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PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE • TAYLOR • SIMON • DICKEY • HOGAN

Chapter 4

Lecture by Edward J. Zalisko

A Tour of the Cell

© 2015 Pearson Education, Inc.


Introduction

• Cells have a cytoskeleton that • provides support and • allows some cells to crawl and others to swim.

• Our understanding of nature often goes hand in hand with the invention and refinement of instruments that extend our senses.


Introduction

• In 1665, Hooke examined a piece of cork under a crude microscope and identified “little rooms” as cells.

• Leeuwenhoek, working at about the same time, used more refined lenses to describe living cells from blood, sperm, and pond water.

• Since the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.


Figure 4.0-1


Figure 4.0-2

Introduction to the Cell

Chapter 4: Big Ideas

The Nucleus and Ribosomes

The Endomembrane System

Energy-ConvertingOrganelles

The Cytoskeleton andCell Surfaces


INTRODUCTION TO THE CELL


4.1 Microscopes reveal the world of the cell

• A variety of microscopes have been developed for a clearer view of cells and cellular structure.

• The first microscopes were light microscopes. In a light microscope (LM), visible light passes through a specimen, then through glass lenses, and finally is projected into the viewer’s eye.

• Specimens can be magnified by up to 1,000 times.



• 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.



• Microscopes have limitations. • The human eye and the microscope have limits of

resolution—the ability to distinguish between small structures.

• Therefore, the light microscope cannot provide the details of a small cell’s structure.



• Using light microscopes, scientists studied • microorganisms, • animal and plant cells, and • some structures within cells.

• In the 1800s, these studies led to cell theory, which states that

• all living things are composed of cells and • all cells come from other cells.


Figure 4.1a


Figure 4.1b


Figure 4.1c


Figure 4.1d


Figure 4.1e-0

Human heightLength of some nerve and muscle cells

Chicken egg

Frog egg

ParameciumHuman egg

Most plant andanimal cellsNucleusMost bacteriaMitochondrion

Smallest bacteriaViruses

Ribosome

ProteinsLipids

SmallmoleculesAtoms

Una

ided

eye

Ligh

t mic

rosc

ope

Elec

tron

mic

rosc

ope

10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 nm

10 nm

1 nm

0.1 nm

100 μm

10 μm

1 μm


Figure 4.1e-1

Human heightLength of some nerve and muscle cells

Chicken egg

Frog egg

ParameciumHuman eggU

naid

ed e

ye

10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 μm


Figure 4.1e-2

Frog egg

ParameciumHuman egg

Most plant andanimal cellsNucleusMost bacteriaMitochondrion

Smallest bacteriaViruses

Ribosome

ProteinsLipids

SmallmoleculesAtoms

Ligh

t mic

rosc

ope

Elec

tron

mic

rosc

ope

1 mm

100 nm

10 nm

1 nm

0.1 nm

100 μm

10 μm

1 μm



• Beginning in the 1950s, scientists started using a very powerful microscope called the electron microscope (EM) to view the ultrastructure of cells.

• Instead of light, EM uses a beam of electrons. • Electron microscopes can

• resolve biological structures as small as 2 nanometers and

• magnify up to 100,000 times.



• Scanning electron microscopes (SEMs) study the detailed architecture of cell surfaces.

• Transmission electron microscopes (TEMs) study the details of internal cell structure.

• Differential interference light microscopes amplify differences in density so that structures in living cells appear almost three-dimensional.


4.2 The small size of cells relates to the need to exchange materials across the plasma membrane

• Cell size must • be large enough to house DNA, proteins, and

structures needed to survive and reproduce, but • remain small enough to allow for a surface-to-

volume ratio that will allow adequate exchange with the environment.


Figure 4.2a

Total volume

3

3

1

1

2 6

Total surface areaSurface-to-volume ratio

27 units3 27 units3

54 units2 162 units2



• The plasma membrane forms a flexible boundary between the living cell and its surroundings.

• Phospholipids form a two-layer sheet called a phospholipid bilayer in which

• hydrophilic heads face outward, exposed to water, and

• hydrophobic tails point inward, shielded from water.



• Membrane proteins are embedded in the lipid bilayer.

• 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.


