Cell Organelles

Cell Organelles

Middle School

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Learning Objectives

• Define an organelle and tell the difference between prokaryotic and eukaryotic cells.

• Describe the parts and jobs of the nucleus, mitochondria, and ribosomes.

• Explain how some organelles work together to move proteins in the cell.

• Compare and contrast the different organelles found in plant and animal cells.

Key Vocabulary

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Organelle

A structure in a eukaryotic cell that has a specific job to do for the cell.

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Nucleus

The cell's control center, containing DNA and regulating all of the cell's many activities.

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Mitochondrion

This is the cell’s powerhouse, making energy by converting nutrients into a more usable form.

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Ribosome

A small cellular structure that is responsible for making all of the proteins the cell needs.

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Eukaryotic Cell

A cell with a nucleus and other organelles, like those in plants and animals.

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Prokaryotic vs Eukaryotic Cells

Eukaryotic Cells

• These cells are complex and include all plant and animal cells.

• They have a nucleus, which holds the genetic material for the cell.

• They contain many specialized structures called membrane-bound organelles.

Prokaryotic Cells

• These are simpler cells, such as those found in bacteria and archaea.

• They do not have a nucleus to hold their genetic material.

• They also lack any other kind of membrane-bound organelles.

Multiple Choice

Which of the following would you expect to find inside a eukaryotic cell but NOT in a prokaryotic cell?

• A membrane-bound nucleus

• Cytoplasm

• Ribosomes

• DNA

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The Nucleus: The Control Center

• The nucleus is the cell's control center, directing all its activities.

• It contains the DNA, which holds instructions for making proteins.

• A nuclear envelope with pores surrounds and protects the nucleus.

• Inside, the nucleolus assembles ribosomes to be sent to the cytoplasm.

Multiple Choice

What is the primary role of the nucleolus, which is located inside the nucleus?

• To control what enters and exits the nucleus

• To assemble ribosomes

• To store the cell's DNA

• To produce energy for the cell

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Energy and Protein Production

Mitochondria

• Mitochondria act as the cell's power plants, breaking down sugars to create usable energy for the cell.

• This process, called cellular respiration, produces a high-energy molecule known as ATP to fuel cell activities.

• They have their own DNA, suggesting they were once separate organisms that formed a partnership with cells.

Ribosomes

• Ribosomes are tiny structures inside cells that are responsible for building all of the cell's proteins.

• They read instructions from RNA to assemble proteins from smaller building blocks called amino acids.

• Ribosomes are found floating in the cytoplasm or attached to the endoplasmic reticulum.

Multiple Choice

Why are mitochondria referred to as the 'power plants' of the cell?

• Because they contain their own DNA, just like a power plant has its own blueprints.

• Because they build proteins for the cell.

• Because they perform cellular respiration to produce energy-rich ATP molecules.

• Because they were once free-living organisms.

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Protein and Lipid Processing

Endoplasmic Reticulum

• The Endoplasmic Reticulum (ER) is a network that helps make and move proteins and lipids.

• Rough ER has ribosomes that build proteins, which are then transported away in small sacs called vesicles.

• Smooth ER does not have ribosomes; it focuses on creating lipids and storing other important substances.

Golgi Apparatus

• The Golgi apparatus acts like a cell's post office, receiving proteins and lipids from the ER.

• It modifies, sorts, and packages these proteins and lipids for their specific jobs within the cell.

• Finally, it labels them for delivery to other parts of the cell or for export outside.

Multiple Choice

A protein has just been made on the Rough ER. What is the most likely pathway it will take next?

• It will go to the Smooth ER to be modified.

• It will go to the Golgi apparatus for packaging.

• It will travel to the nucleus for storage.

• It will be sent directly out of the cell.

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Storage and Cleanup Crew

Vacuoles

• These sac-like organelles store water, food, and waste materials for the cell.

• Plant cells have one large vacuole that helps them maintain their rigid shape.

• Animal cells can have several smaller vacuoles for storing and transporting substances.

Vesicles

• Vesicles are small sacs that transport proteins and other materials within the cell.

• Lysosomes are special vesicles that break down waste and foreign matter.

