Photosynthesis: Light-Dependent Reactions and the Calvin Cycle

Biology Grades High School 4:47 Video
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Lesson Description

Explore the two major stages of photosynthesis: the light-dependent reactions and the Calvin cycle. Understand how light energy is converted into chemical energy to produce sugars and oxygen.

Video Resource

Breaking down photosynthesis stages | High school biology | Khan Academy

Khan Academy

Duration: 4:47
Watch on YouTube

Key Concepts

  • Light-dependent reactions
  • Calvin cycle
  • ATP and NADPH as energy carriers
  • Carbon fixation
  • Conversion of light energy to chemical energy

Learning Objectives

  • Students will be able to describe the two main stages of photosynthesis: light-dependent reactions and the Calvin cycle.
  • Students will be able to explain the inputs and outputs of each stage of photosynthesis.
  • Students will be able to identify the role of ATP and NADPH in the Calvin cycle.
  • Students will be able to explain the origin and importance of oxygen as a byproduct of photosynthesis.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the overall equation for photosynthesis. Ask students what they already know about the process. Introduce the idea that photosynthesis can be broken down into two main stages: light-dependent reactions and the Calvin cycle.
  • Video Viewing (7 mins)
    Play the Khan Academy video "Breaking down photosynthesis stages | High school biology | Khan Academy." Instruct students to take notes on the key inputs and outputs of each stage.
  • Light-Dependent Reactions Discussion (10 mins)
    Discuss the light-dependent reactions. What are the inputs (light energy, water)? What are the outputs (ATP, NADPH, oxygen)? Where does the oxygen come from? Emphasize the role of water as an electron source and the production of oxygen as a byproduct.
  • Calvin Cycle Discussion (10 mins)
    Discuss the Calvin cycle. What are the inputs (ATP, NADPH, carbon dioxide)? What is the output (sugar)? Explain how the energy stored in ATP and NADPH is used to fix carbon dioxide into sugar molecules.
  • Photosynthesis Summary (8 mins)
    Summarize the entire process of photosynthesis, emphasizing the flow of energy and the cycling of matter. Discuss the importance of photosynthesis for life on Earth, particularly for providing oxygen and food for other organisms. Use a diagram to visually represent the two stages and their connections.

Interactive Exercises

  • Photosynthesis Flowchart
    Students create a flowchart that illustrates the inputs, processes, and outputs of both the light-dependent reactions and the Calvin cycle. They should include arrows indicating the flow of energy and matter.
  • Role-Playing Photosynthesis
    Divide the class into groups and assign roles such as water molecules, carbon dioxide molecules, ATP, NADPH, and sugar. Students act out the movement of these molecules through the two stages of photosynthesis.

Discussion Questions

  • Why is water essential for the light-dependent reactions?
  • How does the Calvin cycle depend on the light-dependent reactions?
  • What would happen to the Earth's atmosphere if photosynthesis stopped?
  • Why is photosynthesis important for all life on Earth?

Skills Developed

  • Critical thinking
  • Scientific reasoning
  • Data Interpretation
  • Model building

Multiple Choice Questions

Question 1:

What are the two main stages of photosynthesis?

Correct Answer: Light-dependent reactions and the Calvin cycle

Question 2:

What is the main input of the light-dependent reactions?

Correct Answer: Light energy

Question 3:

What are the main products of the light-dependent reactions?

Correct Answer: ATP, NADPH, and oxygen

Question 4:

What is the main input of the Calvin cycle?

Correct Answer: ATP and NADPH

Question 5:

What is the main product of the Calvin cycle?

Correct Answer: Sugar

Question 6:

What is the role of ATP and NADPH in the Calvin cycle?

Correct Answer: To provide energy for carbon fixation

Question 7:

From what molecule is oxygen produced during photosynthesis?

Correct Answer: Water

Question 8:

What is the process of incorporating carbon dioxide into organic molecules called?

Correct Answer: Carbon fixation

Question 9:

Which of the following is a strong reducing agent produced in the light dependent reactions?

Correct Answer: NADPH

Question 10:

Where does the Calvin cycle take place?

Correct Answer: Stroma of the chloroplast

Fill in the Blank Questions

Question 1:

Photosynthesis uses light energy to synthesize ________.

Correct Answer: sugar

Question 2:

The light-dependent reactions take place in the ________ of the chloroplast.

Correct Answer: thylakoid

Question 3:

The Calvin cycle takes place in the ________ of the chloroplast.

Correct Answer: stroma

Question 4:

The source of electrons for the light-dependent reactions is ________.

Correct Answer: water

Question 5:

Carbon dioxide is 'fixed' during the ________.

Correct Answer: Calvin cycle

Question 6:

________ is a molecule that stores energy and is produced during the light-dependent reactions.

Correct Answer: ATP

Question 7:

________ is a reducing agent that provides energy for the Calvin Cycle.

Correct Answer: NADPH

Question 8:

________ is a byproduct of photosynthesis and is essential for aerobic life.

Correct Answer: Oxygen

Question 9:

The process of using light energy to produce ATP is called ________.

Correct Answer: photophosphorylation

Question 10:

The Calvin cycle is also known as the light-________ reactions.

Correct Answer: independent

Educational Standards

B.LS1.5:[Standard] Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy. B.LS2.5:[Standard] Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere. B.LS2.3:[Standard] Construct and revise an explanation based on evidence for the cycling of matter and the flow of energy in aerobic and anaerobic conditions.

Teaching Materials

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