Eukaryotic Cells and Microorganisms - UPRMacademic.uprm.edu/~lrios/3725/Chapter 4.pdf · The Extraordinary Emergence of Eukaryotic Cells •Mitochondria of eukaryotic cells resembles

Eukaryotic Cells and

Microorganisms

Chapter 4

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

The History of Eukaryotes •Evidence from paleontology indicates the first eukaryotic cells appeared approximately 2 billion years ago •Both prokaryotes and eukaryotes evolved from a precursor cell called the Last Common Ancestor

- this cell was neither prokaryotic nor eukaryotic

- gave rise to both prokaryotic and eukaryotic cells

The Theory of Endosymbiosis

1

2

3 4

5

A Pre-Eukaryotic Cell

Cell would have flexible

membrane.

Smaller Prokaryotic Cell

Nuclear

envelope

Early

endoplasmic

reticulum

Ancestral cell

Early

mitochondria

Photosynthetic bacteria

are also engulfed;

they develop into

chloroplasts.

Chloroplast

The first eukaryotic cells have

emerged.

Algae,

higher plants

Protozoa, fungi,

animals

Smaller prokaryote becomes

established in its host’s

cytoplasm and multiplies;

it can utilize aerobic

metabolism and increase

energy availability for the host.

Ancestral eukaryotic cell

develops extensive membrane

pouches that become the

endoplasmic reticulum and

nuclear envelope.

Larger cell engulfs smaller one;

smaller one survives and begins

an endosymbiotic association.

Early

nucleus


(frog): © Adam Jones/Getty Images (RF); (protozoa): © Melba Photo Agency/PunchStock (RF); (mushroom): © Tinke Hamming/Ingram Publishing (RF);

(algae): © Stephen Durr (RF); (sprout): © Digital Vision (RF)

The Extraordinary Emergence of Eukaryotic Cells •Mitochondria of eukaryotic cells resembles a prokaryotic cell

- contains a circular chromosome

- capable of independent division

- contains prokaryotic ribosomes

- have bacterial membranes that are inhibited by drugs that only affect bacteria

•Chloroplasts likely arose when endosymbiotic cyanobacteria provided their host cells with a built-in feeding mechanism

The History of Eukaryotes (cont’d) •The first primitive eukaryotes were probably single-celled and independent •Cells later began to aggregate and form colonies •Cells became specialized within colonies •Complex organisms later evolved and individual cells lost the ability to survive on their own •Only disease-causing eukaryotes will be discussed in this chapter

- protozoa

- fungi

- helminths

Structure of a Eukaryotic Cell

Prokaryotic Cell


In All Eukaryotes

In Some Eukaryotes

Smooth endoplasmic

reticulum

Rough endoplasmic

reticulum with

ribosomes

Nucleolus

Nucleus

Nuclear

membrane

with pores

Cell membrane

Flagellum Chloroplast Cell wall Glycocalyx Centrioles

Mitochondrion Golgi apparatus Lysosome Actin filaments Microtubule Intermediate

filament

External Structures

Structure Flowchart

Eukaryotic cell

Internal

Boundary of cell

External

Appendages

Flagella

Cilia

Glycocalyx

Capsules

Slimes

Cell wall

Cytoplasmic membrane

Cytoplasm

Nucleus

Organelles

Ribosomes

Cytoskeleton Microtubules

Intermediate filaments

Actin filaments

Chloroplasts

Mitochondria

Golgi apparatus

Endoplasmic reticulum Ribosomes

Lysosomes

Chromosomes

Nucleolus

Nuclear envelope


Appendages for Moving: Flagella •Motility allows microorganisms to move toward nutrients and positive stimuli and away from harmful substances and stimuli

Locomotion via cilia and flagella is common in protozoa, many algae, and a few fungal and animal cells •Eukaryotic vs. prokaryotic flagella

- eukaryotic flagellum is 10x thicker

- covered by an extension of the cell membrane

- a long, sheathed cylinder containing regularly spaced microtubules in a 9+2 arrangement

- microtubules slide past each other creating a whipping motion that requires the expenditure of energy

Appendages for Moving: Cilia

• Cilia are similar in structure to flagella, but are shorter and more numerous

- only found in a single group of protozoa and in certain animal cells

- occur all over the cell surface

- beat in oar-like strokes

- also function as feeding and filtering structures

The Glycocalyx •The outermost layer that comes into direct contact with the environment •Usually composed of polysaccharides and appears as a network of fibers, a slime layer, or a capsule •Functions