Figure 4.2b

Outside cell

Inside cell

Hydrophilicheads

Hydrophobictails

Phospholipid

Channelprotein

Hydrophilicregions ofa protein

Hydrophobicregions ofa protein


Figure 4.UN01


4.3 Prokaryotic cells are structurally simpler than eukaryotic cells

• Bacteria and archaea are prokaryotic cells. • All other forms of life are composed of 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.



• Prokaryotic and eukaryotic cells have • a plasma membrane, • an interior filled with a thick, jellylike fluid called the

cytosol, • one or more chromosomes, which carry genes

made of DNA, and • ribosomes, tiny structures that make proteins

according to instructions from the genes.



• The inside of both types of cells is called the cytoplasm.

• However, in eukaryotic cells, this term refers only to the region between the nucleus and the plasma membrane.



• In a prokaryotic cell, • the DNA is coiled into a region called the nucleoid

(nucleus-like) and • no membrane surrounds the DNA.



• Outside the plasma membrane of most prokaryotes is a fairly rigid, chemically complex cell wall, which

• protects the cell and • helps maintain its shape.

• Some prokaryotes have surface projections. • Short projections help attach prokaryotes to each

other or their substrate. • Longer projections called flagella (singular, flagellum) propel a prokaryotic cell through its liquid environment.


Figure 4.3-0

Fimbriae

Ribosomes

Nucleoid

Plasma membraneCell wall

CapsuleBacterialchromosome

A typical rod-shapedbacterium

A colorized TEM of the bacterium Escherichia coli

Flagella


Figure 4.3-1 Fimbriae

Ribosomes

Nucleoid

Plasma membraneCell wall

CapsuleBacterialchromosome

A typical rod-shapedbacterium Flagella


Figure 4.3-2

A colorized TEM of the bacterium Escherichia coli


4.4 Eukaryotic cells are partitioned into functional compartments

• A eukaryotic cell contains • a membrane-enclosed nucleus and • various other organelles (“little organs”), which

perform specific functions in the cell.



• The structures and organelles of eukaryotic cells perform four basic functions.

1. The nucleus and ribosomes are involved in the genetic control of the cell.

2. The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the manufacture, distribution, and breakdown of molecules.



3. Mitochondria in all cells and chloroplasts in plant cells are involved in energy processing.

4. Structural support, movement, and communication between cells are functions of the cytoskeleton, plasma membrane, and cell wall.



• The internal membranes of eukaryotic cells partition it into compartments.

• Cellular metabolism, the many chemical activities of cells, occurs within organelles.



• Almost all of the organelles and other structures of animals cells are present in plant cells.

• A few exceptions exist. • Lysosomes and centrosomes containing centrioles

are not found in plant cells. • Only the sperm cells of a few plant species have

flagella.



• Plant but not animal cells have • a rigid cell wall that contains cellulose, • plasmodesmata, cytoplasmic channels through cell

walls that connect adjacent cells, • chloroplasts, where photosynthesis occurs, and • a central vacuole, a compartment that stores water

and a variety of chemicals.


Figure 4.4a

Roughendoplasmicreticulum

Smoothendoplasmicreticulum

Golgi apparatus

LysosomeMitochondrion

Centrosome with pair of centrioles

Plasma membrane

Peroxisome

Intermediate filament

MicrofilamentMicrotubule

CYTOSKELETON

NUCLEUSNuclear envelopeNucleolusChromatin

Ribosomes


Figure 4.4b

Roughendoplasmicreticulum

Smoothendoplasmicreticulum

NUCLEUSNuclear envelopeNucleolusChromatin

Ribosomes

Plasma membrane

Peroxisome

Mitochondrion

MicrofilamentMicrotubule

CYTOSKELETON

Cell wall ofadjacent cell Golgi

apparatus

PlasmodesmaCell wall

Chloroplast

Centralvacuole


THE NUCLEUS AND RIBOSOMES


4.5 The nucleus contains the cell’s genetic instructions

• The nucleus • contains most of the cell’s DNA and • controls the cell’s activities by directing protein

synthesis by making messenger RNA (mRNA). • DNA is associated with many proteins and is

organized into structures called chromosomes. • When a cell is not dividing, this complex of proteins

and DNA, called chromatin, appears as a diffuse mass within the nucleus.



