Topic 4: Bioenergetics

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon dioxide + water —> glucose + oxygen

Question 2

What is the symbol equation for photosynthesis?

Answer 2

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

Question 3

Why is photosynthesis an endothermic reaction?

Answer 3

Energy is transferred from the environment to the chloroplasts by light

Question 4

What do plants use glucose for? [5]

Answer 4

1. Respiration
2. Making cellulose
3. Making amino acids
4. Stored as oil and fats
5. Stored as starch

Question 5

What are the 4 limiting factors of photosynthesis?

Answer 5

1. Light
2. Carbon dioxide conc.
3. Temperature
4. Amount of chlorophyll

Question 6

How does increased light affect the rate of photosynthesis? [3]

Answer 6

1. As the light level is increased, the rate of photosynthesis will increase up to a certain point
2. Beyond that, increased light will no longer increase the rate
3. This is because either CO₂ or the temperature is now the limiting factor, not light

Question 7

How does increased CO₂ affect the rate of photosynthesis? [3]

Answer 7

1. As the CO₂ level is increased, the rate of photosynthesis will increase up to a certain point
2. Beyond that, increased CO₂ will no longer increase the rate
3. This is because either light or temperature is now the limiting factor, not CO₂

Question 8

Why does a too low temperature limit the rate of photosynthesis?

Answer 8

The enzymes needed for photosynthesis are working too slowly

Question 9

What would farmers put plants in to create the ideal conditions for photosynthesis?

Answer 9

A greenhouse

Question 10

How would a farmer keep the temperature of a greenhouse ideal? [2]

Answer 10

1. Use a heater in the winter
2. Use shade and ventilation in the summer

Question 11

How would a farmer increase light to a greenhouse?

Answer 11

Use artificial light at night

Question 12

How would farmers increase the amount of CO₂ in a greenhouse?

Answer 12

Use paraffin heaters, which make CO₂ as a by-product

Question 13

What are some further advantages of keeping plants in a greenhouse? [2]

Answer 13

1. Keep plants free from pests and diseases
2. Fertilisers can be added to the soil, to provide all the minerals needed for healthy growth

Question 14

What economic benefits does keeping plants in a greenhouse with ideal conditions have?

Answer 14

Plants will grow much faster and a decent crop could be harvested more often, which could then be sold

Question 15

Why should a farmer not pump a greenhouse full of too much CO₂, light etc?

Answer 15

It wastes money

Question 16

Define ‘respiration’

Answer 16

The process of transferring energy from glucose, which goes into every cell

Question 17

Why is respiration said to be an exothermic reaction?

Answer 17

It transfers energy to the environment

Question 18

What 3 things do organisms need the energy from respiration for?

Answer 18

1. Chemical reactions to make larger molecules
2. Movement
3. Keeping warm

Question 19

Define ‘metabolism’

Answer 19

All the chemical reactions in an organism

Question 20

Describe 3 reactions in the metabolism (smaller molecules to larger ones)

Answer 20

1. Glucose molecules joined together to form starch, glycogen and cellulose
2. Lipid molecules made from 1 molecule of glycerol and 3 fatty acids
3. Glucose combined with nitrate ions to make amino acids, which are then made into proteins

Question 21

Describe 2 reactions in the metabolism (larger molecules to smaller ones)

Answer 21

1. Glucose broken down in respiration
2. Excess protein broken down to form urea for excretion

Question 22

What is the word equation for respiration?

Answer 22

Glucose + oxygen —> carbon dioxide + water

Question 23

What is the symbol equation for respiration?

Answer 23

C₆H₁₂O₆ + 6O₂ —> 6CO₂ + 6H₂O

Question 24

Characteristics of aerobic respiration [3]

Answer 24

1. Lots of oxygen present
2. Releases lots of energy
3. Produces CO₂ and water

Question 25

Characteristics of anaerobic respiration [3]

Answer 25

1. No oxygen present
2. Doesn’t release much energy
3. Produces lactic acid

Question 26

What is the word equation for anaerobic respiration?

Answer 26

Glucose —> lactic acid

Question 27

Why does anaerobic respiration not transfer nearly as much energy as aerobic respiration?

Answer 27

Glucose isn’t fully oxidised

Question 28

What is the word equation for anaerobic respiration in yeast

Answer 28

Glucose —> ethanol + carbon dioxide

Question 29

What is the process of anaerobic respiration in yeast called?

Answer 29

Fermentation

Question 30

Characteristics of anaerobic respiration in yeast [2]

Answer 30

1. Produces ethanol and carbon dioxide
2. Doesn’t release much energy

Question 31

When you exercise, explain why:
i) you respire more
ii) your breathing rate and breath volume increases
iii) your heart rate increases

Answer 31

i) the increased energy required to allow muscles to contract more quickly during exercise comes from increased respiration
ii) to get more oxygen in the blood needed as a result of increased respiration
iii) to get oxygenated blood around the body faster

Question 32

What happens when you do really vigorous exercise?

Answer 32

Your body can’t supply oxygen to your muscles quickly enough, so they start respiring anaerobically

Question 33

What is oxgen debt?

Answer 33

The amount of extra oxygen your body needs to react with the build up of lactic acid to remove it from the cells

Question 34

Why do you keep breathing hard after exercise?

Answer 34

To get more oxygen into your cells to remove lactic acid

Question 35

Liver

What is another way your body deals with lactic acid build-up?

Answer 35

Blood that enters your muscles transports the lactic acid to the liver, where it is converted back to glucose