Fundamentals of Photosynthesis
What is the primary purpose of photosynthesis in plants?
To convert light energy into chemical energy stored in glucose.
What is the main function of the light-dependent reactions?
o convert light energy into chemical energy in the form of ATP and NADPH.
What is carbon fixation, and which enzyme is responsible for it in the Calvin Cycle?
Carbon fixation is the process of converting inorganic CO₂ into an organic compound; Rubisco is the enzyme responsible for it.
What is meant by a "limiting factor" in photosynthesis?
A limiting factor is a condition that, when in short supply, restricts the rate of photosynthesis.
Describe the primary role of the electron transport chain.
To transport electrons to produce ATP.
In which specific part of the chloroplast does the Calvin Cycle occur?
The stroma.
Name the two photosystems involved in the light-dependent reactions and their specific roles.
Photosystem II (PSII) initiates the electron transport chain by splitting water and Photosystem I (PSI) produces NADPH.
What three stages comprise the Calvin Cycle?
Carbon fixation, reduction, and regeneration of RuBP.
How does light intensity affect the rate of photosynthesis?
Increasing light intensity increases the rate of photosynthesis up to a point where another factor becomes limiting.
Where in the chloroplast does the electron transport chain occur?
In the thylakoid membrane of the chloroplast.
What are the primary pigments involved in photosynthesis, and why are they important?
Chlorophyll a and chlorophyll b; they absorb light energy needed for photosynthesis.
Explain the role of the proton gradient in ATP synthesis during the light-dependent reactions.
The proton gradient across the thylakoid membrane drives ATP synthesis as protons flow through ATP synthase, converting ADP to ATP.
Explain why the Calvin Cycle is sometimes called the light-independent reaction.
It does not require light directly and instead uses ATP and NADPH produced in the light-dependent reactions to drive carbon fixation.
Explain how temperature affects enzyme activity in the Calvin Cycle.
Higher temperatures increase enzyme activity until an optimum temperature is reached; beyond this, enzymes may denature, reducing the rate of photosynthesis.
What molecule is the final electron acceptor in the light reactions?
The final electron acceptor in the light reactions is NADP⁺, which combines with electrons and protons to form NADPH.
Identify the waste product released during photosynthesis and its origin.
Oxygen, which is produced when water molecules are split during the light-dependent reactions.
What is non-cyclic photophosphorylation, and why is it significant in photosynthesis?
Non-cyclic photophosphorylation involves the movement of electrons from water to NADP+, producing ATP and NADPH; it is significant because it provides the necessary energy and reducing power for the Calvin Cycle.
How many turns of the Calvin Cycle are required to produce one molecule of glucose?
Six turns, as each turn fixes one carbon dioxide molecule, and glucose requires six carbons.
Describe how low carbon dioxide levels impact the Calvin Cycle.
Low CO₂ levels reduce the rate of carbon fixation, limiting the production of glucose and other organic compounds.
Explain chemiosmosis and its role in ATP synthesis.
Chemiosmosis is the flow of protons across the thylakoid membrane through ATP synthase, which generates ATP from ADP and Pi.
Describe the difference between autotrophic and heterotrophic nutrition.
Autotrophs produce their own food through photosynthesis (or chemosynthesis), while heterotrophs rely on consuming other organisms for energy.
Discuss why cyclic photophosphorylation occurs and what it produces.
Cyclic photophosphorylation produces additional ATP without generating NADPH; it occurs when there is sufficient NADPH but ATP is still needed for the Calvin Cycle.
Why is the regeneration of RuBP critical for the continuation of the Calvin Cycle?
RuBP is the acceptor molecule for CO₂; without its regeneration, the Calvin Cycle would halt, and carbon fixation would stop.
Illustrate how the concept of limiting factors can be applied to improve crop yields in agricultural settings.
By optimizing light, temperature, and CO₂ levels in controlled environments, such as greenhouses, farmers can maximize photosynthetic rates, increasing crop yields.
Describe the proton gradient and its importance in ATP production.
The proton gradient across the thylakoid membrane provides the energy for ATP production as protons flow through ATP synthase.