Hss Aqa Biology Unit 4 Bioenergetics 1

Front 1

What is the word equation for photosynthesis?

Back 1

Carbon dioxide + water —> glucose + oxygen

Front 2

Photosynthesis is an endothermic reaction. Explain what this means.

Back 2

The reaction takes in energy. Energy is transferred from the environment to the chloroplasts by light.

Front 3

Describe what happens to the rate of photosynthesis when the temperature increases and explain why.

Back 3

Increasing the temperature increases the rate of photosynthesis. This is because the carbon dioxide, water molecules and enzymes have more kinetic energy so are more likely to collide.

After a certain temperature however, enzymes which catalyse the reaction are denatured and the rate of photosynthesis slows.

Front 4

Describe what will happen to the rate of photosynthesis if carbon dioxide concentration in the air increases.

Back 4

The rate will increase as the carbon dioxide concentration increases up to a certain point. Then the rate will stay steady as another factor may be limiting.

Front 5

Explain why the rate of photosynthesis increases and then stops increasing as the concentration of carbon dioxide available increases.

Back 5

Carbon dioxide is a reactant and therefore the greater the concentration, the more chance of collisions between carbon dioxide, water and enzymes. At a certain concentration however, the rate will stay steady and stop increasing as another factor may be limiting (such as temperature, light intensity or amount of chlorophyll).

Front 6

Describe what happens to the rate of photosynthesis when the amount of chlorophyll present in the leaves decreases.

Back 6

A decreased amount of chlorophyll will cause the rate of photosynthesis to decrease.

This happens when plants have tobacco mosaic virus and rose black spot.

Front 7

Explain why decreasing the amount of chlorophyll in a plant will decrease the rate of photosynthesis.

Back 7

Chlorophyll absorbs the light energy. If the plant had less chlorophyll then there will be less energy available for photosynthesis.

Front 8

Which plant diseases reduce the amount of chlorophyll present in the leaves of plants.

Back 8

Rose black spot

Tobacco mosaic virus

Front 9

State 3 reasons a decrease in the rate of photosynthesis (and therefore less glucose production) lead to less growth in plants?

Back 9

1. The plant can’t make as much cellulose for cell walls

2. The plant can’t make amino acids for making new proteins

3. The plant doesn’t have enough chemical energy in the form of glucose for respiration.

Front 10

Describe 2 ways that plants store the glucose made in photosynthesis.

Back 10

1. They convert it into insoluble starch which is stored.

2. They use it to produce fats or oils which are stored.

Front 11

What do plants use glucose for to enable plants to grow?

Back 11

Glucose is used to produce cellulose, which strengthens the cell wall.

Glucose is used to produce amino acids for protein synthesis (making proteins).

Front 12

As well as glucose, what else is needed for plants to produce proteins and how does the plant obtain this?

Back 12

Nitrate ions

They are absorbed from the soil by active transport.

Front 13

Through which process does water enter a plant?

Back 13

Osmosis

Front 14

Through what process does carbon dioxide enter and oxygen and water vapour leave plant leaves?

Back 14

Diffusion

Front 15

How do plants that live in water (such as pond weed) get carbon dioxide?

Back 15

It is dissolved in water and diffuses into the leaves.

Front 16

How would you use a graph to calculate the rate of photosynthesis?

Back 16

Amount of carbon dioxide used divided by time

Or

Amount of oxygen produced divided by time

Front 17

In terms of photosynthesis, what is a limiting factor?

Give 4 examples.

Back 17

Any factor that when it increases caused the rate of photosynthesis to increase.

Temperature

Light intensity

Carbon dioxide concentration

The amount of chlorophyll

Front 18

How does glucose get to other parts of the plant that need it either immediately or to store it. What is this process called?

Back 18

It is dissolved in water and is transported in phloem tissue.

The process is called translocation.

Front 19

How does water get from the roots to the leaves?

Back 19

Through the xylem vessels in the transpiration stream.

Front 20

How are root hair cells adapted for the efficient uptake of water by osmosis?

Back 20

They have a large surface area

Front 21

How are root hair cells adapted for the efficient uptake of mineral ions such as nitrates by active transport?

Back 21

They have many mitochondria as energy from respiration is required for active transport.

Front 22

What are stomata?

Back 22

Holes found mainly in the underside of leaves which are surrounded by guard cells.

Front 23

Why do plants have stomata that can open and close.

Back 23

To limit water vapour loss from the plant and to allow transfer of gases to and from the plant cells.

Front 24

When do stomata close?

Back 24

When guard cells are flaccid (not much water in their vacuoles).

Front 25

When do stomata open?

Back 25

When guard cells are turgid (plenty of water in their vacuoles).

Front 26

Which gases diffuse through the stomata?

Back 26

Carbon dioxide - in

Oxygen and water vapour - out

Front 27

Why doesn’t all the oxygen produced during photosynthesis diffuse out of the stomata?

Back 27

Some of it is used by the plant cells in aerobic respiration.

Front 28

Why will a plant which grows in full light grow more than a plant that grows in shade?

Back 28

It receives a greater light intensity.

Therefore it is able to photosynthesise more.

Making more glucose which is converted to useful compounds such as amino acids and cellulose which are needed for growth.