1. Photosynthesis #1
Learning objectives...
•Link leaf structure to efficiency in photosynthesis
•Review chloroplast structure
•Describe and explain the role of photosynthetic
pigments in light harvesting

2. Photosynthesis overview and
chloroplast structure
• (d) state that in plants photosynthesis is a
two-stage process taking place in chloroplasts;
• (e) explain, with the aid of diagrams and
electron micrographs, how the structure of
chloroplasts enables them to carry out their
functions;

3. Stages of photosynthesis...
• Light harvesting
• Light independent
• Light dependent

4. Leaf adaptations…

5. Why might a plant be variegated?

6. Cross-section of a leaf
100 µm
Mesophyll cells

7. How are chloroplasts positioned?
• http://www.saps.org.uk/secondary/teaching-resou

8. Chloroplast structure…
a
h
g f
e
d
cb

9. Schematic chloroplast
sealed thylakoid membrane
membrane-enclosed stroma

10. Thylakoid membrane
• chlorophyll
• light-harvesting
• electron transfer
• O2 evolution
• energy production
Stroma
• Rubisco
• CO2 fixation
• sugar and starch
synthesis
Pea
chloroplast
1 µm

11. a) Membrane-bound sacs containing chlorophyll molecules
b) Liquid that contains a variety of photosynthetic enzymes and
starch grains.
c) Stacks of membrane bounded, flattened, discoid sacs,
arranged like neat piles of coins.
A. Thylakoids
B. Stroma
C. Grana (1 granum)

15. Summary test...
• Leaves are the main site of photosynthesis which occurs
mainly in the (1) cells. They have numerous (2) that allow
exchange of gases between themselves and the air around
them and a network of veins that make up the tissue (3)
that brings water to the leaf and (4) that carries away (5)
produced in photosynthesis. Chloroplasts are surrounded
by a double membrane or (6) and possess both (7) and (8)
that enable them to make their own proteins. Inside, there
is a fluid-filled matrix called the (9) that carries out the (10)
reaction and also contains structures like (11) grains and oil
droplets. Within this matrix are disc-like structures called
(12) stacked in groups called (13) where the (14) reaction
of photosynthesis takes place.

16. Light is absorbed by
individual chlorophylls in the
light-harvesting complexes
Energy is transferred from
one pigment to another via
Resonance Energy Transfer
This transfer funnels the
energy to a reaction centre
where electron transfer starts
Energy transfer in light-harvesting complexes