1. Eukaryotic Cells and Microorganisms
Chapter 5
Eukaryotic Cells and Microorganisms

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

5. Eukaryotic

7. External Structures Locomotor appendages flagella
long, sheathed cylinder containing microtubules in a 9+2 arrangement in the shaft; and a 9+0 in the basal body
covered by an extension of the cell membrane
10X thicker than prokaryotic flagella
function in motility
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

10. 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

11. External Boundary Structures
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

12. External Boundary Structures
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

13. 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

16. Internal Structures Endoplasmic reticulum – two types:
Rough endoplasmic reticulum (RER)– originates from the outer membrane of the nuclear envelop 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, etc.

18. Internal Structures Golgi apparatus
consists of a stack of flattened sacs called cisternae
closely associated with ER
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

20. Cis face
Trans face

21. Internal Structures Lysosomes
vesicles containing enzymes that originate from Golgi apparatus
involved in intracellular digestion of food particles and in protection against invading microbes

23. Internal Structures Mitochondria
consists 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
function in energy production

25. Internal Structures Chloroplast found in algae and plant cells
outer membrane covers inner membrane folded into sacs, thylakoids, stacked into grana
larger than mitochondria
contain photosynthetic pigments
convert the energy of sunlight into chemical energy through photosynthesis
primary producers of organic nutrients for other organisms

27. Internal Structures Ribosomes composed of rRNA and proteins
40S and 60S subunits form 80S ribosomes
larger than prokaryotic ribosomes
function in protein synthesis

28. 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

32. Survey of Eukaryotic Microorganisms
Fungi
Algae
Protozoa
Parasitic worms

33. 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

34. 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

38. 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
Growth temperature 20o-40oC
Extremely widespread distribution in many habitats

40. Fungal Organization Most grow in loose associations or colonies
Yeast – soft, uniform texture and appearance
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

42. Fungal Reproduction
Primarily through spores formed on reproductive hyphae
Asexual reproduction – spores are formed through budding or mitosis; conidia or sporangiospores
Sexual reproduction – spores are formed following fusion of male and female strains and formation of sexual structure
Sexual spores and spore-forming structures are one basis for classification

48. Fungal Classification
The Fungi kingdom is subdivided into two subkingdoms
Amastigomycota - common inhabitants of terrestrial habitats. Several of them are human pathogens
Mastigomycota - primitive filamentous fungi that live primarily in water and may cause disease in potatoes and grapes

49. Amastigomycota Fungi that produce sexual and asexual spores (perfect)
Zygomycota – zygospores; sporangiospores and some conidia
Ascomycota – ascospores; conidia
Basidiomycota – basidiospores; conidia
Fungi that produce only asexual spores
Deuteromycota – majority are yeasts and molds; no sexual spores known; conidia

53. 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

54. Roles of Fungi Adverse impact Beneficial 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

55. Kingdom Protista
Algae
Protozoa

56. Algae Photosynthetic organisms
Kelps, seaweeds, euglenids, green algae, diatoms, dinoflagellates, brown algae, and red seaweeds
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

57. 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
Classified according to types of pigments and cell wall
Used for cosmetics, food, and medical products

60. Protozoa 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
Feed by engulfing other microbes and organic matter

61. 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

63. Protozoan Identification
Classification is difficult because of diversity
Simple grouping is based on method of motility, reproduction, and life cycle
Mastigophora – primarily flagellar motility, some flagellar and amoeboid; sexual reproduction; cyst and trophozoite
Sarcodina – primarily amoeba; asexual by fission; most are free-living
Ciliophora – cilia; trophozoites and cysts; most are free-living, harmless
Apicomplexa – motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic

65. Note:
Entamoeba histolytica is a parasitic amoeba.

69. Important Protozoan Pathogens
Pathogenic flagellates
Trypanosomes – Trypanosoma
T. brucei – African sleeping sickness (Tse-Tse fly)
T. cruzi – Chaga’s disease; South America
Infective amoebas
Entamoeba histolytica – amoebic dysentery; worldwide

72. 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
Acquired though ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors

73. Major Groups of Parasitic Helminths
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
Roundworms (nematodes)- round, a complete digestive tract, a protective surface cuticle, spines and hooks on mouth; excretory and nervous systems poorly developed

76. 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 adult worm, larvae, or eggs

77. Distribution and Importance of Parasitic Worms
Approximately 50 species parasitize humans
Afflict billions of humans
Distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics