Chapter 5 Eukaryotic Cells and Microorganisms

Chapter 5

Eukaryotic Cells and

Microorganisms

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Early

nucleus

Early

endoplasmic

reticulum

Nuclear

envelope

Early

mitochondria

Ancestral cell

Many protozoa, animals Algae, higher plants

Chloroplast

Cell

wall

Smaller bacterium becomes a

permanent resident of its

Host’ s cytoplasm; it multiplies

and is passed on during cell

division. It utilizes aerobic

metabolism and increases

energy availability for the host.

The larger cell engulfs the

smaller one; smaller one

survives and remains

surrounded by the vacuolar

membrane.

Ancestral eukaryotic cell

develops additional membrane

pouches that become the

endoplasmic reticulum and

Golgi apparatus.

Photosynthetic bacteria

(similar to cyanobacteria)

are also engulfed; they

develop into chloroplasts.

A smaller prokaryotic

cell similar to purple

bacteria that can use

oxygen


A larger prokaryotic

cell such as an

archaea has a flexible

outer envelope and

Mesosomelike

internal membranes to

enclose the nucleoid.

2

The History of Eukaryotes

• They first appeared approximately 2 billion years ago

• Evidence suggests evolution from prokaryotic organisms by symbiosis

• Organelles originated from prokaryotic cells trapped inside them

© Image by D. J. Patterson (provided

by micro*scope http://microscope.mbl.edu)

Ancient Eukaryotes

3

Chloroplasts


© Andrew Knoll

Cell wall

y .

© Andrew Knoll

(a) (b)

4

Eukaryotic Microbes

5

The Eukaryotic Cell

Nuclear

membrane

with pores

Nucleolus

Nucleus

Centrioles*

Microvilli/

Glycocalyx

Rough endoplasmic

reticulum with

ribosomes

Mitochondrion Cell wall*

Cell membrane

Golgi apparatus

Microtubules

Chloroplast*

*Structure not present in all cell types

Smooth

endoplasmic

reticulum

Lysosome

Microfilaments

Flagellum*


Organization of the Eukaryotic Cell

6

Endoplasmic reticulum

Golgi complex

Mitochondria

Chloroplasts

Appendages

Flagella

Cilia

Glycocalyx

Capsules

Slimes

Cell wall

Cell/cytoplasmic membrane

Organelles

Cytoplasmic matrix

External

organelles and

other structures

Boundary of cell

Nuclear envelope

Nucleolus

Chromosomes Nucleus

Internal

organelles and

other contents

Microtubules

Microfilaments Cytoskeleton

Ribosomes

Copyright© The McGraw-Hill Companies, Inc. Permission required for reproduction or display. E

ukary

otic c

ell

7

External Structures • Locomotor appendages: Flagella

• Long, sheathed cylinder containing microtubules in a 9+2 arrangement

• Covered by an extension of the cell membrane

• 10X thicker than prokaryotic flagella

• Function in motility

short

glycocalyx

fringe

ciliary

membrane

singlet

B subfiber

of doublet

outer

dynein

arm

(a)


y .

Courtesy Richard Allen

Cell

Membrane

Courtesy Richard Allen

Microtubules

Cilium

bb

(b)

(c) Whips back and

forth and pushes

in snakelike

pattern

Twiddles

the tip

Lashes, grabs

the substrate,

and pulls

Micronucleus

Oral groove with gullet

Macronucleus

Contractile vacuole


External Structures • Locomotor appendages: Cilia

• Similar in overall structure to flagella, but shorter and more numerous

• Found only on a single group of protozoa and certain animal cells

• Function in motility, feeding, and filtering

8 (a) Power stroke Recovery stroke (b)

9

External Structures • Glycocalyx

– An outermost boundary that comes into direct contact with environment

– Usually composed of polysaccharides

– Appears as a network of fibers, a slime layer or a capsule

– Functions in adherence, protection, and signal reception

– Beneath the glycocalyx

• Fungi and most algae have a thick, rigid cell wall

• Protozoa, a few algae, and all animal cells lack a cell wall and have only a membrane

