B4 Bioenergetics

Question 1

Photosynthesis word equation

Answer 1

Carbon dioxide + water –> glucose + oxygen

Question 2

Photosynthesis symbol equation

Answer 2

6(CO2) + 6(H2O) –> (C6H12O6) + 6(O2)

Numbers inside brackets should be subscript

Question 3

Is photosynthesis endothermic or exothermic?

Answer 3

Endothermic

Light energy is used in the reaction

Question 4

How do plants use glucose?

Answer 4

Respiration
Making cellulose
Making amino acids
Stored as fats or oils
Stored a starch

Question 5

How is glucose used in respiration?

Answer 5

Respiration transfers energy from glucose, which enables plants to convert the rest of the glucose into other useful substances

Question 6

How is glucose used to make cellulose?

Answer 6

Glucose can be converted into cellulose for making strong cell walls

Question 7

How is glucose used to make amino acids?

Answer 7

Glucose can be combined with nitrate ions to make amino acids, which are then made into protein.
The nitrate ions are absorbed from the soil.

Question 8

How is glucose stored as fats or oils?

Answer 8

Glucose can be turned into lipids (fats and oils) and stored in seeds

Question 9

How is glucose stored as fats or oils?

Answer 9

Glucose can be turned into lipids (fats and oils) and stored in seeds.

Question 10

How is glucose stored as starch?

Answer 10

Glucose can be turned into starch and stored in roots, stems and leaves.
It can be used when photosynthesis cannot happen, for example in the winter.
Starch’s insolubility makes it good for storage because it doesn’t draw in lots of water or disrupt the plant’s osmosis.

Question 11

Limiting factors of photosynthesis

Answer 11

Carbon dioxide concentration
Light intensity
Temperature
Chlorophyll levels

Question 12

What is a limiting factor?

Answer 12

The thing that is preventing photosynthesis from happening any faster.

Question 13

Why might the chlorophyll levels in a plant be depleted?

Answer 13

Disease (e.g. tobacco mosaic virus)

Lack of nutrients

Question 14

What would it look like if the rate of photosynthesis was plotted against light intensity on a graph?

Answer 14

The rate of photosynthesis would increase as the light intensity increased, but only up to a certain point. This is because light intensity would stop being the limiting factor.

Question 15

What would it look like if the rate of photosynthesis was plotted against carbon dioxide concentration on a graph?

Answer 15

The rate of photosynthesis would increase as the carbon dioxide concentration increased, but only up to a certain point. This is because carbon dioxide concentration would stop being the limiting factor.

Question 16

What would it look like if the rate of photosynthesis was plotted against temperature on a graph?

Answer 16

The rate of photosynthesis would increase as the temperature increased, but only up to around 45°C. After this the enzymes required for photosynthesis would start to denature and the rate would drop.