Photosynthesis: Light Reactions and Calvin Cycle

What is the process by which plants produce their own food?

Photosynthesis

What are the two stages of photosynthesis?

Light reactions and the Calvin Cycle

What do chloroplasts contain that is essential for absorbing sunlight?

Chlorophyll

What is the role of RuBisCo in the Calvin Cycle?

It captures CO2 from the atmosphere and attaches it to ribulose bisphosphate.

What is produced during the light reactions of photosynthesis?

Oxygen, ATP, and NADPH.

What is the main product of the Calvin Cycle that can be converted into glucose?

Glyceraldehyde-3-phosphate (G3P)

In the light reactions, what happens to photons absorbed by chlorophyll?

They excite electrons, which can then be transferred to the primary electron acceptor.

How do photosystem II and photosystem I differ in their products during light reactions?

Photosystem II produces ATP, while photosystem I produces NADPH.

What is the energy currency produced during photosynthesis that is used in the Calvin Cycle?

ATP

What is the opposite of the Calvin Cycle in terms of metabolic processes?

The citric acid cycle, which is catabolic.

What is the function of ATP synthase in photosynthesis?

It synthesizes ATP from the proton gradient generated during the light reactions.

Which phase of the Calvin Cycle involves the conversion of 3-phosphoglycerate to G3P?

Phase two: Reduction.

What is the stable output required to complete one turn of the Calvin Cycle?

One molecule of G3P.

What makes the Calvin Cycle an anabolic pathway?

It builds larger organic molecules from smaller components, requiring energy.

What is created as a byproduct of the light reactions when water is split?

Oxygen

How does linear electron flow in the light reactions occur?

Linear electron flow occurs when light energy is absorbed by chlorophyll, exciting electrons that are transferred through a series of proteins in the thylakoid membrane.

What are the products of linear electron flow in the light reactions?

The products of linear electron flow are ATP, NADPH, and oxygen.

What role does ATP synthase play in the production of ATP during linear electron flow?

ATP synthase uses the proton gradient created by electron transport to convert ADP and inorganic phosphate into ATP.

How is NADPH produced in linear electron flow?

NADPH is produced when electrons from the final electron acceptor (ferredoxin) are transferred to NADP+, reducing it in the process.

What is the source of oxygen produced in linear electron flow?

Oxygen is produced as a byproduct from the splitting of water molecules (photolysis) to replace the electrons lost by chlorophyll.

What is chemiosmosis in the context of light reactions?

Chemiosmosis is the process by which ATP is produced during the light reactions as protons flow back across the thylakoid membrane through ATP synthase.

How does the proton gradient contribute to ATP synthesis during chemiosmosis?

The proton gradient created by the accumulation of protons inside the thylakoid lumen drives protons back into the stroma, which powers ATP synthase to convert ADP and inorganic phosphate into ATP.

What is the role of ATP synthase in chemiosmosis?

ATP synthase is an enzyme that facilitates the synthesis of ATP from ADP and inorganic phosphate as protons flow through it.

Why is the proton gradient important for ATP production in the light reactions?

The proton gradient is crucial because it provides the potential energy needed for ATP synthase to produce ATP, serving as a form of stored energy that can be utilized for ATP generation.

What triggers the formation of the proton gradient in the light reactions?

The formation of the proton gradient is triggered by the movement of electrons through the electron transport chain, which pumps protons into the thylakoid lumen

What are the main energy molecules produced by the light reactions?

The main energy molecules produced by the light reactions are ATP and NADPH.

How does ATP contribute to the Calvin Cycle?

ATP provides the energy needed for various reactions in the Calvin Cycle, including the conversion of 3-PGA to G3P.

What role does NADPH play in the Calvin Cycle?

NADPH provides the reducing power needed to convert 3-PGA into G3P by donating high-energy electrons.

What is G3P and its significance in the Calvin Cycle?

G3P (glyceraldehyde-3-phosphate) is a three-carbon sugar that is a product of the Calvin Cycle and is used to form glucose and other carbohydrates.

In which phase of the Calvin Cycle is G3P produced?

G3P is produced during the reduction phase of the Calvin Cycle after the conversion of 3-PGA.

What adaptations do CAM plants have to survive in arid environments?

CAM plants adapt to dry conditions by opening their stomata at night to minimize water loss, allowing CO2 to be taken in and stored as organic acids.

How do CAM plants perform photosynthesis differently from C3 and C4 plants?

CAM plants fix carbon during the night and perform the Calvin Cycle during the day, while C3 and C4 plants generally fix carbon during the day.

What is the advantage of night-time gas exchange in CAM plants?

Night-time gas exchange reduces water loss due to cooler temperatures and higher humidity at night, allowing CAM plants to thrive in arid environments.

How do CAM plants store CO2?

CAM plants convert CO2 into organic acids (such as malate) during the night and store them until the daytime when they are converted back to CO2 for use in the Calvin Cycle.

Why are CAM plants important for ecosystems in arid regions?

CAM plants play a crucial role in ecosystems by providing food and habitat while efficiently conserving water, thus maintaining biodiversity in dry habitats.