10

Boundary of the Cell

• Cell wall

– Rigid, provides structural support and shape

– Fungi have thick inner layer of polysaccharide fibers composed of chitin or cellulose and a thin layer of mixed glycans

– Algae – varies in chemical composition; substances commonly found include cellulose, pectin, mannans, silicon dioxide, and calcium carbonate

11

Boundary of the Cell

• Cytoplasmic (cell) membrane

– Typical bilayer of phospholipids and proteins

– Sterols confer stability

– Serves as selectively permeable barrier in transport

– Eukaryotic cells also contain membrane-bound organelles that account for 60-80% of their volume

12

Internal Structures

• Nucleus – Compact sphere, most

prominent organelle of eukaryotic cell

– Nuclear envelope composed of two parallel membranes separated by a narrow space and is perforated with pores

– Contains chromosomes

– Nucleolus – dark area for rRNA synthesis and ribosome assembly

Nuclear

envelope

Endoplasmic reticulum

Nuclear

pore

Nucleolus

Chromatin

(a)

© Don Fawcett/Visuals Unlimited

Nuclear pore

Nucleolus Nuclear envelope

(b)


Nuclear changes during Mitosis

13

Cleavage furrow

Chromatin

Nucleolus

Nuclear envelope

Cell membrane

Cytoplasm

Daughter cells

Interphase

Prophase

Chromosome

Early

metaphase

Spindle fibers

Chromosome

Centromere

Metaphase

Early anaphase

Late anaphase

Early telophase

Telophase

Centrioles

1

2

3

4

5

6

7

8

(resting state prior

to cell division)


14

Internal Structures

• Endoplasmic reticulum – two types:

– Rough endoplasmic reticulum (RER) – originates

from the outer membrane of the nuclear envelope

and extends in a continuous network through

cytoplasm; rough due to ribosomes; proteins

synthesized and shunted into the ER for packaging

and transport; first step in secretory pathway

– Smooth endoplasmic reticulum (SER) – closed

tubular network without ribosomes; functions in

nutrient processing, synthesis, and storage of lipids

Rough endoplasmic reticulum

15

(a)

(b)

(c)

RER membrane

mRN A Ribosome

Protein being

synthesized

Small subunit

Large subunit

Cisterna

Polyribosomes

Polyribosomes

Cisterna

Nuclear envelope

Nuclear pore


16

Internal Structures

• Golgi apparatus

– Modifies, stores, and

packages proteins

– Consists of a stack of

flattened sacs called

cisternae

Transport

vesicles

Endoplasmic

reticulum

Condensing

vesicles Cisternae


17

Internal Structures

• Transport Processes

– Transitional vesicles from the ER containing proteins go to the Golgi apparatus for modification and maturation

– Condensing vesicles transport proteins to organelles or secretory proteins to the outside

nucleus RER Golgi vesicles secretion 17

Ribosome

parts

Cell membrane

Secretory vesicle

Secretion by exocytosis

Nucleus

Rough

endoplasmic

reticulum

Transitional

vesicles

Golgi

apparatus

Condensing

vesicles

Nucleolus


18

Internal Structures • Lysosomes

– Vesicles containing enzymes that originate from Golgi apparatus

– Involved in intracellular digestion of food particles and in protection against invading microbes

• Vacuoles – Membrane bound sacs

containing particles to be digested, excreted, or stored

• Phagosome – vacuole merged with a

lysosome

Food vacuole

Lysosome

Merger of

lysosome

and vacuole

Phagosome

Digestion

Digestive vacuole

Engulfment

of food

Formation of food

vacuole

Golgi apparatus

Food

particle

Lysosomes

Cell membrane

Nucleus


Inner membrane

Circular

DNA strand

Matrix

Cristae

(a) Outer membrane

70S ribosomes

19

Internal Structures • Mitochondria

– Function in energy production

– Consist of an outer membrane and an inner membrane with folds called cristae

– Cristae hold the enzymes and electron carriers of aerobic respiration

– Divide independently of cell

– Contain DNA and prokaryotic ribosomes

Cristae

(darker lines)

Matrix

(lighter spaces)

(b) © Don Fawcett/Visuals Unlimited


20

Internal Structures

• Chloroplast – Convert the energy of

sunlight into chemical energy through photosynthesis

– Found in algae and plant cells

– Outer membrane covers inner membrane folded into sacs, thylakoids, stacked into grana

– Primary producers of organic nutrients for other organisms

70S ribosomes

Circular

DNA strand

Granum Thylakoids

Chloroplast envelope

(double membrane)

Stroma matrix


21

Internal Structures

• Ribosomes

– Composed of rRNA and proteins

– Scattered in cytoplasm or associated with RER

– Larger than prokaryotic ribosomes

– Function in protein synthesis

RER membrane

mRN A Ribosome

Protein being

synthesized

Small subunit

Large subunit

Cisterna


Cell

membrane

Ribosomes

Rough

endoplasmic

reticulum

Microtubule

Microfilaments

Mitochondrion

(a) 22

Internal Structures • Cytoskeleton

– Flexible framework of proteins, microfilaments and

microtubules form network throughout cytoplasm

– Involved in movement of cytoplasm, amoeboid

movement, transport, and structural support

(b)

Courtesy of Life Technologies, Carlsbad, CA


23

Comparing Prokaryotes, Eukaryotes & Viruses

Phylogenetic Relationships between Eukaryotes

24


Naegle

ria

Eugle

na

Zea (corn)

Eukarya

(a)

EV

OL

UT

ION

AR

Y A

DV

AN

CE

ME

NT

OF

TH

E E

UK

AR

YO

TE

S

Animals

True Fungi

(Eumycota)

Plants

Stramenopiles

(formerly

heterokonts

or chrysophytes)

Golden-brown and

yellow-green alga Xanthophytes

Brown algae

Diatoms

Water molds

(Oomycota)

Ciliates

Colponema

Dinoflagellates

Haplosporidia

Apicomplexans

Entamoebids

Amoeboflagellates

Kinetoplastids

Euglenids

Parabasilids ( Trichomonas )

Diplomonads ( Giardia )

Oxymonads

Microsporidia

Metazoa

Myxozoa

Choanoflagellates

Zygomycota

Kingdom Animalia

Kingdom Eumycota

Kingdom Plantae

Kingdom Protista

Division Chlorophyta

Division Rhodophyta

Division Chrysophyta

Division Phaeophyta

Division Bacillariophyta

Division Euglenophyta

Phylum Sarcomastigophora

Phylum Ciliophora

Division Pyrrophyta

Phylum Apicomplexa

Traditional Kingdoms

and Subcategories

Taxonomy Based on mRNA Analysis

Ascomycota

Basidiomycota

Chytridiomycota

(chytrids)

Land plants

Green algae

Cryptomonads

Red algae

Alveolates

Entamoebae

Universal

Ancestor

Lack

mitochondria


(b)

25

Survey of Eukaryotic Microbes

• Fungi

• Algae

• Protozoa

• Parasitic worms

26

Kingdom Fungi • 100,000 species divided into 2 groups:

– Macroscopic fungi (mushrooms, puffballs, gill

fungi)

– Microscopic fungi (molds, yeasts)

– Majority are unicellular or colonial; a few have

cellular specialization

© George Barron, University of Guelph, CANADA


27

Microscopic Fungi • Exist in two morphologies:

– Yeast – round ovoid shape, asexual reproduction

– Hyphae – long filamentous fungi or molds

• Some exist in either form – dimorphic –

characteristic of some pathogenic molds

Septum

© Dr. Judy A. Murphy, San Joaquin Delta College, Department of Microscopy, Stocton, CA Janice Carr/CDC


