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Campbell Biology: Concepts &

Connections

Tenth Edition

Chapter 4

A Tour of the Cell

Introduction

• Improved microscopes and techniques have vastly

expanded our view of the cell.

– In 1665, Hooke used a crude microscope to examine a

piece of bark from an oak tree. Hooke compared the

structures he saw to “little rooms”—cellulae in Latin—

and the term “cell” stuck.

– A few decades later Leeuwenhoek used more refined

microscope to view numerous subjects, including

blood, sperm, and pond water.

• In this chapter, we will explore the cellular basis of life.

Figure 4.0_1

Figure 4.0_2

Introduction to the Cell

4.1 Microscopes Reveal the World of

the Cell (1 of 2)

• The light microscope can display living cells.

• The greater magnification and resolution of scanning and

transmission electron microscopes reveal the

ultrastructure of cells.

– Magnification is the increase in an object’s image size

compared with its actual size.

– Resolution is a measure of the clarity of an image. In

other words, it is the ability of an instrument to show

two nearby objects as separate.

4.1 Microscopes Reveal the World of

the Cell (2 of 2)

• In the mid-1800s, early studies of cells led to cell theory,

which states that

– all living things are composed of cells and

– all cells come from other cells.

Checkpoint question Which type of microscope would you

use to study (a) the changes in shape of a living human

white blood cell; (b) the finest details of surface texture of a

human hair; (c) the detailed structure of an organelle in a

liver cell?

Figure 4.1a

Figure 4.1b

Figure 4.1c

Figure 4.1d

Figure 4.1e

Figure 4.1e_1

Figure 4.1e_2

Figure 4.1e_3

4.2 The Small Size of Cells Relates to

the Need to Exchange Materials

Across the Plasma Membrane (1 of 2)

• The microscopic size of most cells provides a large

surface-to-volume ratio.

• The plasma membrane is a phospholipid bilayer with

embedded proteins.

– Some proteins form channels (tunnels) that shield ions

and other hydrophilic molecules as they pass through

the hydrophobic center of the membrane.

– Other proteins serve as pumps, using energy to

actively transport molecules into or out of the cell.

4.2 The Small Size of Cells Relates to

the Need to Exchange Materials

Across the Plasma Membrane (2 of 2)

Checkpoint question To convince yourself that a small cell

has a greater surface area relative to volume than a large

cell, compare the surface-to-volume ratios of the large cube

and one of the small cubes in Figure 4.2A.

Figure 4.2b

4.3 Prokaryotic Cells Are Structurally

Simpler Than Eukaryotic Cells

• All cells have a plasma membrane, D N A, ribosomes, and

cytosol.

• Bacteria and Archaea consist of prokaryotic cells.

• All other forms of life are placed in domain Eukarya and

have eukaryotic cells.

• Eukaryotic cells are distinguished by having

– a membrane-enclosed nucleus and

– many membrane-enclosed organelles that perform

specific functions.

• Prokaryotic cells are smaller and simpler in structure.

Figure 4.3

Figure 4.3_1

Figure 4.3_2

4.4 Eukaryotic Cells Are Partitioned

into Functional Compartments (1 of 2)

• Membrane-enclosed organelles compartmentalize a cell’s

activities.

• The organelles and other structures of eukaryotic cells can

be organized into four basic functional groups:

1. The nucleus and ribosomes carry out the genetic

control of the cell.

2. Organelles involved in the manufacture, distribution,

and breakdown of molecules include the endoplasmic

reticulum, Golgi apparatus, lysosomes, vacuoles, and

peroxisomes.

4.4 Eukaryotic Cells Are Partitioned

into Functional Compartments (2 of 2)

3. Mitochondria in all cells and chloroplasts in plant cells

function in energy processing.

4. Structural support, movement, and communication

between cells are the functions of the cytoskeleton,

plasma membrane, and plant cell wall.

Checkpoint question Identify the structures in the plant cell

that are not present in the animal cell.

Figure 4.4a

Figure 4.4b

The Nucleus and Ribosomes

4.5 The Nucleus Contains the Cell’s

Genetic Instructions

• The nucleus houses the cell’s D N A, which directs protein

synthesis via messenger R N A.

• Subunits of ribosomes are assembled in the nucleolus.

Checkpoint question Describe the processes that occur in

the nucleus.

Figure 4.5

4.6 Ribosomes Make Proteins for Use

in the Cell and Export

• Ribosomes

– are composed of ribosomal R N A and proteins and

– synthesize proteins according to directions from D N A.

• Cells that make a lot of proteins have a large number of

ribosomes.

Figure 4.6

The Endomembrane System

4.7 Many Organelles Are Connected

in the Endomembrane System

• Many of the membranes within a eukaryotic cell are part of

the endomembrane system.

• Many of these organelles interact in the

– synthesis,

– distribution,

– storage, and

– export of molecules.

4.8 The Endoplasmic Reticulum is a

Biosynthetic Workshop

• The E R is a membranous network of tubes and sacs.

– Smooth E R synthesizes lipids and processes toxins.

– Rough E R produces membranes, and ribosomes on

its surface make membrane and secretory proteins.

Checkpoint question Explain why we say that the

endoplasmic reticulum is a biosynthetic workshop.

Figure 4.8a

Figure 4.8b

4.9 The Golgi Apparatus Modifies,

Sorts, and Ships Cell Products (1 of 2)

• The Golgi apparatus consists of stacks of sacs in which

products of the ER are processed and then sent to other

organelles or to the cell surface.

Figure 4.9

4.9 The Golgi Apparatus Modifies,

Sorts, and Ships Cell Products (2 of 2)

Checkpoint question What is the relationship of the Golgi

apparatus to the ER in a protein-secreting cell?

4.10 Lysosomes Are Digestive

Compartments Within a Cell (1 of 2)

3. Mitochondria in all cells and chloroplasts in plant cells

function in energy processing.

4. Structural support, movement, and communication

between cells are the functions of the cytoskeleton,

plasma membrane, and plant cell wall.

Checkpoint question Identify the structures in the plant cell

that are not present in the animal cell.

4.10 Lysosomes Are Digestive

Compartments Within a Cell (2 of 2)

• Lysosomes house enzymes that break down ingested

substances and damaged organelles.

Checkpoint question How is a lysosome like a recycling

center?

Figure 4.10a_1

Figure 4.10a_2

Figure 4.10a_3

Figure 4.10a_4

Figure 4.10b_1

Figure 4.10b_2

Figure 4.10b_3

Animation: Lysosome Formation

4.11 Vacuoles Function in the General

Maintenance of the Cell

• Vacuoles are large vesicles that have a variety of

functions.

– Some protists have contractile vacuoles.

– Plant cells contain a large central vacuole that stores

molecules and wastes and facilitates growth.

Checkpoint question Is a food vacuole part of the

endomembrane system? Explain.

Figure 4.11a

Figure 4.11b

Video: Paramecium Vacuole

4.12 A Review of the Structures

Involved in Manufacturing and

Breakdown (1 of 3)

• The organelles of the endomembrane system are

interconnected structurally and functionally.

• Figure 4.12 summarizes the relationships among the major

organelles of the endomembrane system.

Figure 4.12

4.12 A Review of the Structures

Involved in Manufacturing and

Breakdown (2 of 3)

Checkpoint question How do transport vesicles help tie

together the endomembrane system?

4.12 A Review of the Structures

Involved in Manufacturing and

Breakdown (3 of 3)

• Peroxisomes are metabolic compartments that do not

originate from the endomembrane system.

Energy-Converting Organelles

4.13 Mitochondria Harvest Chemical

Energy from Food

• Mitochondria are organelles that carry out cellular

respiration in nearly all eukaryotic cells.

• Mitochondria have two internal compartments.

1. The intermembrane space is the narrow region

between the inner and outer membranes.

2. The mitochondrial matrix contains the mitochondrial

D N A, ribosomes, and many enzymes that catalyze

some of the reactions of cellular respiration.

