CB6

Question 1

How do plants get their energy?

Answer 1

Through the process of Photosynthesis.

Question 2

What is photosynthesis?

Answer 2

A process carried out by Protists (particularly plants) to trap energy transferred by light from the sun for its own use.

Question 3

How does photosynthesis work?

Answer 3

Protists (particularly plants) trap energy transferred by light from the sun. This energy is then converted to molecules of glucose which the plant can absorb for its energy.

Question 4

What is biomass?

Answer 4

The materials in an organism.

Question 5

Where are plants and algae on the food chain and what do they do?

Answer 5

They are producers which means they produce food for themselves and almost all other life on earth.

Question 6

What is the word equation for photosynthesis

Answer 6

Carbon Dioxide + Water (Reactants) –> Glucose + Oxygen (Products)

Question 7

Where does photosynthesis occur?

Answer 7

In the chlorplasts.

Question 8

What is chlorophyll’s use in photosynthesis?

Answer 8

It is a green substance that traps energy transferred by light.

Question 9

What type of reaction is photosynthesis and why?

Answer 9

It is an Endothermic reaction as the products of photosynthesis have more energy than the reactants as energy enters from the surroundings.

Question 10

How is starch formed through photosynthesis and what happens to it after?

Answer 10

As glucose molecules are made, they are linked together to form a polymer (starch). This stays in the chloroplasts until photosynthesis stops. The starch is then broken down into simpler substances, which are moved into the cytoplasm and used to make sucrose which is transported around the plant.

Question 11

What is sucrose?

Answer 11

A type of sugar found in the phloem of plants, and used as table sugar.

Question 12

What is sucrose used to make?

Answer 12

1. Starch (in a storage organ such as a potato).
2. Other molecules for the plant (such as cellulose, lipids or proteins).
3. Glucose for respiration (to release energy).

Question 13

What is a storage organ?

Answer 13

A plant organ used to energy-rich substances such as starch (e.g. A potato).

Question 14

How is the surface of a leaf adapted for photosynthesis?

Answer 14

Leaves are often broad and flat, giving them a large surface area. They also have palisade cells near the top of the leaf packed with chloroplasts which allow a leaf to absorb a great deal of light.

Question 15

What are palisade cells?

Answer 15

Tall, column-shaped cells near the upper surface of a plant leaf that are packed with chloroplasts.

Question 16

What are stomata (singular: stoma)?

Answer 16

Tiny pores in the lower surface of a leaf which allow gases (such as carbon dioxide) to diffuse into and out of the leaf.

Question 17

What are guard cells?

Answer 17

Cells which (when in pairs) open and close plant stomata.

Question 18

How are stomata opened and closed?

Answer 18

By the use of specialized guard cells.

Question 19

How do stomata change in the light and night?

Answer 19

In the light, water flows into pairs of guard cells making them rigid. This opens the stoma. At night, water flows out of guard cells. They lose their rigidity and the stoma shuts.

Question 20

How does gas exchange occur in leaves?

Answer 20

Leaves are thin, so carbon dioxide does not have far to diffuse into the leaf before reaching cells that need it. Stomata also allow the oxygen produced by photosynthesis to escape into the air, as well as water vapour. The flow of different gases into and out of the leaf is gas exchange in a leaf.

Question 21

How does the rate of photosynthesis vary in different altitudes?

Answer 21

There are fewer molecules in each cubic centimeter of air at the top of a mountain than at the bottom. This reduced concentration of air molecules causes a lower rate of photosynthesis in high mountains compared with sea level.

Question 22

What temperatures do the enzymes of photosynthesis work best at?

Answer 22

The reactions in photosynthesis are catalyzed by enzymes that work better at warmer temperatures. High mountains are cold which is another reason why photosynthesis is slower at the top of a mountain than at the bottom.

Question 23

What is a limiting factor?

Answer 23

A single factor that when in short supply can limit the rate of a process from increasing.

Question 24

What are some examples of limiting factors in photosynthesis?

Answer 24

Carbon dioxide concentration, temperature and light.

Question 25

How can you use a limiting factor to change the rate of a reaction (e.g. photosynthesis)?

