Unit 1: What is Biology?Unit 2: EcologyUnit 3: The Life of a CellUnit 4: GeneticsUnit 5: Change Through TimeUnit 6: Viruses, Bacteria, Protists, and FungiUnit 7: PlantsUnit 8: InvertebratesUnit 9: VertebratesUnit 10: The Human Body

Unit 1: What is Biology?

Chapter 1: Biology: The Study of LifeUnit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and ConservationUnit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell

Unit 4: Genetics

Chapter 10: Mendel and Meiosis

Chapter 11: DNA and Genes

Chapter 12: Patterns of Heredity and Human Genetics

Chapter 13: Genetic Technology

Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity

Unit 6: Viruses, Bacteria, Protists, and Fungi

Chapter 18: Viruses and Bacteria

Chapter 19: Protists

Chapter 20: Fungi

Unit 7: Plants

Chapter 21: What Is a Plant?

Chapter 22: The Diversity of Plants

Chapter 23: Plant Structure and Function

Chapter 24: Reproduction in Plants

Unit 8: Invertebrates

Chapter 25: What Is an Animal?

Chapter 26: Sponges, Cnidarians, Flatworms, and

Roundworms

Chapter 27: Mollusks and Segmented Worms

Chapter 28: Arthropods

Chapter 29: Echinoderms and Invertebrate

Chordates

Unit 9: Vertebrates Chapter 30: Fishes and Amphibians

Chapter 31: Reptiles and Birds

Chapter 32: Mammals

Chapter 33: Animal Behavior

Unit 10: The Human Body

Chapter 34: Protection, Support, and Locomotion

Chapter 35: The Digestive and Endocrine Systems

Chapter 36: The Nervous System

Chapter 37: Respiration, Circulation, and Excretion

Chapter 38: Reproduction and Development

Chapter 39: Immunity from Disease

The Life of a Cell

The Chemistry of Life

A View of the Cell

Cellular Transport and the Cell CycleEnergy in a Cell

Chapter 7 A View of a Cell

7.1: The Discovery of Cells

7.1: Section Check

7.2: The Plasma Membrane

7.2: Section Check

7.3: Eukaryotic Cell Structure

7.3: Section Check

Chapter 7 Summary

Chapter 7 Assessment

What You’ll Learn

You will identify the parts of prokaryotic and eukaryotic cells.

You will identify the structure and function of the plasma membrane.

You will relate the structure of cell parts to their functions.

Cells are the foundation for the development of all life forms. Birth, growth, death, and all life functions begin as cellular functions.

What You’ll Learn

Plasma Membrane

Lysosomes

Nucleus

Mitochondrion

Endoplasmic Reticulum

• Relate advances in microscope technology to discoveries about cells and cell structure.

Section Objectives:

• Compare the operation of a microscope with that of an electron microscope.

• Identify the main ideas of the cell theory.

The History of the Cell TheoryThe History of the Cell Theory• Before microscopes were invented, people

believed that diseases were caused by curses and supernatural spirits.

• Microscopes enabled scientists to view and study cells, the basic units of living organisms.

• As scientists began using microscopes, they quickly realized they were entering a new world–one of microorganisms.

• The first person to record looking at water under a microscope was Anton van Leeuwenhoek.

• The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects.

Development of Light MicroscopesDevelopment of Light Microscopes

Compound light microscopes use a series of lenses to magnify objects in steps.

These microscopes can magnify objects up to 1 500 times.

Development of Light MicroscopesDevelopment of Light Microscopes

Microscope Lab TechniquesMicroscope Lab Techniques

Click image to view movie.

• Robert Hooke was an English scientist who lived at the same time as van Leeuwenhock.

The Cell TheoryThe Cell Theory

• Hooke used a compound light microscope to study cork, the dead cells of oak bark.

Cells are the basic building blocks of all living things.

The cell theory is made up of three main ideas:

All cells come from preexisting cells.