28

Fungal Nutrition

• All are heterotrophic

• Majority are harmless

saprobes living off dead

plants and animals

• Some are parasites, living

on the tissues of other

organisms, but none are

obligate

– Mycoses – fungal

infections

• Extremely widespread

distribution in many

habitats

(a)

(b)

© Kathy Park Talaro

© New Zealand Dermatological Society


29

Fungal Organization

• Yeast – soft, uniform texture and appearance

– Reproduce through an asexual process called budding

Janice Carr/CDC

Fungal (Yeast) Cell (a)

Ribosomes

Mitochondrion

Endoplasmic

reticulum

Nucleus

Nucleolus

Cell membrane

Golgi apparatus

Cell wall

Storage vacuole

Bud scar Bud


Bud

Nucleus Bud scars

Pseudohypha (c)

(b)

Septa

Septate hyphae

Nucleus

Nuclei Septum with pores

As in Penicillium As in Rhizopus

Nonseptate hyphae


30

Fungal Organization

• Filamentous fungi – mass of hyphae called mycelium; cottony, hairy, or velvety texture – Hyphae may be divided by cross walls – septate

– Vegetative hyphae – digest and absorb nutrients

– Reproductive hyphae – produce spores for reproduction

30

31

Fungal Reproduction

• Primarily through spores formed on reproductive

hyphae

• Asexual reproduction – spores are formed through

budding or mitosis; conidia or sporangiospores

© George Barron, University of Guelph, CANADA

(a) Vegetative Hyphae (b) Reproductive Hyphae

Surface

hyphae

Submerged

hyphae

Hypha

Germ tube

Rhizoids

Spore

Substrate

Spores

(c) Germination


(d)

32

Types of Asexual Mold Spores

Arthrospores Chlamydospores Phialospores

Porospore

Microconidia

Macroconidia

Sporangiophore

Sporangiospore

Columella

Sporangium

1

4 5

1

2

2 3

Conidia Sporangiospore

Sterigma

Conidiophore

Blastospores

(a) (b)


33

Fungal Reproduction

• Sexual reproduction – spores are formed

following fusion of two different strains and

formation of sexual structure

– Zygospores, ascospores, and basidiospores

• Sexual spores and spore-forming structures

are one basis for classification

34

Formation of zygospores

Sporangium

Stolon

Rhizoid

+ Strain

Spores germinate.

Germinating

zygospore

– Strain

Mature zygospore

Zygote

Asexual Phase

Sexual Phase


35

Production of ascospores

Ascospores

Asci

Fruiting

body

Cup fungus

Antheridium (male)

+ Hypha

Ascogonium

(female)

Sterile hyphae

Ascogenous

hyphae

– Hypha


Zygote nuclei

that undergo meiosis

prior to formation

of asci

36

Formation of basidiospores in a mushroom

Pair of nuclei fuse

to form diploid nucleus. Basidium

Portion of gill

covered with

basidia

Cap

Gill

Annulus

Stalk

+ Basidiospore

Button

Basidiospore

Basidium

Diploid nucleus

undergoes meiosis

to produce four

haploid nuclei.

Soil,

plant

litter


– Basidiospore

37

Fungal Classification

Kingdom Eumycota is subdivided into several phyla

based upon the type of sexual reproduction:

1. Phylum Zygomycota – zygospores; mostly

sporangiospores and some conidia

2. Phylum Ascomycota – ascospores; conidia

3. Phylum Basidiomycota – basidiospores; conidia

4. Phylum Chytridomycota – flagellated spores

5. Fungi that produce only Asexual Spores (Imperfect)

Chytrid cells

Diatom cell

10.0 mm

Diversity of Fungi

38

© Kathy Park Talaro © George Barron, University of Guelph, CANADA © George Barron, University of Guelph, CANADA

© Gregory M. Filip © Joyce E. Longcore, University of Maine


39

Fungal Identification

• Isolation on specific media

• Macroscopic and microscopic observation of:

– Asexual spore-forming structures and spores

– Hyphal type

– Colony texture and pigmentation

– Physiological characteristics

– Genetic makeup

40

Roles of Fungi

• Adverse impact – Mycoses, allergies, toxin production

– Destruction of crops and food storages

• Beneficial impact – Decomposers of dead plants and animals

– Sources of antibiotics, alcohol, organic acids, vitamins

– Used in making foods and in genetic studies

41

Human Fungal Infections

42

The Protists

• Algae - eukaryotic

organisms, usually

unicellular and colonial,

that photosynthesize

with chlorophyll a

• Protozoa - unicellular

eukaryotes that lack

tissues and share

similarities in cell

structure, nutrition, life

cycle, and biochemistry


EV

OL

UT

ION

AR

Y A

DV

AN

CE

ME

NT

OF

TH

E E

UK

AR

YO

TE

S

Animals

True Fungi

(Eumycota)

Plants

Stramenopiles

(formerly

heterokonts

or chrysophytes)

Golden-brown and

yellow-green alga Xanthophytes

Brown algae

Diatoms

Water molds

(Oomycota)

Ciliates

Colponema

Dinoflagellates

Haplosporidia

Apicomplexans

Entamoebids

Amoeboflagellates

Kinetoplastids

Euglenids

Parabasilids ( Trichomonas )

Diplomonads ( Giardia )

Oxymonads

Microsporidia

Metazoa

Myxozoa

Choanoflagellates

Zygomycota

Kingdom Animalia

Kingdom Eumycota

Kingdom Plantae

Kingdom Protista

Division Chlorophyta

Division Rhodophyta

Division Chrysophyta

Division Phaeophyta

Division Bacillariophyta

Division Euglenophyta


Phylum Ciliophora

Division Pyrrophyta

Phylum Apicomplexa

Traditional Kingdoms

and Subcategories

Taxonomy Based on mRNA Analysis

Ascomycota

Basidiomycota

Chytridiomycota

(chytrids)

Land plants

Green algae

Cryptomonads

Red algae

Alveolates

Entamoebae

Universal

Ancestor

Lack

mitochondria


43

Algae

• Photosynthetic organisms

• Microscopic forms are

unicellular, colonial,

filamentous

• Macroscopic forms are

colonial and multicellular

• Contain chloroplasts with

chlorophyll and other

pigments

• Cell wall

• May or may not have

flagella

Ribosomes

Flagellum

Cytoplasm

Nucleus

Nucleolus

Golgi

apparatus

Cell membrane

Mitochondrion

Starch vacuoles

Cell wall

Chloroplast

Algal Cell (a)

(b)

© Jan Hinsch/Photo Researchers, Inc


44

Algae

• Most are free-living in fresh and marine water – plankton

• Provide basis of food web in most aquatic habitats

• Produce large proportion of atmospheric O2

• Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms

45

• Classified according to types of pigments and cell wall

• Used for cosmetics, food, and medical products

Algae Classification

46

Protozoa

• Diverse group of 65,000 species

• Vary in shape, lack a cell wall

• Most are unicellular; colonies are rare

• Most are harmless, free-living in a moist habitat

• Some are animal parasites and can be spread by insect vectors

• All are heterotrophic – lack chloroplasts

• Cytoplasm divided into ectoplasm and endoplasm

• Feed by engulfing other microbes and organic matter

47

Protozoa

• Most have locomotor structures – flagella, cilia, or pseudopods

• Exist as trophozoite – motile feeding stage

• Many can enter into a dormant resting stage when conditions are unfavorable for growth and feeding – cyst

• All reproduce asexually, mitosis or multiple fission; many also reproduce sexually – conjugation

Trophozoite

is reactivated.

Trophozoite

(active, feeding stage)

Cell rounds up,

loses motility.

Cyst wall

breaks open.