Checkpoint question What is cellular respiration?

Figure 4.13

4.14 Chloroplasts Convert Solar

Energy to Chemical Energy (1 of 2)

• Photosynthesis is the conversion of light energy from the

sun to the chemical energy of sugar molecules.

• Chloroplasts are the photosynthesizing organelles of

plants and algae.

4.14 Chloroplasts Convert Solar

Energy to Chemical Energy (2 of 2)

Checkpoint question

Which membrane in a

chloroplast appears to be

the most extensive?

Why might this be so?

4.15 Evolution Connection: Mitochondria and

Chloroplasts Evolved by Endosymbiosis

• The endosymbiont theory states that mitochondria and

chloroplasts were formerly small prokaryotes that began

living within larger cells.

Checkpoint question All eukaryotes have mitochondria, but

not all have chloroplasts. What is the evolutionary

explanation?

Figure 4.15

Figure 4.15_1

Figure 4.15_2

Figure 4.15_3

The Cytoskeleton and Cell

Surfaces

4.16 The Cell’s Internal Skeleton

Helps Organize Its Structure and

Activities (1 of 2)

• The cytoskeleton includes microfilaments, intermediate

filaments, and microtubules. Their functions include

– maintenance of cell shape,

– anchorage and movement of organelles,

– amoeboid movement, and

– muscle contraction.

4.16 The Cell’s Internal Skeleton

Helps Organize Its Structure and

Activities (2 of 2)

Checkpoint question Which component of the cytoskeleton

is most important in

a. holding the nucleus in place within an animal cell;

b. guiding transport vesicles from the Golgi to the plasma

membrane;

c. contracting muscle cells?

Figure 4.16

Figure 4.16_1

Figure 4.16_2

Figure 4.16_3

Figure 4.16_4

Figure 4.16_5

Figure 4.16_6

4.17 Scientific Thinking: Scientists

Discovered the Cytoskeleton Using

the Tools of Biochemistry and

Microscopy (1 of 2)

• In the 1940s, biochemists first isolated and identified the

proteins actin and myosin from muscle cells.

• In 1954, scientists, using newly developed techniques of

microscopy, established how filaments of actin and myosin

interact in muscle contraction.

• In the next decade, researchers identified actin filaments in

all types of cells.

4.17 Scientific Thinking: Scientists

Discovered the Cytoskeleton Using

the Tools of Biochemistry and

Microscopy (2 of 2)

• Researchers then tagged actin proteins with fluorescent

molecules and injected them into living cells.

• This technique enabled scientists to visualize the dynamic

behavior of cytoskeletal proteins in living cells.

Figure 4.17

4.18 Cilia and Flagella Move When

Microtubules Bend (1 of 2)

• Eukaryotic cilia and flagella are locomotor appendages

made of microtubules in a “9 + 2” arrangement.

– Flagella, longer than cilia, propel a cell by an

undulating, whiplike motion.

• Cilia work more like the coordinated oars of a rowing team.

– Though different in length and beating pattern, cilia

and flagella have a common structure and mechanism

of movement.

4.18 Cilia and Flagella Move When

Microtubules Bend (2 of 2)

Checkpoint question Primary ciliary dyskinesia (PCD), also

known as immotile cilia syndrome, is a fairly rare disease in

which cilia and flagella are lacking motor proteins. PCD is

characterized by recurrent respiratory tract infections and

immotile sperm. How would you explain these seemingly

unrelated symptoms?

Figure 4.18a

Figure 4.18b

Figure 4.18c

Figure 4.18c_1

Figure 4.18c_2

Animation: Cilia and Flagella

Video: Chlamydomonas

4.19 The Extracellular Matrix of

Animal Cells Functions in Support

and Regulation (1 of 2)

• Animal cells synthesize and secrete an elaborate

extracellular matrix (E C M), which

– binds tissue cells together,

– supports the plasma membrane, and

– communicates with the cytoskeleton.

