B2 - Photosynthesis

Question 0

Which parts of the plant have chloroplasts in their cells?

Answer 0

Leaves and stem

Question 1

Where does photosynthesis take place?

Answer 1

Chloroplasts in plant cells

Question 2

Why is the large surface area of leaves useful for photosynthesis?

Answer 2

Absorb as much light as possible

Question 3

What do chloroplasts contain?

Answer 3

The green pigment chlorophyll

Question 4

Why is light needed for photosynthesis?

Answer 4

To break apart the bonds in carbon dioxide and water

Question 5

How do plants get carbon dioxide?

Answer 5

From the air

Enters the leaves through stomata

Question 6

What are stomata?

Answer 6

Tiny holes in the bottom of leaves that carbon dioxide passes through to get to the inside of the leaf

Question 7

How does the water enter the plant?

Answer 7

From the ground and up the roots

It then travels to the leaves and stem through the pipe-like xylem

Question 8

Describe what happens inside the chloroplasts

Answer 8

The light breaks apart the bonds in the carbon dioxide and water so that they form glucose and oxygen

Question 9

Why do plants need glucose?

Answer 9

As energy for growth and repair

Question 10

What happens to the glucose and oxygen after photosynthesis?

Answer 10

Glucose is either used for the energy immediately or stored

Oxygen is released through the stomata

Question 11

How is the stored glucose used for energy? Give the chemical reaction

Answer 11

Glucose + Oxygen –> Carbon dioxide + Water (+ Energy)

Question 12

How is glucose stored?

Answer 12

Long strands of glucose called starch

Question 13

Give 2 reasons that some parts may not have been photosynthesising

Answer 13

Kept in darkness

No chlorophyll

Question 14

Give 4 parts of a plant which store glucose?

Answer 14

Fruits
Seeds
Roots
Tubers

Question 15

How do plants get protein?

Answer 15

The glucose combines with nitrate ions in soil to form amino acids
Amino acids form strands which are proteins

Question 16

What is photosynthesis?

Answer 16

The process that gives plants and some bacteria food

Question 17

Describe all parts of the leaf and what they do

Answer 17

The upper epidermis is a transparent surface that protects the inside that light passes through

The palisade layer which is where photosynthesis takes place because of the chloroplasts in the cells

The second mesophyll layer is where the carbon dioxide waits to be used in photosynthesis and where the oxygen waits to pass out of the leaf

The lower epidermis acts as protection as has stomata that gases and air can flow through

Question 18

How can you measure the rate of photosynthesis?

Answer 18

Amount of oxygen or glucose is produced in a certain amount of time

Question 19

What is a limiting factor?

Answer 19

A factor that, if too low, will affect the process regardless of other limiting factors

Question 20

What are the 3 limiting factors of photosynthesis?

Answer 20

Carbon dioxide
Temperature
Light intensity

Question 21

Why does temperature affect the rate of photosynthesis?

Answer 21

Because the enzymes work at different rates depending on the temperature

Question 22

What are palisade leaf cells?

Answer 22

The cells that contain many chloroplasts so that photosynthesis can take place

Question 23

How are palisade cells adapted?

Answer 23

The tall shape means that a lot of surface area is exposed down the side for absorbing carbon dioxide from the air in the leaf

The thin shape means that you can pack loads of them in at the top of the leaf

Question 24

Describe what guard cells do

Answer 24

They open and close the stomata in a leaf

When the plant has lots of water, the guard cells fill with it and become plump which opens the stomata and allows gases to be exchanged for photosynthesis

When the plant is short of water, the guard cells lose water making the stomata close which stops water vapour escaping

Thin outer walls and thicker inner walls make the opening and closing work

They are also sensitive to light and close at night to save water without losing out on photosynthesis

Question 25

What are the 3 main tissues in plants?

Answer 25

Mesophyll tissue (photosynthesis occurs here)

Xylem and phloem (transports water, minerals, sugars around plant)

Epidermal tissue (covers and protects plant)

Question 26

How would you measure the effect of a limiting factor?

Answer 26

Let a plant photosynthesise in a flask and use a gas syringe to collect the oxygen given off so that the rate of photosynthesis can be measured

Do the whole thing again but change the factor you are testing inside the flask and measure the rate of photosynthesis again to see the difference

Question 27

Describe a graph showing the rate of photosynthesis against the level of carbon dioxide

Answer 27

They increase together until you reach a specific point where the rate of photosynthesis stays the same

This is because a different limiting factor is stopping the rate from increasing

Question 28

Describe the graph showing rate of photosynthesis against light

Answer 28

Same as carbon dioxide graph

Question 29

Describe the graph showing rate of photosynthesis against temperature

Answer 29

They would increase together until 37 to 40C is reached where the rate of photosynthesis would rapidly decrease because the enzymes become denatured (about 45C)

Question 30

Describe how greenhouses work

Answer 30

They trap the Sun’s heat meaning that temperature is never really a problem that limits the rate of photosynthesis

In winter, a heater could be used to keep the temperature up

The plants are exposed to sunlight in the day and artificial lighting is used at night

Paraffin burners are often put in a greenhouse because they release carbon dioxide as a by-product (they can be also used to keep temperature up)

Keeping plants in a greenhouse also makes it easier to keep them free from pests and diseases

Question 31

Describe the 5 ways that plants use glucose

Answer 31

For respiration (glucose can be used to release energy so that the rest of the glucose can be used for other reasons)

Making cell walls (can be converted to cellulose)

Making proteins (combined with nitrate ions in the soil to make amino acids that can be made into proteins)

Stored in seeds (glucose turned into fats for storing in seeds)

Stored as starch (glucose turned into starch and stored in roots, stems, leaves and seeds)

Question 32

Why is glucose turned into starch to be stored?

Answer 32

It is insoluble which means that water isn’t drawn into cells so that they don’t dwell up