B8 Photosynthesis

Question 1

Which product produced in photosynthesis is ‘food’ for the plant?

Answer 1

Glucose

Question 2

What gas is used in photosynthesis?

Answer 2

Carbon dioxide

Question 3

Name the part of a plant cell that contains chlorophyll

Answer 3

Chloroplasts

Question 4

Which gas is produced in photosynthesis?

Answer 4

Oxygen

Question 5

What role does chlorophyll play in photosynthesis?

Answer 5

Absorbs energy from light

Question 6

Write the word equation for photosynthesis

Answer 6

Carbon dioxide + water –> Glucose + oxygen

Question 7

Why is photosynthesis so important for humans?

Answer 7

• Photosynthesis produces oxygen, without this, we would not be able to breathe and survive.
• Photosynthesis also produces sugars and provides food for us either directly when we eat plants or indirectly as it feeds the animals when we eat meat.

Question 8

Photosynthesis

Answer 8

The process by which plants make food using carbon, dioxide, water, and light

Question 9

Chloroplasts

Answer 9

The organelles in which photosynthesis takes place

Question 10

Chlorophyll

Answer 10

The green pigment contained in the chloroplasts, that absorbs energy from sunlight

Question 11

Where do plants get carbon dioxide from?

Answer 11

The air

Question 12

Where do plants get water from?

Answer 12

The soil

Question 13

Which happens to excess glucose produced in photosynthesis?

Answer 13

It is converted to starch

Question 14

Leaf adaptations

Answer 14

• Broad leaves, captures more sunlight
• Thin leaves, short diffusion distances
• Veins (containing xylem and phloem), xylem supply water and minerals, phloem transports sugars to other parts of the plant
• Palisade cells, packed full of chloroplasts containing chlorophyll to absorb sunlight for photosynthesis
• Stomata, allows gases in and out of cells
• Air spaces, allows faster diffusion of gases

Question 15

Diffusion

Answer 15

The movement of particles from an area of high concentration to an area of lower concentration

Question 16

Is photosynthesis endothermic or exothermic?

Answer 16

Endothermic

Question 17

The law of limiting factors

Answer 17

At any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value

Question 18

Which molecule is used to strengthen cell walls?

Answer 18

Cellulose

Question 19

The rate of photosynthesis - Light

Answer 19

• If there is plenty of light, lots of photosynthesis can take place
• If there is very little or no light, photosynthesis will stop, whatever the other conditions are around the plant
• For most plants, the brighter the light, the faster the rate of photosynthesis

Question 20

The rate of photosynthesis - Temperature

Answer 20

• Temperature affects all chemical reactions, including photosynthesis
• As the temperature rises, the rate of photosynthesis increases as the reaction speeds up
• However, photosynthesis is controlled by enzymes. Most enzymes are denatured once the temperature rises to around 40-50 degrees
• If the temperature gets too high, the enzymes controlling photosynthesis are denatured and the rate of photosynthesis will fall

Question 21

The rate of photosynthesis - carbon dioxide concentration

Answer 21

• Plants need carbon dioxide to make glucose
• The atmosphere is only about 0.04% carbon dioxide, this means carbon dioxide often limits the rate of photosynthesis
• Increasing the carbon dioxide concentration will increase the rate of photosynthesis

Question 22

Carbon dioxide concentration on a sunny day

Answer 22

• On a sunny day, carbon dioxide concentration is the most common limiting factor for plants. The carbon dioxide concentrations around a plant tend to rise at night, because in the dark a plant respires but doesn’t photosynthesise
• As light intensity and temperature increase in the morning, most of the carbon dioxide around the plant gets used up

Question 23

Light intensity and the inverse square law

Answer 23

• As the distance of the light from the plant increases, the light intensity decreases. That is an inverse relationship
• However the relationship between distance and light intensity is not linear
• light intensity = 1 / distance²

Question 24

Uses of glucose in plants

Answer 24

• Respiration
• Make and strengthen cellulose cell wall
• Make starch for storage
• Make lipids as energy store

Question 25

Factors maintained in a greenhouse for optimal plant growth

Answer 25

• High carbon dioxide levels
• Constant light
• Appropriate temperatures
• Regulate watering