• The E C M may attach to the cell through other

glycoproteins that then bind to membrane proteins called

integrins.

Figure 4.19

4.19 The Extracellular Matrix of

Animal Cells Functions in Support

and Regulation (2 of 2)

Checkpoint question Referring to Figure 4.19, describe the

structures that provide support to the plasma membrane.

4.20 Three Types of Cell Junctions

Are Found in Animal Tissues

• Neighboring cells often adhere, interact, and communicate

through specialized junctions between them.

– Tight junctions bind cells to form leakproof sheets.

– Anchoring junctions rivet cells into strong tissues.

– Gap junctions allow ions and small molecules to flow

from cell to cell.

Checkpoint question A muscle tear injury would probably

involve the rupture of which type of cell junction?

Figure 4.20

Animation: Desmosomes

Animation: Gap Junctions

Animation: Tight Junctions

4.21 Cell Walls Enclose and Support

Plant Cells

• A plant cell, but not an animal cell, has a rigid cell wall that

– protects and provides skeletal support that helps keep

the plant upright on land and

– is primarily composed of cellulose.

• Plant cells have cell junctions called plasmodesmata that

allow plant tissues to share water, nourishment, and

chemical messages.

Checkpoint question Which animal cell junction is

analogous to a plasmodesma?

Figure 4.21

4.22 Review: Eukaryotic Cell

Structures Can Be Grouped on the

Basis of Four Main Functions (1 of 2)

• Eukaryotic cell structures can be grouped on the basis of

four functions:

1. genetic control,

2. manufacturing, distribution, and breakdown of

materials,

3. energy processing, and

4. structural support, movement, and intercellular

communication.

4.22 Review: Eukaryotic Cell

Structures Can Be Grouped on the

Basis of Four Main Functions (2 of 2)

Checkpoint question How do mitochondria, smooth ER,

and the cytoskeleton all contribute to the contraction of a

muscle cell?

Table 4.22 Eukaryotic Cell Structures

and Their Functions (1 of 3)

Table 4.22 Eukaryotic Cell Structures

and Their Functions (2 of 3)

Table 4.22 Eukaryotic Cell Structures

and Their Functions (3 of 3)

You Should Now Be Able to (1 of 4)

1. Describe the importance of microscopes in understanding

cell structure and function.

2. Describe the two parts of cell theory.

3. Distinguish between the structures of prokaryotic and

eukaryotic cells.

4. Explain how cell size is limited.

5. Describe the structure and functions of cell membranes.

You Should Now Be Able to (2 of 4)

6. Explain why compartmentalization is important in

eukaryotic cells.

7. Compare the structures of plant and animal cells. Note

the function of each cell part.

8. Compare the structures and functions of chloroplasts and

mitochondria.

9. Describe the evidence that suggests that mitochondria

and chloroplasts evolved by endosymbiosis.

You Should Now Be Able to (3 of 4)

10. Compare the structures and functions of microfilaments,

intermediate filaments, and microtubules.

11. Relate the structure of cilia and flagella to their

functions.

12. Relate the structure of the extracellular matrix to its

unctions.

13. Compare the structures and functions of tight junctions,

anchoring junctions, and gap junctions.

You Should Now Be Able to (4 of 4)

14. Relate the structures of plant cell walls and

plasmodesmata to their functions.

15. Describe the four functional categories of organelles in

eukaryotic cells.

Table 4.1 Metric Measurement

Equivalents

( )

( ) ( )

( )

-2

-3

-6 -3

-9 -3

1 meter m = 100 cm = 1, 000 mm = 39.4 inches

1 centimeter cm = 10 m 0.01 or 1 / 100 m = 0.4 inch

1 millimeter mm = 10 m 0.001 or 1 / 1, 000 m

1 micrometer μm = 10 m 0.000001 m = 10 mm

1 nanometer nm = 10 m = 10 μm

Figure 4.UN01

Figure 4.UN02

Figure 4.UN03

Figure 4.UN04

Figure 4.UN04_1

Figure 4.UN04_2

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