Topic 4

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

Higher Q. Suggest ways in which gardeners can optimise conditions for photosynthesis in greenhouses.

Answer 4

• Heater – to increase temperature (e.g. in winter)
• Shade/ventilation/opening windows – to decrease temperature (e.g. in summer)
• Artificial lights – to increase the light intensity
• Paraffin heaters – to increase both temperature and carbon dioxide levels

Question 5

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

Answer 5

• 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 6

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

Answer 6

Nitrates (that they absorb from the soil)

Question 7

Higher Q. Use the inverse square law to calculate the light intensity when a lamp is placed 20 cm from some pondweed.

Answer 7

Use the equation: light intensity ∝ 1/distance²

Light intensity = 1/(20)²

Light intensity = 0.0025 arbitrary units

Question 8

Is respiration an endothermic or exothermic reaction?

Answer 8

Exothermic reaction

Question 9

1. Which type of respiration releases most energy?
2. Which type of respiration requires oxygen?

Answer 9

1. Aerobic Respiration
2. Aerobic Respiration

Question 10

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

Answer 10

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

Question 11

Write the word and symbol equations for aerobic respiration.

Answer 11

glucose + oxygen → carbon dioxide + water

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Question 12

Write the word equation for anaerobic respiration in muscles.

Answer 12

glucose → lactic acid

Question 13

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

Answer 13

glucose → ethanol + carbon dioxide

Question 14

Name the process of anaerobic respiration in yeast cells.

Answer 14

Fermentation

Question 15

Give the two main industrial uses of fermentation.

Answer 15

Bread making and alcoholic drinks

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Anaerobic Respiration

Question 18

What type of respiration involves the incomplete oxidation of glucose?

Answer 18

Anaerobic Respiration

Question 19

What happens to muscles after long periods of exercise?

Answer 19

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

Question 20

Higher Q. How do the muscles get rid of excess lactic acid?

Answer 20

• Blood transports lactic acid to the liver.
• In the liver lactic acid is converted back into glucose.

Question 21

Higher Q. What is ‘oxygen debt’?

Answer 21

Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.

Question 22

What is ‘metabolism’?

Answer 22

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

Question 23

List 5 processes involved in metabolism.

Answer 23

• 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 24

Why does temperature affect the rate of photosynthesis?

Answer 24

• 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 25

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

Answer 25

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