Mature cyst

(dormant, resting stage)

Early cyst wall

formation


48

Protozoan Identification • Classification is difficult because of diversity

• Simple grouping is based on method of motility, reproduction, and life cycle

1. Mastigophora – primarily flagellar motility, some flagellar and amoeboid; sexual reproduction

2. Sarcodina – primarily amoeba; asexual by fission; most are free-living

3. Ciliophora – cilia; trophozoites and cysts; most are free-living, harmless

4. Apicomplexa – motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic

49

Mastigophora

Protozoan Cell (a)

Cell membrane

Glycocalyx

Ribosomes

Mitochondrion

Endoplasmic

reticulum

Nucleus

Pellicle

Nucleolus

Cell membrane

Golgi apparatus

Water vacuole

Centrioles

Flagellum


(b) Janice Carr/CDC

50

Sarcodina

50

Nucleus

Food vacuoles

Contractile

vacuoles Pseudopods (a) (b)

© David Patterson/MBL/Biological Discovery in Woods Hole

51

Ciliophora

51

(a)

Oral cilia

in groove

Gullet

Food

vacuoles

Macronucleus

Micronucleus

Water

vacuole © Eric Russell, BioMEDIA ASSOCIATES


© Yuuji Tsukii, Protist Information Server

(b)

52

Apicomplexa

52

(a)

Cytostome

(mouth)

Food

vacuole

Endoplasmic

reticulum

Nucleus

Cell membrane

Mitochondrion

Cytostome Food vacuoles Nucleus

(b) Michael Riggs et al, Infection and Immunity, Vol. 62, #5, May 1994, p. 1931

© ASM


Pathogenic Protozoa

53

54

Important Protozoan Pathogens

• Pathogenic flagellates – Trypanosomes –

Trypanosoma

• T. brucei – African sleeping sickness

• T. cruzi – Chaga’s disease; South America

(a) Infective

Trypanosome

(b) Mode of

infection

Cycle in

the Wild

Reduviid

bug

Cycle in

Human

Dwellings


55

Important Protozoan Pathogens

• Infective amoebas – Entamoeba

histolytica – amebic

dysentery; worldwide

55

Cysts in

food, water

(a)

Trophozoites

released

(b)

Large

intestine

site of

infection

Eaten

Food,

water Feces

Cysts exit Mature cysts

Small

intestine

Mature

trophozoites

Stomach

(c)

(d)


56

Parasitic Helminths

• Multicellular animals, organs for reproduction, digestion, movement, protection

• Parasitize host tissues

• Have mouthparts for attachment to or digestion of host tissues

• Most have well-developed sex organs that produce eggs and sperm

• Fertilized eggs go through larval period in or out of host body

57

Major Groups of Parasitic Helminths

1. Flatworms – flat, no definite body cavity;

digestive tract a blind pouch; simple excretory

and nervous systems

• Cestodes (tapeworms)

• Trematodes or flukes, are flattened, nonsegmented

worms with sucking mouthparts

2. Roundworms (nematodes) – round, a

complete digestive tract, a protective surface

cuticle, spines and hooks on mouth; excretory

and nervous systems poorly developed

58

Helminth Classification and

Identification • Classify according to shape, size, organ development,

presence of hooks, suckers, or other special structures, mode

of reproduction, hosts, and appearance of eggs and larvae

• Identify by microscopic detection of worm, larvae, or eggs

Esophagus

Ventral

sucker

Cuticle

Uterus

Testes

(b) (a)

Scolex

Cuticle

Proglottid

Fertile eggs Immature eggs Suckers

Pharynx

Intestine

Vas deferens

Ovary

Seminal

receptacle

Excretory

bladder

Oral sucker


59

Distribution and Importance of

Parasitic Worms

• Approximately 50 species parasitize humans

• Distributed worldwide; some restricted to certain

geographic regions with higher incidence in

tropics

• Acquired through ingestion of larvae or eggs in

food; from soil or water; some are carried by

insect vectors

• Afflict billions of humans

60

Lifecycle of the Pinworm

Cross-

infection

Self-

infection

Fertile

egg

Female Anus

Copulatory

spicule

Male Eggs

Mouth

Cuticle Mouth

Autoinoculation


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Chapter 5 Eukaryotic Cells and Microorganisms

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