Anatomy of a Cell

Anatomy of a Cell

Middle School

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Learning Objectives

• Describe the key differences between prokaryotic and eukaryotic cells.

• Identify the major organelles in plant and animal cells and explain their functions.

• Explain the role of the cell membrane in both active and passive transport.

• Compare the basic structures of different lipids, including fatty acids and steroids.

• Understand the Endosymbiosis Theory as a proposed origin for eukaryotic cells.

Key Vocabulary

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Prokaryotic Cell

A simple type of cell that does not have a nucleus or other membrane-bound organelles.

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Eukaryotic Cell

A complex cell type that contains a nucleus and other specialized membrane-bound organelles within it.

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Organelle

A specialized subunit found within a cell that is responsible for a very specific function.

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Cytoplasm

The jellylike substance that fills the entire cell and carefully surrounds all of the organelles.

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Mitochondria

These organelles transform food energy into a usable form of energy for the cell called ATP.

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Active Transport

The movement of molecules from a low to high concentration, a process that requires energy.

Key Vocabulary

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Passive Transport

The movement of molecules across the cell membrane that doesn't require energy.

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Endosymbiosis

The evolutionary theory of how eukaryotic cells evolved from prokaryotic cells.

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Fatty Acids

Fatty acids are the building blocks of fat in living things and are a type of carboxylic acid with a long hydrocarbon chain.

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Homeostasis

The process of maintaining a stable internal environment within an organism.

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The Two Main Types of Cells

Prokaryotic Cells

• ​Prokaryotic cells are very simple and do not have a nucleus to hold their genetic material.

• ​​These cells also lack other small, membrane-bound structures called organelles, which perform specific jobs.

• ​You can find prokaryotic cells in unicellular organisms such as bacteria, which are all around us.

Eukaryotic Cells

• ​Eukaryotic cells are more complex and contain a true nucleus that protects their genetic information.

• ​​They have many specialized, membrane-bound organelles that each have a unique function within the cell.

• ​These cells make up more complex organisms like plants, animals, fungi, and even protists.

Multiple Choice

What is the primary characteristic that distinguishes a eukaryotic cell from a prokaryotic cell?

• The presence of a nucleus

• The type of genetic material it holds

• The existence of a cell membrane

• The ability to move independently

Multiple Choice

How do the internal structures of prokaryotic and eukaryotic cells relate to their overall complexity?

• Eukaryotic cells are more complex because they have many specialized organelles, while prokaryotic cells are simpler and lack them.

• Prokaryotic cells are more complex because they must perform all functions without a nucleus.

• Both cell types have the same complexity, but use different structures.

• Eukaryotic cells are simpler because their organelles are contained by membranes.

Multiple Choice

A scientist observes a cell from a newly discovered fungus. Based on the information provided, what would the scientist most likely find inside this cell?

• A nucleus and other membrane-bound organelles

• Genetic material floating freely in the cell

• A simple structure similar to a bacterium

• No specialized structures for specific jobs

Prokaryotic Cell Structures

• The nucleoid contains the cell's main circular DNA.

• A cell wall, capsule, and plasma membrane protect the cell.

• Flagella aid in movement, while pili are used for attachment.

Multiple Choice

What is the primary function of the nucleoid in a prokaryotic cell?

• To contain the cell's main circular DNA.

• To help the cell move through its environment.

• To protect the cell from external threats.

• To allow the cell to attach to surfaces.

Multiple Choice

What is the relationship between the function of a prokaryotic cell's wall and its flagella?

• The cell wall provides protection, while flagella enable movement.

• The cell wall stores genetic material, while flagella help with attachment.

• The cell wall allows for attachment, while flagella provide energy.

• The cell wall enables movement, while flagella offer protection.

Multiple Choice

If a prokaryotic cell was missing its pili, what would be the most likely direct consequence?

• The cell would be unable to attach to surfaces.

• The cell's DNA would not be protected.

• The cell would not be able to move.

• The cell would lose its main protective layer.

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Core Organelles in Eukaryotic Cells

• The nucleus is the control center, and ribosomes build essential proteins.

• Mitochondria are powerhouses that create energy in the form of ATP.

• The ER and Golgi apparatus transport, package, and distribute proteins and lipids.

• Lysosomes act as the recycling center, breaking down food and waste.

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Multiple Choice

What is the primary role of the nucleus within a eukaryotic cell?

• To act as the cell's control center

• To create energy for the cell

• To transport proteins and lipids

• To break down food and waste

Multiple Choice

How do ribosomes, the ER, and the Golgi apparatus work together?

• Ribosomes build proteins, which are then transported by the ER and Golgi apparatus.

• The nucleus creates energy, which is used by the mitochondria to build proteins.

• Lysosomes package proteins, which are then distributed by the ribosomes.

• Mitochondria build proteins, which are then broken down by the ER and Golgi apparatus.

Multiple Choice

A cell is observed to have a harmful buildup of old, non-functional parts and undigested food. Which organelle is most likely malfunctioning, and why?

• The lysosomes, because they are responsible for breaking down waste.

• The mitochondria, because they are failing to create enough energy.

