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?
Leaves <br />Green tissue in the interior of the leaf (mesophyll) = contains chloroplasts<br />CO2 enters the leaf and O2 exits through the stoma<br />Stomata =bottom of leaf<br />
Chloroplasts<br />similar to mitochondria<br />outer and inner membrane<br />membranous sacs: THYLAKOIDS<br />thylakoids = concentrated in stacks called GRANA<br />thylakoids: contain chlorophyll (capture light)<br />filled with fluid: STROMA (where sugars are made from CO2 )<br />
The 2 stages of Photosynthesis<br />Light Dependent Reactions:<br />convert light energy to chemical energy (ATP + NADPH) and produce oxygen gas as a waste product<br />Light Independent Reactions (Calvin Cycle):<br />make sugar using carbon dioxide and the energy-containing products of the light-reactions (ATP + NADPH) <br />
Light Dependent Reaction<br />Light can be..<br />Absorbed<br />Reflected<br />Transmitted<br />Occurs in thylakoids<br />Chlorophyll A and B = main photosynthetic pigments (also carotenes, anthocyanins)<br />
Light Dependent Reaction<br />Light energy is used to split water. <br />H + is released = used by ATP Synthase to produce ATP<br />NADP + is reduced to NADPH+<br />ATP and NADPH = used in light independent reactions<br />O2 = waste product<br />
Photosystems<br />Photosystem: place in thylakoid where light is harvested<br />Photon is absorbed by a pigment molecule = electrons gain energy<br />Excited electron is passed to a neighboring molecule - the primary acceptor<br />
Photosystems I & II work together<br />Both photosystems absorb light<br />Electron Transport Chain= electrons go down an energy hill = lose energy at each step - this energy is stored in ATP or NADPH<br />Electrons released from PSI is replaced by electrons coming from PSII<br />