ENERGY TRANSFERS IN AND BETWEEN ORGANISMS

Question 1

What is the structure of chloroplasts?

Answer 1

Small, flat organelles surrounded by double membrane
Stacks of thylakoids = grana which are linked together by lamellae
Contained within inner membrane of chloroplast & surrounding thylakoids is stroma

Question 2

What are photosynthetic pigments?

Answer 2

Coloured substances that absorb light energy needed for photosynthesis, found in thylakoids attached to proteins
Protein & pigment = photosystem

Question 3

Where does the light-dependent reaction take place?

Answer 3

Thylakoid membranes

Question 4

Where does the light-independent reaction take place?

Answer 4

Stroma

Question 5

What are the steps involved in the light-dependent reaction?

Answer 5

1. Chlorophyll absorbs light energy in the photosystems
2. Light energy excites electrons, moving them to a higher energy level & released from chlorophyll (photoionisation)
3. Energy released from electrons used to add Pi to ADP forming ATP, and to reduce NADP
4. Electrons transferred down electron transfer chain