Cell Structure and Function

Size: px

Start display at page:

Download "Cell Structure and Function"

Ellen Barrett
6 years ago
Views:

1 CHAPTER 2 Cell Structure and Function LESSON 2 The Cell 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. Key Concepts How are prokaryotic cells and eukaryotic cells similar, and how are they different? What do the structures in a cell do? Before Statement After 3. Different organisms have cells with different structures. 4. All cells store genetic information in their nuclei. 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. 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. ACADEMIC VOCABULARY function (noun) the purpose for which something is used Reading Essentials Cell Structure and Function 23

Mitochondrion Ribosome Plant Cell Rough endoplasmic Smooth endoplasmic Central vacuole Visual Check 1. Describe the location of the cell wall.

Identify Circle the names of two parts in the animal cell that are also found in the plant cell. Cell Membrane All cells have some parts, or structures, in common.

2 Mitochondrion Ribosome Plant Cell Rough endoplasmic Smooth endoplasmic Central vacuole Visual Check 1. Describe the location of the cell wall. Vesicle Cytoskeleton Cell wall Nucleus Genetic material Nucleolus Nuclear membrane Chloroplast Cell membrane Golgi apparatus 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. Cell Membrane All 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. Smooth endoplasmic Vesicle Nucleus Genetic material Nucleolus Nuclear envelope Centriole Animal Cell Lysosome Cell membrane Rough endoplasmic Ribosome Cytoskeleton Mitochondrion Golgi apparatus 24 Cell Structure and Function Reading Essentials

Cell Wall Every 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.

3 Cell Wall Every 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 Appendages If 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 taillike. 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 Cytoskeleton The 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 Types Microscopes 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 Cells The 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. Ribosome Cytoplasm Flagellum DNA Cell membrane Cell wall Capsule 4. Describe the structure of the cytoskeleton. Visual Check 5. Name three parts of a prokaryotic cell. Reading Essentials Cell Structure and Function 25

4 Key Concept Check 6. Compare and Contrast How are prokaryotic cells and eukaryotic cells the same? How are they different? SCIENCE USE V. COMMON USE envelope Science Use an outer covering Common Use a flat paper container for a letter 7. Contrast smooth ER and rough ER. Eukaryotic Cells The 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 Organelles The 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 Nucleus The 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 Molecules You 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 (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. 26 Cell Structure and Function Reading Essentials

5 Processing Energy All 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 Molecules The 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. Make a half-book to record information about cell organelles and their functions. Cell Organelles and Their Functions 8. Identify the types of cells that contain chloroplasts. Key Concept Check 9. Explain the function of the Golgi apparatus. Reading Essentials Cell Structure and Function 27

6 Mini Glossary 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 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 cytoplasm: a fluid inside a cell that contains salts and other molecules 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. What do you think 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? ConnectED Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson s resources. END OF LESSON 28 Cell Structure and Function Reading Essentials

Unit 3: Cells. Objective: To be able to compare and contrast the differences between Prokaryotic and Eukaryotic Cells.

Unit 3: Cells. Objective: To be able to compare and contrast the differences between Prokaryotic and Eukaryotic Cells. Unit 3: Cells Objective: To be able to compare and contrast the differences between Prokaryotic and Eukaryotic Cells. The Cell Theory All living things are composed of cells (unicellular or multicellular).