• The double membrane nuclear envelope has pores that

• regulate the entry and exit of large molecules and • connect with the cell’s network of membranes called

the endoplasmic reticulum.



• The nucleolus is • a prominent structure in the nucleus and • the site of ribosomal RNA (rRNA) synthesis.


Figure 4.5

NucleolusNuclearenvelope

Endoplasmic reticulum

Ribosome

Pore Chromatin


4.6 Ribosomes make proteins for use in the cell and export

• Ribosomes are involved in the cell’s protein synthesis.

• Ribosomes are the cellular components that use instructions from the nucleus, written in mRNA, to build proteins.

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


4.6 Ribosomes make proteins for use in the cell and export

• Some ribosomes are free ribosomes; others are bound.

• Free ribosomes are suspended in the cytosol. • Bound ribosomes are attached to the outside of the

endoplasmic reticulum or nuclear envelope.


Figure 4.6

Rough ER

Bound ribosomeEndoplasmic reticulum

Protein

Ribosome

Free ribosomemRNA


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.

• Some of these membranes are physically connected, and others are linked when tiny vesicles (sacs made of membrane) transfer membrane segments between them.



• Many of these organelles interact in the • synthesis, • distribution, • storage, and • export of molecules.



• The endomembrane system includes the • nuclear envelope, • endoplasmic reticulum (ER), • Golgi apparatus, • lysosomes, • vacuoles, and • plasma membrane.



• The largest component of the endomembrane system is the endoplasmic reticulum (ER), an extensive network of flattened sacs and tubules.


4.8 The endoplasmic reticulum is a biosynthetic workshop

• There are two kinds of endoplasmic reticulum, which differ in structure and function.

1. Smooth ER lacks attached ribosomes. 2. Rough ER has bound ribosomes that stud the

outer surface of the membrane.


Figure 4.8a

Rough ER

Smooth ER

Ribosomes

Rough ERSmooth ER


Figure 4.8b

mRNA

1

2

3

4

Bound ribosome

Transport vesiclebuds off

Secretoryproteininside trans-port vesicle

Sugar chain

Rough ER

GlycoproteinGrowing polypeptide



• Smooth ER is involved in a variety of metabolic processes, including

• the production of enzymes important in the synthesis of lipids, oils, phospholipids, and steroids,

• the production of enzymes that help process drugs, alcohol, and other potentially harmful substances, and

• the storage of calcium ions.



• Rough ER makes • additional membrane for itself and • secretory proteins.


4.9 The Golgi apparatus modifies, sorts, and ships cell products

• The Golgi apparatus serves as a molecular warehouse and processing station for products manufactured by the ER.

• Products travel in transport vesicles from the ER to the Golgi apparatus.

• One side of the Golgi stack serves as a receiving dock for transport vesicles produced by the ER.


4.9 The Golgi apparatus modifies, sorts, and ships cell products

• Products of the ER are modified as a Golgi sac progresses through the stack.

• The “shipping” side of the Golgi functions as a depot, where products in vesicles bud off and travel to other sites.



Figure 4.9

Golgi apparatus

1

2

3

4

“Receiving” side of Golgi apparatusTransport vesiclefrom the ER

Transportvesicle from the Golgi

“Shipping” side of Golgi apparatus


4.10 Lysosomes are digestive compartments within a cell

• A lysosome is a membrane-enclosed sac of digestive enzymes

• made by rough ER and • processed in the Golgi apparatus


4.10 Lysosomes are digestive compartments within a cell

• Lysosomes • fuse with food vacuoles and digest food, • destroy bacteria engulfed by white blood cells, or • fuse with other vesicles containing damaged

organelles or other materials to be recycled within a cell.


Animation: Lysosome Formation


Figure 4.10a-1

Digestive enzymes

Lysosome

Plasma membrane


Figure 4.10a-2

Digestive enzymes

Lysosome

Food vacuole

Plasma membrane


Figure 4.10a-3

Digestive enzymes

Lysosome

Food vacuole

Plasma membrane


Figure 4.10a-4

Digestive enzymes

Lysosome

Food vacuole

Plasma membrane

Digestion


Figure 4.10b-1

Lysosome

Vesicle containingdamaged mitochondrion


Figure 4.10b-2

Lysosome

Vesicle containingdamaged mitochondrion


Figure 4.10b-3

Lysosome

DigestionVesicle containingdamaged mitochondrion


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, which help to eliminate water from the protist.

