Lecture 04 - Eukaryotes
Topics
– Eukaryotes
– External structures
– Internal structures
– Fungi
– Protists
– Helminths
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Some Eukaryotes
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What makes something
eukaryotic?
• External and internal structures are more
complex than prokaryotes
• Lots of membranes to divide things inside
• Examples of eukaryotes
–
–
–
–
–
Yeast
Protozoa
Algae
Helminths
Animal cells
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External Structures
• Appendages
– Flagella
– Cilia
• Glycocalyx
• Cell wall
• Cell membrane
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Eukaryotic Flagella
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Figure 3.31a / b
Eukaryotic Movement - Flagella and Cilia
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Figure 3.32
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A flagellum enables locomotion, and is composed of microtubules,
arranged in a 9 + 2 fashion.
Longitudinal section
Cross section
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microtubules
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Eukaryotic Cilia
•
•
•
Shorter, more numerous
than flagella
Coordinated beating
Also used to move
substances past the
surface of the cell
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More Cilia
Paramecium have
cilia, similar to
flagella but smaller
and more
numerous.
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Glycocalyx
• Complex outer layer
– polysaccharides and network fibers
• Protection
• Adherence
• Reception of signals from other cells
and the environment
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Cell wall
• Chitin
• Glycoprotein
• Mixed glycans
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Cell membrane
• Various sterols within the membrane will
increase rigidity and stability
• Some cells will only possess a
membrane
• Embedded transport proteins
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Glycocalyx , glycan layer, and
membrane.
Boundary structure
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Internal Structures
•
•
•
•
•
•
•
Nucleus
*Endoplasmic reticulum
*Golgi apparatus
Mitochondria
*Chloroplast (photosynthetic cells only)
Ribosomes
Cytoskeleton
* Not covered specifically in this lecture
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Nucleus
• Membrane bound
organelle
• Chromatinchromosomal DNA
• Nucleolus- site for
RNA synthesis
• Histones-proteins
that associate with
DNA during mitosis
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An transmission electron micrograph (TEM) of a nucleus and its
contents
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Organelles cooperate in protein synthesis and transport.
The transport
process
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Lysosomes are
transitional vesicles
containing enzymes for
digestion.
The origin and action of
lysosomes in phagocytosis
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Mitochondria
• Site of energy
generation
• Cristae-folds of the
inner membrane
• Matrix-consist of
ribosomes, DNA,
and enzymes
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Ribosomes
• Associated with
proteins synthesis
• Present in the
cytoplasm and the
surface of the ER
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Cytoskeleton
• Anchor organelles
• Cellular structural
support
• Enable cell shape
changes
• Two types
– Microfilaments
– Microtubules
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Image from: http://www.williamsclass.com/
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Microfilaments allow movement of molecules in the cytoplasm.
Microtubules maintain cell shape and enable molecule movement
within the cell
Model of the cytoskeleton
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Fungi – just everywhere!
• Present in
nature (ex.
mushrooms)
• Medically
important (ex.
athlete’s foot)
• Industrially
important (ex.
fermentation)
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Fungi
• Classification
– Morphology
– Reproduction (asexual and sexual)
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Morphology and Reproduction
• Hyphae cell
– Septate
– nonseptate
• Yeast cells
– Single cells
– Pseudohyphae
• Reproduction
– Asexual and sexual process
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A scanning electron micrograph (SEM) of hyphae cells
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Diplodia maydis, a pathogenic fungus
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SEM of yeast cells, and budding reproductive process .
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Rhizopus, and its stages of hyphae reproduction.
Functional hyphae types.
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Asexual spore formation –
involves mitotic division of a single parental cell
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Types of asexual mold spores
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Sexual spore formation involves the fusion of two parental nuclei
followed by meiosis
Formation of zygospores
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Mushrooms undergo sexual spore formation.
Formation of basidiospores
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Subkingdoms of Fungi
• Amastigomycota (non-flagellated)
– Perfect
(both sexual and asexual stage is known)
[examples: Penicillium sp. (ascomycete), Rhizopus
sp.(zygomycete)]
– Imperfect [Deuteromycetes]
(no sexual stage is known, only asexual)
[example Mycelium sp.]
• Mastigomycota
(spores and gametes are motile, flagellated)
[example Chytridiomycetes sp.]
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Black bread mold is classified as a Amastigomycota (Perfect).
Representative Zygomycete
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Penicillium is another example Amastigomycota (Perfect).
A common Ascomycete
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Mycelium is classified as an Amastigomycota (Imperfect).
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Mycelium and spores of a representative of Deuteromycota
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Fungi can cause superficial and systemic infections.
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There is a table in the book that lists
major
human
fungal infections.
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Protista
• Algae
• Protozoa
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Algae
•
•
•
•
•
Photosynthetic
Inhabitants of fresh and marine waters
Most are not considered human pathogens
Pathogens produce toxins (ex. red tide)
Unique morphology enables identification
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Algae contain chlorophylls, green, yellow, red and brown.
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Representative microscopic algae
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Protozoa
• Complex structure and function
– Ectoplasm and endoplasm
– Pseudopods, flagella, cilia
• Inhabitants of fresh water and soil
– Heterotrophs
• Reproduction (asexual)
– Trophozoite
– Encystment
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Complex structure associated with the protozoa Trichomonas
vaginalis.
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Structure of a typical mastigophoran
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Typical life cycle for protozoa
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Medically important protozoa
• Amoeboid protozoa
– Causes brain infections
• Flagellated protozoa
– Example: Giardiasis
• Apicomplexan protozoa
[organelle called an apical complex]
– Example: Malaria
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Pathogenic amoebas, and nonpathogenic shelled amoebas
Examples of sarcodinians
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Ciliated protozoa, generally free-living and harmless
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Apicomplexia, artist’s rendition-, usually intracellular
parasite. Defined by presence of apical complex (next
slide). Malaria (Plasmodium sp.) is a good example.
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Apical complex
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Cycle of protozoan transmission:
can include the protozoa, host and vectors, often a complex life
cycle.
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Transmission in Schistosoma Micro
sp. infection.
Thanks to CDC.
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Stages of development and transmission amoebic dysentery in the human host.
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Helminths – 3 kinds
• Tapeworms
(Cestodes, “flat”, segments, hermaphroditic)
• Flukes
(Trematodes, “flat”, no segments, some
hermaphroditic, blood flukes are bisexual )
• Roundworms
(Nematodes, cylindrical, bisexual)
Unique structural morphology enables
identification
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Helminths are multicellular animals with organ-like systems.
Fig. 5.34 Parasitic flatwormsMicro for health Sciences
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The pinworm (round) life cycle in the human host.
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Humans serve as a host for the life cycle of many different
parasitic helminths.
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Major helminths of humans and their modes of transmission.
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