Module 1 Lecture 9 - Assisted Membrane Transport (Vesicular)

Question 1

Two forms of vesicular active transport

Answer 1

Endocytosis (bringing molecules in) and Exocytosis (releasing molecules)

Question 2

How many forms of Endocytosis are there? What are they called?

Answer 2

Pinocytosis (fluid drinking) , Receptor-mediated endocytosis, phagocytosis

Question 3

How is ATP being used in vesicular transport?

Answer 3

To form the vesicles themselves

Question 4

What does endocytosis have fused to it that exocytosis does not?

Answer 4

Lysosomes (hydrolytic enzymed organelle to destroy contents in the vesicles)

Question 5

How does pinocytosis work?

Answer 5

Non selective uptake of fluids from ECF; Immune cells do macropinocytosis to non-selectively catch a pathogen

Pinocytosis in action

Question 6

How does receptor-mediated endocytosis work?

Answer 6

Receptors bind specfic (selectively) ligands (target molecule) and that forms the endocytotic vesicle. That vesicle has clathrin surrounding the outside of the vesicle

Receptor-Mediated Endocytosis

Helps with insulin, iron, vitamins by insulin for example binding to the receptors which sends a signal to open up Glucose channels to let glucose in

Question 7

What is phagocytosis

Answer 7

Selectively taking in a very large molecule; taking in pathogens or even cellular debris

Phagocytosis can only be done by specialized endocytotic cells

Question 8

Two purposes of Exocytosis

Answer 8

1. Secreting large polar molecules (enzymes and hormones)
2. Adding components to membrane

Does not fuse with lysosome; Golgi apparatus helps with putting proteins in vesicle and exporting them

Question 9

Explain how exocytosis works in detail (golgi lumen to membrane)

Answer 9

1. Proteins have been sorted in the golgi lumen and there are specific recognition markers for a specific protein to attach to
2. Once the vesicle slowly starts to form that specific protein attaches itself to the recognition marker and the vesicle is made
3. Vesicle then goes from golgi to membrane and there is a docking marker (v-snare)
4. Vesicle goes to the membrane and the docking marker in the vesicle attaches itself to the docking-acceptor (t-snare) of the membrane and releases it’s contents

Question 10

What is a v-snare and t-snare

Answer 10

V-snare is the docking marker on the vesicle and t-snare is the docking marker acceptor on the membrane

Question 11

Fact about endocytosis+exocytosis and the plasma membrane

Answer 11

100% of the lipids on the membrane are recycled every hour by endocytosis and exocytosis

Must contain constant cell volume and membrane surface area