eukaryotic microbes - cell structure Flashcards
what is a eukaryote?
a eukaryote is any cell or organism that possesses a clearly defined nucleus.
what are eukaryotic microbes?
eukaryotic microbes are largely unicellular organisms.
the cell structure has greater complexity compared to prokaryotes containing a defined membrane bound nucleus and a range of membrane bound cell organelles.
examples of eukaryotic microorganisms.
- fungi
- algae
- protozoans
what are the characteristics of fungi?
fungi lack chlorophyll.
all fungi are heterotrophic, requiring organic food.
most fungi are aerobes, although some like the yeast are facultative anaerobes.
examples of unicellular fungi.
yeasts are unicellular fungi.
examples of multicellular fungi.
all other fungi, including moulds, and macroscopic filamentous fungi like mushrooms are multicellular fungi.
examples of yeast.
saccharomyces cerevisiae
candida albicans.
characteristics of yeast
yeast possess a single nucleus and reproduce either asexually by budding, or sexually by spore formation.
yeast have a bud scar on their cell surface.
what is a bud scar?
a bud scar is a characteristic of asexual reproduction - this happens by budding off a smaller daughter cell.
candida albicans
candida albicans is a common yeast that forms pseudohyphae (chains of cells).
C.albicans is associated with various infections in humans, including vaginal yeast infections oral thrush, and candidiasis of the skin.
characteristics of moulds
moulds may be saprophytic or saprotrophic, this means they feed on dead or decaying organic substances.
what are the cellular components of fungi that are the same as human cells?
- cell wall
- cell membrane
- nucleus
- mitochondria
- vacuoles
- rough & smooth endoplasmic reticulum
- peroxisomes
these are all essential like in human cells.
what is the function of peroxisomes in fungal cells?
involved in cellular lipid homeostasis
invovled in metabolising reactive oxygen
involved in the making of secondary metabolites.
what are the cellular components of fungi that are unique to fungi?
- sporangium
- sexual spores
- hyphae
- wornoin bodies
- chitin
what is sporangium?
sporangium are the asexual spore-producing / spore-bearing structure of the fungi cell.
example of sexual spores.
fungi have sexual spores that are usually named after the organism.
e.g. zygospores which are sexual spores from the species of fungi called the zygomycetes fungi (black bread mould)
zygomycetes fungi
black bread mould
these fungi thrive in soil and dead plant material. they also have an exquisite taste for dung.
hyphae
individual microscopic filaments.
hyphae are used for obtaining food
hyphae are involved in growth at the top of the cell
hyphae branch to form a network of hyphae called a mycellium.
classifications of hyphae
septate
aseptate (Coenocytic)
septate hyphae
divided into cells by internal cell walls called septa
aseptate hyphae (Coenocytic)
large multinucleated cells without a septum
what is the function of woronin bodies?
woronin bodies block septal pores, following damage to hyphae.
woronin bodies protect the hyphae by preventing the extensive loss of cytoplasm.
fungi: cell wall
cell (hypha) is surrounded by a rigid wall
composed primarily of chitin and glucans - these fibres exist in a gel-like matrix within the cell wall.
what is chitin?
chitins are major polysaccharides
chitin is a polymer of N-acetylglucosamine (NAG)
what is glucan?
glucan is a polymer of D-glucose
what is the function of the fungal cell wall?
protection of the yeast cell or hypha
maintains the shape of the yeast cell or hypha
is the interface between the fungus and its environment
involved in communication
attachment to surfaces
acts as a binding site for some enzymes
possess antigenic properties (immune response)
what are algae
algae are aquatic organisms that have the ability to conduct photosynthesis.
algae are photoautotrophic so require light for growth.
algae reproduce by the asexual process binary fission
algae are found in ponds, lakes and streams.
examples of algae
seaweeds, pond scum, algal blooms.
what are the components of an algal cell?
nucleus, nucleolus, golgi apparatus, ribosomes, cell membrane, cell wall, centrioles, cytoplasm, starch vacuole, mitochondrion, flagellum, chloroplast.
what are protozoans?
protozoans are microscopic unicellular organisms existing singly or in colonies, without tissues and organs, having one or more nuclei.
protozoans are classified by their features for movement.
what is trophozoite?
trophozoite is the stage of life where protozoans are feeding
with a macronucleus, a micronucleus, a contractile vacuole, an oral groove, a cytosome, a cytoproct, an anal pore, a food vacuole, and a secretory vacuole.
what is the function of the contractile vacuole?
osmoregulation, found in freshwater protozoans where water regulation is a problem.
what is the function of the secretory vacuole?
contains enzymes
what is the function of the food vacuole?
phagocytic vacuoles used to ingest food by phagocytosis.
protozoan classifications for movement.
- sarcomastigophora
> sarcodina
> mastigophora - ciliophora
- microspora
characteristics of sarcodina
form pseudopodia
characteristics of mastigophora
move by flagella
characteristic of ciliophora
move by cilia
characteristics of microspora
are parasites
have no locomotory organelles.
protozoan locomotory organelles
- flagella > mastigophora
- cilia > cilates
- pseudopodia > sarcodina
protozoan: locomotory organelles - flagella
e.g. trypanosoma
cells may have one or more flagella which are long, thread-like extensions from the cell.
flagella move by spinning, whipping or moving like tentacles.
flagella are embedded in the ectoplasm.
protozoan: locomotory organelles - cilia
e.g. balantidium
short, hair-like structures in large numbers on the cell.
move the cell by an oar-like stroke with a high degree of coordination.
cilia are embedded in the ectoplasm.
protozoan: locomotory organelles - pseudopodia
e.g. rhizopods, entamoeba
are produced by pinching of the cell and extending the cell membrane, which sticks to most surfaces, and the rest of the cell then ‘flows’ into the extension thus the cell moves to the new position.
act as tentacles in movement
used to engulf food in feeding.
