Endomembrane + Bulk Transport

Question 1

Define Endomembrane System:

Answer 1

A system interconnected by direct physical contact or transfer by vesicles.

Question 2

Function of the Endomembrane system:

Answer 2

To synthesise, tag and deliver the proteins that are made within the cell.

Question 3

Components of the Endomembrane system:

Answer 3

• nuclear envelope
• er
• golgi
• Vesicles
• Lysosomes
• vacuoles
• plasma memebrane

Question 4

Structual differences between smooth and rough ER:

Answer 4

rER has a rough appearance due to ribosomes

Question 5

Function of sER

Answer 5

Metabolism of carbohydrates
Lipid synthesis for membranes
Detoxification of drugs and poisons
Storage of calcium ions (used as a signal in the cell)
Extensive sER cells are active in these processes
The amount of sER can be increased or decreased to meet demand

Question 6

Function of rER

Answer 6

Rough appearance due to ribosomes
Involved in protein synthesis
Secreted and membrane bound proteins enter the lumen (interior) of the rER
And are processed by the rER and rest of endomenbrane system for realease from the cell or retention on the cell membrane

(Synthesis if cytoplasmic proteins occur in free ribosomes)

Question 7

What is the golgi complex?

Answer 7

A series of membrane sacs and associated vesicles.

Question 8

What does the golgi complex do ( briefly) - polarity?

Answer 8

Receives, modifies, sorts and ships proteins arriving from the rER.

Has polarity:
- Vesicles from endoplasmic reticulum arrive at the cis face
- Processed vesicles leave at the trans face

Question 9

Functions of the Golgi complex:

Answer 9

Glycosylation
Sorting Protiens
Directing vesicle trafficking

Question 10

What is glycosylation?

Answer 10

• Addition or modification of carbohydrates to proteins
• Important for secreted or cell surface protiens
• Golgi also produces many polysaccharides which may also be secreted from the cell

Question 11

How does the Golgi sort proteins?

Answer 11

Adds molecular markers to direct protiens to the correct vesicles before ‘budding’ from the trans face

• E.g: mannose 6-phosphate identifies proteins that will become lysosomal enzymes

Question 12

Hoe does the Golgi direct vesicles trafficking?

Answer 12

• Adds molecular tags to vesicles leaving the trans face to direct them to correct targets
• Such tags are often short proteins exposed on the vesicle surfaces
• Tags direct vesicles to lysosomes, or secretory pathways, or the plasma membrane to add membrane proteins
• Act as docking sites when they reach their target.

Question 13

What is Exocytosis?

Answer 13

Transport of material (glycoproteins) out of the cell or delivers it to the cell surface

Question 14

Two types of exocytosis and what they do

Answer 14

Constitutive exocytosis:
- Releases extracellar matrix proteins
- doesn’t really need a signal - continuos

Regulates exocytosis:
- Releases hormones and neurotransmitters
- usually requires a signal

Question 15

Endcytosis definiton

Answer 15

The cell takes in molecules and particulate matter at the plasma membrane

Question 16

3 types of endocytosis

Answer 16

Phagocytosis:

Pinocytosis:

Receptor mediated endocytosis:

Question 17

How lysosomes help digest “food”

Answer 17

• Phagocytic vacuoles fuse with lysosomes
• Interior of the lysosomes is acidic which is required for the enzymes to be active
• They degrade proteins, lipids, carbohydrates and Nucleic acids and release breakdown products into the cell

Question 18

Lysosomes definition

Answer 18

Membrane bound organelles made by the rER and Golgi body containing hydrolytic enzymes

Question 19

Autophagy

Answer 19

When lysosomes digest and recycle unwanted cellular materials - important for cell health

Question 20

What allows ‘budding to occur in pinocytosis?

Answer 20

Coat protiens

Question 21

Vacuoles definition

Answer 21

Large vesicles derived from the rER and Golgi

(Food vacuoles involved in phagocytosis)

Question 22

What is phagocytosis

Answer 22

Phagocytosis:
- cell ‘eating’, uptake of ‘food’ particles
- forms a phyagocytic vacuole which is digested by the lysosomes - in humans occurs in macrophages

Question 23

What is Pinocytosis?

Answer 23

Pinocytosis:
- cell ‘drinking’, up-take if extracellular fluid containing various solutes such as protien and sugars
- uptake is formed with the aid of a coat protien ( uptake non selective)

Question 24

What is receptor mediated endocytosis

Answer 24

Receptor mediated endocytosis:

• allows the cell to take up bulk quantities of specific substances which may be present at only low concentrations in the extracellular fluid
• receptor proteins are used to selectively capture the required solute

Question 25

Lysosomal digestion

Answer 25

programmed cell death in which cells intentionally die

Question 26

Trafficking ?