Intracellular membrane trafficking

Question 1

What is gated /protein translocation /vesicular transport ?

Answer 1

each transfer is mediated by sorting signals .

Question 2

What does Vesicle budding and fusion maintain ?

Answer 2

Maintain compartmental , topology and integrity

Question 3

What occurs during Exocytosis ?

Answer 3

A transport vesicle fuses with the plasma membrane , its content is released into extracellular space, vesicle membrane becomes continuous with plasma membrane

Question 4

What occurs during endocytosis ?

Answer 4

A plasma membrane patch internalised forming a transport vesicle , its content desires from extracellular space .

Question 5

What is Cargo?

Answer 5

Transport vesicles continually bud off from the membrane and fuse with another carrying membrane components and soluble lumen molecules known as cargo

Question 6

What do vesicles do ?

Answer 6

They carry materials as cargo from lumen and the membrane of donor compartment to membrane and lumen of target compartment.

Question 7

What does Vesicle transport do ?

Answer 7

Perform it functions each transport vesicle buds from compartments must be selective .It makes take up appropriate molecules an fuse with target membrane.

Such as a vesicle carrying cargo to Golgi apparatus example must exclude proteins and only fuse with Golgi apparatus and not others .

Question 8

What are the various types of Coated vesicles ? 3

Answer 8

Clarin Coates
COPI coated
COP11 coated

Question 9

What do vesicles bud from specialised coated regions ?

Answer 9

Have distinctive cage of proteins covering cystolic surface .

Question 10

What are the two main functions of the coat ?

Answer 10

Outer coats layer assembles into a curve . basketball .lattice and deforms the membrane pat cnad thereby shapes vesicles

Question 11

What is the Function of Clarthrin coated vesicles ?

Answer 11

Vesicles transport material from the plasma membrane to the Golgi apparatus

Question 12

What is COPI AND COPII coated vesicles ? Function

Answer 12

Transport materials from ER- Golgi

Question 13

Clarthrin coated vesicles ( the first coasted vesicles to be identified )

Answer 13

Transport material from plasma membrane between endosomal and Golgi compartments

Question 14

What is the major components of clathrin coated vesicles ?

Answer 14

Clathrin itself ,forms outer layer of the coat

Each Clarathin subunits consists of three large three small polypeptide chain that together form a three legged structure called triskelion

Clathrin triskelion dissemble into a basketlike framework of hexagon and pentagons to form buds on cystolic surface of membranes

Question 15

What about under appropriate conditions ,isolated triskelions>?

Answer 15

Spontaneoulsy self assemble into typical polyhedral cages in a test tube ,even in absence of the membrane vesicles that these baskets enclose

Question 16

What is Adaptor proteins function ?

Answer 16

Select cargo into clathrin coated vesicles

Another major coat component in clathrin coated vesicles from discrete inner layer of the coat , positioned between clathrin cage and membrane .

Bind the clathrin coat to membrane /trap variations transmembrane proteins including transmembrane receptor inside vesicles known as cargo receptors

Adaptor proteins select a specific set of transmembrane proteins , together with soluble proteins interact with them , package them into newly formed clathrin coated transport vesicle

Dynamin is one of the examples of adaptor proteins

Question 17

There are several types of adaptor proteins , each specific for cargo receptors ?

Answer 17

Found in other coats , they bind to phosphoinsited which not only have a major role in directing when where coats assemble in the cell , used much widely as molecular makers of compartments help to control ventricular traffic .

Question 18

What is the role of adaptor proteins AP2 ?

Answer 18

AP2 serves as well understood example , when it binds to specific phosphorylated , phosphatidylinositol lipid it alters the conformation , exposing binding sites for cargo receptors /Lipid head group enhancing binding of AP2 to membrane

Acts as a coincidence detector

Upon binding , the induce membrane curvature , makes binding of additional AP2 proteins in proximity

Question 19

Specificity of targeting is mediated through RAB proteins

Answer 19

• Rab proteins are GTPases , each Rab proteins associated with one or more membrane enclosed organelles

Interact with Rab effector on target membrane

Snare proteins dock residues to the target and catalyse the fusion of the two bilayer

Once a V-snare and t -snare have mediated the fusion of a transport residue they dissemble

The dissociations of SNARE complex .
Once a V -SNARE and T-SNARE have mediated the fusion of transport vesicles they disassemble

Crucial to ensure that only appropriate membrane fuse .

Question 20

What are the proteins and their organelle ?

Answer 20

RAB 1 - ER and Golgi complex

RAB 2 - Cis Golgi network

RAB 3A - Synaptic vesicles , secretory residues

RAB 4 - Recyling endosomes

RAB 5 - Early endosomes ,plasma membrane .clarathin coates vesciles

RAB 6 - Medial and trans GOLGI

RAB 7 - Late endosomes

RAB 8 - Cilia

RAB 9 - Late Endosomes trans Golgi