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1. Cell Biology > Vesicular Transport > Flashcards

Vesicular Transport Flashcards

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1
Q

How do small molecules travel across the membrane?

A

Water and small molecules enter and leave the cell by passing through the lipid bilayer of the cell membrane by means of passive and active transport

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2
Q

How do large molecules travel across the membrane?

A

Proteins and polysaccharides and larger particles cross the membrane using vesicles

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3
Q

How do the membranes of organelles communicate with each other?

A

They communicate through vesicular transport

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4
Q

What are the two key processes of vesicular transport?

A

Exocytosis

Endocytosis

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5
Q

What is exocytosis?

A

The secretion of macromolecules through fusion of vesicles with the plasma membrane

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6
Q

What is endocytosis?

A

The cell takes in macromolecules by forming new vesicles from the plasma membrane.

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7
Q

How does fusion of vesicles work?

6

A

Budding of a vesicle from donor organelle

Vesicle transported to target organelle in the cytoplasm

Fusion with target

Membrane is transferred

Proteins retain original configuration

Soluble components transferred

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8
Q

Write a note on vesicles.

6

A

They form part of the endomembrane system

They are small membrane-bound sacs

They transport or store substances

Their membrane is made of two layers = lipid bilayer

Can fuse with organelles to release their contents within the cell

Can fuse with plasma membrane and release contents out of cell

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9
Q

List the six types of vesicles.

A

Vacuoles

Lysosomes

Peroxisomes

Endosomes

Transport vesicles

Secretory vesicles

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10
Q

Write a note on how exocytosis works.

5

A

A transport vesicle buds from the golgi apparatus and moves to the plasma membrane

The vesicular membrane and plasma membrane then make contact

The bilayers then re-arrange to allow fusion

Vesicle’s cargo is then released into extracellular fluid

Vesicular membrane then becomes part of the plasma membrane

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11
Q

What are the two types of exocytosis?

A

Constitutive exocytosis

Regulated exocytosis

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12
Q

Explain constitutive exocytosis.

2

A

A steady stream of transport vesicles from trans Golgi to plasma membrane

New lipids and proteins are continuously supplied to the plasma membrane for membrane growth, rejuvenation and remodelling

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13
Q

In constitutive exocytosis, where do the transport vesicles come from?

A

They come from the trans face of the Golgi and they go to the plasma membrane

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14
Q

Why is constitutive exocytosis needed?

A

It is needed for a continuous supply of new lipids and proteins for the plasma membrane

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15
Q

Why does the plasma membrane need new lipids and proteins?

A

It needs them for membrane growth, rejuvenation and modelling

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16
Q

Explain regulated exocytosis.

3

A

This functions only in cells specialised for secretion

Lots of secretory vesicles are found in specialised secretory cells - hormones, mucous, digestive enzyme

An extracellular signal will stimulate their fusion with the plasma membrane and release into the extracellular fluid

17
Q

Explain endocytosis.

3

A

New vesicles are formed by the plasma membrane

It is the reverse process of exocytosis, using different proteins

There are three types of endocytosis

18
Q

How are endocytic vesicles formed?

A

Plasma membrane pinches in to form a vesicle containing extracellular material

19
Q

What are the three types of endocytosis?

A

Phagocytosis

Pinocytosis

Receptor-mediated endocytosis

20
Q

Explain phagocytosis.

A

The engulfment of a particle (usually food or microorganisms), by wrapping cell membrane around it to form a vacuole

21
Q

Explain pinocytosis.

A

The taking in of fluids into small vesicles (Cellular drinking)

22
Q

Explain receptor-mediated endocytosis.

A

Receptors in a receptor-coated pit interact with a specific protein, initiating formation of a vesicle

23
Q

How does a cell carry out phagocytosis?

2

A

A cell engulfs a particle by wrapping pseudopodia around it and packaging it into a membrane enclosed sac

The particle is then digested when the vacuole fuses with a lysosome

24
Q

Explain how pinocytosis works.

2

A

The cell ‘gulps’ droplets of extracellular fluid in tiny vesicles

These pinocytic vesicles are returned to the cell surface after ingestion

25
Q

What is receptor-mediated endocytosis?

A

The selective uptake of specific macromolecules from extracellular fluid

26
Q

How does receptor-mediated endocytosis work?

2

A

Receptor proteins in the membrane are exposed to the extracellular fluid

Extracellular substances bind to the receptor sites on receptor proteins

27
Q

What are extracellular substances also called?

A

Ligands

28
Q

Where are receptor proteins located?

A

They are clustered in parts of the membrane known as ‘coated pits’

29
Q

Give three types of coated vesicles.

A

Clathrin

COP I

COP II

30
Q

What is clathrin?

2

A

A protein comprised of 3 light chains and 3 heavy chains

Its a triskelion

31
Q

What do clathrin coated vesicles do?

A

They traffic between the golgi network and the lysosomes; and between the plasma membrane and the endosomes

32
Q

What is a triskelion?

A

They form a framework of hexagons and pentagons to form coated pits on the membrane surface

33
Q

How is a clathrin coated vesicle formed?

3

A

Molecules bind to surface receptors of the plasma membrane proteins located in areas of clathrin-coated pits

Pits bud to form clathrin-coated vesicles

Fusion with endosomes or lysosomes

34
Q

What are endosomes?

2

A

They appear as a complex set of connected membrane tubes and larger vesicles

It’s the main sorting station in the endocytic pathway

35
Q

What are the two populations of endosomes?

A

Early endosomes

Late endosomes

36
Q

Where are early endosomes found?

A

Beneath plasma membrane

37
Q

Where are late endosomes found?

A

Near the nucleus

38
Q

How do endosomes promote cargo release?

A

Endosomes have acidic environments which promote this

1. Cell Biology (6 decks)

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