Comprehensive Study Guidance for Biology 104 Exam 3 Topics

Q1. What are the inputs and outputs of the light reactions and the Calvin cycle? Where do the inputs come from? Where do the outputs go?

Background

Topic: Photosynthesis – Light Reactions and Calvin Cycle

This question tests your understanding of the two main stages of photosynthesis, the substances required for each, and what is produced. It also asks you to connect these processes to their sources and destinations within the cell and the environment.

Key Terms and Concepts:

• Light reactions

• Calvin cycle (dark reactions)

• Inputs: water, carbon dioxide, light energy, NADP+, ADP

• Outputs: oxygen, ATP, NADPH, glucose (or G3P)

Step-by-Step Guidance

1. List the main reactants (inputs) and products (outputs) for the light reactions. Consider where each comes from (e.g., water from the environment, light from the sun).

2. Identify the main reactants and products for the Calvin cycle. Think about which molecules are recycled and which are new inputs.

3. For each input and output, specify its source (e.g., atmosphere, water, previous reaction) and its destination (e.g., released as gas, used in next step, stored as sugar).

4. Consider how the outputs of the light reactions are used as inputs for the Calvin cycle.

Try solving on your own before revealing the answer!

Q2. What happens in the thylakoid vs. what happens in the stroma of the chloroplast?

Background

Topic: Chloroplast Structure and Function

This question focuses on the compartmentalization of photosynthetic processes within the chloroplast and the specific roles of the thylakoid and stroma.

Key Terms:

• Thylakoid: membrane-bound sacs inside chloroplasts

• Stroma: fluid-filled space surrounding thylakoids

• Light reactions, Calvin cycle

Step-by-Step Guidance

1. Recall which stage of photosynthesis occurs in the thylakoid membranes and what is produced there.

2. Identify which stage occurs in the stroma and what is synthesized there.

3. Think about why these processes are separated into different compartments.

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Q3. What is the role of the thylakoid membrane in photosynthesis?

Background

Topic: Photosynthetic Membranes

This question asks you to explain the functional significance of the thylakoid membrane in the process of photosynthesis.

Key Terms:

• Thylakoid membrane

• Photosystems

• Electron transport chain

• ATP synthase

Step-by-Step Guidance

1. Describe the main structures embedded in the thylakoid membrane (e.g., photosystems, electron carriers).

2. Explain how the thylakoid membrane facilitates the light reactions, including the generation of a proton gradient.

3. Consider how the membrane's properties contribute to ATP synthesis.

Try solving on your own before revealing the answer!

Q4. How do the inputs and outputs of cellular respiration and photosynthesis ‘match up’ with one another? What are the consequences of this for the biosphere?

Background

Topic: Relationship Between Photosynthesis and Cellular Respiration

This question tests your ability to compare and contrast the two major energy-transforming processes in living organisms and to understand their ecological significance.

Key Terms and Concepts:

• Photosynthesis: $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$

• Cellular respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy}$

• Biosphere, carbon cycle, oxygen cycle

Step-by-Step Guidance

1. Write out the overall equations for both photosynthesis and cellular respiration.

2. Compare the reactants and products of each process. Notice how the outputs of one are the inputs of the other.

3. Discuss the ecological consequences of this relationship for life on Earth (e.g., cycling of oxygen and carbon dioxide).

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Q5. What is the relationship between the electron transport chain and the photosystems of photosynthesis?

Background

Topic: Light Reactions – Electron Flow

This question examines your understanding of how electrons move through the light reactions and the roles of photosystems and the electron transport chain.

Key Terms:

• Photosystem II (PSII), Photosystem I (PSI)

• Electron transport chain (ETC)

• NADP+ reduction

Step-by-Step Guidance

1. Identify where the electron transport chain is located within the chloroplast.

2. Describe the sequence of electron flow from water through PSII, the ETC, PSI, and finally to NADP+.

3. Explain how the movement of electrons is coupled to the generation of ATP and NADPH.

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Q6. How is the increased H+ concentration in the thylakoid generated?

Background

Topic: Chemiosmosis in Photosynthesis

This question focuses on the mechanisms that create a proton gradient across the thylakoid membrane during the light reactions.

Key Terms and Concepts:

• Proton gradient (H+ gradient)

• Water splitting (photolysis)

• Electron transport chain

Step-by-Step Guidance

1. Recall what happens to water molecules during the light reactions and where the protons go.

2. Describe how the movement of electrons through the ETC is coupled to the pumping of H+ into the thylakoid lumen.

3. Consider the role of the proton gradient in ATP synthesis.

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Q7. What is the role of ATP synthase in the light reaction and how does it compare to its role in cellular respiration?

Background

Topic: ATP Synthesis in Bioenergetics

This question asks you to compare the function of ATP synthase in chloroplasts and mitochondria.

Key Terms:

• ATP synthase

• Proton-motive force

• Photophosphorylation vs. oxidative phosphorylation

Step-by-Step Guidance

1. Describe how ATP synthase uses the proton gradient to generate ATP in the chloroplast during the light reactions.

2. Compare this process to ATP synthesis in mitochondria during cellular respiration.

3. Identify similarities and differences in the source of the proton gradient and the location of ATP production.

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Q8. What does ‘carbon fixation’ refer to in the context of photosynthesis? When/where does it occur?

Background

Topic: Calvin Cycle – Carbon Fixation

This question tests your understanding of how inorganic carbon is incorporated into organic molecules during photosynthesis.

Key Terms:

• Carbon fixation

• Calvin cycle

• RuBisCO enzyme

Step-by-Step Guidance

1. Define carbon fixation and explain its significance in the biosphere.

2. Identify the enzyme responsible for carbon fixation and the stage of photosynthesis where it occurs.

3. Describe the location within the chloroplast where carbon fixation takes place.

Try solving on your own before revealing the answer!