CHAPTER 10 LESSON 2 Cell Structure and Function · Every cell has a cell membrane. But some cells...

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Key Concepts • How are prokaryotic cells

and eukaryotic cells similar, and how are they different?

• What do the structures in a cell do?

Cell Shape and Movement Cells come in many shapes and sizes. The size and shape

of a cell is part of the function of the cell. Some cells, such as human red-blood cells, can be seen only by using a microscope. The cells can pass easily through small blood vessels because of their small size. Their disk shapes are important for carrying oxygen. Nerve cells have parts that jut out. These projections on nerve cells can send signals over long distances. Some plant cells are hollow. These hollow cells make up tubelike structures that can carry water and dissolved substances to parts of the plant.

The size and shape of a cell make it possible for the cell to carry out its functions. The parts that make up a cell have their own functions as well. A cell’s parts are like the players on a football team who perform different tasks on the playing field. A cell is made up of different parts that perform different functions to keep the cell alive.

What do you think? Read the two statements below and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you’ve read this lesson, reread the statements to see if you have changed your mind.

Before Statement After

3. Different organisms have cells with different structures.

4. All cells store genetic information in their nuclei.

ACADEMIC VOCABULARYfunction(noun) the purpose for which something is used

Use Prior Knowledge Before you read this lesson, look at the figures and headings to learn what the lesson is about. Write what you know about the cell on a piece of paper. As you read the lesson, fill in what you learned about the cell.

Cell Structure and Function

The Cell

LESSON 2

CHAPTER 10

Reading Essentials Cell Structure and Function 167

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Cell MembraneAll cells have some parts, or structures, in common. One

of these structures is a cell membrane. A cell membrane is a flexible covering that protects the inside of a cell from the environment outside the cell. You can see the cell membrane in both drawings on this page. Cell membranes are made of proteins and phospholipids . Reading Check

2. Describe What are cell membranes made of?

Visual Check 3. Identify Circle the names of two parts in the animal cell that are also found in the plant cell.

Visual Check 1. Describe the location of the cell wall.

Cytoskeleton

Cell membrane

Cell wall

Mitochondrion

Geneticmaterial

Nuclearmembrane

Nucleolus

Vesicle

Ribosome Central vacuole

Rough endoplasmicreticulum

Smooth endoplasmicreticulum

Golgi apparatusChloroplast

Nucleus

Plant Cell

Animal Cell

Cytoskeleton

Ribosome

Cell membrane

Mitochondrion

Vesicle

Lysosome

Smoothendoplasmicreticulum

Rough endoplasmic

reticulum

Golgiapparatus

Centriole

Geneticmaterial

Nuclearenvelope

NucleolusNucleus

168 Cell Structure and Function Reading Essentials


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Reading Check 4. Describe the structure of the cytoskeleton.

Visual Check5. Name three parts of a prokaryotic cell.

Cell wall

Cellmembrane

DNA

Cytoplasm

Flagellum

Ribosome

Capsule

Cell WallEvery cell has a cell membrane. But some cells also have

a cell wall. Plant cells, fungal cells, bacterial cells, and some protists have cell walls. A cell wall is a stiff structure outside the cell membrane. A cell wall protects a cell from viruses and other harmful organisms. In some plant and fungal cells, the cell wall helps the cell keep its shape and gives it support.

Cell AppendagesIf you look at a cell using a microscope, you might see

structures on the outside of the cell. These appendages might look like hairs or long tails. They often help a cell move. Flagella (fluh JEH luh) (singular, flagellum) are long and tail-like. They whip back and forth to move the cell. Cilia (SIH lee uh) (singular, cilium) are short, hairlike structures. They can move a cell or move molecules away from a cell. The cilia in your windpipe move harmful particles away from your lungs.

Cytoplasm and the CytoskeletonThe fluid inside a cell is made of water, salts, and other molecules

and is called the cytoplasm. The cytoplasm contains a cell’s cytoskeleton. The cytoskeleton is made of threadlike proteins that are joined together. The cytoskeleton is a framework that gives a cell its shape and helps it move.

Cell TypesMicroscopes helped scientists discover that cells can be

grouped into two types. There are prokaryotic (proh ka ree AH tihk) cells and eukaryotic (yew ker ee AH tihk) cells.

Prokaryotic CellsThe genetic material in a prokaryotic cell is not

surrounded by a membrane. Look at the drawing below. Prokaryotic cells also do not have many of the cell parts other cells have. Most prokaryotic cells are unicellular organisms and are called prokaryotes.



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SCIENCE USE V. COMMON USEenvelopeScience Use an outer covering

Common Use a flat paper container for a letter

Reading Check7. Contrast smooth ER and rough ER.

