Photosynthesis

Question 1

Raw materials required for photosynthesis

Answer 1

Carbon dioxide, water and light energy

Question 2

Photosynthesis

Answer 2

An anabolic (building up) process in which the radiant/ sunlight is captured by chlorophyll in the chloroplasts and is stored as chemical potential energy in the bonds of glucose and other organic molecules for later.

Question 3

Chloroplast

Answer 3

Organelle where photosynthesis occurs and has a double-membrane surrounding it

Question 4

Stroma

Answer 4

Found in the chloroplasts.

Question 5

Grana / Granum

Answer 5

Suspended in the stroma and structures called grana. Each granum is a stack of thylakoid discs and this is where chlorophyll molecules are found

Question 6

Chlorophyll

Answer 6

Absorbs energy from the sun in order for photosynthesis to take place in the chloroplasts.

Question 7

Intergrana

Answer 7

Membranes that connect grana together. These keep the stacks apart from each other and move substances into and out of the thykaloids

Question 8

Starch granules

Answer 8

Where excess glucose is stored

Question 9

How chloroplasts are suited to performing photosynthesis

Answer 9

1. Chlorophyll molecules are situated in the grana which trap radiant energy from the sun. Chlorophyll reflects the green part of the light spectrum and absorbs blue and red wavelengths - making leaves appear green in colour
2. Membranes are arranged in layers called grana - which increase surface area for chemical reactions in the light dependent phase
3. Stroma - contains enzymes needed to speed up the chemical reactions that take place during the light independent phase of photosynthesis
4. Double membrane - selectively permeable and allows entry of water, carbon dioxide and exit of glucose and oxygen

Question 10

Cuticle (leaf)

Answer 10

Non-cellular, water proof and transparent. Allows light to pass through

Question 11

Upper epidermis (leaf)

Answer 11

Single layer of cells on the upper surface of the leaf. Allows light to pass to cells below

Question 12

Palisade mesophyll (leaf)

Answer 12

Cells are vertically arranged so that many can fit into small place. Have large number of chloroplasts and are positioned a top region of leaf

Question 13

Spongy mesophyll (leaf)

Answer 13

Have large air spaces for fast diffusion of gases to and from the photosynthesizing cells. Cells have few chloroplasts and are positioned at the lower region of leaf near stomata

Question 14

Veins - vascular bundles (leaf)

Answer 14

Act as drain pipes distributing water and minerals to the leaves and conducting away manufactured food to other parts of a plant

Question 15

Stomata (leaf)

Answer 15

Pores that allow gaseous exchange to take place. Carbon dioxide enters through stomata and oxygen leaves

Question 16

Thin lamina (leaf)

Answer 16

Provides a short distance over which diffusion of gases takes place

Question 17

Factors affecting rate of photosynthesis

Answer 17

1. Light intensity = light intensity increases, photosynthesis increases
2. Temperature = Increase in temperature, leads to an increase in rate of photosynthesis (too hot can cause enzymes to denature)
3. Carbon dioxide concentration = more carbon dioxide, faster rate of photosynthesis until maximum is reached
4. Water availability = photosynthesis is slowed down when transpiration is reduced.

Question 18

Limiting factor

Answer 18

A factor that is not adequate / when in short supply may reduce rate of photosynthesis

Question 19

Importance of photosynthesis

Answer 19

Produces oxygen required by all living organisms for respirating. Maintains balance of carbon dioxide in the atmosphere and reduces excess carbon dioxide, helping to prevent greenhouse effect. It also provides living organisms with organic compounds needed. Provides us with fossil fuels.

Question 20

Autotrophs

Answer 20

Produce organic molecules from carbon dioxide and other inorganic raw materials obtained from the environment. Ultimate source of organic compounds for heterotrophs

Question 21

Photoautotrophs

Answer 21

Use light as their source of energy to synthesize organic compounds. Occurs in all plants, algae and cyanobacteria

Question 22

Chemoautotrophs

Answer 22

Harvest energy from oxidizing inorganic substances such as sulphur and ammonia. Is unique to prokaryotes such as bacteria

Question 23

Heterotrophs

Answer 23

Live on organic compounds produced by other organisms. Are dependent on photoautotrophs for food and oxygen