AP Biology - Photosynthesis

What is photosynthesis?

The process by which chloroplasts capture light energy from the sun and convert it into chemical energy stored in sugars and other organic molecules.

What are autotrophs?

Organisms that produce organic molecules from CO2 and inorganic raw materials, serving as the ultimate source of organic compounds for heterotrophic organisms.

What do heterotrophs depend on for nourishment?

Heterotrophs depend on organic compounds produced by other organisms.

What is the primary pigment involved in photosynthesis?

Chlorophyll, which is located in the thylakoid membranes of chloroplasts.

Define the equation for photosynthesis.

6CO2 + 6H2O + light energy → C6H12O6 + 6O2.

What is the Calvin cycle?

The second stage of photosynthesis that uses ATP and NADPH to incorporate CO2 from the atmosphere into sugar.

What are the two main stages of photosynthesis?

The light reactions and the Calvin cycle.

Where does photosynthesis occur in plant cells?

In chloroplasts, primarily in the mesophyll cells of leaves.

What is the role of stomata in photosynthesis?

Stomata are microscopic pores that allow CO2 to enter and O2 to exit the leaf.

What is the main carbohydrate product of the Calvin cycle?

Glyceraldehyde-3-phosphate (G3P), which can be used to make glucose.

What is photorespiration?

A process where the enzyme rubisco adds O2 to RuBP instead of CO2, leading to a decrease in photosynthetic output.

What is the difference between C3 and C4 plants?

C3 plants fix CO2 directly, while C4 plants first fix CO2 into a four-carbon compound to minimize photorespiration.

What are the light reactions of photosynthesis?

Processes that convert solar energy to chemical energy in the form of ATP and NADPH.

What happens during the light reactions?

Water is split, electrons are transferred to NADP+ forming NADPH, and ATP is generated via chemiosmosis.

What is the role of ATP in the Calvin cycle?

ATP provides energy needed to synthesize sugars during the Calvin cycle.

What is NADPH?

An electron carrier that provides reducing power during the Calvin cycle to convert CO2 into sugars.

What is the primary electron acceptor in photosystem II?

A protein complex that captures the excited electron from P680 chlorophyll.

Describe cyclic electron flow.

An alternative pathway in photosynthesis where electrons cycle back to photosystem I, generating ATP without producing NADPH or O2.

What is the endosymbiont theory?

A theory suggesting that chloroplasts originated from photosynthetic prokaryotes living inside a eukaryotic cell.

What are grana?

Stacked columns of thylakoids in chloroplasts where the light reactions of photosynthesis take place.

How do chlorophyll pigments contribute to photosynthesis?

Chlorophyll absorbs light energy, which excites electrons to drive the light reactions.

What is the source of oxygen produced during photosynthesis?

Oxygen produced during photosynthesis comes from the splitting of water (H2O) molecules.

What are the reactants of photosynthesis?

The reactants of the overall photosynthesis equation are carbon dioxide (CO2) and water (H2O).

What is the significance of the action spectrum?

It measures the effectiveness of different wavelengths of light in driving photosynthesis.

What is chemiosmosis?

The process of generating ATP from ADP and inorganic phosphate using the proton gradient established by the electron transport chain.

What is the primary purpose of the light reactions?

To convert solar energy into chemical energy in the form of ATP and NADPH for use in the Calvin cycle.

What types of plants use CAM photosynthesis?

Succulent plants like cacti and pineapples, which fix CO2 at night and use it during the day.

What is the result of photorespiration?

It reduces the efficiency of photosynthesis by consuming ATP and releasing CO2 instead of fixing it.

How does photosynthesis contribute to the biosphere?

Photosynthesis is fundamental for life, providing essential organic compounds and oxygen for living organisms.

What happens during carbon fixation in the Calvin cycle?

CO2 is attached to ribulose bisphosphate (RuBP) to begin the cycle.

How does a spectrophotometer work in studying pigments?

It measures the light absorption of pigments at different wavelengths to create an absorption spectrum.