3.1 (b) Photosynthesis

Question 1

Light energy is..

Answer 1

Light energy is absorbed by photosynthetic pigments to generate ATP and for
photolysis

Question 2

Carotenoids

Answer 2

Carotenoids extend the range of wavelengths absorbed and pass the energy to chlorophyll for photosynthesis

Question 3

What happens to light energy not absorbed?

Answer 3

Light energy not absorbed is transmitted or reflected

Question 4

Each pigment..

Answer 4

Absorbs a different range of wavelengths of light

Question 5

The first step in photosynthesis

Answer 5

Absorbed light energy excites electrons in the

pigment molecule

Question 6

The second step in photosynthesis

Answer 6

Transfer of these electrons through the electron transport chain releases energy to generate ATP by ATP synthase

Question 7

Step in photolysis

Answer 7

Energy is also used for photolysis, in which water is split into oxygen, which is evolved, and hydrogen, which is transferred to the coenzyme NADP.

Question 8

First step in the carbon fixation stage

Answer 8

In the carbon fixation stage (Calvin cycle), the enzyme RuBisCO fixes carbon dioxide by attaching it to ribulose bisphosphate (RuBP)

Question 9

Second step in the carbon fixation stage

Answer 9

The 3-phosphoglycerate (3PG) produced is phosphorylated by ATP and combined with hydrogen from NADPH to form glyceraldehyde-3-phosphate (G3P)

Question 10

Third step in the carbon fixation stage

Answer 10

G3P is used to regenerate RuBP and for the synthesis of glucose

Question 11

What can the glucose made by photosynthesis be used for?

Answer 11

Glucose may be used as a respiratory substrate, synthesised into starch or cellulose or passed to other biosynthetic pathways. These biosynthetic pathways can lead to the formation of a variety of metabolites such as DNA, protein and fat