The cell is the basic unit of organization of organisms.

All organisms are composed of one or more cells.

• The electron microscope was invented in the 1940s.

• This microscope uses a beam of electrons to magnify structures up to 500 000 times their actual size.

Development of Electron MicroscopesDevelopment of Electron Microscopes

There are two basic types of electron microscopes.

The transmission electron microscope allows scientists to study the structures contained within a cell.

The scanning electron microscope scans the surface of cells to learn their three dimensional shape.

Development of Electron MicroscopesDevelopment of Electron Microscopes

Cells that do not contain internal membrane-bound structures are called prokaryotic cells.

• The cells of most unicellular organisms such as bacteria do not have membrane bound structures and are therefore called prokaryotes.

Two Basic Cell TypesTwo Basic Cell Types

Click here

• Most of the multi-cellular plants and animals we know are made up of cells containing membrane-bound structures

and are therefore called eukaryotes.

Cells containing membrane-bound structures are called eukaryotic cells.

7.17.1

Two Basic Cell TypesTwo Basic Cell Types

Click here

The membrane-bound structures within eukaryotic cells are called organelles.

• Each organelle has a specific function that contributes to cell survival.

Two Basic Cell TypesTwo Basic Cell Types

The nucleus is the central membrane-bound organelle that manages cellular functions.

• Separation of organelles into distinct compartments benefits the eukaryotic cells.

Two Basic Cell TypesTwo Basic Cell Types

Question 1 How did the invention of the microscope

impact society's understanding of disease?

B. Microscopes were invented after the development of the cell theory.

A. Scientists were able to view microorganisms that were previously unknown.

D. Scientists could view membrane-bound organelles of prokaryotes.

C. It was once believed that viruses, not bacteria, caused diseases.

How did the invention of the microscope impact society's understanding of disease?

Question 1

The answer is A. Before microscopes were invented, people believed that curses and supernatural spirits caused diseases. Microscopes enabled scientists to view cells, which led to the discovery that microorganisms cause some diseases.

Which of the following uses a beam of light and a series of lenses to magnify objects in steps?

Question 2

D. simple light microscope

C. transmission electron microscope

B. scanning electron microscope

A. compound light microscope

NC: 1.02

The answer is A. Most microscopes use at least two convex lenses. Compound light microscopes use a light beam and a series of lenses and can magnify objects up to about 1500 times. Electron microscopes use a beam of electrons and can magnify structures up to 500 000 times.

NC: 1.02

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 What makes this cell eukaryotic?

A. Because it has a cell wall.

B. Because it contains DNA.

NC: 2.02

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 What makes this cell eukaryotic?

C. Because it has membrane-bound organelles.

D. Because it does not have DNA.

NC: 2.02

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 The Answer is C. Eukaryotic cells contain

membrane-bound organelles that have specific functions in the cell; prokaryotic cells do not.

NC: 2.02

Section Objectives

• Relate the function of the plasma membrane to the fluid mosaic model.

• Explain how a cell’s plasma membrane functions.

All living cells must maintain a balance regardless of internal and external conditions. Survival depends on the cell’s ability to maintain the proper conditions within itself.

Why cells must control materials

The plasma membrane is the boundary between the cell and its environment.

It is the plasma membrane’s job to:

• allow waste and other products to leave the cell.

• remove excess amounts of these nutrients when levels get so high that they are harmful.

• allow a steady supply of glucose, amino acids, and lipids to come into the cell no matter what the external conditions are.

This process of maintaining the cell’s environment is called homeostasis.

Selective permeability is a process used to maintain homeostasis in which the plasma membrane allows some molecules into the cell while keeping others out.

Water

Plasma Membrane

Structure of the Plasma Membrane

The plasma membrane is composed of two layers of phospholipids back-to-back.

Phospholipids are lipids with a phosphate attached to them.

The lipids in a plasma membrane have a glycerol backbone, two fatty acid chains, and a phosphate group.

