1. Photosynthesis revision
For F214 January 25th 2010

2. Revising photosynthesis
Basic knowledge
Explain the similarities and differences between an autotroph and a heterotroph
Describe the relationship between photosynthesis and respiration in living organisms
Write the overall chemical equation for photosynthesis
Name the 2 sets of reactions involved in photosynthesis and state where exactly each occurs
Explain why the very large surface area provided by the grana is important in photosynthesis
Draw a diagram of a chloroplast and label it to show how it is adapted for photosynthesis

3. Autotrophs
Autotrophs are organisms that can synthesise complex organic molecules such as
carbohydrates, lipids, proteins, DNA, RNA, vitamins
from inorganic molecules, using an energy source.

4. Heterotrophs
Heterotrophs digest complex organic molecules into simpler, soluble ones. They then synthesise molecules they need from these.
Examples of heterotrophs are
Animals Fungi Some bacteria

5. Photosynthesis: 2 stage process
Takes place in chloroplasts
Carbon dioxide
Water
CHLOROPHYLL
Light
Carbohydrate
Oxygen
Light independent reaction
Light dependent reaction

6. The cells and tissues of a leaf

7. Chloroplasts under LM and EM
Chloroplasts in an Elodea leaf using LM
2. Chloroplasts in a maple leaf using TEM
TEM of a single chloroplast

8. Chloroplast

9. Revising photosynthesis
Light dependent reactions
1) List the products of the light dependent reaction
2) Distinguish between an absorption spectrum and an action spectrum
3) State the wavelength of visible light at which least photosynthesis takes place. Why is this?
4) State the role of accessory pigments in a photosystem
5) Describe the different roles of photosystems 1 and 2
6) Describe the similarities and differences between cyclic and non-cyclic photophosphorylation

10. Photosynthesis biochemistry p17 workbook p63 textbook
The light dependent stage on the thylakoid membranes of the chloroplast
Using light energy to make ATP
(= photophosphorylation)
Also produces reduced NADP
(= coenzyme NADPH)
There are 2 parts – cyclic and non-cyclic photophosphorylation

11. Light harvesting clusters or photosystems p12-13 workbook, p61 textbook
Quite complex animation!
info!)

12. cyclic photophosphorylation
excited electrons 2e-
chlorophyll a in photosystem I
P 700
electron acceptor +
chain of electron
carriers
2e-
ADP + Pi  ATP

13. photolysis of water
H2O  OH- + H+
NADP + H+
oxygen O2
reduced
NADP
e e-
Non-cyclic
photophosphorylation
ADP + Pi
ATP
photosystem II P photosystem I P700

14. Non-cyclic photophosphorylation p

15. This is also called chemiosmosis
Making ATP by photophosphorylation and chemiosmosis (needed in the light independent stage) p14
A photon of light hits a chlorophyll molecule
2 electrons get excited!
They are released from chlorophyll to electron acceptors
They travel along electron carriers on thylakoid membranes
Energy released during electron transport is used to pump H+ into thylakoid space between membranes
H+ (proton) gradient is formed
H+ move down gradient through ATP synthase enzymes  making ATP
So ATP is made using light energy = photophosphorylation
This is also called chemiosmosis

16. The role of water in the light dependent stage
Light energy makes it split = photolysis
Produces hydrogen ions (protons) + electrons + oxygen atoms
Hydrogen ions  ATP synthase
Hydrogen ions  reduce NADP
Electrons  electron acceptors and carriers
Oxygen  waste product (but needed in respiration)

17. Revising photosynthesis
Light independent reactions / Calvin cycle
1) Explain the term carbon dioxide acceptor
2) Describe the reaction catalysed by the enzyme rubisco
3) State the roles of ATP and reduced NADP in the Calvin cycle
4) List the possible fates of triose phosphate formed in the Calvin cycle. Which is the most likely to happen?

18. NADPH
NADP
2 x3C
2x GP
ATP
ADP+Pi
RUBISCO
2x Triose P
2 x3C
CO2
RuBP 5C
ATP
ADP
Hexose sugar
RuP 5C 6C

19. Revising photosynthesis
Limiting factors
Explain what is meant by a limiting factor
List 3 factors that could limit the rate of photosynthesis at a high concentration of carbon dioxide
Explain why the rate of photosynthesis increases as the light increases from low to high.
Explain why increasing the light intensity does not produce a continuous increase in the rate of photosynthesis
Exaplin why at low light intensities temperature changes have little effect on the rate of photosynthesis
Describe how to investigate experimentally the factors that affect the rate of photosynthesis. Include how you will make the data valid and reliable.

20. How did Engelmann explain these results?

21. Light intensity and the compensation point refer to bicarbonate indicator expt