lecture 5 - endomembrane system

Question 1

How is the endomembrane system interconnected?

Answer 1

By vesicles which move between the organelles

Question 2

What are the key organelles of the endomembrane system?

Answer 2

Nuclear envelope, endoplasmic reticulum (smooth and rough), golgi apparatus, vesicles, lysosome, vacuoles, plasma membrane

Question 3

What is the structure of the endoplasmic reticulum (ER)

Answer 3

A series of flattened sacs, connected by tubules, and divided into two regions (smooth and rough).

Question 4

What are the spaces within the ER?

Answer 4

lumen

Question 5

What are the key functions of the smooth ER?

Answer 5

Metabolises carbohydrates, synthesise lipids for membranes, detoxificate toxins, store calcium ions.

Question 6

Is the amount of sER in a cell fixed?

Answer 6

No - it can change to fit cell function requirements.

Question 7

Does the sER contain ribosomes?

Answer 7

No

Question 8

Why does the rER have a rough appearance?

Answer 8

It has ribosomes.

Question 9

What is the function of ribosomes?

Answer 9

They synthesise proteins in the rER

Question 10

Where are proteins processed in the rER?

Answer 10

In the lumen

Question 11

Where does synthesis of cytoplasmic proteins occur?

Answer 11

The free ribosomes

Question 12

How do proteins leave the ER?

Answer 12

In vesicles that ‘bud off’ the surface of the ER.

Question 13

What is the main function of the golgi?

Answer 13

Receive, sort and distribute proteins from the rER.

Question 14

What are the two faces of the golgi?

Answer 14

Cis and trans face

Question 15

What part of the golgi do vesicles arrive at?

Answer 15

The cis face

Question 16

Where do processed vesicles leave the golgi?

Answer 16

The trans face

Question 17

What is glycosylation, and where does it occur?

Answer 17

Addition of carbohydrates to, or modification of, proteins, in the golgi

Question 18

What do golgi produce?

Answer 18

Polysaccharides

Question 19

How does the golgi sort proteins?

Answer 19

By adding markers to the proteins that direct them to the appropriate vesicles for transport.

Question 20

How does the golgi direct leaving vesicles?

Answer 20

Vesicles leaving the trans face are tagged with short proteins that direct them to the targets, and act as ‘docking sites’ when they get there.

Question 21

What is bulk transport?

Answer 21

A process that allows lots of substance to pass through the cell membrane, in one place, at the same time

Question 22

What is exocytosis?

Answer 22

The process of transporting glycoproteins out of the cell into the extracellular matrix via vesicles.

Question 23

What is constituitive exocystosis?

Answer 23

A continuous default process, where proteins are transported to the extracellular matrix.

Question 24

What is regulated exocytosis?

Answer 24

The release of hormones and neurotransmitters from the cell, only when the required signal is received.

Question 25

What is endocytosis?

Answer 25

The transport (in bulk) of molecules and particles into the cell from the extracellular matrix.

Question 26

What is phagocytosis?

Answer 26

The process in which food vacuoles absorb and break down food or bacteria particles with the aid of lysosomes.

Question 27

Where does phagocytosis occur commonly in humans?

Answer 27

In macrophages, a type of white blood cell, which attacks bacteria.

Question 28

How do macrophages kill bacteria?

Answer 28

They engulf detected bacteria (which release proteins that attract macrophages), trap them in the phagosome, and break them down using enzymes from lysosomes.

Question 29

What is pinocytosis?

Answer 29

The process in which vesicles ‘drink up’ extracellular fluid, and take with it various solutes into the cell.

Question 30

What is the function of the coat protein in pinocytosis?

Answer 30

Aids in the formation of the up-take vesicle

Question 31

Why is pinocytosis non-selective?

Answer 31

Any solutes dissolved in the extracellular fluid captured will be brought into the cell.

Question 32

What is receptor-mediated endocytosis?

Answer 32

A specialised form of pinocytosis, in which receptors in vasicles bind to and capture specific solutes from the extracellular fluid and bring them into the cell.

Question 33

Where are lysosomes made?

Answer 33

The rER. (rough endoplasmic reticulum) and golgi body. rER makes proteins that create the lysosome enzymes. These enzymes are then enclosed by vesicles from the golgi complex

Question 34

How do lysosomes aid food vacuoles?

Answer 34

They fuse with the vacuoles, passing on their digestive enzymes.

Question 35

What feature of the lysosome keeps the enzymes active?

Answer 35

Acidic interior

Question 36

What is autophagy?

Answer 36

When lysosomes digest and recycle unwanted cellular material.

Question 37

How is programmed cell death facilitiated?

Answer 37

Through lysosomal digestion of organelles.

Question 38

Where are vacuoles derived from?

Answer 38

the rER and golgi. ( in plants, the vacuole is formed when vesicles from the rER and golgi merge together)

Question 39

What is the function of the central vacuole in plant cells?

Answer 39

The perform lysosome-like fucntion and are able to absorb water to allow the cell to grow without the need for a large increase in the amount of cytoplasm.

Question 40

What is the size of a ribosome?

Answer 40

25-30nm

Question 41

What are the enzymes used by lysosomes?

Answer 41

Hydrolytic enzymes

Question 42

How are phospholipids delivered to the cell membrane?

Answer 42

Via exocytosis