Key Concept Check 6. Compare and Contrast How are prokaryotic cells and eukaryotic cells the same? How are they different?

Eukaryotic CellsThe cells of plants, animals, fungi, and protists are

eukaryotic cells. The genetic material of eukaryotic cells is surrounded by a membrane. Every eukaryotic cell also has organelles—other parts that are surrounded by a membrane and have specialized functions. Eukaryotic cells are usually larger than prokaryotic cells.

Cell OrganellesThe organelles of eukaryotic cells have different functions

in the cell. Organelles help a cell carry out different functions at the same time. These functions include getting energy from food, storing information, and getting rid of waste material.

The NucleusThe largest organelle inside most eukaryotic cells is the

nucleus. The nucleus is the part of a eukaryotic cell that directs cell activities and contains genetic information stored in DNA.

DNA is in structures called chromosomes. The number of chromosomes in a nucleus is different for different species of organisms.

The nucleus also contains proteins and an organelle called the nucleolus (new KLEE uh lus). The nucleolus makes ribosomes, organelles that help produce proteins. Two membranes form the nuclear envelope that surrounds the nucleus. The nuclear envelope has many pores. Certain molecules, such as ribosomes and RNA, move into and out of the nucleus through these pores.

Manufacturing MoleculesYou learned that proteins are important molecules in

cells. Proteins are made of small organelles called ribosomes. A ribosome is not surrounded by a membrane. Ribosomes are in the cytoplasm of a cell. Ribosomes can be attached to an organelle called the endoplasmic reticulum (en duh PLAZ mihk • rih TIHK yuh lum), or ER. ER with ribosomes on its surface is called rough ER. Rough ER is where proteins are produced. ER without ribosomes on its surface is called smooth ER. It makes lipids such as cholesterol. Smooth ER also helps remove harmful substances from a cell.



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Reading Check 8. Identify the types of cells that contain chloroplasts.

Key Concept Check9. Explain the function of the Golgi apparatus.

Make a half-book to record information about cell organelles and their functions.

Cell Organelles and Their Functions

Processing EnergyAll living things must have energy to survive. Cells

process some energy in specialized organelles called mitochondria (mi tuh KAHN dree uh) (singular, mitochondrion). Most eukaryotic cells contain hundreds of mitochondria. Some cells in a human heart can contain 1,000 mitochondria.

ATP A mitochondrion is surrounded by two membranes. Chemical reactions within mitochondria release energy. This energy is stored in high-energy molecules called ATP—adenosine triphosphate (uh DEH nuh seen • tri FAHS fayt). The energy in ATP molecules is used by the cell for growth, cell division, and transporting materials.

Chloroplasts The cells of some organisms, such as plants and algae, contain organelles called chloroplasts (KLOR uh plasts). Chloroplasts are membrane-bound organelles that use light energy and make food, a sugar called glucose, from water and carbon dioxide in a process called photosynthesis (foh toh SIHN thuh sus). The sugar has stored energy that can be used when the cells need it.

Processing, Transporting, and Storing MoleculesThe Golgi (GAWL jee) apparatus is an organelle that looks

like a stack of pancakes. It gets proteins ready for their specific jobs. It then packages the proteins into tiny membrane-bound, ball-like structures called vesicles. Vesicles are organelles that transport substances to other parts of the cell. Some vesicles in an animal cell are called lysosomes. Lysosomes help break down and recycle different parts of the cell.

Some cells also have structures called vacuoles (VA kyuh wohlz). Vacuoles are organelles that store food, water, and waste materials for a cell. A plant cell usually has one large vacuole. Some animal cells have many small vacuoles.



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Mini Glossary

Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind?

What do you think

END OF LESSON

Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson’s resources.

ConnectED

cell membrane: a flexible covering that protects the inside of

a cell from the environment outside a cell

cell wall: a stiff structure outside the cell membrane

chloroplast (KLOR uh plast): a membrane-bound

organelle that uses light energy and makes food—a sugar

called glucose—from water and carbon dioxide in a process

known as photosynthesis

cytoplasm: a fluid inside a cell that contains salts and other

molecules

cytoskeleton: a network of threadlike proteins that are

joined together

nucleus: the part of a eukaryotic cell that directs cell activities

and contains genetic information stored in DNA

organelle: a membrane-surrounded component of a cell that

has specialized functions

1. Review the terms and their definitions in the Mini Glossary. Write a sentence that lists two functions of the nucleus of a eukaryotic cell.

2. Fill in the table below to identify the functions of each organelle.

Organelle Function

Chloroplast

Golgi apparatus

Smooth ER

Nucleus

3. Name three tasks carried out by the organelles of eukaryotic cells.



CHAPTER 10 LESSON 2 Cell Structure and Function · Every cell has a cell membrane. But some cells...

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