• Peroxisomes are vesicles that use oxygen to break down and neutralize poisons.

Multiple Choice

What is the main difference in the function of a lysosome compared to a vacuole?

• Lysosomes are large in plant cells, while vacuoles are small in animal cells.

• Lysosomes store water, while vacuoles break down poisons.

• Lysosomes break down materials with enzymes, while vacuoles primarily store materials.

• Lysosomes transport proteins, while vacuoles are only for waste.

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Specialized Structures: Plant vs. Animal Cells

Plant Cells

• ​Only plant cells have a cell wall, a tough outer layer for support and protection.

• ​​They contain chloroplasts, which capture sunlight to produce food for the plant.

• ​Chloroplasts are green because they contain a pigment called chlorophyll.

Animal Cells

• ​Centrioles are special structures found only in animal cells, located near the nucleus.

• ​​They play a very important role in helping the cell divide to make new cells.

• ​Centrioles make sure that chromosomes are organized correctly during cell division.

Multiple Choice

A scientist discovers a new cell that has a cell wall and chloroplasts. What can she conclude about this cell?

• It is an animal cell.

• It cannot be a eukaryotic cell.

• It is a plant cell.

• It must have centrioles.

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The Cellular Environment

Cell Membrane

• The cell membrane is a protective barrier that encloses the entire cell.

• It controls what substances enter and exit the cell, giving it protection and some structure.

• This important organelle is found in both plant cells and in animal cells.

Cytoplasm

• The cytoplasm is the jelly-like fluid that fills the cell and surrounds the organelles.

• It contains all the water and nutrients that the cell's organelles are suspended in.

• Its main role is to hold these components and be a solution for cellular activities.

Multiple Choice

What is the primary function of the cell membrane?

• To control what enters and exits the cell.

• To create proteins.

• To produce energy for the cell.

• To hold all the organelles in place.

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Common Misconceptions About Cells

Misconception	Correction
Only animal cells have mitochondria.	Plant cells also have mitochondria to get energy from the food they make.
All cells have a nucleus.	Prokaryotic cells and mature red blood cells do not have a nucleus.
Vacuoles are only found in plant cells.	Animal cells have smaller and more numerous vacuoles than plant cells.

Multiple Choice

How do the structure and location of the cell membrane and cell wall differ, and how do these differences relate to their functions?

• The cell membrane is a rigid outer layer, while the cell wall is a flexible inner layer.

• The cell wall controls passage in all cells, while the cell membrane is only for support in plants.

• Both are identical in function, but the cell wall is only found in animal cells for extra protection.

• The flexible cell membrane in both cells controls passage, while the rigid outer cell wall in plants provides structural support.

Multiple Choice

Which statement about mitochondria is incorrect?

• They are the powerhouses of the cell, generating most of the cellular ATP.

• They are found in all eukaryotic cells.

• They are the sites of glycolysis which is a step of Photosynthesis.

• They increase the surface crea for process of protein synthesis in a cell.

Multiple Choice

A certain toxin destroys ribosomes. What would be the most immediate effect on a cell exposed to this toxin?

• The cell would be unable to produce energy (ATP).

• The cell would be unable to synthesize new proteins.

• The cell's genetic material would be destroyed.

• The cell would lose control over what enters and exits.

Multiple Choice

Based on the endosymbiotic theory, what evidence suggests mitochondria were once independent organisms, and how did this relationship benefit the larger host cell?

• Evidence: Mitochondria make proteins; Benefit: The host cell learned to make its own DNA.

• Evidence: All cells have mitochondria; Benefit: The mitochondria received a place to live.

• Evidence: Mitochondria can leave the cell; Benefit: The host cell was protected from the mitochondria.

• Evidence: Mitochondria have their own DNA; Benefit: The host cell gained extra energy from the mitochondria.

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Summary

• Organelles are structures in cells that perform specific jobs.

• The nucleus controls the cell, and mitochondria provide energy.

• The ER, Golgi apparatus, and vesicles transport materials.

• Plant cells have a cell wall and chloroplasts; animal cells have centrioles.

Poll

On a scale of 1-4, how confident are you about the functions of different cell organelles?

• 1

• 2

• 3

• 4