Glycerol Backbone

Two Fatty Acid Chains

Phosphate Group

Makeup of the phospholipid bilayer

The phosphate group is critical for the formation and function of the plasma membrane.

Phosphate Group

Makeup of the phospholipid bilayer

The fluid mosaic model describes the plasma membrane as a flexible boundary of a cell. The phospholipids move within the membrane.

Other components of the plasma membrane:

Cholesterol plays the important role of preventing the fatty acid chains of the phospholipids from sticking together.

CholesterolMolecule

Other components of the plasma membrane:

Transport proteins allow needed substances or waste materials to move through the plasma membrane.

Click image to view movie.

Which of the following best describes the plasma membrane's mechanism in maintaining homeostasis?

Question 1

A. protein synthesis

B. selective permeability

C. fluid composition

D. structural protein attachment

NC: 2.03

The answer is B. Selective permeability is the process in which the membrane allows some molecules to pass through, while keeping others out.

NC: 2.03

Describe the structure of the plasma membrane.

Question 2

NC: 2.03

The plasma membrane is composed of a phospholipid bilayer, which has two layers of phospholipids back-to-back. The polar heads of phospholipid molecules contain phosphate groups and face outward.

NC: 2.03

Why is the phosphate group of a phospholipid important to the plasma membrane?

Question 3

Polar head (includes phosphate group)

Nonpolar tails (fatty acids)

Phospholipid molecule

NC: 2.03

When phospholipid molecules form a bilayer, the phosphate groups lie to the outside. Because phosphate groups are polar, they allow the cell membrane to interact with its watery (polar) environments inside and outside the cell.

Polar head (includes phosphate group)

Nonpolar tails (fatty acids)

Phospholipid molecule

NC: 2.03

Explain why the model of the plasma membrane is called the fluid mosaic model.

Question 4

NC: 2.03

It is fluid because the phospholipid molecules move within the membrane. Proteins in the membrane that move among the phospholipids create the mosaic pattern.

NC: 2.03

Section Objectives

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

• Explain the advantages of highly folded membranes.

• Understand the structure and function of the parts of a typical eukaryotic cell.

The plasma membrane acts as a selectively permeable membrane.

Cellular Boundaries

The cell wall The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection.

Nucleus and cell control

Chromatin

Nucleolus

Nuclear Envelope

Assembly, Transport, and Storage

The endoplasmic reticulum (ER) is an organelle that is suspended in the cytoplasm and is the site of cellular chemical reactions.

Assembly, Transport, and Storage Endoplasmic

Reticulum (ER)

Ribosomes

Assembly, Transport, and Storage

Golgi Apparatus

Vacuoles and storage Vacuoles are membrane-bound spaces used for temporary storage of materials. Notice the difference between vacuoles in plant and animal cells.

VacuoleAnimalCell

PlantCell

Lysosomes and recycling

Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.

Energy Transformers:

Chloroplasts are cell organelles that capture light energy and produce food to store for a later time.

Chloroplasts and energy

The chloroplasts belongs to a group of plant organelles called plastids, which are used for storage.

Chloroplasts contain green pigment called chlorophyll. Chlorophyll traps light energy and gives leaves and stems their green color.

Chloroplasts and energy

Mitochondria are membrane-bound organelles in plant and animal cells that transform energy for the cell.

Mitochondria and energy

A mitochondria, like the endoplasmic reticulum, has a highly folded inner membrane. Energy storing molecules are produced on inner folds.

Mitochondria and energy

Cells have a support structure called the cytoskeleton within the cytoplasm. The cytoskeleton is composed of microtubules and microfilaments. Microtubules are thin, hollow cylinders made of protein and microfilaments are thin solid protein fibers.

Structures for Support and Locomotion

Some cell surfaces have cilia and flagella, which are structures that aid in locomotion or feeding. Cilia and flagella can be distinguished by their structure and by the nature of their action.