• In plants, vacuoles may • have digestive functions, • contain pigments, or • contain poisons that protect the plant.


Video: Paramecium Vacuole


Figure 4.11a

Contractile vacuoles

Nucleus


Figure 4.11b

Central vacuole

Chloroplast

Nucleus


4.12 A review of the structures involved in manufacturing and breakdown

• The following figure summarizes the relationships among the major organelles of the endomembrane system.


Figure 4.12

Nucleus

Smooth ER

Rough ER

Transport vesicle

Lysosome

Nuclear envelope

Golgi apparatus

Plasma membrane

Transportvesicle


4.12 A review of the structures involved in manufacturing and breakdown

• Peroxisomes are metabolic compartments that do not originate from the endomembrane system.

• How they are related to other organelles is still unknown.

• Some peroxisomes break down fatty acids to be used as cellular fuel.


ENERGY-CONVERTING ORGANELLES


4.13 Mitochondria harvest chemical energy from food

• Mitochondria are organelles that carry out cellular respiration in nearly all eukaryotic cells.

• Cellular respiration converts the chemical energy in foods to chemical energy in ATP (adenosine triphosphate).



• 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 DNA, • ribosomes, and • many enzymes that catalyze some of the reactions of

cellular respiration.



• Folds of the inner mitochondrial membrane, called cristae, increase the membrane’s surface area, enhancing the mitochondrion’s ability to produce ATP.


Figure 4.13

Mitochondrion

Intermembrane space

Outer membrane

Inner membrane

CristaMatrix


4.14 Chloroplasts convert solar energy to chemical energy

• 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

• Chloroplasts are partitioned into compartments. • Between the outer and inner membrane is a thin

intermembrane space. • Inside the inner membrane is a thick fluid called

stroma, which contains the chloroplast DNA, ribosomes, many enzymes, and a network of interconnected sacs called thylakoids, where green chlorophyll molecules trap solar energy.

• In some regions, thylakoids are stacked like poker chips. Each stack is called a granum.


Figure 4.14

Chloroplast

Granum

Stroma

Inner and outer membranes

Thylakoid


4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis

• Mitochondria and chloroplasts contain • DNA and • ribosomes.

• The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells.


4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis

• The endosymbiont theory states that • mitochondria and chloroplasts were formerly small

prokaryotes and • they began living within larger cells.


Figure 4.15Endoplasmic reticulum

Nucleus

Ancestor ofeukaryotic cells (host cell)

Mitochondrion

Engulfing of photosynthetic prokaryote

Mitochondrion

Photosynthetic eukaryote

Chloroplast

Nonphotosynthetic eukaryote

At leastone cell

Engulfing of oxygen- using prokaryote


Figure 4.15-1Endoplasmic reticulum

Nucleus




Nucleus


Mitochondrion





Nucleus


Mitochondrion

Engulfing of photosynthetic prokaryote

Mitochondrion

Photosynthetic eukaryote

Chloroplast


At leastone cell



THE CYTOSKELETON AND CELL SURFACES


4.16 The cell’s internal skeleton helps organize its structure and activities

• Cells contain a network of protein fibers, called the cytoskeleton, which organize the structures and activities of the cell.


Video: Cytoplasmic Streaming



• Microtubules (made of tubulin) • shape and support the cell and • act as tracks along which organelles equipped with

motor proteins move. • In animal cells, microtubules grow out from a region

near the nucleus called the centrosome, which contains a pair of centrioles, each composed of a ring of microtubules.



• Intermediate filaments • are found in the cells of most animals, • reinforce cell shape and anchor some organelles,

and • are often more permanent fixtures in the cell.



• Microfilaments (actin filaments) • support the cell’s shape and • are involved in motility.


Figure 4.16-0

Nucleus

Nucleus

Microtubule

25 nmIntermediate filament

10 nm

Microfilament

7 nm


Figure 4.16-1

Nucleus

Microtubule

25 nm


Figure 4.16-2

Nucleus

Intermediate filament

10 nm


Figure 4.16-3

Microfilament

7 nm


Figure 4.16-4

Nucleus


Figure 4.16-5

Nucleus


Figure 4.16-6


4.17 SCIENTIFIC THINKING: Scientists discovered the cytoskeleton using the tools of biochemistry and microscopy

• 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

• In the 1970s, scientists were able to visualize actin filaments using fluorescent tags and in living cells.

