Organelles

tiny structures with highly specialized functions for the cell that are suspended in the cytoplasm of the cell

Locomotion (motility)

- allows a microorganism to locate nutrients
- move toward positive stimulus
- permits avoidance of harmful substances and stimuli
- locomotion of flagella common in protozoa, algae, few fungal and few animal cells
- cilia only in protozoa and animal cells

Eukaryotic flagella

- function in motility
- larger and more complex than prokaryotes
- long, sheathed cylinder containing microtubules extending along entire length in (9x2)+2 arrangement (same for cilia)
- covered by extension of cell membrane
- 10x thicker than prokaryotic flagella
- anchored by cell basal body (not by a hook like in prokaryotes)

(9x2)+2 arrangement (flagella and cilia)

- 9 pairs of peripheral microtubules and two central microtubules
- universal pattern for eukaryotic flagella and cilia

Microtubules (of flagella)

- long hollow tubes
- extend along entire length of flagella
- made up of tubulin (protein)

Glycocalyx

- outermost boundary comes into direct contact with environment
- usually composed of polysaccharides
- appears as network of fibers, slime layer, or capsule (much like prokaryotes)
- functions in adherence to surfaces in biofilms, receptor and communication functions, protection against environment

1. Eukaryotic cell wall (fungi and algae)

2. Fungi cell wall 

3. Algae cell wall 

1. - rigid and provide structural support and shape; generally simpler than those of prokaryotes -- no peptidoglycan; composed of various polysaccharides and other chemicals

2. composed of chitin (polysaccharide fibers) and mixed glycans

3. varies in chemical composition (cellulose, pectin, mannans, minerals like silicon dioxide, calcium carbonate)

Eukaryotic cell membrane

- structure and function similar to prokaryote
- bilayer of phospholipids and proteins that acts as the outer boundary of a cell
- sterols in some organisms: rigid, confer stability and strength to otherwise fluid membrane (important in cells w/out cell wall)
- serves as selectively permeable barriers in transport
- membrane-bound organelles account for 60-80% of the cell’s endomembrane system

1. Chromatin

2. Chromosomes

3. Nucleolus

1. tightly coiled DNA around proteins; condenses during cell division to form chromosomes 

2. threadlike structures of condensed chromatin that contain genetic material (genes) to be passed from one generation to the next

3. the site for rRNA synthesis and ribosome assembly; located as a dark sphere in the nucleus 

Eukaryotic cell reproduction

- during cell division, chromosomes are extremely coiled and folded into discrete structures -- readily visible
- DNA becomes highly condensed by forming coils and supercoils around histones prevent chromosomes from tangling as they separate in meiosis/mitosis

Endoplasmic reticulum

- part of endomembrane system

- tubular network for storage and transport
- rough vs smooth

Nucleus

- compact sphere, most prominent organelle
- nuclear envelope composed of 2 parallel membranes separated by narrow space and perforated with pores

- contains all of the cell's DNA (chromatin) which is the coded instructions for making proteins for the cell

Rough endoplasmic reticulum 

- originates from outer membrane of nuclear envelope and extends in continuous network through cytoplasm
- studded with ribosomes, proteins synthesized and shunted into lumen (cisternae) of ER for packing/transport (first step of secretory pathway)

Smooth endoplasmic reticulum

- closed tubular network without ribosomes, synthesis and storage
- synthesis and transport of non-protein macromolecules

Golgi apparatus

- modifies, stores, packages proteins
- stack of flattened sacs - cisternae

Transport process

- transitional vesicles from ER with proteins go to Golgi for modification and maturation
- condensing vesicles transport proteins to organelles or secretory proteins to outside of cells
- nucleus-->ribosome-->ER-->transitional vesicles-->Golgi -->condensing vesicles -->secretion

Lysosomes

- vesicles that originate from Golgi
- contain hydrolytic enzymes and reactive oxygen species (ROS) which kill and digest the pathogens.

- involved in intracellular digestion of food particles and protection against invading microbes

Phagosome

- a vesicle formed around a particle engulfed by a phagocyte via phagocytosis

- professional phagocytes: macrophages, neutrophils, and dendritic cells

- have membrane-bound proteins to recruit and fuse with lysosomes to form mature phagolysosomes

Mitochondria

- the site of energy production in all cells
- outer and inner membrane with folds called cristae
- cristae hold enzymes and electron carriers (ETC) of aerobic respiration
- divide independently 
- contain circular DNA and prokaryotic ribosomes

Chloroplasts

- responsible for photosynthesis in plants

Ribosomes

- composed of rRNA and proteins
- scattered in cytoplasm or associated with RER
- larger than prokaryotic ribosomes - 80S
- proteins synthesis
- 60% rRNA, 40% proteins
- 40S (sm) + 60S (lrg) subunits form 80S ribosomes; numerous