• The ribosomes, because they are not building essential proteins.

• The Golgi apparatus, because it is not packaging materials correctly.

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Eukaryotic Cells: Specialized Structures

• Plant cells, fungi, and protists have a rigid cell wall for support.

• Plant cells and some protists have chloroplasts to perform photosynthesis.

• A large central vacuole in plant cells stores water, food, and waste.

• Cilia and flagella are structures that help some eukaryotic cells to move.

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Multiple Choice

What is the primary function of a cell wall in organisms like plants, fungi, and protists?

• To provide structural support

• To help the cell move from place to place

• To convert sunlight into food

• To store water, food, and waste materials

Multiple Choice

What is the relationship between the functions of chloroplasts and the central vacuole in a plant cell?

• Chloroplasts produce food, and the vacuole stores materials.

• The cell wall helps with movement, and cilia help with support.

• Chloroplasts store waste, and the vacuole produces food.

• The cell wall produces energy, and the vacuole provides support.

Multiple Choice

A scientist observes a eukaryotic cell that has a rigid cell wall and contains chloroplasts, but it does not have cilia or flagella. What can be concluded about this cell?

• It likely gets energy from the sun and cannot move on its own.

• It likely moves using flagella and absorbs food from its environment.

• It likely has a flexible shape and gets energy by eating other cells.

• It likely stores water in chloroplasts and uses a cell wall to move.

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The Role of the Cell Membrane

Active Transport

• Molecules are moved from an area of low concentration to an area of high concentration.

• This movement goes against the natural flow, so it requires the cell to use its energy.

• The energy used for this process is known as ATP, which powers the transport of molecules.

Passive Transport

• Molecules are moved from an area of high concentration to an area of low concentration.

• This process works to maintain a stable internal balance in the cell, which is called homeostasis.

• This natural movement of molecules does not require the cell to use any of its energy.

Multiple Choice

What is the function of ATP in the transport of molecules across the cell membrane?

• To power the movement of molecules from an area of low concentration to high concentration.

• To help molecules move naturally from a high concentration to a low one.

• To create a stable internal balance known as homeostasis.

• To store energy that the cell does not currently need.

Multiple Choice

What is the key difference in how molecules are moved during active transport compared to passive transport?

• Passive transport moves molecules from high to low concentration, while active transport moves them from low to high concentration.

• Passive transport requires energy to maintain balance, while active transport allows molecules to flow naturally.

• Passive transport is used to store energy, while active transport is used to release energy.

• Passive transport creates homeostasis, while active transport disrupts it.

Multiple Choice

A cell needs to bring in a substance that is already more concentrated inside the cell than it is outside. Which statement best explains how the cell can accomplish this?

• The cell must use active transport to move the substance against the concentration gradient.

• The substance will move into the cell naturally through passive transport.

• The cell will achieve homeostasis by allowing the substance to enter without using energy.

• The cell membrane will block the substance from entering to save energy.

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Cell Origins and Key Molecules

Endosymbiosis Theory

• The Endosymbiosis Theory explains how complex eukaryotic cells may have evolved over time.

• It suggests that organelles like mitochondria were once free-living prokaryotic cells.

• These prokaryotes were engulfed by larger host cells, forming a beneficial relationship.

Essential Lipids

• Triglycerides are lipids formed from three fatty acid chains attached to a glycerol molecule.

• Phospholipids form cell membranes and have two fatty acid chains and a phosphate group.

• Steroids are another class of lipids with a distinct structure of four fused carbon rings.

Multiple Choice

What is the main idea of the Endosymbiosis Theory?

• That complex cells evolved from a beneficial relationship between simpler cells.

• That all cells originate from non-living molecules.

• That lipids are the most important molecules for cell origins.

• That steroids control the evolution of new cell types.

Multiple Choice

How does the structure of a phospholipid differ from a triglyceride?

• Phospholipids contain a phosphate group, while triglycerides have three fatty acid chains.

• Phospholipids are made of four fused carbon rings, while triglycerides are not.

• Triglycerides form cell membranes, while phospholipids are used for structure.

• Steroids are formed from glycerol, while phospholipids are not.

Multiple Choice

The Endosymbiosis Theory describes a smaller cell being engulfed by a larger one. Which molecular structure would have been essential for forming the boundaries of both cells?

• A cell membrane made of phospholipids

• A rigid structure of four fused carbon rings

• A large supply of triglycerides for energy

• A shared wall made of steroids

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Common Misconceptions

Misconception	Correction
All cells have a nucleus.	Only eukaryotic cells have a nucleus; prokaryotic cells have a nucleoid region.
The cell membrane is a solid, immovable wall.	The cell membrane is a flexible and semi-permeable barrier.
Plant and animal cells are completely different.	They share many organelles. Key differences are the cell wall and chloroplasts.
Prokaryotic cells are just simple, empty bags.	They are complex and contain vital structures like ribosomes, plasmids, and flagella.

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Summary

• All life is made of prokaryotic or eukaryotic cells.

• Eukaryotic cells have a nucleus and other organelles with specific jobs.

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

• The cell membrane controls movement in and out of the cell.

Poll

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

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