Seminar 4: Exploring Eukaryotes Flashcards
How did the nucleus originate?
Invaginations of plasma membrane around nucleoid of ancient prokaryote.
what is primary endosymbiosis?
when a eukaryotic cell engulfs a prokaryote, creating new organelles.
describe the process of primary endosymbiosis
- eukaryotic cell engulfs prokaryote via phagocytosis
- vacuole forms around the prokaryote (endosymbiont)
- mutations either in vacuole or bacteria causes vacuole membrane to come apart
- causes endosymbiont to transfer its genetic info to host cell (part of it now)
- more endosymbionts can be made now
what is secondary endosymbiosis
product of primary symbiosis is engulfed by another eukaryotic cell & retained by it
benefits of cell compartmentalisation
- increase efficiency (many processes can occur at same time)
- increase cell specialisation
- able to concentrate metabolites in defined space
what is part of the endomembrane system?
- cell membrane
- nuclear envelope
- ER
- golgi apparatus
- lysosome
function of vesicles
shuttle substances b/w components of endomembrane system
functions of nucleus
- contain most of cells DNA, site of DNA replication
- where gene transcription is turned on/off
- nucleolus: where ribosomes are assembled from RNA & proteins
functions of cytoskeleton
- controls & maintain cell shape
- facilitates cell movement
- maintains intracellular organisation
- interacts w/ extracellular structures
SER function
- chemically modifies small molecules taken in by cell that may be toxic (make them more polar to be easily removed)
- site for glycogen degradation (animals)
- site where lipids & steroids are synthesised (+ some polysacc in plants)
stores calcium ions, trigger cell responses when released
RER function
- prod most membrane bound proteins
- chemically mod & alter protein func, “tag” for delivery in/out of cell
- transport proteins
what occurs in the lumen?
- forms disulfide bridges
- folds into 3D structure
golgi apparatus func
- receives protein (in vesicles) from RER
- mod, concentrates, sorts & packages proteins to their destination
- adds carbs to proteins, mods other carbs attached to them
- synthesis of SOME polysacc in plants
- cuts large precursor proteins from RER > smaller, func, fragments
order of transport from ER
ER>cis-Golgi>medial-Golgi>trans-Golgi>cell membrane OR lysosome
lysosome func
- hydrolyse proteins, polysacc, nucleic acids, lipids via phagocytosis
- contain digestive enzymes
autophagy
programmed destruction of cell components
describe the structure of mitochondria
- smooth outer membrane
- folded inner membrane, cristae (increases SA)
- mitochondrial matrix (enclosed by inner)
desc chloroplast struc
- 2 membranes
- internal membrane: flat, stacks (thylakoid, contain chlorophyll)
peroxisomes function
- accumulate toxic products (hydrogen peroxide)
- break it down without mixing w/ other parts of cell
vacuoles function
- contain pigments for reproduction (flowering plants)
- contain molecules for digestion
- store toxic molecules & waste prod
- give cell its structure
structure of cytoskeleton
- microfilaments
- intermediate filaments
- microtubules
role of microfilaments
- help entire cell/parts of it move
- determine & stabilise cell shape
role of intermediate filaments
- anchor cell structure in place (help maintain position of nucleus & other organelles)
- resist tension, maintains rigidity in body surface tissues (stretch cytoplasm, connect desmosomes)
role of microtubules
- form rigid internal skeleton for some cells
- act as framework, motor proteins move structures w/in cell
