Cells and Cell Organelles

Cells and Cell Organelles

Middle School

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Learning Objectives

• Define a cell and differentiate between prokaryotic and eukaryotic cells.

• Identify major organelles in a eukaryotic cell and describe their specific functions.

• Compare and contrast the structures of animal cells and plant cells.

• Explain the roles of the nucleus, mitochondria, and ribosomes in cell function.

• Describe how the endoplasmic reticulum and Golgi apparatus work together to transport materials.

Key Vocabulary

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Cell

The cell is the smallest unit of life and the basic building block of all organisms.

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Organelle

An organelle is a tiny structure inside a cell that has a specific job to do.

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Nucleus

The nucleus is the cell's control center, containing the DNA that manages all cell activities.

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Mitochondria

Known as the cell's powerhouse, mitochondria create energy to power all of the cell's functions.

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Eukaryotic Cell

A eukaryotic cell is a complex cell that has a nucleus and other membrane-bound organelles.

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Prokaryotic vs Eukaryotic Cell

Prokaryotic Cells

• These are simple cells that do not have a nucleus.

• They also lack other complex parts called membrane-bound organelles.

• Bacteria are common examples of organisms with prokaryotic cells.

Eukaryotic Cells

• These are complex cells that have a membrane-enclosed nucleus.

• They contain many different organelles that perform specific jobs.

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

Multiple Choice

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

• The presence of a cell membrane

• The presence of cytoplasm

• The presence of a membrane-enclosed nucleus

• The presence of ribosomes

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The Nucleus: The Cell's Control Center

• The nucleus is the cell's control center, containing the DNA in chromosomes.

• It is enclosed by a double membrane with pores to control movement.

• Inside is a thick liquid called nucleoplasm and a structure called the nucleolus.

• The nucleolus is responsible for assembling ribosomes to be sent to the cytoplasm.

Multiple Choice

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

• To regulate what enters and leaves the nucleus

• To store the cell's DNA

• To produce energy for the cell

• To assemble ribosomes for protein synthesis

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Energy Production and Protein Synthesis

Mitochondria

• Often called the 'powerhouse of the cell,' they are responsible for producing the cell's energy.

• They convert energy from food into a usable form called ATP through a process called cellular respiration.

• These organelles have a unique double membrane and contain their own special DNA.

Ribosomes

• These small structures are the cell's factories for building the proteins it needs to function.

• Ribosomes read genetic instructions to link amino acids together, forming long protein chains.

• They are found in all types of cells, either free or attached to the endoplasmic reticulum.

Multiple Choice

According to the slide, why is the mitochondrion called the 'powerhouse of the cell'?

• It converts organic compounds into ATP energy.

• It contains its own DNA.

• It synthesizes proteins for the cell.

• It supports the endosymbiotic theory.

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The Cellular Transport System

Endoplasmic Reticulum

• The ER is the cell's highway, helping to make and transport proteins and lipids.

• Rough ER is studded with ribosomes, which are small factories for making proteins.

• Smooth ER does not have ribosomes; it is used to make lipids and store substances.

Golgi Apparatus

• This organelle acts like a post office, receiving proteins and lipids from the ER.

• It then modifies, sorts, and packages these materials for delivery to other locations.

• Materials are transported to and from the Golgi in small sacs called vesicles.

Multiple Choice

Which organelle acts like a 'post office' by modifying, sorting, and packaging proteins for delivery?

• Rough ER

• Golgi apparatus

• Mitochondrion

• Ribosome

Storage, Cleanup, and Division

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Vesicles and Vacuoles

• ​These sac-like organelles are used for storage and transport in the cell.

• ​​Vacuoles are larger sacs that mainly store water, food, and waste.

• ​Vesicles are smaller sacs that transport molecules like proteins around the cell.

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Lysosomes

• ​Known as the cell's "garbage disposal," they are special types of vesicles.

• ​​They have digestive enzymes to break down materials for recycling and disposal.

• ​Lysosomes break down old cell parts, bacteria, and other waste materials.

