1.5 Eukaryotes

eukaryote

cell with a defined nucleus and organelles

• fungi and parasites (protozoa and helminths)

• can be unicellular or multicellular

protozoa cellularity

unicellular

fungi

either

helminths

multicellular

Flagella

motility— thicker and more structurally complex than bacterial flagella. Covered by an extension of cell membrane (protozona

Cilia

motility- shorter and more numerous than flagella. Beat in coordination

cell wall

present on fungi, protozoa and helminths do not (parasites need flexibility to function as a worm so they dont have a cell wall)

• gives structure and shape

• inner layer of chitin or cellulose, outer layer of glycans (no peptidoglycan)

cell membrane

phospholipid bilayer (semi permeable)

• intermixed with cholesterol to give the membrane structure

nucleus

nuclear envelope and chromatin (linear DNA wound around histones to form chromosomes)

Lysosome

contains variety of enzymes that break down food

mitochondria

generates energy (ATP) for the cell

types of fungi

yeasts- round/oval shape, asexual reproduction

hyphae (mold)- long, threadlike cells

dimorphic

some fungi are dimorphic and can transition between forms depending on the growth conditions

• medically important fungi- yeasts at body temperature and hyphae at room temperature

saprobes

most fungi are saprobes and obtain nutrients from dead plants and animals

parasite

some fungi are parasites and live in/on the body of a living host

colonies

growth of fungi in associations

• appear soft, hairy, velvety

mycelium

the intertwining mass of hyphae that makes a colony

septate hyphae

segmented branches with breaks

non-septate hyphae

continuous cell without breaks

vegetive hyphae

growth phase, absorb nutrients from substrate (like roots)

reproductive hyphae

branches from vegetive hyphae, forms fungal reproductive bodies called spores

Protozoa

diverse and not necessarily genetically related, but they share similar physical characteristics

form and function of protozoa

• move through fluid with pseudopods, flagella, cilia

• no cell wall

cyst

dormant, resting stage that occurs when environment changes

helminths

flatworms- cestodes, trematodes

round worms-

cestodes

long, ribbonlike arrangements (tapeworm)

trematodes

flat, ovoid bodies

life stages of helminths

fertilized egg (infect humans), larval (infect humans), adult (pathogenesis occurs)

intermediate (secondary) host

host in which larval development occurs

definitive (final) host

host in which adulthood and mating occur