L19

Question 1

Photosynthesis

Answer 1

The process by which green plants convert light energy into glucose (chemical energy).

carbon dioxide + water → glucose +oxygen

Question 2

How do green plants absorb light energy?

Answer 2

By photosynthetic pigments (e.g. chlorophyll a & b) in the chloroplast to generate ATP for photolysis.

Question 3

What is the fate of light on green leaves?

Answer 3

• Absorbed
• Transmitted
• Reflected

Question 4

What is a pigment?

Answer 4

• A substance that can absorb and reflect visable light.
• Pigment colour indicates the light which the pigment cannot absorb (eg green pigment absorbs red and blue but NOT green).

Question 5

Name four types of pigments:

Answer 5

Main pigments: -Chlorophyll a
-Chlorophyll b

Carotenoids: -Carotene
-Xanthophyll

Question 6

How to identify which colours of light have been absorbed by a pigment?

Answer 6

White light passed through leaf pigment extract, and then passed through a spectroscope, when the spectrum is observed there will be areas of black in place of the colours which have been absorbed.

Question 7

Which colours of light do Chlorophyll a and b absorb best?

Answer 7

Blue and Red

Question 8

How do plants extend the range of wavelengths of light which they can use for photosynthesis?

Answer 8

their catatenoids absorb other regions of the spectrum which don’t correspont to red or blue light. This energy is then passed on to chlorophyll.

Question 9

What is an ‘Absorption spectrum’

Answer 9

The wavelengths of light absorbed by each pigment

Question 10

What is an ‘Action spectrum’

Answer 10

It shows the extent to which different wavelengths of light are used for photosynthesis.

Question 11

What are the two stages of photosynthesis and were does each stag occur?

Answer 11

1) Light-dependent stage
2) Carbon fixation (Calvin cycle)

Both stage take place in the chloroplast:

1) The grana, since this is where photosynthetic pigments are contained
2) The stroma

Question 12

Photosynthesis: Light-dependent stage

Answer 12

• Light energy absorbed, exciting elecrons in the leaf pigments. The high energy electrons are transferred along the electron transport chain, this releases energy which is used for:
• Photophosphorylation of ADP to form ATP by the enzyme ATP synthase.
• Photolysis of water into oxygen and hydrogen

Question 13

Which products in the light-dependent stage are used in the calvin cycle and for what?

Answer 13

• ATP: to provide energy for the Calvin cycle to take place.

- Hydrogen: binds to NADP to form NADPH

Question 14

Uses of sugar produced durin the Calvin cycle

Answer 14

• Respiration
• Starch (storage of carbohydrates)
• Cellulose (structural carbohydrate)
• Biosynthetic pathways which can lead to the formation of metabolites such as DNA, lipid, proteins and nuclei