MS-LS1-2: Cell Structure and Function

MS-LS1-2
Cell Structure and Function

Middle School

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Learning Objectives

• Describe how a cell works together as a complete system.

• Identify the main jobs of the nucleus, chloroplasts, and mitochondria.

• Explain how the cell membrane and cell wall support and protect the cell.

• Use a model to show the main differences between plant and animal cells.

Key Vocabulary

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Cell Theory

The cell theory states that all living things are composed of one or more cells.

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Prokaryote

A prokaryote is a simple, single-celled organism that does not have a true nucleus.

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Eukaryote

A eukaryote is an organism whose cells contain a true nucleus and other membrane-bound organelles.

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Organelle

An organelle is a specialized structure within a cell that performs a specific, vital job.

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Nucleus

The nucleus is a large organelle that contains the cell's essential genetic material, or DNA.

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Mitochondrion

The mitochondrion is known as the powerhouse of the cell as it converts food to energy.

Key Vocabulary

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Cellular Respiration

The process inside cells that converts food, like sugar, into the energy needed to power life's activities.

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Cell Membrane

This is the thin, flexible outer layer that controls everything that enters and leaves the cell.

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Cell Wall

A tough, strong layer found outside the cell membrane that gives plant cells their shape and support.

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Chloroplast

This is the special organelle inside a plant cell where photosynthesis occurs to make the plant's food.

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Cytoplasm

A jelly-like fluid that fills up the entire cell and keeps all of the organelles in place.

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The Cell Theory

• This theory was developed by scientists Schleiden, Schwann, and Virchow.

• All living things are composed of one or more cells.

• Cells are the basic units of structure and function in organisms.

• New cells are produced from other existing living cells through division.

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Multiple Choice

Which statement best summarizes the central idea of the Cell Theory?

• Cells are the basic units of structure and function for all living things.

• All living things are developed by scientists Schleiden, Schwann, and Virchow.

• New cells are created from non-living materials in an organism.

• Organisms are the basic units of structure and function in cells.

Multiple Choice

According to the principles of the Cell Theory, what is the origin of new cells?

• From the organism's environment.

• From a combination of non-living matter.

• From other living cells that divide.

• From the work of Schleiden and Schwann.

Multiple Choice

A scientist discovers a new specimen. Which of the following observations would provide the best evidence for classifying the specimen as a living organism according to the Cell Theory?

• The object is moving and appears to consume nutrients from its surroundings.

• The object is composed of at least one cell and is capable of cell division.

• The object has a complex structure and was discovered by a famous scientist.

• The object is very small and can only be seen with a powerful microscope.

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Types of Cells: Prokaryotes vs. Eukaryotes

Prokaryotes

• Prokaryotic cells are the simplest type of cells and do not have a nucleus.

• Their genetic material (DNA) floats freely in the watery cytoplasm of the cell.

• Organisms like Bacteria and Archaea are examples of prokaryotes.

Eukaryotes

• Eukaryotic cells are more complex and have a true nucleus that holds the DNA.

• Their cytoplasm contains many specialized structures called organelles that perform specific jobs.

• Plants, animals, fungi, and protists are all made of eukaryotic cells.

Multiple Choice

What is the main feature that distinguishes a eukaryotic cell from a prokaryotic cell?

• A eukaryotic cell has a nucleus, while a prokaryotic cell does not.

• A prokaryotic cell is more complex than a eukaryotic cell.

• A eukaryotic cell has DNA that floats in the cytoplasm, while a prokaryotic cell does not.

• A prokaryotic cell is found in plants, while a eukaryotic cell is found in bacteria.

Multiple Choice

How is the genetic material (DNA) organized differently in prokaryotic and eukaryotic cells?

• In a eukaryotic cell, the DNA is held in a nucleus, while in a prokaryotic cell, it floats freely.

• Prokaryotic cells use organelles to store their DNA, while eukaryotic cells do not.

• Eukaryotic cells do not have DNA, but prokaryotic cells do.

• The DNA in both cell types is located within the cytoplasm, but only eukaryotes have a cell wall.

Multiple Choice

A scientist observes a cell and notes that its genetic material is floating freely in the cytoplasm instead of being enclosed in a nucleus. What conclusion can be drawn about this cell?

• It is a prokaryote, because it lacks a nucleus and specialized organelles.

• It is a eukaryote, because it is a single-celled organism like a protist.

• It is a plant cell, because it has cytoplasm.

• It is an animal cell, because all animals are complex organisms.

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The Cell as a System

• A cell is like a tiny factory with many parts working together.

