Vesicular Transport Endo and Exocytosis

BIOL3000

Budding and Fusion of Transport vesicles

transport from the Er to the Golgi and from the gold to other compartments

Outwards from the ERR to the

plasma membrane

Inwards from the plasma membrane to

lysosomes

Import material

endocytosis

secrete intracellular material

exocytosis

Vesitcles that bud off from membrane can also have

distinctive protein coat on their cytosolic surface

Donar compartment

which material originates

Target compartment

compartment to which material is carried

Clattering coated vesticles are made of outer coat made up of

protein clathrin

After budding the coat is shed so it can

vesicles to interact with the membrane to which is fuse

Role of clathrin molecules

shaping the membrane into vesicles

role of Adaptins

decide which content will be transported inside the vesicle

role of dynamin

assembles as a ring around the neck of each deeply invaginated coated pit causing it to constrict

adapting captures captures the

cargo receptors and cargo molecules (specific transport signals)

dynamic causes the vesicles to

pinch of from the membrane

steps of vesicular transport

1. sorting or selecting of cargo

2. vesicles movement of vesicles along cytoskeletal elements (microtubules)

3. tethering and docking onto the acceptor compartment membrane

4. vesicle fusions with their acceptor compartment and release of contents

How do transport vesicles find their way to the correct destination to deliver their content

Rab and SNARE proteins

Rab proteins

ensures that the transport vesicles fuses with the correct target membrane

tethering proteins

acts as bridges between transport vesicles and target membrane to ensure correct docking and fusion

v SNARE

vesicles SNARE

t Snare

target snare on the target membrane

Docking

forms a trans snare complex

Secretory Pathways unregulated and constitutive: exo

happens contunousley and newly synthesizes material arrives int rans Golgi networks and package into transport vesicles

regulated exostosis

social types of signals and the material become stored in secortoruy vesicles until a signal is recieved

regulated exocytosis example ithe secretory vesicles stores insulin in a pancreatic B cell but when they is an increase in glue what happens

releases if insulin in the extracellular space in response to an increase in glucose in the blood

3 different forms of endocytosi

pinocytosis, phagocytosis, and receptor mediated

Pinocytosis

‘cellular drinking’, ingestion of fluid and molecules via small vesicles (<150 nm diameter)

Phagocytosis

ngestion of large particles (microorganisms or cell debris) via large vesicles (>250 nm diameter), usually by specialised cells called phagocytic cells.

Receptor mediated

cargo binds to specialised transmembrane proteins called receptors

where are pinocytosis mainly carried out

clathrin-coated pits and vesicles.

Receptor mediated endocytosis of cholesterol

1. LDL particles binds to a particular transmembrane protein, (only bind), and will concentrated the Cathrin coated pits

2. this allows the Cathrin coated vesicle to form and in the lumen of the vesicles, LDL particles are bound to the LDL receptor which is part of the membrane of the Cathrin coated vesicles

3. 3. then the vesicles uncoats and move to endosomes

4. vesicle with fuse with endoscopes and release the content

why does the ldl receptors can no longer binds to LDL and releases it into the endoomes

ph level (low)

what happens after the release and what happens to the LDL particle

it is brought to the lysomes and they contain a lot of hydrolytic enzymes that degrade material and LDL particles are degraded

What happens to the receptors

it is recycled