protists structure and environment Flashcards
protozoan
single celled microscopic animal of a group of phyla of the kingdom protista, such as an amoeba, flagellate, ciliate or sporozoan
definition of a protist
is any eukaryotic organism that is not an animal, plant or fungus. The protists do not form a natural group, or clade, but are often grouped together for convenience, like algae or invertebrates.
microtubules are known as
conserved structures
what are microtubules made up of
alpha and beta tbuln
investigation of alpha tubular phylogeny shows that eukaryotic organisms can be divided into three classes:
1) animal parabasalids, plant-protists, and the diplomonads
role of microtubules
1) cell shape
2) chromosome movement and cell division
3) cell motility (cilia and flagella)
difference between flagella in bacteria and protists
in bacteria: energy from proton pump in membrane
in protists: energy rom ATPase dynein
microfilaments
another cytoskeletal structure
- 7nm in diameter
- polymers of actin
- maintaining and chasing cell shape
6 main groups of protists
Opisthokonts Excavates Archaeplastids Amoebozoa CCTH SAR (stramenopiles, alvolates, rhizaria)
mitochondria in Opisthokonts
flattened cristae
mitochondria in Excavates
mitochondria discoba- lacking ‘classical’ mitochondria
mitochondria in Archeoplastids
plastids
mitochondria in Amoebozoa
mitochondria with irregular cristae
two ways in which protists feed
pinocytosis and phagocytosis
pinocytosis
- the uptake of nutrients present in solution
- characteristic of protists without a differential oral cavity
- unlikely that dissolved nutrients are utilised by free-living protozoans
which organisms rely on diffusive transport of essential compounds across their plasma membrane- pinocytosis
parasitic protists
pinocytosis vesicles
pinosomes
phagocytosis
three strep: food capture, phagosome formation and digestion
organelles required for phagocytosis
cytosome, oral funnel, pharyngeal basket
two types of phagocytosis
filter feeders and gulpers
filter feeders
paramecium and vorticella
two types of gulpers
vegetarians and predators
vegetarian gulpers
Chilodonella and Pseudomicrothorax
predator gulpers
Actinophrys and Homalozoon
filter feeding
suspended particles are concentrated through the actin of flagella or cilia in areas where endocytosis can take place.
how are flagella and cilia useful during filter feeding
direct a current of water to the cell and especially in ciliated towards a filter device
what special organelles allow ‘gulper’ protists to obtain food
extrusomes
extrusomes
membrane bound structures ins one eukaryotes which, under certain conditions, discharge their contents outside of the cell
which the organelles like extrusomes are used to obtain food
toxicysts
toxicysts
toxycysts filemtns carry a poison that can kill other protozoa.
- odd because they eat ciliates which should be able to swim away
process of gulping
- yeast cell taken in
- food vacuole forms around yeast cell
- vacoule becomes acidic
- alkalinity re-established
- waste material expelled
cytopharyngeal baskets
a circle of trichites that reinforces and stiffens the gullet of various predaceous ciliates.
other energy generating mechanisms (not mitochondria)
hydrogenosomes
hydrogenosomes
lack cristae and the TCA cycle
- present in aerobic protists
- metabolism is fermentative
- oxidation of pyruvate
where are hydrogenosomes found
in anaerobic protists
where does energy come from in hydrogenosomes
oxidation of pyruvate
- NO TCA cycle
the eyespots
a photoreceptive organelle which through photoreceptor proteins causes flagellar to move through signal transduction
what can be utilised to direct flagellar
the eyespot
what is a significant problem for ciliates and many freshwater protozoans
they are hypotonic, therefore removal of water crossing the cell membrane by osmosis is a significant problem. one commonly employed mechanism is a contractile vacoule
which organelle is used to remove water from cells
the contractile vacuole
how does the contractile vacuole work
1) canals on the outside of the CV take up water from the cytoplasm
2) water moves from canals to vacuole
3) CV becomes full
4) Pore opens and vacuole contracts
5) contraction of vacuole expels water from the cell
6) empty vacuole
how to protists sense
eyespot
where are eyespots found
in flagellate cells of green algae and other unicellular photosynthetic organisms e.g. euglenids
which protists provide 80% of coral energy needs via photosynthesis
Zooxanthellae- also takes up nutrients released by the coral metabolism such as nitrogen and carbon dioxide
zooxanthellae
symbiont dinoflagellate protists that live within hard or stony coral e.g. Symbiodinium
Zooxanthellae provides….. and the coral provides….
zooxanthellae produces photosynthesis produce and the coral produces CO2 and shelter
bleaching in coral symbiodinium causes
death
why may coral reef bleaching occurs
- change in water temp
- oxygen starvation caused by zooplankton
- increases sedimentation
- bacterial and fungal infection
- changes in salinity
- herbicides
- low tide and UV exposure
- elevated sea levels due to global warming
abundance of protists in marine and terrestrial environments is
a guessing game
colonisation of zooxanthellae by Dino’s
hypothesis: bleached coral can acquire new photosynthetic endosymbionts from their environment
conclusion: corals can recover Symbiodinium zooxanthellae from environment
most abundant protists
- Heteroloboseans
- Gliding Bodonids
- Glissomonads
least abundant protists
- Leptomyxa
- Lopopod transparent testate amoebae
- Apusomonads
dealing with stress: starvation
between cell mechanism.
One cell begins to secrete cAMP in response to starvation. Other cells detect this signal and respond in two ways:
1) the cell over towards the signal
2) the cell secretes more cAMP to boost the signal
modes of multicellularity -within cell mechanism
1) cAMP detection at the cell membrane activates G protein
2) G-protein activation stimulates Adenylate cyclase
3) cAMP diffuses out into medium
4) internal cAMP inactivates the external cAMP receptor
5) a diff G protein stimulates phospholipase C
6) IP3 induces calcium ion release
7) calcium ions act on the cytoskeleton to induce the extension of pseudopodia
why does the cAMP conc show oscillatory behaviour
because the internal cAMP conc inactivates the receptor for external cAMP
best protist predators
- euglena spirogyra
- aserionella formosa
- amoeba proteus
- nitschia sp
- Blepharisma sp
how many genera of Dinoflagellates are bioluminescent
18- majority editing blue-green light
bioluminescence comes from
SCINTILLONS
Scintillons
where bioluminescence comes from. Distributed in the cortical region of the cells as off-shoots of the main vacoule
what regulates scintillions
circadian clock
what is the main enzyme involved in luminescence in dinoflagellates?
Dinoflagellate luciferase
Dinoflagellate luciferase
with luciferin, a chlorophyll derived tetrapyrrole ring acting as a substrate to the light producing reaction
luminescence in dinoflagellates
produced by dinoflagellate luciferase
- 0.1s blue flash
- max 476nm
what causes luminescence in dinoflagellates
a mechanical disturbance
why are CVs needed
in freshwater environments, the conc of solute inside the cell is higher than the side of the cell (outside is hypotonic). Under these conditions waters goes from the outside into the cell. The CV is a protective mechanism that prevents the cells from absorbing too much water and lysing.
the stage in which water flows into the CV is called
DIASTOLE (1-2s)
the contraction of the CV and the expulsion of water out of the cell is called
SYSTOLE
what are the structures attached to the CV called
SPONGIOME
-together called the contractile vacuole complex- CVC
example of where protists come to the resuce
Kneallhazia solenopsae is a pathogenic intracellular microsporidium that infects two invasive fire ant species in N and S america. Gradually introduced from such america to Alabama in 1918
