Photosynthesis IBDP Biology: HL/Option C Stephen Taylor Bandung International School Title slide. Bandung International School.

Photosynthesis title, definition and equation.

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.

Laminaria saccharina uses carotenoids as accessory pigments Laminaria saccharina uses carotenoids as accessory pigments. Light is limited underwater.

Chloroplast: colour TEM, parts and functions.

Image source unknown. Question from the IBO. Chloroplast: structure’s relationship with function Image source unknown. Question from the IBO.

Light Dependent Reactions title and brief overview.

Photoactivation of chlorophyll – electrons are excited and return to their original state, releasing oxygen. e-

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.

Useful light dependent reaction animations: Links to light dependent reactions animations.

Light Independent Reactions title – quick overview.

Carbon fixcation using CO2 and rubisco

Reduction of glycerate 3-phosphate

Carbohydrate formation and re-generation of RuBP

Calvin cycle overview.

Simple Calvin Cycle animations: Calvin cycle animation links.

Methods of measuring the rate of photosynthesis.

plateau CO2 is a substrate in an enyme-catalysed light-dependent reaction. At low CO2 concentration, rate is positively correlated with concentration CO2 affects rate of photosynthesis. CO2 is the substrate in carbon fixation (Calvin cycle) – rubisco is the enzyme.

plateau At low light intensity, rate of photosynthesis is proportional to light intensity. Light intensity affects rate of photosynthesis.

Above the optimum temp., enzymes are denatured and rate drops steeply. Optimum temperature Above the optimum temp., enzymes are denatured and rate drops steeply. Increased temp. gives increased energy and increased rate of photosynthesis Which enzymes are used in respiration? Temperature affects the rate of photosynthesis. Remember enzyme theory. Enzymes used in respiration: rubisco is the main one. ATP synthase can also be denatured.

Team analogy for the limiting factors theory Team analogy for the limiting factors theory. Time to vote off the weakest link.

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.”

What are the conditions of each of these trials? Rate of photosynthesis This graph suggests that CO2 is more important than temperature. Why? Light intensity

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?

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