Answer 25

You can change the rate of a reaction by changing the supplies of the limiting factor (e.g. if temperature was the limiting factor of photosynthesis, increasing the temperature will increase the rates of photosynthesis).

Question 26

How do you calculate new light intensity?

Answer 26

L(new)=L(orig) x d(orig)² /d(new)² (L=light, d=distance)

Question 27

How do buttress roots help trees?

Answer 27

1. Like all roots, they absorb water and dissolved mineral ions from the soil.
2. However, buttress roots help stop the tall trees from falling over in thin rainforest soils, by acting as props.
3. They also trap leaves and other dead vegetation, which then rot to provide additional minerals for the tree.

Question 28

What is water absorbed by plant roots used for?

Answer 28

1. Carrying dissolved mineral ions.
2. Keeping cells rigid (otherwise plants will wilt).
3. Cooling the leaves (when it evaporates from them).
4. Photosynthesis.

Question 29

What is the function of the hairs on the root hair cells?

Answer 29

They are extensions of the cell that provide a large surface area so that water and mineral ions can be quickly absorbed. They also have thin cell walls so that the flow of water into the cells is not slowed down.

Question 30

What type of particle movement occurs inside root hair cells?

Answer 30

1. Diffusion occurs in root hair cells as the cell walls in the root hair cells have an open structure allowing water particles to diffuse towards the middle of the root (around the cell).
2. Osmosis also occurs as water passes through the cytoplasm of root hair cells Osmosis (through the cell).

Question 31

What is transpiration?

Answer 31

The flow of water into a root, up the stem and out of the leaves.

Question 32

Why is transpiration good for plants?

Answer 32

The evaporation of water from leaves keeps them cool and helps move water (and dissolved mineral ions) up the plant.

Question 33

What are xylem vessels?

Answer 33

A long, thick-walled tube found in plants, formed from many dead xylem cells. The cells carry water and dissolved mineral salts through the plant.

Question 34

How do xylem vessels work?

Answer 34

Xylem vessels form tiny continuous pipes leading from a plant’s roots up into its leaves. Inside the vessels is an unbroken chain of water, due to the weak forces of attraction between water molecules. Water is pulled up the xylem vessels in the stem as water evaporates from the xylem vessels in the leaves. As the water vapour diffuses out of a leaf, more water evaporates from the xylem inside the leaf.

Question 35

Why do water molecules diffuse out of leaves?

Answer 35

The concentration of water vapour in the air spaces inside a leaf is greater than outside it. So, water molecules diffuse down the concentration gradient out of the leaf. A bigger difference between the concentrations makes the gradient steeper, which makes diffusion faster. Any factors that reduce the concentration of water molecules outside the stomata will increase transpiration.

Question 36

What factors can reduce the concentration of water molecules outside the stomata?

Answer 36

1. Wind - moves water molecules away from stomata.
2. Low humidity (little water vapour in the air).

Question 37

How are xylem cells rigid and why?

Answer 37

As they have thick side walls and rings of hard lignin, and so water pressure inside the vessels does not burst or collapse them. They also help to support the plants.

Question 38

What are Phloem?

Answer 38

Living tissue formed of sieve tubes and companion cells that transport sugars and other compounds around a plant.

Question 39

How do plants make sucrose?

Answer 39

Plants make sucrose from the glucose and starch made by photosynthesis.

Question 40

How is sucrose translocated (transported)?

Answer 40

Sucrose is translocated (transported) in the sieve tubes of the phloem tissue. The large central channel in each sieve cell is connected to its neighbours by holes, through which sucrose solution flows.

Question 41

How does sucrose solution flow?

Answer 41

Companion cells actively pump sucrose into or out of the sieve cells that form the sieve tubes. As sucrose is pumped into sieve tubes, the increase pressure causes the sucrose solution to flow up to growing shoots or down to storage organs.

Question 42

What are sieve tubes?

Answer 42

Tubes formed of plant phloem. The tubes carry sugars and other compounds around the plant.

Question 43

What are companion cells?

Answer 43

A specialised cell located in the phloem of plants.