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Centrioles

• ​Found only in animal cells, they help with cell division processes.

• ​​Their main job is to help organize the chromosomes during cell division.

• ​This ensures each new cell gets the correct number of chromosomes.

Multiple Choice

Which organelle is known as the cell's 'garbage disposal' because it contains enzymes to break down waste and foreign matter?

• Vesicles

• Centrioles

• Lysosomes

• Vacuoles

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Structural Components: Boundaries

Cell Membrane

• A protective layer that surrounds every cell, acting as a boundary.

• It is semi-permeable, controlling what substances enter and exit the cell.

• It is made of a phospholipid bilayer with proteins embedded in it.

Cell Wall

• Found in plant and bacterial cells, but not in animal cells.

• A rigid barrier outside the cell membrane that provides a fixed shape.

• It provides the cell with extra support, strength, and protection.

Multiple Choice

What is a key difference between the cell wall and the cell membrane described on the slide?

• The cell wall is found in all cells, while the cell membrane is only in animal cells.

• The cell membrane is made of cellulose, while the cell wall is a phospholipid bilayer.

• The cell membrane provides rigid protection, while the cell wall is flexible.

• The cell wall is a rigid structure for support, while the cell membrane regulates passage of materials.

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Plant vs. Animal Cells

Plant Cells

• Plant cells have a strong, rigid cell wall that provides structural support and protection.

• They contain chloroplasts, which are the sites of photosynthesis for making food.

• A large central vacuole stores water and helps the cell maintain its shape and pressure.

Animal Cells

• Animal cells do not have a cell wall, giving them a more flexible cell shape.

• They have lysosomes, which are responsible for breaking down waste materials within the cell.

• Animal cells contain centrioles, which play an important role in the process of cell division.

Multiple Choice

Which of the following organelles would you expect to find in a plant cell but not an animal cell?

• Mitochondria and a nucleus

• Chloroplasts and a cell wall

• Ribosomes and a cell membrane

• Lysosomes and centrioles

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Common Misconceptions About Cells

Misconception	Correction
All cells have a nucleus.	Prokaryotic cells, like bacteria, do not have a nucleus.
Ribosomes are membrane-bound organelles.	Ribosomes are not enclosed within a membrane.
'Cytoplasm' and 'cytosol' are the same thing.	Cytosol is the jelly-like fluid part of the cytoplasm.
Mitochondria create new energy.	Mitochondria convert food into a usable energy form called ATP.

Multiple Choice

Why is the rough endoplasmic reticulum (RER) studded with ribosomes, and how does this structure relate to its function?

• The ribosomes synthesize proteins, which are then processed and transported by the RER.

• The studs help the RER connect to the Golgi apparatus for packaging.

• The ribosomes store energy that the RER uses for transport.

• The ribosomes are used to produce lipids for the cell membrane.

Multiple Choice

A certain toxin destroys ribosomes in a cell. What process would be immediately and most significantly affected?

• Energy conversion (ATP production)

• Waste breakdown

• Protein synthesis

• Cell division

Multiple Choice

A scientist observes a cell that is unable to properly modify, package, and export proteins. A malfunction in which two organelles is the most likely cause?

• Ribosome and Centriole

• Endoplasmic Reticulum and Golgi Apparatus

• Lysosome and Vacuole

• Nucleus and Mitochondria

Multiple Choice

The endosymbiotic theory suggests mitochondria were once free-living organisms. What piece of evidence strongly supports this theory?

• Mitochondria are present in all eukaryotic cells.

• Mitochondria have a folded inner membrane (cristae).

• Mitochondria are known as the 'powerhouse' of the cell.

• Mitochondria contain their own DNA, separate from the nucleus.

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Summary

• Cells are basic life units, either prokaryotic or eukaryotic.

• The nucleus is the cell's control center; ribosomes build proteins.

• Mitochondria create energy, while the ER and Golgi transport materials.

• Plant cells have a cell wall, chloroplasts, and a large central vacuole.

Poll

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

• 1

• 2

• 3

• 4