- protection

- adherence of cells to surfaces

- reception of signals from other cells and the environment

The Cell Wall •Protozoa and helminths do not have cell walls •Cell walls of fungi

- rigid and provide structural support and shape

- different in chemical composition from prokaryotic cell walls

- thick layer of polysaccharide fibers composed of chitin or cellulose

- thin outer layer of mixed glycans

A Cross-Sectional Views of Fungal Cell Walls

Cell Wall

(b) (a)

Glycocalyx

Mixed glycans

Glycoprotein

Chitin

Cell membrane

Ce

ll w

all


© John J. Cardamone, Jr./Biological Photo Service

The Cytoplasmic Membrane •Typical bilayer of phospholipids in which protein molecules are embedded •Contain sterols of various kinds

- relative rigidity give stability to the membrane

- important in cells that do not have a cell wall •Cytoplasmic membrane serves as a selectively permeable barrier

The Nucleus •Most prominent organelle of eukaryotic cells •Separated from the cytoplasm by the nuclear envelope

- composed of two membranes separated by a narrow space

- perforated with small, regularly spaced pores, formed at sites where the membranes unite

- macromolecules migrate through the pores to the cytoplasm and vice versa

The Nucleus (cont’d)

• Nucleolus - found in the nucleoplasm

- site of RNA synthesis

- collection area for ribosomal subunits

• Chromatin - made of DNA and histone proteins

- genetic material of the cell

The Nucleus

(a) (b) Endoplasmic

reticulum

Nuclear pores

Nuclear

envelope

Nucleolus

Nuclear

pore

Nuclear

envelope Nucleolus Endoplasmic

reticulum

Nucleus


a: © Donald Fawcett/Visuals Unlimited

Endoplasmic Reticulum •A series of microscopic tunnels used in transport and storage •Rough endoplasmic reticulum (RER)

- originates from the outer membrane of the nuclear envelope and extends in a continuous network to the cell membrane

- allows transport materials from the nucleus to the cytoplasm and ultimately to the cell’s exterior

- ribosomes are attached to its membrane surface

- proteins synthesized on the RER are transported into the lumen and held for packaging and transport

Detailed Structure of the Rough Endoplasmic Reticulum

Ribosomes

Nucleus

Rough endoplasmic

reticulum

Protein being

synthesized

RER membrane

Cistern

Large subunit

(of ribosome)

mRNA

Small subunit

(of ribosome)

Polyribosomes

Cistern

(b)

(c) (a)

Nuclear

envelope

Nuclear pore

Endoplasmic Reticulum


© Don W. Fawcett/Photo Researchers

Endoplasmic Reticulum (cont’d) •Smooth endoplasmic reticulum

- closed tubular network without ribosomes

- nutrient processing

- storage of nonprotein macromolecules such as lipids

Golgi Apparatus •Site of protein modification and shipping •Consists of several flattened, disc-shaped sacs called cisternae •Cisternae do not form a continuous network •Always closely associated with the endoplasmic reticulum

- transitional vesicles from the endoplasmic reticulum are picked up at the face of the Golgi apparatus

- proteins are modified within the cisternae by the addition of polysaccharides and lipids

- condensing vesicles pinch off of the Golgi apparatus and are then conveyed to lysosomes or transported outside the cell

Detail of the Golgi Apparatus

Endoplasmic

reticulum

Transitional

vesicles

(b)

(a)

Golgi body

Cisternae

Condensing

vesicles

Golgi Apparatus


The Transport Process


Nucleus

Rough endoplasmic

reticulum Secretory

vesicle

Nucleolus

Golgi

apparatus

Cell membrane

Secretion by

exocytosis

Ribosome

parts

Transitional

vesicles

Condensing

vesicles

Vesicles •Lysosomes

- contain a variety of enzymes involved in the intracellular digestion of food particles and protection against invading microorganisms

- participate in the removal of cell debris and damaged tissue

•Vacuoles

- membrane bound sacs containing fluids or solid particles to be digested, excreted, or stored

- formed in phagocytic cells in response to food and other substances that have been engulfed

- contents of a food vacuole are digested through a merger of a vacuole and a lysosome

