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3.8 8.2 Photosynthesis PPT
- 1. Topics 3.8 + 8.2 Photosynthesis IB Biology
- 3. Leaves Green tissue in the interior of the leaf (mesophyll) = contains chloroplasts CO2 enters the leaf and O2 exits through the stoma Stomata =bottom of leaf
- 4. Chloroplasts similar to mitochondria outer and inner membrane membranous sacs: THYLAKOIDS thylakoids = concentrated in stacks called GRANA thylakoids: contain chlorophyll (capture light) filled with fluid: STROMA (where sugars are made from CO2 )
- 5. Overview
- 10. The 2 stages of Photosynthesis Light Dependent Reactions: convert light energy to chemical energy (ATP + NADPH) and produce oxygen gas as a waste product Light Independent Reactions (Calvin Cycle): make sugar using carbon dioxide and the energy-containing products of the light-reactions (ATP + NADPH)
- 11. Light Dependent Reaction Light can be.. Absorbed Reflected Transmitted Occurs in thylakoids Chlorophyll A and B = main photosynthetic pigments (also carotenes, anthocyanins)
- 12. Light Dependent Reaction Light energy is used to split water. H + is released = used by ATP Synthase to produce ATP NADP + is reduced to NADPH+ ATP and NADPH = used in light independent reactions O2 = waste product
- 13. Photosystems Photosystem: place in thylakoid where light is harvested Photon is absorbed by a pigment molecule = electrons gain energy Excited electron is passed to a neighboring molecule - the primary acceptor
- 14. Photosystems I & II work together Both photosystems absorb light Electron Transport Chain= electrons go down an energy hill = lose energy at each step - this energy is stored in ATP or NADPH Electrons released from PSI is replaced by electrons coming from PSII
- 21. H + flow allows ATP production
- 24. Light Independent Reaction (Calvin Cycle) Glucose phosphate is produced = stored as starch CO2 , ATP and NADPH are used
- 26. Simple Calvin Cycle animations:
- 27. Summary Light dependent reaction Light independent reaction
- 30. plateau CO2 is a substrate in an enyme-catalysed light-dependent reaction. At low CO2 concentration, rate is positively correlated with concentration
- 31. plateau At low light intensity, rate of photosynthesis is proportional to light intensity.
- 32. Optimum temperature Increased temp. gives increased energy and increased rate of photosynthesis Above the optimum temp., enzymes are denatured and rate drops steeply.
- 34. What are the conditions of each of these trials? Rate of photosynthesis Light intensity
Notas do Editor
- Photosynthesis title, definition and equation.
- Chloroplast: colour TEM, parts and functions.
- Why does a leaf look green?
- Action spectrum of photosynthesis shows wavelengths used for light dependent reactions. Different colours are different wavlengths. The green region is not used, so green light is reflected and seen.
- Absorption spectrum of chlorophyll a vs action spectrum of photosynthesis. Chlorophyll b is used to ‘fill the gaps’ in the action spectrum.
- Photolysis of water produces high-energy electrons, H+ protons and oxygen.
- Protons are pumped into stroma using energy from electrons
- Photosystem I is activated
- Non-cyclic phosphorylation produces ATP.
- Reduction of NADP+ by ferredoxin.
- Calvin cycle overview.
- Calvin cycle animation links.
- Team analogy for the limiting factors theory. Time to vote off the weakest link.
- CO2 affects rate of photosynthesis. CO2 is the substrate in carbon fixation (Calvin cycle) – rubisco is the enzyme.
- Light intensity affects rate of photosynthesis.
- Temperature affects the rate of photosynthesis. Remember enzyme theory. Enzymes used in respiration: rubisco is the main one. ATP synthase can also be denatured.
- Explain the effects of limiting each of the three factors on the process of photosynthesis. It’s not enough to just say “it slows down.”
- This graph suggests that CO2 is more important than temperature. Why?
- Iron is limiting – seeding algae with iron stimulates algal blooms. Iron is used in ferroxidase – responsible for reduction of NADP+ in the light dependent reactions. Results with CO2 were short-term. Levels dropped in the immediate area, but the seeding is too expensive to work. Pros: possible reduced CO2 levels, algal blooms provide food for grazers and thus fisheries. Cons: large blooms block light to lower levels, may cause eutrophication; Diatoms block gills of some species; iron seeding may encourage blooms of toxic algae; who owns the ocean?