Chapter 3 - Photosynthesis Flashcards
What is the overall equation of photosynthesis?
6CO2 + 6H2O –(light)–> C6H12O6 + 6O2
How is the structure of the leaf adapted for photosynthesis?
- Large SA to collect light
- The leaves are arranged to avoid overlap and shadowing
- Thin to shorten diffusion distance for light
- Transparent cuticle and epidermis let light to mesophyll cells
- Upper mesophyll cells packed with lots of chloroplasts
- A lot of stomata for gaseous exchange
- Air spaces in lower mesophyll for the diffusion of CO2 and O2
Where in the chloroplast does the light-dependent stage of photosynthesis occur?
The thylakoid membranes
Where in the chloroplast does the light-independent stage of photosynthesis occur?
The stroma
Explain the steps of the Light-Dependent Reaction.
1) Light energy reaches chlorophyll pigments in photosystem II (PSII) and transfers energy to e- in the chlorophyll A molecule.
2) These e- get ‘excited’ and leave to an electron carrier. They are passed along a number of them by redox reactions to lower the energy level of the e-.
3) Energy here used to make ATP.
4) Photolysis of water produces e- to replace the ones lost…
What is the photolysis of water and what are the products used for?
2H2O –> 4H+ + 4e- + O2
Water molecules are split using light energy.
The electrons replace those lost on PSII.
The protons are picked up by NADP and the NADP is reduced (NADPH2).
The O2 is used in respiration or is a waste product.
What are the products of the light-dependent reaction?
ATP and NADPH2
What is the role of water in photosynthesis?
It provides the H+ ions for reduction of NADP and provides the electrons to replace those lost in PSII
Explain the Calvin Cycle.
RuBP (+CO2 & catalysed by Rubisco) > 6C > 2 x GP > 2 x TP > 20% - other substances (e.g. Glucose, lipids, proteins, etc) 80% - RuBP.
What are the limiting factors of photosynthesis?
- Light
- Temperature (for enzyme action)
- CO2
- H2O
- pH
- Chlorophyll
