Practice Questions

Identify the specific location within the chloroplast where the light-dependent reactions occur.

Formulate a hypothesis explaining why light saturation for photosynthesis occurs at only 10% of full sunlight.

Justify the need for 12 molecules of water in the balanced equation for photosynthesis: $6\text{CO}_2 + 12\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{H}_2\text{O} + 6\text{O}_2$.

Name the primary photosynthetic pigment in higher plants.

List the two main products of the light-dependent reactions that are utilized in the Calvin cycle.

Propose a reason why the reaction centre of a photosystem is composed of a single chlorophyll 'a' molecule, while the antennae complex has hundreds of pigment molecules.

Examine the primary functional significance of 'Kranz' anatomy in the leaves of C4 plants.

Apply Blackman's Law of Limiting Factors to a scenario where a plant is provided with optimal light and temperature, but the atmospheric $CO_2$ concentration is very low (e.g., 0.01%).

Examine why the action spectrum of photosynthesis closely follows the absorption spectrum of chlorophylls, showing peaks in the blue and red regions of light.

Critique the experimental setup of Joseph Priestley. What was a major uncontrolled variable in his bell jar experiments?

Define the process of photosynthesis.

Critique the term 'dark reaction' for the biosynthetic phase of photosynthesis. Propose a more accurate term and justify your proposal.

Explain Blackman's Law of Limiting Factors in the context of photosynthesis.

Examine the statement: 'The biosynthetic phase of photosynthesis is often called the dark reaction, but this is a misnomer.' Analyze the validity of this statement with supporting reasons.

Contrast the location and function of the ATP synthase complex in a chloroplast with its counterpart in a mitochondrion.

List the four main types of pigments found in the leaves of higher plants and their characteristic colors in a chromatogram.

Explain the role of accessory pigments like chlorophyll b and carotenoids in photosynthesis.

Recall the overall balanced chemical equation for photosynthesis.

What is 'Kranz' anatomy? Identify the type of plants in which it is found.

Name the primary $\text{CO}_2$ acceptor molecule in the C3 pathway and the C4 pathway.

Compare the primary roles of Photosystem I (PS I) and Photosystem II (PS II) during the light-dependent reactions of photosynthesis.

Analyze the provided graph (Figure 11.10) showing the effect of light intensity on the rate of photosynthesis. If the plant is operating at point C, what would likely happen to the rate of photosynthesis if the $CO_2$ concentration was doubled?

Compare cyclic and non-cyclic photophosphorylation based on the photosystems involved, the final electron acceptor, and the net products.

Contrast the initial carboxylation step in C3 and C4 plants by comparing the primary $CO_2$ acceptor, the enzyme involved, the initial product, and the cellular location of the reaction.

Apply the chemiosmotic hypothesis to explain why ATP synthesis would stop if a chemical agent made the thylakoid membrane fully permeable to protons ($H^+$).

A scientist replicates T.W. Engelmann's experiment by illuminating a filament of the green alga Cladophora with light split by a prism and then introducing aerobic bacteria. Analyze where the bacteria would be expected to accumulate and explain what this result demonstrates about photosynthesis.

A C3 plant is supplied with water containing a heavy isotope of oxygen, $H_2^{18}O$, while the carbon dioxide provided is normal ($C^{16}O_2$). Analyze which of the products of photosynthesis ($C_6H_{12}O_6$ or $O_2$) will contain the $^{18}O$ isotope and provide a reason for your answer.

Evaluate the significance of the chemiosmotic hypothesis in explaining ATP synthesis during photophosphorylation. Why is a proton gradient essential for this process?

Justify the assertion that cyclic photophosphorylation is a necessary supplement to non-cyclic photophosphorylation for the Calvin cycle to proceed.

Design a simple experiment using a variegated leaf to demonstrate that both chlorophyll and light are necessary for photosynthesis. Outline the expected results and justify your conclusion.

Evaluate the role of RuBisCO's dual carboxylase and oxygenase activity. Why might this 'inefficient' oxygenase function have been conserved through evolution?

A plant is exposed to light with wavelengths only beyond 680 nm. Evaluate which photosynthetic processes will continue and which will cease. Justify your reasoning based on the functions of PS I and PS II.

Formulate a hypothesis to explain why $\text{C}_4$ plants are more productive in tropical climates than $\text{C}_3$ plants. Your hypothesis must integrate leaf anatomy, enzyme efficiency, and photorespiration.

Describe the process of photorespiration and state why it is considered a wasteful process.

Analyze the consequences for a typical C3 plant if the enzyme RuBisCO were to lose its oxygenase activity, meaning it could only function as a carboxylase.

Summarize the chemiosmotic hypothesis for ATP synthesis during photophosphorylation.

Describe the three main stages of the Calvin cycle.

Propose a strategy for a farmer to maximize the yield of greenhouse tomatoes (a $\text{C}_3$ plant) by manipulating environmental factors. Justify each component of your strategy based on the principles of limiting factors in photosynthesis.

Calculate the total number of ATP and NADPH molecules that are required by the Calvin cycle to produce one molecule of sucrose ($C_{12}H_{22}O_{11}$).

A scientist proposes creating a genetically modified $\text{C}_3$ plant that expresses high levels of PEP carboxylase in its mesophyll cells. Evaluate the potential benefits and drawbacks of this modification in terms of photosynthetic efficiency and biomass yield.

Explain what is meant by the terms 'action spectrum' and 'absorption spectrum' in the context of photosynthesis.

Solve for the net inputs and outputs of the Calvin cycle required for the synthesis of one molecule of triose phosphate (G3P).

Summarize the key findings from Jan Ingenhousz's experiments on photosynthesis.

Create a flowchart to illustrate how a $\text{C}_4$ plant spatially separates the initial carbon fixation from the Calvin cycle. Justify why this separation minimizes photorespiration.

Design an experiment to prove that oxygen evolved during photosynthesis comes from water, not carbon dioxide, using radioisotope techniques. Justify the choice of isotopes.