid

Question 11

Write the word equation for anaerobic respiration in plant and yeast cells.

Answer 11

glucose → ethanol + carbon dioxide

Question 12

Name the process of anaerobic respiration in yeast cells.

Answer 12

Fermentation

Question 13

Give the two main industrial uses of fermentation.

Answer 13

Bread making and alcoholic drinks

Question 14

Explain how the human body reacts to the increased demand for energy during exercise.

Answer 14

• Heart rate increases
• Breathing rate increases
• Breath volume increases
• So the muscles receive more oxygenated blood

Question 15

What type of respiration takes place if there is an insufficient amount of oxygen?

Answer 15

Anaerobic Respiration

Question 16

What type of respiration involves the incomplete oxidation of glucose?

Answer 16

Anaerobic Respiration

Question 17

What happens to muscles after long periods of exercise?

Answer 17

• There is a build up of lactic acid.
• This causes oxygen debt.
• The muscles become fatigued.
• Muscles stop contracting efficiently.

Question 18

What is ‘metabolism’?

Answer 18

The sum of all chemical reactions in a cell or the body.

Question 19

List 5 processes involved in metabolism.

Answer 19

• Conversion of glucose to starch, glycogen and cellulose.
• Formation of lipid molecules from one molecule of glycerol and three molecules of fatty acids.
• Making amino acids (then proteins) using glucose and nitrate ions.
• Respiration
• Breakdown of excess proteins to form urea for excretion.

Question 20

Sketch a graph to show how light intensity affects the rate of photosynthesis

Answer 20

Question 21

Sketch a graph to show how carbon dioxide affects the rate of photosynthesis.

Answer 21

Question 22

Sketch a graph to show how temperature affects the rate of photosynthesis.

Answer 22

Question 23

Why does temperature affect the rate of photosynthesis?

Answer 23

• Because enzymes are needed for photosynthesis to work.
• There is an optimum temperature for the enzymes to work at.
• If the temperature is too low, the enzymes will work too slowly.
• If the temperature is too high, the enzymes will denature and not work.

Question 24

Describe how you would use the following equipment to investigate how light intensity affects the rate of photosynthesis.

Answer 24

• Measure ‘10’ cm from pondweed using ruler and place lamp here.
• Turn lamp on and count the number of bubbles produced in one minute (or attach gas syringe and measure the volume of gas produced per minute).
• Repeat 2 more times at this distance.
• Repeat for different distances of lamp to pondweed (e.g. 5 cm, 15 cm, 20 cm).