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Module 8 Lesson 2 Progress Check

Prompt

Read M8 Lesson 2. Answer the "Check Your Progress" questions (p208 #3, 4, and the additional 2 questions below) and submit your answers here.

Response

  1. Explain why water is essential for the light reactions.

    Water is crucial in the light reactions of photosynthesis because it provides the necessary electrons and protons. When water is split during photolysis, it releases electrons, which are vital for replenishing those lost by chlorophyll in the photosystem II. This process also produces oxygen as a by-product, essential for life on earth. Additionally, the protons released contribute to creating a proton gradient across the thylakoid membrane, utilized by \(ATP\) synthase to generate \(ATP\) for the Calvin cycle.

  2. Summarize the steps in the Calvin cycle.

    The Calvin cycle begins with carbon fixation, where \(CO_2\) is attached to ribulose bisphosphate (\(RuBP\)), forming a six-carbon compound that splits into two three-carbon molecules. These molecules undergo reduction, using \(ATP\) and \(NADPH\) from light reactions, to produce \(G3P\), a precursor for glucose. One \(G3P\) molecule exits the cycle per three \(CO_2\) molecules fixed, while the rest regenerate \(RuBP\), enabling the cycle's continuation.

  3. Name the products and reactants of both light-dependent and light-independent reactions, as well as identify the location within the chloroplast where each of the two reactions occur.

    The light-dependent reactions, occurring in the thylakoid membranes, use water and light to produce oxygen, \(ATP\), and \(NADPH\). Water provides electrons and protons, while light energy drives the process. In contrast, the Calvin cycle, happening in the chloroplast stroma, utilizes \(CO_2\), \(ATP\), and \(NADPH\) to generate glucose and regenerate \(ADP\) and \(NADP^+\), continuing the cycle.

  4. What are 3 factors that could change the rate of reaction of photosynthesis?

    The rate of photosynthesis is influenced by light intensity, carbon dioxide concentration, and temperature. Increased light intensity enhances photosynthesis to a saturation point. Higher CO₂ levels accelerate the process until reaching an optimum. Temperature affects enzyme activity; thus, photosynthesis rates increase with temperature until a peak, after which they decline due to enzyme denaturation.

  5. Name the products and reactants of both light-dependent and light-independent reactions, as well as identify the location within the chloroplast where each of the two reactions occur.

    In the light-dependent reactions of photosynthesis, water and light energy are the reactants, and the products are \(O_2\), \(ATP\), and \(NADPH\). These reactions take place in the thylakoid membranes of the chloroplast. In contrast, the light-independent reactions, also known as the Calvin Cycle, use \(CO_2\), \(ATP\), and \(NADPH\) as reactants to produce glucose, \(ADP\), and \(NADP^+\). The Calvin Cycle occurs in the stroma of the chloroplast, the fluid-filled area surrounding the thylakoids.

  6. What are 3 factors that could change the rate of reaction of photosynthesis?

    Three main factors that can change the rate of photosynthesis are light intensity, \(CO_2\) concentration, and temperature. The rate typically increases with higher light intensity until it reaches a saturation point. An increase in carbon dioxide concentration can boost the rate up to a certain level, after which it plateaus. Temperature affects the rate of photosynthesis as it influences enzyme activities; it increases with temperature up to an optimum point, beyond which high temperatures can inhibit the process due to enzyme denaturation.