Cellular Respiration

Cellular Respiration

Middle School

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Learning Objectives

• Define cellular respiration and identify its reactants and products.

• Model how food molecules rearrange to release energy for cell growth and repair.

• Explain that matter is conserved as atoms form new molecules in reactions.

• Describe the relationship between cellular respiration and photosynthesis.

Key Vocabulary

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Cellular Respiration

The process of breaking down glucose and oxygen to release energy for the cell's activities.

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Atom

An atom is the smallest unit of matter and the basic building block of all molecules.

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Molecule

A molecule is a group of two or more atoms that are bonded together, like water.

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Chemical Reaction

A process that involves the rearrangement of atoms in molecules to form entirely new substances.

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Mitochondrion

The mitochondrion is the organelle where the second stage of cellular respiration takes place.

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Glucose

A simple sugar molecule that serves as the main and most important source of energy for cells.

Key Vocabulary

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Fermentation

The process of releasing energy from food sources without the need for oxygen.

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Alcoholic Fermentation

This type of fermentation produces alcohol, carbon dioxide (CO₂), and a small amount of energy.

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Lactic Acid Fermentation

This fermentation process occurs in your muscle cells and produces a substance called lactic acid.

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What Is Cellular Respiration?

Breathing

• Breathing is the physical process of moving air into and out of your lungs.

• This important action brings the oxygen your body needs for cellular respiration into the body.

• It also helps to remove waste products like carbon dioxide from your body.

Cellular Respiration

• This is a chemical reaction that happens inside the cells of all living things.

• It uses oxygen to break down food molecules, like glucose, to release energy.

• This released energy powers all of the activities that keep you alive and active.

Multiple Choice

What is the main purpose of cellular respiration?

• To release energy from food molecules for the body to use.

• To move air into and out of the lungs.

• To bring oxygen into the body from the environment.

• To remove carbon dioxide from the body.

Multiple Choice

What is the relationship between breathing and cellular respiration?

• Breathing is a physical process, while cellular respiration is a chemical reaction.

• Breathing supplies the oxygen that cellular respiration uses to release energy.

• Cellular respiration creates the oxygen that breathing removes from the body.

• Breathing and cellular respiration are two names for the same process.

Multiple Choice

If a person's cells were unable to take in oxygen, what would be the most direct result?

• The process of breathing would stop immediately.

• Food molecules like glucose could not be broken down to release energy.

• Waste products like carbon dioxide could not be removed from the body.

• The lungs would not be able to move air in and out.

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The Two Stages of Cellular Respiration

Stage 1

• ​This stage takes place in the fluid-filled cytoplasm of the cell.

• ​​Glucose is broken down into smaller molecules without the need for oxygen.

• ​This initial breakdown process releases only a small amount of energy.

Stage 2

• ​This stage occurs inside the mitochondria, known as the cell's powerhouses.

• ​​Oxygen is used to break down the smaller molecules to release energy.

• ​A large amount of energy is released during this final stage.

Multiple Choice

What is the main purpose of the two stages of cellular respiration described?

• To create oxygen for the cell to breathe

• To build larger molecules like proteins

• To break down glucose to release energy for the cell

• To store water inside the cell's cytoplasm

Multiple Choice

What is a key difference between the two stages of cellular respiration?

• Stage 1 requires oxygen, while Stage 2 does not.

• Stage 1 occurs in the cytoplasm, while Stage 2 occurs in the mitochondria.

• Stage 1 releases a large amount of energy, while Stage 2 releases a small amount.

• Stage 1 builds large molecules, while Stage 2 breaks them down.

Multiple Choice

If a cell were unable to take in oxygen, what would be the most likely outcome for energy production?

• The cell would produce a very large amount of energy because Stage 1 would work harder.

• The cell would not be able to break down glucose at all.

• The cell would produce only a small amount of energy because only Stage 1 could be completed.

• The cell would move the function of the mitochondria to the cytoplasm.

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Matter and Energy Transformation

• Matter is conserved in reactions: atoms are not created or destroyed, just rearranged.

• Atoms from glucose and oxygen rearrange to form carbon dioxide and water, releasing energy.

• This released chemical energy is used by the cell to power its functions.

• The rearranged atoms also provide the raw materials for growth and tissue repair.

