Vesicular Transport

Question 1

Vesicular transport explanation

Answer 1

Extends outwards from er to Pm and inward from pm to lysosomes - thus providing routes of communication between the interior of cell and its surroundings
As proteins/lipids are transported outwards along these pathways- many of then undergo various types of chemical modifications ie addition of carbohydrate side chains
- reserved for large molecules - material is unable to cross the plasma membrane even with assistance - too big for channels- no carriers exist
- transported by being wrapped in a membrane- enclosed vesicles
- vt requires energy expenditure by the cell- is an active method of membrane transport- energy to form vesicles/vesicle movement within the cell

Question 2

What are secretory pathways

Answer 2

Is where synthesis and delivery of soluble proteins occur that have been secreted into the extracellular space
Series of steps-
Begins with translation of mRNA is cytosol
Protein enters endoplasmic reticulum lumen
Transferred to Golgi
Exits Golgi in vesicle
Exocytosis at Plasma membrane - secretion

Question 3

Exocytosis

Answer 3

Membrane enclosed vesicle formed within the cell- fuses with the plasma membrane
Then opens its contents ton exterior
Materials packaged for export by endoplasmic reticulum and golgi complex are externalised by Exocytosis

Question 4

Constitutive and regulated Exocytosis

Answer 4

Constitutive- occurs continuously in cell without having to wait for specific signal, secretory materials are released continuously, does not form secretory storage vesicles- important in transporting proteins like receptors that function in pm

Regulated- occurs in response to specific conditions/signals/biochemical triggers
Material is released into secretory vesicles, forms secretory storage vesicles, important in many intracellular signaling

Question 5

Endocytosis

Answer 5

Whereby the plasma membrane surrounds the substance to be ingested and then fuses over the surface- pinching off a membrane enclosed vesicle - engulfed material is entrapped within cell
There are 3 forms- pinocytosis, pagocyosis, receptor mediated endocytosis

Question 6

Phagocytosis

Answer 6

Cell eating- involves ingestion of l;arge particles- ie microorganisms/cell debris- via large vesicles = phagosomes

Question 7

Pinocytosis

Answer 7

Where a cell ingests tiny particles suspended in the ecf by forming an endocytotic vesicle= pinosome
Liquid droplets are ingested with tiny particles
Cell drinking

Question 8

Receptor mediated endocytosis

Answer 8

Clatherin mediated endocytosis - process by which cells absorb metabolites /hormones/proteins
By the inward budding of the pm
Forms vesicles containing the absorbed substance- is strictly mediated by receptors on the surface of the cell
The vesicles membranes are coated in protein clatherin - eich vesicle starts off as a clatherin coated pit
Dynamic assembles as a ring around the neck of each deeply invaginated coated pit-