Cilia and flagella

Cilia are short, numerous, hair-like projections that move in a wavelike motion.

Cilia and flagella Cilia

Flagella are long projections that move in a whip-like motion. Flagella and cilia are the major means of locomotion in unicellular organisms.

Cilia and flagella

Flagella

What is the primary function of the cell wall?

Question 1

D. acquire nutrients from environment

C. control activity of organelles

B. provide support

A. act as selectively permeable membrane

NC: 2.02, 2.03

The answer is B. The cell wall is an inflexible, porous barrier that provides support but does not select which molecules can enter the cell.

NC: 2.02, 2.03

Question 2

DNA

Plasma membrane

Cell wall

Describe the control center of a prokaryotic cell.

Ribosomes

NC: 2.02

DNA

Plasma membrane

Cell wall

Prokaryotic cells do not have true nuclei; their DNA is not separated from the rest of the cell by a membrane.

Ribosomes

NC: 2.02

Which of the following structures is the site of protein synthesis?

Question 3

D. Lysosome

C. Vacuole

B. Ribosome

A. Golgi apparatus

NC: 2.02

The answer is B. Ribosomes are the sites where the cell produces proteins according to the directions of DNA. They can be attached to the surface of the endoplasmic reticulum or float freely in the cytoplasm.

NC: 2.02

What is the advantage of having numerous folds in the ER?

Question 4

B. It can create more vesicles in a smaller space.

A. It enables the ER to lie snugly against the nucleolus.

NC: 2.02

D. A large amount of work can be done in a small space.

What is the advantage of having numerous folds in the ER?

Question 4

C. It can capture more light energy with more folds.

NC: 2.02

The answer is D. The ER is arranged in a series of folded membranes, which, if spread out, would take up tremendous space.

NC: 2.02

B. It contains a greater number of plastids.

What could you predict about a plant cell that contains fewer chloroplasts than other plant cells?

Question 5

A. It contains less chlorophyll.

D. It will appear darker green in color.

C. It will have an increased rate of light energy capture.

NC: 2.02

The answer is A. Chloroplasts are among the plant organelles known as plastids and contain the green pigment chlorophyll. Chlorophyll traps light energy from the Sun and gives leaves and stems their green color.

NC: 2.02

A mutation results in the inner membranes of a liver cell's mitochondria being smooth, rather than folded. Which of the following would you expect?

Question 6

B. It can create more vesicles in a smaller space

A. more efficient storage of cellular energy

NC: 2.02

A mutation results in the inner membranes of a liver cell's mitochondria being smooth, rather than folded. Which of the following would you expect?

Question 6

D. fewer ribosomes available for protein synthesis

C. decreased energy available to the cell

NC: 2.02

The answer is C. Mitochondria transform energy for the cell. A highly folded inner membrane provides a greater surface area for producing energy-storing molecules.

NC: 2.02

• The cell theory states that the cell is the basic unit of organization, all organisms are made up of one or more cells, and all cells come from preexisting cells.

Main Ideas

• Microscopes enabled biologists to see cells and develop the cell theory.

• Cells are classified as prokaryotic and eukaryotic based on whether or not they have membrane-bound organelles.

Main Ideas Continued

• Using electron microscopes, scientists can study cell structure in detail.

• The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with embedded proteins.

Main Ideas

• Through selective permeability, the plasma membrane controls what enters and leaves a cell.

Main Ideas• Eukaryotic cells have a nucleus and

organelles, are enclosed by a plasma membrane, and some have a cell wall that provides support and protection.

• Cells make proteins on ribosomes that are often attached to the highly folded endoplasmic reticulum. Cells store materials in the Golgi apparatus and vacuoles.

• The cytoskeleton helps maintain cell shape, is involved in the movement of organelles and cells, and resists stress placed on cells.

Main Ideas Continued

• Mitochondria break down food molecules to release energy. Chloroplasts convert light energy into chemical energy.

