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Biology - Photosynthesis

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    Study Guide Biology – Photosynthesis 1. Photosynthesis Defined Many living things on Earth — especially green plants — can make their own food. They do this using very simple materials like carbon dioxide and water . To turn these simple molecules into food, they need energy , and that energy comes from sunlight . This food - making process is called photosynthesis . 1.1 How Energy Moves Through a Plant Cell Photosynthesis and energy use in plant cells are closely connected. Here’s the big picture: • Chloroplasts capture light energy from the sun • That energy is used to make glucose (C ₆ H ₁₂ O ₆ ) , a sugar that stores energy • Oxygen (O ₂ ) is released as a waste product • The glucose and oxygen are then used in the mitochondria • In the mitochondria, energy is released and used to make ATP from ADP and phosphate • Carbon dioxide (CO ₂ ) and water are released and reused in photosynthesis This creates a continuous cycle of energy use and recycling inside the cell.

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    Study Guide 1.2 What Is Photosynthesis? Photosynthesis is the process by which organisms use light energy to make carbohydrates, such as glucose. It allows plants to store energy in a form they can use later. Photosynthesis happens in two main stages , each with a specific role. Stage 1: Capturing Light Energy In the first stage, light energy excites energy - rich electrons . These electrons move through a series of coenzymes and other molecules . As this happens: • The energy from the electrons is trapped • ATP is produced • NADPH (nicotinamide adenine dinucleotide phosphate hydrogen) is formed Both ATP and NADPH store energy and act as energy carriers for the next stage.

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    Study Guide Stage 2: Making Carbohydrates In the second stage, the energy stored in ATP and NADPH is used to combine carbon dioxide molecules . This process: • Builds carbohydrates • Produces organic molecules such as glucose • Stores energy in chemical bonds that the plant can use later 2. Quiz Photosynthesis 1. Question Fill in the blank: Which of the following statements about photosynthesis is FALSE ? Answer Choices • Carbon dioxide molecules are bound into carbohydrates during the second half of the process. • It is a catabolic process that releases the energy stored in glucose molecules. • Oxygen is released as a waste product. Correct Answer It is a catabolic process that releases the energy stored in glucose molecules. Why This Is Correct Photosynthesis is an anabolic process , not a catabolic one. It uses energy (from sunlight) to build glucose molecules from carbon dioxide and water. The other statements are true:

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    Study Guide • Carbon dioxide is fixed into carbohydrates during the Calvin cycle (the second half of photosynthesis). • Oxygen is released as a waste product during the light - dependent reactions when water is split. 2. Question Fill in the blank: How does photosynthesis occur? Answer Choices • Glucose is broken down into carbon dioxide using the energy of the sun. • The products of the light reaction are used to create glucose from carbon dioxide. • The sunlight directly powers ATP synthase, which catalyzes the creation of glucose. Correct Answer The products of the light reaction are used to create glucose from carbon dioxide. Why This Is Correct Photosynthesis occurs in two main stages : 1. The light reactions , which capture energy from sunlight and produce energy - rich molecules (ATP and NADPH). 2. The Calvin cycle , which uses those products to build glucose from carbon dioxide . The other options are incorrect because: • Glucose breakdown happens during cellular respiration , not photosynthesis. • Sunlight does not directly create glucose ; it first powers the light reactions, which then support glucose production.

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    Study Guide 3. Chloroplast Photosynthesis takes place inside a special cell structure called the chloroplast . Chloroplasts are found in the leaves and green stems of plants — anywhere the plant can capture sunlight. 3.1 What Is a Chloroplast Like Inside? Chloroplasts are relatively large organelles with a detailed internal structure designed for photosynthesis. Inside each chloroplast is a watery, protein - rich fluid called the stroma . The stroma is where some photosynthetic reactions take place and where important enzymes are found. 3.2 Grana and Thylakoids: The Energy Centers Floating in the stroma are many small membrane structures that look like stacks of coins . • Each stack is called a granum • The plural form is grana • Each “coin” in the stack is a thylakoid The thylakoid membranes are especially important. Many of the key reactions of photosynthesis occur right in these membranes, where light energy is captured and converted into chemical energy. 3.3 A Helpful Comparison Thylakoids in chloroplasts are similar in function to the cristae found in mitochondria. In both organelles, folded membranes increase surface area and make energy - related reactions more efficient. 4. Quiz Chloroplast 1. Question Fill in the blank: Which of the following statements about the chloroplast is FALSE ?

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