Topic_H_Photosynthesis_lecture_notes_(2015)

NANYANG JUNIOR COLLEGE H2 Biology Photosynthesis J1/2015 1 TOPIC H: PHOTOSYNTHESIS Learning Outcomes Candidates should be able to: Core Topic 6 – Cellular Physiology and Biochemistry (a) With reference to the chloroplast structure, explain the light dependent reactions of photosynthesis (no biochemical details are needed but will include the outline of cyclic and non -cyclic light dependent reactions, and the transfer of energy for the subsequent manufacturing o f carbohydrates from carbon dioxide). (b) Outline the three phases of the Calvin cycle: (i) CO 2 uptake (ii) carbon reduction and (iii) ribulose bisphosphate (RuBP) regeneration and indicate the roles of ATP and NADP in the process. (c) Discuss limiting factors in photosynthesis and carry out investigations on the effects of limiting factors, such as light intensity, CO2 concentration and temperature, on the rate of photosynthesis. Content Outline 1. Autotrophs: Producers for the Earth 2. Structure of the Chloroplast 3. Photosynthetic Pigments (a) Chlorophylls (b) Carotenoids 4. Absorption and Action Spectra 5. Light-dependent Reactions (a) Photosynthetic Units (b) Excitation of Primary Pigments by Light (Absorption of Light Energy) (c) Non-cyclic Photophosphorylation (d) Cyclic Photophosphorylation 6. Light-independent Reactions (Calvin Cycle) (a) CO2 Uptake (CO2 Fixation) (b) Carbon Reduction (c) Regeneration of RuBP 7. Limiting Factors in Photosynthesis (a) Light (b) Temperature (c) Carbon Dioxide

NANYANG JUNIOR COLLEGE H2 Biology Photosynthesis J1/2015 2 1. Autotrophs: Producers for the Earth Photosynthesis nourishes almost all life on earth directly or indirectly. Autotrophs are organisms that sustain themselves without feeding on other organisms. Autotrophs can produce their own organic (carbon -containing) compounds from carbon dioxide (an inorganic source of carbon) and other inorganic compounds obtained from the environment using the energy harnessed from the environment. As plants use light as a source of energy to synthesise these organic compounds, they are specifically known as photoautotrophs. Heterotrophs feed on other organisms as they are unable to make their own organic compounds, unlike autotrophs. Autotrophs undergo photosynthesis where light energy is used to synthesize carbohydrate s from carbon dioxide and water. Oxygen is given out in the process as a by-product. The product formed is a sugar that is soon converted to starch for storage. There are two main stages in photosynthesis, namely the light-dependent and light-independent reactions / Calvin cycle.

NANYANG JUNIOR COLLEGE H2 Biology Photosynthesis J1/2015 3 2. Structure of the Chloroplast The two major steps for photosynthesis take place in specific regions within the chloroplast: 1) Light-dependent reactions – Thylakoids of the grana 2) Light-independent reactions (the Calvin cycle) - Stroma The thylak