Photosynthesis Questions and Revision | MME - Free Printable

The image you provided illustrates the process of photosynthesis in plants. Photosynthesis is a fundamental biological process by which plants, algae, and some bacteria convert light energy (from the sun) into chemical energy stored in glucose, while releasing oxygen as a byproduct. Let's break down the process step by step:

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Key Components Shown in the Image:

1. Sunlight (Light Energy): The yellow arrow from the sun represents the light energy absorbed by the plant.
2. Carbon Dioxide (CO₂): The orange arrows entering the leaves represent carbon dioxide, which is taken in from the atmosphere.
3. Water (H₂O): The blue arrows entering the roots represent water absorbed from the soil.
4. Oxygen (O₂): The purple arrows exiting the leaves represent oxygen released into the atmosphere as a byproduct.
5. Glucose (C₆H₁₂O₆): Although not explicitly shown in the diagram, glucose is produced during photosynthesis and serves as an energy source for the plant.

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Explanation of the Process:

#### 1. Absorption of Light Energy:
- The plant absorbs light energy from the sun using a green pigment called chlorophyll, which is primarily located in the chloroplasts of leaf cells.
- This light energy is captured by the chlorophyll molecules and converted into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).

#### 2. Carbon Dioxide Uptake:
- Carbon dioxide (CO₂) enters the plant through small pores on the leaves called stomata.
- CO₂ is essential for the synthesis of glucose during the process of photosynthesis.

#### 3. Water Uptake:
- Water (H₂O) is absorbed by the plant's roots from the soil and transported to the leaves via the xylem.
- Water plays a crucial role in both the light-dependent reactions and the Calvin cycle (light-independent reactions) of photosynthesis.

#### 4. Photosynthesis Reactions:
Photosynthesis occurs in two main stages:
- Light-Dependent Reactions: These occur in the thylakoid membranes of the chloroplasts. Light energy is used to split water molecules (photolysis), producing oxygen (O₂), protons, and electrons. Oxygen is released as a byproduct, while the electrons and protons are used to generate ATP and NADPH.
- Calvin Cycle (Light-Independent Reactions): These occur in the stroma of the chloroplasts. Using the ATP and NADPH generated in the light-dependent reactions, carbon dioxide (CO₂) is fixed into organic molecules like glucose (C₆H₁₂O₆). This process is also known as the "dark reaction" because it does not directly require light, but it depends on the products of the light-dependent reactions.

#### 5. Release of Oxygen:
- During the light-dependent reactions, water molecules are split, and oxygen (O₂) is released as a byproduct. This oxygen exits the plant through the stomata and is essential for supporting life on Earth.

#### 6. Production of Glucose:
- The ultimate product of photosynthesis is glucose (C₆H₁₂O₆), which serves as an energy source for the plant. Excess glucose can be stored as starch or used for growth and other metabolic processes.

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Chemical Equation for Photosynthesis:

The overall process of photosynthesis can be summarized by the following equation:
\[
6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{Light Energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2
\]
- Reactants: Carbon dioxide (CO₂), water (H₂O), and light energy.
- Products: Glucose (C₆H₁₂O₆) and oxygen (O₂).

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Significance of Photosynthesis:

1. Energy Source: Photosynthesis provides the primary energy source for nearly all life on Earth, either directly (for plants) or indirectly (for animals that consume plants).
2. Oxygen Production: It is responsible for maintaining the oxygen levels in the atmosphere, which are essential for aerobic respiration in animals and humans.
3. Carbon Dioxide Reduction: Photosynthesis helps regulate the levels of carbon dioxide in the atmosphere, playing a critical role in mitigating climate change.

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Final Answer:

The image depicts the process of photosynthesis, where plants use sunlight, water, and carbon dioxide to produce glucose and release oxygen. The key steps involve the absorption of light energy, uptake of CO₂ and H₂O, conversion of these materials into glucose and O₂, and the release of oxygen into the atmosphere. The overall equation for photosynthesis is:
\[
\boxed{6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{Light Energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2}
\]