Multiple Choice

What is the main purpose of rearranging atoms from food molecules during cellular respiration?

• To create new atoms for the body to use

• To destroy food molecules completely

• To release chemical energy stored in food molecules

• To store energy from the sun in food molecules

Multiple Choice

What is the relationship between the atoms in food and the energy released for a cell's functions?

• The atoms from food are converted directly into energy.

• Energy is used to break down food into individual atoms.

• The rearrangement of atoms into simpler molecules releases the stored energy.

• Atoms are destroyed, which causes a release of energy.

Multiple Choice

After a person eats a hamburger, which statement best explains how their cells can use the food to build new muscle?

• The hamburger is converted entirely into energy, which then builds muscle.

• The atoms from the hamburger are destroyed to release the energy needed for muscle growth.

• The atoms from the hamburger can provide both the energy and the raw materials for muscle growth.

• The hamburger provides raw materials, but energy for growth must come from another source.

Opposite Processes: Photosynthesis and Respiration

• Photosynthesis and cellular respiration are opposite reactions, forming a continuous cycle.

• Plants make food using sunlight; animals eat plants for energy and matter.

• This cycle helps keep oxygen and carbon dioxide levels stable in the atmosphere.

Multiple Choice

What is the primary relationship between photosynthesis and cellular respiration?

• They are opposite reactions that form a continuous cycle.

• They are the exact same process in nature.

• They are completely unrelated to each other.

• They only occur in animals and not in plants.

Multiple Choice

How do the roles of plants and animals differ in the cycle of photosynthesis and respiration?

• Plants make their own food, while animals consume other organisms to get energy.

• Animals make their own food, while plants consume other organisms to get energy.

• Both plants and animals make their own food using sunlight.

• Both plants and animals get all their energy and matter by eating other organisms.

Multiple Choice

Based on the relationship between photosynthesis and respiration, what is the most significant impact of this cycle on the Earth's atmosphere?

• The cycle helps regulate the amount of oxygen and carbon dioxide in the air.

• The cycle is the main source of water for all living things.

• The cycle is responsible for creating sunlight for plants.

• The cycle causes the temperature of the atmosphere to increase.

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Fermentation: Energy Without Oxygen

Alcoholic Fermentation

• This process occurs in yeast and other single-celled organisms, breaking down food for energy.

• It produces alcohol and carbon dioxide (CO₂) as byproducts.

• The carbon dioxide released is what causes bread dough to rise.

Lactic Acid Fermentation

• This type of fermentation happens in your muscle cells during intense exercise.

• It occurs when your muscles use oxygen faster than it can be supplied.

• Glucose is broken down to supply energy, producing a compound called lactic acid.

Multiple Choice

What is the main purpose of both alcoholic and lactic acid fermentation?

• To produce energy without using oxygen

• To create carbon dioxide for breathing

• To build muscle tissue during rest

• To cool down an organism's body

Multiple Choice

How does alcoholic fermentation in yeast differ from lactic acid fermentation in muscles?

• It produces different byproducts (alcohol and CO₂ vs. lactic acid)

• It uses oxygen while lactic acid fermentation does not

• It happens in animals while lactic acid fermentation happens in plants

• It breaks down protein while lactic acid fermentation breaks down fat

Multiple Choice

A baker is making bread, but the dough is not rising. Based on the process of fermentation, what is the most likely cause?

• The yeast is not producing carbon dioxide through fermentation.

• The dough has too much lactic acid in it.

• The dough does not have enough oxygen.

• The yeast is producing alcohol instead of carbon dioxide.

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Common Misconceptions

Misconception	Correction
Food is 'burned' and disappears.	Food atoms are rearranged into new molecules (CO
Plants only photosynthesize.	Plants also perform cellular respiration to break down glucose for energy.
Cellular respiration is the same as breathing.	Breathing gets oxygen into the body; cellular respiration uses it in cells.

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Summary

• Cellular respiration is a chemical reaction that releases energy from food by rearranging atoms.

• The equation is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.

• Photosynthesis and cellular respiration are opposite processes that cycle matter and energy.

• Fermentation is a process that releases a small amount of energy from food without oxygen.

Poll

On a scale of 1-4, how confident are you about how food is rearranged to provide both energy and materials for growth?

• 1

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• 3

• 4