Question 1

Which of the following is a main idea of the cell theory?

D. All cells come from preexisting cells.

C. All cells come from two parent cells.

B. The organelle is the basic unit structure and organization of organisms.

A. All organisms are composed of one cell.

NC: 2.02

The answer is D. The cell theory states that a cell divides to form two identical cells.

NC: 2.02

Question 2

In what type of cell would you find chlorophyll?

D. fungus

C. plant

B. animal

A. prokaryote

NC: 2.02

The answer is C. Chlorophyll is the green pigment found in the chloroplasts of plant cells.

NC: 2.02

Question 3

Which of these structures packs proteins into membrane-bound structures?

A. B.

C. D.

NC: 2.02

Answer C depicts the Golgi apparatus, which sorts proteins and packs them into vesicles.

NC: 2.02

Question 4

What is the difference between the cell wall and the plasma membrane?

Cell wall

Plasma membrane

Inside cell

Outside cell

NC: 2.02, 2.03

The plasma membrane is a flexible boundary between the cell and its environment that controls the supply of nutrients, waste, and other products entering and leaving the cell. The cell wall is a rigid structure found in plant cells, fungi, bacteria and some protists that provides support and protection but does not select which molecules can enter or leave the cell.

Cell wall

Plasma membrane

Inside cell

Outside cell

NC: 2.02, 2.03

Question 5

Which of the following organelles is not bound by a membrane?

D. lysosome

C. vacuole

B. Golgi apparatus

A. ribosome

NC: 2.02

The answer is A. Ribosomes are simple structures made of RNA and protein and are not bound by membranes.

Ribosomes

NC: 2.02

Question 6

Explain the importance of cholesterol to the plasma membrane.

Cholesterol molecule

Phospholipid molecules

NC: 2.03

Cholesterol helps to stabilize the phospholipids in the plasma membrane by preventing their fatty acid tails from sticking together.

Cholesterol molecule

Phospholipid molecules

NC: 2.03

Question 7

In which of the following pairs are the terms related?

D. plastid – storage

C. microfilaments – locomotion

B. prokaryote – mitochondria

A. cell wall – selective permeability

NC: 2.02

The answer is D. Plastids are plant organelles that are used for storage.

NC: 2.02

Question 8

Which of the following structures is found in both plant and animal cells?

D. thylakoid membrane

C. mitochondrion

B. cell wall

A. chloroplast

NC: 2.02

The answer is C. Mitochondria are the organelles in both plant and animal cells that transform energy for the cell.

NC: 2.02

Question 9 __________ span the entire plasma membrane

and regulate which molecules enter and leave the cell.

D. Microtubules

C. Ribosomes

B. Cholesterol molecules

A. Transport proteins

NC: 2.03

The answer is A. Transport proteins form the selectively permeable membrane and move needed substances or waste materials through the plasma membrane.

NC: 2.03

Question 10

Compare the cytoskeleton of a cell to the skeleton of the human body.

NC: 2.02, 2.03

The cytoskeleton and skeleton are similar in that both form a framework. However, the cytoskeleton is a constantly changing structure with the ability to be disassembled in one place and reassembled in another.

NC: 2.02, 2.03

A prokaryotic cell does not have internal organelles surrounded by a membrane. Most of a prokaryote’s metabolism takes place in the cytoplasm.

1. Ribosomes

2. DNA 3. Plasma membrane

4. Cell wall

Click here to return to chapter summary

NC: 2.02, 2.03

This eukaryotic cell from an animal has distinct membrane-bound organelles that allow different parts of the cell to perform different functions.

4. Plasma membrane

1. Nucleus

2. Nucleolus

3. Chromosomes

5. OrganellesClick here to return to chapter summary

NC: 2.02, 2.03

Photo CreditsPhoto Credits

• Digital Stock

• PhotoDisc

• Alton Biggs

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