• Each part, an organelle, has a specific job to keep the cell alive.

• For the cell to function, all its organelles must work together correctly.

• The nucleus provides instructions and mitochondria produce the energy.

Multiple Choice

What is the best way to describe a cell based on how its parts work?

• A system where different parts work together

• A single part that does one job

• A collection of unrelated parts

• A storage container for energy

Multiple Choice

What is the relationship between the nucleus and the mitochondria within the cell system?

• The nucleus provides instructions, while the mitochondria produce energy.

• The nucleus produces energy, while the mitochondria provide instructions.

• Both organelles are responsible for storing water.

• The nucleus and mitochondria work against each other.

Multiple Choice

What would most likely happen to a cell if its mitochondria stopped producing energy?

• The cell would not be able to carry out its functions.

• The cell would receive too many instructions from the nucleus.

• The cell would create new organelles to replace the mitochondria.

• The cell would continue to function normally without energy.

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Energy for the Cell: Mitochondria & Chloroplasts

Mitochondria

• These are called the 'powerhouses' of the cell because they release energy from food.

• They are found in both animal cells and plant cells to provide them with energy.

• This process of releasing energy from food is called cellular respiration.

Chloroplasts

• These organelles are found only in plant cells and are where photosynthesis happens.

• They capture energy from sunlight to make food in the form of sugar (glucose).

• This food can then be used by the mitochondria to produce energy for the cell.

Multiple Choice

What is the main function of the mitochondria in both plant and animal cells?

• To release energy from food for the cell to use.

• To capture energy from sunlight to make food.

• To store food and water inside the cell.

• To control all of the cell's activities.

Multiple Choice

What is the relationship between chloroplasts and mitochondria inside a plant cell?

• Chloroplasts produce food using sunlight, and mitochondria release energy from that food.

• Mitochondria create food from sunlight, and chloroplasts release energy from it.

• Both organelles are found in animal cells to help them move.

• Both organelles work independently and do not affect each other.

Multiple Choice

If a healthy plant cell were moved from a sunny environment to a completely dark one, what would be the most likely impact on its energy processes?

• The chloroplasts would fail to make food, leaving the mitochondria with nothing to convert into energy.

• The mitochondria would start capturing sunlight to produce their own energy.

• The cell would not be affected because mitochondria are found in both plant and animal cells.

• The chloroplasts would start releasing energy directly without needing the mitochondria.

Structure and Control: Nucleus, Membrane, & Wall

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Nucleus

• ​The nucleus is the control center of the cell.

• ​​It contains the cell's genetic material, also known as DNA.

• ​DNA holds instructions for all of the cell's essential functions.

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Cell Membrane

• ​This flexible barrier is found surrounding every type of cell.

• ​​It carefully controls what substances can enter and leave the cell.

• ​This helps maintain a stable and healthy internal cell environment.

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Cell Wall

• ​This is a rigid outer layer found in plant cells.

• ​​It provides the plant cell with structural support and protection.

• ​Animal cells do not have this rigid outer cell wall.

Multiple Choice

Which part of the cell acts as the control center by holding the instructions for all cell functions?

• Nucleus

• Cell membrane

• Cell wall

• Genetic material

Multiple Choice

How does the function of a cell wall differ from the function of a cell membrane?

• It provides the cell with rigid structural support.

• It carefully controls what enters and leaves the cell.

• It is a flexible barrier found in all types of cells.

• It holds the instructions for all the cell's functions.

Multiple Choice

A plant cell is observed to have lost its rigid shape, but it can still regulate which substances enter and leave. Which part has most likely failed, and why?

• The cell wall, because it is responsible for providing rigid support.

• The cell membrane, because it failed to maintain a stable environment.

• The nucleus, because it no longer contained the cell's DNA.

• The cell membrane, because animal cells do not have a cell wall.

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Common Misconceptions

Misconception	Correction
Organelles work independently.	A cell is a complex system where all organelles work together.
Only plant cells have a cell membrane.	All cells have a cell membrane, but some also have a cell wall.
Bacteria are not alive because they lack a nucleus.	Bacteria are living organisms that show all the characteristics of life.

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Summary

• A cell is a system with its organelles working together.

• The cell membrane controls passage, while the cell wall adds structure.

• The nucleus acts as the control center, holding the cell’s DNA.

• Mitochondria release energy for the cell through cellular respiration.

• Chloroplasts use sunlight to make food during photosynthesis.

• Prokaryotes are simple cells, while eukaryotes are more complex.

Poll

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

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• 3

• 4