Bioenergetics

Question 1

What is the word equation for photosynthesis?

Answer 1

carbon dioxide + water –light–> glucose + oxygen

Question 2

What is the symbol equation for photosynthesis?

Answer 2

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 3

What type of reaction is photosynthesis and why?

Answer 3

Endothermic because energy is transferred from the environment to the chloroplasts by light

Question 4

State the four factors that affect the rate of photosynthesis

Answer 4

Temperature, light intensity, carbon dioxide concentration and amount of chlorophyll

Question 5

Why does a change in temperature affect the rate of photosynthesis?

Answer 5

Because photosynthesis involves enzymes which work better at higher temperatures but denature at extremes of temperature

Question 6

Why would the line on a graph of rate of photosynthesis against light intensity level off?

Answer 6

Because at high light intensities, something else is limiting the rate, such as carbon dioxide concentration

Question 7

How could we use the inverse square law to work out the light intensity in the pondweed investigation?

Answer 7

Calculate 1/distance^2 so when the distance doubles, the light intensity is divided by 4.

Question 8

Why do plant growers need to consider limiting factors when deciding how much to spend on enhancing conditions in a greenhouse?

Answer 8

Increasing a limiting factor (e.g. light intensity) can increase the rate of photosynthesis, but only up to a point. Increasing it further wouldn’t make a difference and can also be expensive.

Question 9

What are the ways in which the plants use the glucose produced in photosynthesis?

Answer 9

Respiration; converted to starch; fats and oils; cellulose to strengthen cell wall; amino acids for protein synthesis

Question 10

Why is glucose converted to starch for storage by plants and not just left as glucose?

Answer 10

Starch is insoluble. This means it will not move out of the cell and will not affect osmosis

Question 11

Plants can convert glucose from photosynthesis into amino acids for protein synthesis. What ions are added from the soil to do this?

Answer 11

Nitrate ions

Question 12

What type of reaction is cellular respiration and why?

Answer 12

Exothermic because energy is released

Question 13

What is the purpose of respiration?

Answer 13

To transfer energy for living processes

Question 14

Which type of respiration requires oxygen?

Answer 14

Aerobic respiration

Question 15

Which type of respiration does not require oxygen?

Answer 15

Anaerobic respiration

Question 16

Which type of respiration releases less energy per molecule of glucose?

Answer 16

Anaerobic respiration

Question 17

What is produced in anaerobic respiration but not in aerobic respiration?

Answer 17

Lactic acid

Question 18

Give 3 reasons why energy from respiration is needed in the body

Answer 18

For chemical reactions to build larger molecules; for movement; for keeping warm

Question 19

Write the word equation for aerobic respiration

Answer 19

glucose + oxygen –> carbon dioxide + water

Question 20

What is the symbol equation for respiration?

Answer 20

C6H12O6 + 6O2 –> 6CO2 + 6H2O

Question 21

Write the word equation for anaerobic respiration in muscles

Answer 21

glucose –> lactic acid

Question 22

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

Answer 22

glucose –> ethanol + carbon dioxide

Question 23

Why is less energy transferred in anaerobic respiration than in aerobic respiration

Answer 23

Oxidation (breakdown) of glucose is incomplete, so not all the energy is released

Question 24

What is the name of anaerobic respiration in yeast cells?

Answer 24

Fermentation

Question 25

Why is fermentation useful?

Answer 25

Produces ethanol for alcoholic drinks and carbon dioxide to make bread rise

Question 26

State 3 things that increase in the body during exercise

Answer 26

Heart rate, breathing rate and breath volume

Question 27

Why does heart rate increase during exercise?

Answer 27

To supply the muscles with more oxygenated blood for respiration

Question 28

Why might a person doing exercise experience muscle pain and fatigue?

Answer 28

There is insufficient oxygen for aerobic respiration, so they do anaerobic respiration too. This causes lactic acid to build up in the muscles.

Question 29

What is meant by the 'oxygen debt' during exercise?

Answer 29

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

Question 30

What happens to the lactic acid after exercise and in which organ?

Answer 30

Converted back into glucose in the liver

Question 31

What is metabolism?

Answer 31

The sum of all the reactions in a cell or body

Question 32

What are some examples of metabolism in humans?

Answer 32

Conversion of glucose to starch, glycogen & cellulose; formation of lipids from glycerol & 3 fatty acids; use of glucose & nitrate ions to form amino acids for protein synthesis; respiration; breakdown of excess proteins to form urea for excretion.