ANAT 262 Lecture Notes - Transferrin Receptor, Epidermal Growth Factor Receptor, Ldl Receptor

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plumcod665

21 Aug 2012

School

McGill University

Department

Anatomy & Cell Biology

Course

ANAT 262

Professor

John Presley

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Document Summary

Most of the membrane is recycled back to the surface, and what is inside of the early endosome goes onto the multi-vesicular body (late endosome) and then to the lysosome Clathrin is a major way of budding at the cell surface. Excess membranes containing lipids and receptors are recycled back to the surface (recycling of receptors is really efficient) Clathrin is made of a heavy chain and a light chain, adaptor proteins bind to the cargo and to the clathrin. In the picture below receptors are blue, ligands are red, adaptors are light green. Main adaptor protein on the surface is ap2 which does not require binding to arf. A number of alternate adaptors can work like ap2 this is an ldl particle, it is mostly made of cholesterol esters surrounded by a phospholipid monolayer (size varies) - bigger ldl is better. Then this will bind to a ldl receptor and get exocytosed. 1960 - calthrin was discovered by em.

Related Questions

Answer true or false for the following

a. NSF unwinds the v-SNARE/t-SNARE complex to allow membrane fusion during docking

b. Clathrin forms âcagesâ on vesicles that originate from plasma membrane.

c. Clathrin binds to adaptor proteins that link clathrin to membrane proteins.

d. Clathrin vesicles are used for endocytosis â bringing material across the plasma membrane and often delivering it to the early endosome

e. Clathrin mediates the fusion of the vesicles with early endosomes

f. Coated pits are formed from not wearing antiperspirant.

g. Rab (small GTPases) bound with GTP is critical for proper tethering of a vesicle/target organelle pair

h. Clathrin exhibits quaternary structure, defined by the assembly of three heavy chains and three light chains to form a triskelion

i. Compare to other filaments, only intermediate filaments have intrinsic ability to assembly and require no nucleation or assembly proteins

Cholesterol is transported in the bloodstream in lipoproteinparticles. There are several classes of lipoprotein particles, butone of the most important classes is called Low-densitylipoproteins (LDL). LDL particles are composed of a single moleculeof a large protein called apolipoprotein, as well as thousands ofcholesterols molecules and phospholipids. Part of theapolipoprotein forms the surface of the particles and faces theaqueous phase, while other parts face the hydrophobic interior ofthe particle where they interact with cholesterol and thehydrophobic tails of the phospholipids. When cells need additionalcholesterol, they produce a receptor protein on the surface oftheir plasma membrane that binds to the apolipoprotein andinitiates the uptake of LDL particles into the cell via a processcalled endocytosis.

1. What is the likely reason that LDL particles are used totransport cholesterol in the blood stream?

a. Cholesterol in LDL particles easily inserts into lipidbilayers

b. Cholesterol id largely insoluble in aqueous solutions

c. Cholesterol is synthesized within LDL particles

d. LDL particles can form lipid rafts in the lipid bilayer

2. What is the most likely location of phospholipids in LDLparticles?

a. Bound to the hydrophilic domain of apolipoprotein

b. In the lipid bilayer that surrounds LDL particles

c. On the surface interacting with the aqueous environment aswell as interacting with the hydrophobic core of the particle

d. Within the hydrophobic core of the particle

3. What best describes the class of protein that apolipoproteinbelongs to?

a. Amphipathic proteins

b. Cell surface proteins

c. Membrane associated protein

d. Multipass membrane proteins

4. What kind of molecule on the surface of the cell would bemost likely to serve as a receptor for LDL particles?

a. a cholesterol binding protein

b. a glycolipid

c. a phospholipid

d. trans membrane protein

5. What conditions would be most likely to trigger increaseduptake of LDL particles by cells?

a. increased glycolipid synthesis

b. increased plasma membrane growth

c. increased protein secretion

d. increase protein synthesis

1) Which of the following statements about transport into the mitochondria is FALSE?

a) The signal sequence on proteins destined for the mitochondria is recognized by a receptor protein in the outer membrane of the mitochondria.

b) Proteins that are transported into the mitochondria are unfolded as they are being transported.

c) Transport of proteins into the mitochondria requires SRP and the SRP receptor.

d) After a protein is made in the cytosol it must move through two protein translocators to reach the inner mitochondrial matrix.

2.Which coat protein is involved in vesicle formation during endocytosis â vesicle forms from plasma membrane and fuses with endosomes?

a) COPI
b) COPII

c) v-SNARES d) Clathrin

3. Which of the following statements about vesicular membrane fusion is TRUE?

a) Membrane fusion does not always immediately follow vesicle docking.

b) The interactions of the v-SNAREs and t-SNAREs pull the vesicle membrane and the target organelle together so that their lipids can intermix.

c) NSF and SNAP disassemble the SNARE complex so the SNAREs can be recycled.

d) All of the above are true.

ANAT 262 Lecture Notes - Transferrin Receptor, Epidermal Growth Factor Receptor, Ldl Receptor

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