6: Plant Nutrition

Question 1

Define photosynthesis

Answer 1

The process by which plants synthesise carbohydrates from raw materials using energy from light

Question 2

State the word equation for photosynthesis

Answer 2

carbon dioxide + water —-> glucose + oxygen

in the presence of light and chlorophyll

Question 3

What is chlorophyll?

Answer 3

green pigment found in chloroplasts

Question 4

What does chlorophyll do?

Answer 4

It transfers energy from light into energy in chemicals, for the synthesis of carbohydrates

Question 5

Outline the subsequent use and storage of the carbohydrates made in photosynthesis.

Answer 5

1: starch as an energy store
2: cellulose to build cell walls
3: glucose used in respiration to provide energy
4: sucrose for transport in the phloem
5: nectar to attract insects for pollination

Question 6

Why are nitrate ions and magnesium ions so important?

Answer 6

Nitrate ions are used for making amino acids and magnesium ions are used for making chlorophyll

Question 7

State the balanced chemical equation for photosynthesis

Answer 7

6CO2 + 6H2O —-> C6H12O6 + 602

Question 8

State two characteristics of a leaf

Answer 8

Thin and have a large surface area

Question 9

Why is it better for a plant to convert glucose into starch for storage?

Answer 9

Starch is more compact than glucose, and glucose dissolves very easily in water

Question 10

What is the function of the waxy cuticle and how does the structure of it help its function?

Answer 10

function: prevents water loss from leaf tissues.
how structure helps function: Waxy material provides waterproof layer, which reduces evaporation from leaf surfaces. Thicker on upper surface (hotter/more sunlight) and thinner on lower surface (cooler/more shaded)

Question 11

What is the function of the upper epidermis and how does the structure of it help its function?

Answer 11

function: light goes through this layer

how structure helps function: Single layer of cells with no chloroplasts so that light can pass through

Question 12

What is the function of the palisade mesophyll and how does the structure of it help its function?

Answer 12

function: contains chloroplasts to carry out photosynthesis

how structure helps function: palisade mesophyll cells are packed tightly together to maximise light absorption

Question 13

What is the function of the spongy mesophyll and how does the structure of it help its function?

Answer 13

function: diffuses CO2 to mesophyll cells

how structure helps function: large air spaces allow a faster rate of diffusion

Question 14

What is the function of the chloroplasts and how does the structure of it help its function?

Answer 14

function: absorbs light

how structure helps function: there are many of them in order to absorb as much light as possible

Question 15

What is the function of the air spaces and how does the structure of it help its function?

Answer 15

function: diffusion of gases (oxygen and carbon dioxide) and water vapour through the leaf tissue
how structure helps function: air spaces are connected directly to the outside atmosphere when the stomatal pores are open. Water vapour and gases can moe through the spongy mesophyll by diffusion down concentration gradients and pass to/from other leaf tissues

Question 16

What is the function of the lower epidermis and how does the structure of it help its function?

Answer 16

function: allows gases to diffuse in and out

how structure helps function: has a lot of small holes called stomata which allow gases to diffuse in and out

Question 17

What is the function of the guard cells and stomata and how does the structure of it help its function?

Answer 17

function: can open or close to allow gases (CO2 needed for photosynthesis, O2 produced) to diffuse in and out of the leaf and to allow water vapour to diffuse out
how structure helps function: can prevent gases and water vapour from diffusing out when it need it

Question 18

What is the function of the xylem and how does the structure of it help its function?

Answer 18

function: carry water needed for photosynthesis and minerals from the roots up the stem and to the leaves
how structure helps function: cells joined into a continuous tube with end walls and cell contents removed to allow an unencumbered flow of water and minerals

Question 19

What is the function of the phloem and how does its structure help its function?

Answer 19

function: carry organic molecules (products of photosynthesis) from the leaves or storage organs to the site they are needed
how structure helps function: Cells adapted to actively transport materials into the phloem tubes

Question 20

What would happen if you added hydrogen carbonate indicator to increasing levels of CO2?

Answer 20

It would turn yellow as the carbon dioxide concentration increases (pH is lower)

Question 21

What would happen if you added hydrogen carbonate indicator to decreasing levels of CO2?

Answer 21

It would change from red through pink to purple as carbon dioxide concentration falls (pH is higher)

Question 22

What are the factors affecting the rate of photosynthesis?

Answer 22

> availability of light
the presence of chlorophyll molecules inside the leaf
a supply of carbon dioxide and water
a suitable temperature for enzyme activity