Cytoskeleton

- flexible framework of proteins 
- microfilaments and microtubules form network throughout cytoplasm
- involved in movement in cytoplasm, amoeboid movement, transport, and structural support

Fungi

- 100,000 species divided into 2 groups
- macroscopic (mushrooms, puffballs, gill)
- microscopic (molds, yeasts)
- unicellular or filamentous multicellular

Microscopic fungi

- exist in 2 morphologies
1. yeast: round, ovoid shape, asexual reproduction through buds (daughter cell)
2. hyphae: long filamentous fungi/molds
- some exist in either form = DIMORPHIC - characteristic of some pathogenic molds

Fungal nutrition

- all heterotrophic (no chlorophyll, depend on multiple sources)
- majority harmless saprobes living off dead plants and animals
- some are parasites, living on tissues of other organisms
- extremely widespread distribution in many habitats

- mycoses; fungal infections; yeast

- soft, uniform texture and appearance
- reproduce asexually (budding)

Filamentous fungi

- what most fungi are
- mass of hyphae called mycelium
- cottony, hairy or velvet texture
- hyphae may be divided by cross walls (SEPTATE)
- vegetative hyphae - digest and absorb nutrients (bread - stuck into agar/bread = anchoring hyphae)
- reproductive hyphae - produce spores for reproduction 

Fungal reproduction

- primarily through spores formed on reproductive hyphae
- asexual: budding or in conidia/sporangiospores
- sexual: spores formed following fusion of male and female strains and formation of sexual structures

Adverse impact of fungi

- mycoses, allergies, toxin production
- destruction of crops and food storage

Beneficial impact of fungi

- saprobes: decomposers of dead plants and animals
- sources of antibiotics, alcohol, organic acids, vitamins
- used in making foods (bread, cheese) 

Algae

- photosynthetic eukaryotic organisms
- microscopic forms of unicellular, colonial, filamentous
- macroscopic forms of colonial and multicellular
- contain chloroplasts with chlorophyll and other pigments
- cell walls
- may or may not have flagella
- most free-living in fresh and marine water -- PLANKTON
- provides basis of food web in most aquatic habitats
- produce large proportion of atmospheric oxygen
- dinoflagellates can cause red tide and give off toxins that cause food poisoning with neurological symptoms
- classified according to types of pigments and cell wall
- used for cosmetics, food, medical products

Protozoa

- unicellular eukaryotes and share similarities in cell structure, nutrition, life cycle, and biochemistry

- diverse group of 65000 species
- vary in shape; no cell wall
- most harmless, free living in moist habitat
- some are animal parasites and can be spread by insect vectors
- all are heterotrophic and lack chloroplasts
- feed by engulfing other microbes and organic matter
- most have locomotor structures (flagella, cilia, pseudopodia)
- exist as TROPHOZOITE: motile feeding stage
- many can enter into dormant resting stage CYST when conditions are unfavorable for growth and feeding

- all reproduce asexually, mitosis or multiple fission; many also reproduce sexually - CONJUGATION

Entamoeba histolytica

- amoeboid protozoa
- reservoir/source: human/water and food
- "traveler's diarrhea" -- drink bottled water

Giardia lamblia

- flagellated protozoa
- zoonotic/water and fluid
- beavers - avoid drinking from streams with beaver dams
- diarrheal problem - lasts 6 months

Trichomonas vaginalis

- flagellated protozoa
- reservoir/source: human
- causes UTIs and trichomoniasis

Trypanosoma cruzi, Trypanosoma brucei

- pathogenic flagellated protozoa
- hemoflagellates

- trypanosomiasis (sleeping sickness in S.America and Africa)

Entamoeboa histolytica

- infective amoeba
- amebic dysentery; worldwide
- cysts in food, sets up in intestines

Malaria

- Apicomplexan protozoa 
- Plasmodium vivax, P. falciparum, P. malariae
- human/vector-borne
- mosquito bites

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 - diagnose and identify usually by looking at eggs

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/eggs in food; from soil/water; some carried by insect vectors

Helminth classification and identification

- classify according to shape, size, organ development, presence of hooks, suckers or other special structures, mode of reproduction, hosts, appearances of eggs and larvae
- identify by microscope detection of worm, larvae, or eggs

Flatworms

- flat, no definite body cavity; digestive tract is a blind pouch; simple excretory and nervous systems
- cestodes – segmented flat worms (tapeworms)
- trematodes or flukes: flattened, non-segmented worms with sucking mouth parts

Roundworms (nematodes)

- round body form

- complete digestive tract, excretory and nervous systems poorly developed

- protective surface made of cuticle

- spines and hooks on mouth