The Origin and Action of Lysosomes in Phagocytosis

1

2

3

4 Digestion

Digestive vacuole

Merger of lysosome

and vacuole

Formation of food

vacuole

Mitochondria

Cell membrane

Engulfment of food

Nucleus

Lysosomes

Food particle

Golgi apparatus

Food vacuole

Lysosome

Phagosome


Mitochondria •Generate energy for the cell •Appear as round or elongated particles scattered throughout the cytoplasm •Composed of a smooth, continuous outer membrane •Inner membrane has tubular inner folds called cristae

- hold the enzymes and electron carriers of aerobic respiration

- extracts chemical energy contained in nutrient molecules and stores it as ATP

•Unique organelles

- divide independently of the cell

- contain circular strands of DNA

- have prokaryotic-sized 70S ribosomes

General Structure of a Mitochondrion

Mitochondria

(a) Cristae

(darker lines)

Matrix

(lighter spaces)


© Donald Fawcett/Visuals Unlimited

Outer membrane

(b)

Cristae

Inner membrane Matrix

DNA strand

70S ribosomes

Chloroplasts •Found in algae and plant cells •Capable of converting energy from sunlight into chemical energy through photosynthesis •Produce oxygen gas as a byproduct of photosynthesis •Resemble mitochondria but are larger, contain special pigments, and are more varied in shape

Ribosomes •Numerous, tiny particles that give a “dotted” appearance to the cytoplasm •Distributed throughout the cell

- scattered freely in the cytoplasm and cytoskeleton

- intimately associated with rough endoplasmic reticulum

- inside mitochondria and chloroplasts •Can be found in short chains of polyribosomes •Size and structure

- large and small subunits of ribonucleoprotein

- eukaryotic ribosome is 80S, a combination of 60S and 40S subunits

•Staging areas for protein synthesis

The Cytoskeleton

•A flexible framework of molecules criss-crossing the cytoplasm •Functions

- anchoring organelles

- moving RNA and vesicles

- permitting shape changes

- movement

The Cytoskeleton (cont’d)

•Actin filaments - long, thin protein strands, about 7 nm in diameter

- found throughout the cell, but most highly concentrated just inside the cell membrane

- responsible for cellular movements such as contraction, crawling, pinching, and formation of cellular extensions

The Cytoskeleton (cont’d) •Microtubules

- long hollow tubes

- maintain the shape of eukaryotic cells without cell walls

- transport substances from one part of the cell to another

- spindle fibers play a role in mitosis

•Intermediate filaments

- rope-like structures 10 nm in diameter

- structural support to the cell and organelles

Fluorescence emission intensity from a

culture of Indian Muntjac cells that were

labeled with phalloidin conjugated to Alexa

Fluor 488 for the intracellular actin

cytoskeletal

http://www.microscopyu.com/articles/fluorescence/filtercubes/blue/b2e/b2emu

ntjacactinlarge.html Figure 11.2.1 Human mesenchymal stem cell labeled with CellLight Tubulin-GFP (C10509, C10613) and CellLight Histone 2B-RFP (C10595) reagents

http://www.lifetechnologies.com/pr/en/home/references/molec

ular-probes-the-handbook/probes-for-cytoskeletal-

proteins/probes-for-tubulin-and-other-cytoskeletal-

proteins.reg.us.b2bcmgt.html

Image of a human cell showing microtubules in

green, chromosomes (DNA) in blue, and

kinetochores in pink

http://en.wikipedia.org/wiki/Kinetochore

http://www.lifetechnologies.com/order/catalog/product/C10509

http://www.lifetechnologies.com/order/catalog/product/C10509

http://www.lifetechnologies.com/order/catalog/en/US/adirect/lt?cmd=catProductDetail&entryPoint=adirect&productID=C10613&messageType=catProductDetail




http://en.wikipedia.org/wiki/File:Kinetochore.jpg

A General Comparison of Prokaryotic Cells and Eukaryotic Cells and Viruses

A General Comparison of Prokaryotic and Eukaryotic Cells

The Fungi •Approximately 100,000 species of fungi •Macroscopic fungi: mushrooms, puffballs, gill fungi •Microscopic fungi: molds, yeasts •Forms

- unicellular

- colonial

- complex/multicellular (mushrooms, puffballs)

Fungal Cells •Yeasts

- round to oval shape

- asexual reproduction

- budding •Hyphae

- long, threadlike cells found in the bodies of filamentous fungi

- pseudohypha: chain of yeast cells

•Some fungal cells are considered dimorphic and can take either form depending on growth conditions

