Photosynthesis and Cellular Respiration

Photosynthesis and Cellular Respiration

Middle School

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Learning Objectives

• Explain how photosynthesis helps matter cycle and energy flow in organisms.

• Model how chemical reactions rearrange food to form new molecules for growth.

• Trace the path of energy from the sun to food to the creation of ATP.

• Relate photosynthesis and cellular respiration to the global carbon cycle.

Key Vocabulary

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Photosynthesis

The process plants use to convert light, water, and CO₂ into their own food.

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Cellular Respiration

The process of breaking down glucose to produce usable energy for a cell's activities.

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ATP

The main energy-carrying molecule used to power all chemical activities and functions within a cell.

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Conservation of Matter

This scientific law states that atoms are not created or destroyed during any chemical reaction.

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Cycling of Matter

The continuous movement of essential elements through an ecosystem's living and nonliving parts.

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How Organisms Get Energy

Producers

• Producers are living things, like plants, that are able to make their own food.

• They create their food through a special process which is known as photosynthesis.

• This incredible process uses the energy that comes directly from the bright sunlight.

Consumers

• Consumers are organisms that cannot make their own food, so they eat other organisms.

• They get the energy they need to live and grow by eating other living things.

• For example, a rabbit gets its energy by eating plants like grass and carrots.

Multiple Choice

What is the main difference in how producers and consumers obtain energy?

• Producers make their own food, while consumers get energy by eating other organisms.

• Producers get energy by eating other organisms, while consumers make their own food.

• Producers get energy from water, while consumers get energy from sunlight.

• Producers require energy to live, while consumers do not.

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Photosynthesis and Cellular Respiration

Photosynthesis

• This process uses light energy, carbon dioxide (6CO₂), and water (6H₂O) as its inputs.

• It produces glucose (C₆H₁₂O₆) to store energy and releases oxygen (6O₂) as a byproduct.

• This is the essential process through which plants make their own food by converting light into chemical energy.

Cellular Respiration

• This process uses glucose (C₆H₁₂O₆) and oxygen (6O₂) to release stored chemical energy.

• It produces carbon dioxide (6CO₂), water (6H₂O), and energy for the cell called ATP.

• The inputs for respiration are the outputs of photosynthesis, creating a continuous cycle in ecosystems.

Multiple Choice

What is the relationship between the substances involved in photosynthesis and cellular respiration?

• The products of photosynthesis are the reactants for cellular respiration.

• The reactants of photosynthesis are the same as the reactants for cellular respiration.

• Both processes produce glucose for the organism.

• Both processes require an input of light energy to begin.

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The Role of Photosynthesis in Ecosystems

• Photosynthesis is the foundation for energy and matter in most ecosystems.

• It captures sunlight and converts it into chemical energy stored in glucose.

• This provides the primary source of energy for the entire food web.

• It turns simple CO₂ and H₂O into complex organic food molecules.

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Multiple Choice

How does photosynthesis transfer matter from the non-living world into the food web?

• By converting carbon dioxide and water into food molecules.

• By releasing energy from the non-living world.

• By taking in food molecules from the soil.

• By turning chemical energy back into light energy.

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How Food Provides Energy and Matter

Energy for Life

• Food gives organisms energy through a process called cellular respiration.

• Large food molecules are broken down into smaller molecules like glucose.

• In mitochondria, glucose reacts with oxygen to release energy as ATP.

Matter for Growth

• Food provides the matter that your body needs to grow and repair itself.

• This demonstrates the law of conservation of matter, as atoms are rearranged.

• Atoms from food are reassembled to form your skin, muscles, and bones.

Multiple Choice

Which statement best describes how the body uses matter from food for growth, according to the principle of conservation of matter?

• Atoms from food are rearranged to form new molecules and tissues.

• The body creates entirely new atoms to build skin and muscles.

• Food molecules are stored until they are needed for energy, then disappear.

• The body converts food directly into skin and muscle without changing it.

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Common Misconceptions

Misconception	Correction
Plants only do photosynthesis, not respiration.	Plants use photosynthesis for food and respiration for energy.
Cellular respiration is the same as breathing.	Breathing is gas exchange. Respiration is a chemical process inside cells.
Food is 'burned' and disappears in our bodies.	Food atoms are rearranged into new molecules like CO2 and water.
Plants create energy from sunlight.	Plants convert light energy into stored chemical energy in food.

Multiple Choice

Why are photosynthesis and cellular respiration often described as a cycle?

• Because the products of one process are the reactants of the other.

• Because they both occur in the same part of the cell.

• Because they both produce the same amount of energy.

• Because they both require sunlight to function properly.

Multiple Choice

If all plant life on Earth suddenly stopped performing photosynthesis, what would be the most immediate effect on the atmosphere?

• The amount of oxygen would decrease, and carbon dioxide would increase.

• The amount of carbon dioxide would decrease, and oxygen would increase.

• The atmosphere would fill with excess glucose.

• There would be no significant change to the atmosphere.

Multiple Choice

A person eats an apple. How does the law of conservation of matter apply to the atoms in that apple?

• The atoms are rearranged to provide energy (ATP) and build the person's body tissues.

• The atoms are converted directly into pure energy and disappear.

• The atoms are destroyed during the process of digestion.

• The atoms pass through the body unchanged.

Multiple Choice

Predict what would happen to an animal cell that has access to glucose but is deprived of oxygen.

• It would not be able to perform cellular respiration to produce a significant amount of ATP.

• It would start performing photosynthesis to create its own oxygen.

• It would produce an excess of ATP, causing the cell to stop working.

• It would break down ATP to create glucose and oxygen.

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Summary

• Photosynthesis uses light, CO₂, and water to make glucose and oxygen.

• Cellular respiration breaks down glucose to release energy, CO₂, and water.

• The products of one process are the reactants of the other.

• Energy flows through ecosystems, while matter is recycled and conserved.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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