• In the 1980s, biologists were able to record the changing architecture of the cytoskeleton.


Figure 4.17


4.18 Cilia and flagella move when microtubules bend

• The short, numerous appendages that propel protists such as Paramecium are called cilia (singular, cilium).

• Other protists may move using flagella, which are longer than cilia and usually limited to one or a few per cell.

• Some cells of multicellular organisms also have cilia or flagella.


Video: Paramecium Cilia


Video: Chlamydomonas


Figure 4.18a

Cilia


Figure 4.18b

Flagellum



• A flagellum, longer than cilia, propels a cell by an undulating, whiplike motion.

• Cilia work more like the oars of a boat. • Although differences exist, flagella and cilia have a

common structure and mechanism of movement.



• Both flagella and cilia are composed of microtubules wrapped in an extension of the plasma membrane.

• In nearly all eukaryotic cilia and flagella, a ring of nine microtubule doublets surrounds a central pair of microtubules.

• This arrangement is called the 9 + 2 pattern. • The microtubule assembly is anchored in a basal

body with nine microtubule triplets arranged in a ring.


Animation: Cilia and Flagella


Figure 4.18c-0

Outer microtubule doublet

Central microtubules

Cross-linkingproteinsMotor proteins (dyneins)

Plasma membrane


Figure 4.18c-1





Figure 4.18c-2




Plasma membrane



• Cilia and flagella move by bending motor proteins called dynein feet.

• These feet attach to and exert a sliding force on an adjacent doublet.

• This “walking” causes the microtubules to bend.


4.19 The extracellular matrix of animal cells functions in support and regulation

• Animal cells synthesize and secrete an elaborate extracellular matrix (ECM), which

• helps hold cells together in tissues and • protects and supports the plasma membrane.


4.19 The extracellular matrix of animal cells functions in support and regulation

• The ECM may attach to the cell through other glycoproteins that then bind to membrane proteins called integrins.

• Integrins • span the membrane and • attach on the other side to proteins connected to

microfilaments of the cytoskeleton.


Figure 4.19

Collagen fiber

EXTRACELLULAR FLUID

CYTOPLASM

Glycoproteincomplex with long polysaccharide

Connectingglycoprotein

Integrin

Plasma membrane

Microfilaments of cytoskeleton


4.20 Three types of cell junctions are found in animal tissues

• Adjacent cells adhere, interact, and communicate through specialized junctions between them.

• Tight junctions prevent leakage of fluid across a layer of epithelial cells.

• Anchoring junctions fasten cells together into sheets.

• Gap junctions are channels that allow small molecules to flow through protein-lined pores between cells.


Animation: Desmosomes


Animation: Gap Junctions


Animation: Tight Junctions


Figure 4.20

Tight junction

Anchoringjunction

Gap junction

Plasma membranesof adjacent cells

Ions or small molecules Extracellular matrix

Tight junctions prevent fluid from moving across alayer of cells


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 and

• is primarily composed of cellulose. • Plant cells have cell junctions called

plasmodesmata that allow plants tissues to share • water, • nourishment, and • chemical messages.


Figure 4.21

Vacuole

Plant cellwalls

Plasmodesmata

Primary cell wallSecondary cell wallPlasma membrane

Cytosol


4.22 Review: Eukaryotic cell structures can be grouped on the basis of four main functions

• 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.


Table 4-22-0


Table 4-22-1


Table 4-22-2


You should now be able to

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.



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.



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 functions.

13. Compare the structures and functions of tight junctions, anchoring junctions, and gap junctions.



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


Figure 4.UN02


Figure 4.UN03

a. b.c.

d.

e.

f.

g.

h.

i.

j.k.

l.


Figure 4.UN04-0

Poles of dividing cell

Mark


Figure 4.UN04-1

Poles of dividing cell

Mark


Figure 4.UN04-2

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Chapter 4jfalabella.weebly.com/uploads/2/5/2/4/25249222/chapter_4.pdf · Campbell Biology: Concepts & Connections, ... Chapter 4 Lecture by Edward J. Zalisko ... 4.6 Ribosomes make