Photosynthesis: Light-dependent Reactions

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Questions and Answers

What is the optimum temperature for photosynthesis according to the experiment?

30°C

35°C

25°C (correct)

20°C

In the experiment, increasing the light intensity decreases the rate of photosynthesis.

False

What limiting factor is addressed in the experiment to ensure enough carbon dioxide is available?

CO2

The process of photosynthesis is anabolic, converting ______ into energy-rich glucose.

carbon dioxide Signup and view all the answers

Match the following processes in photosynthesis with their descriptions:

Light-dependent reactions = Convert light energy into chemical energy Light-independent reactions = Use ATP and NADPH to synthesize glucose Cyclic photophosphorylation = Produces ATP only Non-cyclic photophosphorylation = Produces both ATP and NADPH Signup and view all the answers

What is the main product of cyclic photophosphorylation?

ATP Signup and view all the answers

In non-cyclic photophosphorylation, electrons are not replaced after they leave the chlorophyll.

False Signup and view all the answers

What process breaks down water molecules to provide electrons in non-cyclic photophosphorylation?

Photolysis Signup and view all the answers

The electrons ejected from chlorophyll during cyclic photophosphorylation return to the ______.

chlorophyll Signup and view all the answers

Match the type of photophosphorylation with its characteristics:

Cyclic photophosphorylation = Electrons return to the chlorophyll Non-cyclic photophosphorylation = Produces oxygen gas Both = Produce ATP Signup and view all the answers

Which of the following statements is true about the electron transport chain in cyclic photophosphorylation?

The chain produces ATP as electrons pass through. Signup and view all the answers

High-energy electrons produced in non-cyclic photophosphorylation are used in the light-independent reactions.

True Signup and view all the answers

What gas is produced as a byproduct of non-cyclic photophosphorylation?

Oxygen Signup and view all the answers

What molecule is produced when NADP picks up electrons and a hydrogen ion?

NADPH Signup and view all the answers

In cyclic photophosphorylation, the electron removed from chlorophyll returns back to it.

True Signup and view all the answers

What is the main product of the light-independent stage when hydrogen ions and CO2 combine?

Glucose Signup and view all the answers

ATP is formed from ADP and a ______.

phosphate Signup and view all the answers

Which process does not return the electron to chlorophyll?

Non-cyclic photophosphorylation Signup and view all the answers

The energy for glucose formation in the light-independent stage primarily comes from NADPH.

False Signup and view all the answers

Match the following terms with their correct descriptions:

Cyclic photophosphorylation = Electron returned to chlorophyll Non-cyclic photophosphorylation = Electron not returned to chlorophyll Light-dependent reactions = Require light to occur Light-independent reactions = Produce glucose using CO2 Signup and view all the answers

What molecule is regenerated after NADPH delivers hydrogen ions?

NADP Signup and view all the answers

Study Notes

Light-dependent Stage: Cyclic and Non-Cyclic Photophosphorylation

Cyclic Photophosphorylation: Electrons energised from chlorophyll return to the chlorophyll after passing through the electron transport chain, losing energy and producing ATP.
Electron Transport Chain: High-energy electrons released from chlorophyll are accepted by an electron acceptor, which transmits them along the chain, generating ATP.
Non-Cyclic Photophosphorylation: Electrons leave chlorophyll and are replaced by electrons from photolysis of water, resulting in oxygen production and ATP synthesis for glucose formation.
Photolysis of Water: This process breaks down water to provide high-energy electrons and produce oxygen, which can be used in respiration or released into the atmosphere.
Proton Pool: Hydrogen ions from photolysis enter a proton pool, contributing to glucose synthesis in the light-independent stage.

Formation of NADPH

NADP Reduction: Electrons from chlorophyll and hydrogen from the proton pool combine with NADP to form NADPH, which transports hydrogen to the light-independent stage.

Light-independent Stage (Calvin Cycle)

Carbon Dioxide Uptake: CO2 diffuses into the stroma, where it is converted into glucose using electrons and hydrogen from NADPH.
ATP Role: Energy for glucose formation is supplied by ATP produced in the light-dependent stage.
NADPH Recycle: Once it delivers its electrons and protons, NADPH is converted back to NADP°, ready to participate again.

Experimental Investigation of Photosynthesis

Method: Set up and adjust distance from a light source to elodea. Record oxygen bubble production after 3 minutes of acclimation at varied distances.
Results and Conclusion: Closer light increases oxygen bubble production, indicating a direct relationship between light intensity and the rate of photosynthesis.
Temperature Monitoring: Maintaining an optimal temperature (approximately 25°C) is crucial as photosynthesis is enzyme-driven.
Sodium Bicarbonate: Ensures CO2 availability, preventing it from becoming a limiting factor.

Limiting Factors in Photosynthesis

Definition: Limiting factors are conditions that restrain the growth of a population, such as CO2 levels in the experiment.
Enhancing Growth in Greenhouses: CO2 enrichment and artificial lighting can optimize photosynthesis.

Variables Affecting Photosynthesis

Key Variables: Light intensity, CO2 concentration, and temperature, all of which impact the photosynthetic rate.
Anabolism in Photosynthesis: Photosynthesis is an anabolic process, converting small molecules into larger ones (e.g., from CO2 to glucose).

Reason for Using Aquatic Plants

Aquatic setups allow for the observation of visible oxygen bubble production, facilitating accurate measurement of photosynthesis rates.

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Description

Explore the mechanisms of cyclic and non-cyclic photophosphorylation in photosynthesis. This quiz covers key processes such as the electron transport chain, photolysis of water, and NADP reduction. Test your understanding of how these processes contribute to ATP and NADPH formation.