Hyphal Structure

(a)

Septum

Septate Hyphae

(b)

Nonseptate Hyphae

as in Rhizopus

(c)

as in Penicillium

Septa

a,b: Courtesy of Dr. Judy A. Murphy, Murphy Consuitancy Microscopy & Digital Imaging, Stockton, CA


Microscopic Morphology of Yeasts

Pseudohypha Bud scars Nucleus

(c)

Bud (b)

(a)

Bud

Bud scar

Fungal (Yeast) Cell

Ribosomes

Mitochondrion

Cell wall

Cell membrane

Endoplasmic reticulum

Nucleus

Nucleolus

Storage vacuole

Golgi apparatus

© David M. Phillips/Visuals Unlimited


Fungi and Human Disease •Primary pathogens: can sicken even healthy persons •Opportunistic pathogens: attack persons who are already weakened in some way •Mycoses (fungal infections) vary in the way the pathogen enters the body and the degree of tissue involvement

Other Harmful Effects Caused by Fungi •Harmless spores can cause opportunistic infections in AIDS patients •Fungal cell walls give off substances that cause allergies •Toxins produced by poisonous mushrooms can cause death •Aspergillus flavus produces a potentially lethal poison to animals who eat contaminated grain •A number of fungal species are pathogenic to field plants •Cause spoilage of fresh produce during shipping and storage

Beneficial Functions of Fungi •Play an essential role in decomposing organic matter •Form stable associations with plant roots and increase their ability to absorb water and nutrients •Fungi have been engineered to produce large quantities of antibiotics, alcohol, organic acids, and vitamins •Some fungi are eaten or used to impart flavoring to food

Fungal Nutrition •Heterotrophic: acquire nutrients from a wide variety of organic substrates •Saprobic: obtain nutrients from the remnants of dead plants and animals in soil or aquatic habitats •Parasitic: grow on the bodies of living animals or plants, although very few require a living host •Fungus penetrates the substrate and secretes enzymes that reduce it to small molecules that can be absorbed by cells •Thrive in nutritionally poor or adverse environments, and those with high salt or sugar content

Morphology of Fungi •Cells of most microscopic fungi grow in loose associations or colonies •Colonies of yeasts are much like bacteria; have a soft, uniform texture and appearance •Colonies of filamentous fungi have a cottony, hairy, or velvety texture

Types of Asexual Mold Spores

Porospore

(5)

(4)

Microconidia

Macroconidia

(2) (3)

Phialospores Blastospores

Chlamydospores

Conidiospores

Arthrospores

(1) (2)

(1)

Sporangiophore

Sporangiospore

Sporangiospores

Sporangium

(a)

(b)


Solar-Powered Sea Slugs. Mollusc/Algal Chloroplast Symbiosis1,2

Mary E. Rumpho * ,1,2,

Elizabeth J. Summer2 and

James R. Manhart3

Plant Physiology May 2000 vol. 123 no. 1 29-38

Elysia chlorotica

http://www.plantphysiol.org/content/123/1/29.full








The Protozoa •Name comes from the Greek for “first animals” •65,000 species of single-celled organisms •Most are harmless, free-living inhabitants of water and soil •A few species of parasites are responsible for hundreds of millions of infections each year

Protozoan Form and Function •Single cells containing all of the major eukaryotic organelles except chloroplasts •Cytoplasm divided into two parts

- ectoplasm: clear outer layer involved in locomotion, feeding, and protection

- endoplasm: granular inner region housing the nucleus, mitochondria, and food and contractile vacuoles

Nutritional and Habitat Range •Heterotrophic, requiring food in a complex organic form •Free-living species scavenge dead plant or animal debris or graze on bacteria and algae •Some species have special feeding structures, such as oral grooves •Some protozoa absorb food directly through the cell membrane •Parasites live on fluids of their host

Nutritional and Habitat Range (cont’d) •Main limiting factor for growth is availability of moisture

- predominant habitats are fresh and marine water, soil, plants, and animals

- can survive in extremes of temperature and pH

- many protozoa can convert to a resistant, dormant stage called a cyst

Life Cycles and Reproduction •Trophozoite: motile feeding stage requiring ample food and moisture to stay active •Cyst

