more on the endomembrane Flashcards
extracellular vesicles
(EVs) are membrane-contained vesicles released in an evolutionally conserved manner by cells ranging from organisms such as prokaryotes to higher eukaryotes and plants
where are these extracellular transport vesicles released from
cells
where in the body are extracellular transport vesicle found
body fluids: urine, blood, fluid found around the brain and spinal
2 kinds of extracellular vesicles
micro vesicles and exosomes
role of exosomes and microvesicles
-immunology
-in blood
-central never system
0in bone
role of exosomes and micro vesicles in the blood
stimulation of coagulation, blood vessel formation and thrombosis
role of exosomes and micro vesicles win central nervous system
integration of neurones and various glial cell types, control of synaptic function, neuronal plasticity, neuronal glial communication and myelination
role of exosomes and micro vesicles in bones
modifying enzyme activity
extracellular vesicles can..
spread cancer
how can extracellular vesicles cause cancer
release content to extracellular space, due to the release of RNA and proteins causing a change in expression patterns within the nucleus
micro vesicles (ectosomes) size
500nm-1000nm diameter
microvesicles formation
occurs at donor plasma membrane and contains transfer proteins, mRNA and miRNAs. Uptake occurs via fusion with plasma membrane
exosome size
40-100nm
exosome formation
formed at early endosomes, released from late endosomes. Contain transfer proteins, mRNA and miRNA ( controls protein expression). Uptake via endocytosis or fusion with recipient plasma membrane
what are inside extracellular vesicles
transfer proteins, mRNA and miRNA
exosomes are non cytotoxic and therefore
well tolerated.
transfer of information using extracellular vesicles
RNAs and proteins are derived from donor cells and the exosomes protect their content against degradation and targets specific tissue.
extracellular vesicles can be
purified from blood and other fluids
peroxisomes
single membrane bound organelles that contain many enzymes- major site of oxygen utilisation and involved in lipid metabolism
mamalian peroxisomes contain … diff enzymes and over… peroxins
50 different enzymes and over 20 peroxides that mediate import
detoxification in peroxisomes generates
hydrogen peroxide which is degraded by catalase
hydrogen peroxide is degraded by
catalase
lipid droplets
fat storage droplets–> vary in size and are enclosed by a monolayer
when in starvation mode
the lipid droplet is broken down
where are lipid droplets produced
smooth endoplasmic reticulum
process of forming a lipid droplet
1) fatty acids cholesterol build up in the inner membrane of the SER
2 proteins attach to the outside of this area and a circular organelle is formed
3) Fat-acid-bdining protein (FABP) make gatty acid water soluble (thy shield the fatty acid by binding it in a hydrophobic pocket
FABP
fat-acid binding protein –> used to make fatty acids water soluble –> needed for burning fat
how much of the protein in liver cells do FABP make up
5%
peroxisome genesis
part of the ER forms a precursor vesicle with a few cytosolic proteins and lipid. The growth by uptake of cytosolic proteins and lipid to form a peroxisome. . This will grow and fission will occur to form two peroxisomes
important roles of peroxisomes
biosynthesis of cholesterol and breakdown of very long chain fatty acids (beta-oxidation)
in plants what converts fats to sugar
glyoxysomes found close to lipid droplets
nucleomorph
Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. They are thought to be vestiges of primitive red and green algal nuclei that were engulfed by a larger eukaryote.
where are nucleomorphs found
in some algae
nucleomorph simple
a DNA containing relict of an engulfed eukaryote
definition of cytoskeleton
cytoskeleton consist of filamentous bio-polymers (microtubules, F-actin and intermediate filaments) and oaf associated proteins that modulate the activity, dynamics and organisation of the cytoskeleton (actin binding or microtubule binding proteins, such as molecular motors)
filamentous bio-polymers in the cytoskeleton
microtubules, F-actin, intermediate filaments)
proteins associated with the cytoskeleton
actin binding or microtubule binding proteins, such as molecular motors
eukaryotic cytoskeleton provides
tracks that link the regions of the cell
skeleton
- -> connects all parts of the cell
- -> supports motility
- -> helps spatial organisation
F actin location
found closest to the membrane
microtubules location
spans from the centrosome to the outside of the cell
intermediate filaments
found all around the cell
three classes of filaments that make up the cytoskeleton
f actin, microtubules, intermediate filaments
f actin also known as
microfilaments
F actin
7-9nm –> short range transport and cell migration
Microtubule
25nm –> long range transport and chromosome inheritance (mites, meioses)
intermediate filaments
10nm –> mechanical strength
cytoskeleton as well as proving tracks for intracellular trafficking, also provides..
stability for the cell e.g. extreme example: membrane cytoskeleton of red blood cells make them stiff and strong
structure of F actin
- made up of G actin monomers
- f actin is made up of 2 photo filaments
- actin exists as monomers and polymers
- F actin will release G actin
- cell switches between g and f actin
most actin in the cell is
G actin
how many different actin binding proteins ar known
160
what do actin binding proteins d
they modify actin organisation
actin forms
cellular protrusion
e.g. sterocilia on hair cells in the inner ear
e.g. microvilli on an intestine epithelium
examples of different formations of actin
stabilising, capping, depolymerising, cross-linking, severing, moving, bundling
ordered bundling
microvilli, sterocilia
dynamic crosslinking
stress-fibres and muscle
cross linking
network formation
myosin is used in
actin in a ‘moving’ formation
firkin, alpha-actinic is used in
bundling and stabilising
filamin, spectrum are used in
sequestering/recycling and branching