- dormant resting stage when conditions in the environment become unfavorable

- resistant to heat, drying, and chemicals

- can be dispersed by air currents

- important factor in the spread of disease

Life Cycles and Reproduction (cont’d) •Encystment

- trophozoite cell rounds up into a sphere

- ectoplasm secretes a tough, thick cuticle around the cell membrane

1

2

3

5

Mature cyst

(dormant, resting stage)

Cell rounds up,

loses motility Trophozoite

is reactivated

Trophozoite

(active, feeding stage)

Trophozoite

CDC/Dr. Stan Erlandsen

Early cyst

wall formation

4 Cyst wall

breaks open

Cyst


Life Cycles and Reproduction (cont’d) •Some protozoan groups exist only in the trophozoite phase •Many alternate between trophozoite and cyst stage depending on the habitat •Trichomonas vaginalis, a common STD, does not form cysts and must be transmitted by intimate contact •Entamoeba histolytica and Giardia lamblia form cysts and are readily transmitted in contaminated water and food

Life Cycles and Reproduction (cont’d) •All protozoa reproduce by simple, asexual mitotic cell division or multiple fission •Sexual reproduction also occurs in most protozoa

- ciliates participate in conjugation in which two cells fuse and exchange micronuclei

- this results in new and different genetic combinations

Major Pathogenic Protozoa

The Helminths •Include tapeworms, flukes, and roundworms •Adult specimens are usually large enough to be seen with the naked eye •Not all flatworms and roundworms are parasites; many live free in soil and water •Parasitic helminths spend part of their lives in the gastrointestinal tract

The Helminths (cont’d) •Flatworms (Phylum Platyhelminthes)

- also called nematodes

- have a thin, often segmented body plan

- divided into cestodes (tapeworms) and nematodes (flukes)

•Roundworms (Phylum Aschelminthes)

- have an elongated, cylindrical, unsegmented body

Parasitic Flatworms

Suckers

Proglottid

Cuticle

Fertile eggs Immature eggs Excretory

bladder (b)

Testes

Uterus

Cuticle

Ventral

sucker

Esophagus

Oral sucker Pharynx

Intestine

Vas deferens

Ovary

Seminal

receptacle

(a)

Scolex

1 mm

1 cm

(liver fluke): © Arthur Siegelman/Visuals Unlimited; (tape worm): © Carol Geake/Animals Animals


Fasciola hepatica

en higado

Cortesía de Caleb Ruiz-Jiménez, Ph.D. Student, UPR_RCM

Fasciola hepatica

en hígado

Cortesía de Caleb Ruiz-Jiménez, Ph.D. Student, UPR_RCM

Parasitic Roundworm

Mouth

(b)

(a) Anus

Spicules

Cloaca

Seminal

vesicle

Testis

Sperm

duct

Ventral

nerve cord

Excretory

pore

Gut

Lateral

nerve cord

Dorsal

nerve cord

Brain

Pharynx

Cuticle

Pseudocoelom

Centers for Disease Control


General Worm Morphology •Multicellular animals equipped with organs and organ systems •Most developed organs are the reproductive tract •Reduction in the digestive, excretory, nervous, and muscular systems

Life Cycles and Reproduction •Complete life cycle includes the fertilized egg, larval, and adult stages •Adults derive nutrients and reproduce sexually in a host’s body •Nematodes: sexes are separate and different in appearance •Trematodes: sexes can be separate or hermaphroditic •Cestodes: generally hermaphroditic

Life Cycles and Reproduction (cont’d) •Helminth life cycle

- must transmit an infective form (egg or larva) to the body of another host

- the host in which the larva develops is known as the intermediate host

- adulthood and mating occur in the definitive host

•Sources for human infection are contaminated food, soil, and water or infected animals •Routes of infection are by oral intake or penetration of unbroken skin

Examples of Helminths and Their Modes of Transmission

The Life Cycle of the Pinworm

A n u s

Eggs transferred

to new host

(cross-infection).

Scratching

contaminates

hands.

Eggs emerge

from anus.

Swallowed

(self-infection) Copulatory

spicule

Fertile

egg

Female

Mouth

Cuticle

Mouth

Eggs Male


Documents

Eukaryotic Cells and Microorganisms - UPRMacademic.uprm.edu/~lrios/3725/Chapter 4.pdf · The Extraordinary Emergence of Eukaryotic Cells •Mitochondria of eukaryotic cells resembles