Endomembrane System & Bulk Transport Processes

Question 1

what is the endomembrane system?

Answer 1

a membrane system interconnected by direct physical contact or transfer by vesicles.

Question 2

what does the endomembrane system include?

Answer 2

• nuclear envelope
• endoplasmic reticulum (smooth & rough)
• Golgi apparatus
• vesicles
• lysosomes
• vacuoles
• plasma membrane (made up of phospholipid bilayer)

Question 3

How to move proteins out of the cell?

Answer 3

• synthesize
• tag and package
• deliver

Question 4

How to move proteins out of the cell through synthesise?

Answer 4

• endoplasmic reticulum (ER)

Question 5

How to move proteins out of the cell through tag and package?

Answer 5

• Golgi apparatus

Question 6

How to move proteins out of the cell through deliver?

Answer 6

• vesicles transport protein
• vesicles can fuse with membranes of organelles/the cell

Question 7

what are the two types of ER?

Answer 7

• smooth ER
• rough ER

Question 8

what are the functions of the smooth endoplasmic reticulum (sER)?

Answer 8

• 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 in cells active in these processes
• The amount of sER can be increased or decreased to meet the demand

Question 9

why does rough endoplasmic reticulum appear rough?

Answer 9

because of ribosomes that sit on the surface

Question 10

what are the functions of the Rough Endoplasmic Reticulum (rER)?

Answer 10

• 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 the rest of the endomembrane system for release from the cell or retention on the cell membrane

Question 11

where does the synthesis of cytoplasmic proteins occur?

Answer 11

Synthesis of cytoplasmic proteins occurs on free ribosomes

Question 12

what are the functions of Golgi apparatus?

Answer 12

• Series of membrane sacs and associated vesicles
• Receives, modifies, sorts and ships proteins arriving from the rER

Question 13

how does Golgi apparatus have polarity?

Answer 13

• Vesicles from the endoplasmic reticulum arrive at the cis face
• Processed vesicles leave at the trans face (away from the ER towards the plasma membrane)

Question 14

what happens in the cis face of the Golgi apparatus?

Answer 14

• Vesicles from the endoplasmic reticulum arrive at the cis face
• faces towards the ER - receive vesicles from the endoplasmic reticulum
• modification and sorting happen throughout the Golgi

Question 15

what are the functions of the Golgi apparatus?

Answer 15

• Series of membrane sacs and associated vesicles
• Receives, modifies, sorts, and ships proteins arriving from the rER

Question 16

what functions happen in between the golgi complex?

Answer 16

• glucosylation
• sorting proteins
• directing vesicle trafficking

Question 17

what happens during glucosylation in the Golgi?

Answer 17

• Addition (or modification) of carbohydrates to proteins
• Important for secreted or cell surface proteins
• Golgi also produces many polysaccharides which may
  also, be secreted from the cell e.g. pectin & hemicellulose

Question 18

what happens during sorting protein function in the Golgi?

Answer 18

• Adds molecular markers to direct proteins to the correct vesicles before ”budding” from the trans face

Question 19

what happens during directing vesicle trafficking function in the Golgi?

Answer 19

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

Question 20

what are the different types of vesicles?

Answer 20

Names reflect the function:
- Transport vesicles
- Secretory vesicles
- Vacuoles

Question 21

what is a vesicle?

Answer 21

Membrane-bound (phospholipid bilayer), cytoplasm/fluid-filled organelles

Question 22

what is exocytosis?

Answer 22

• out of the cell - releases stuff we just made and tagged
• Transports material (glycoproteins) out of the cell or delivers it to the cell surface

Question 23

what is exocytosis?

Answer 23

• out of the cell - releases stuff we just made and tagged
• Transports material (glycoproteins) out of the cell or delivers it to the cell surface

Question 24

what are the two different types of exocytosis?

Answer 24

• constitutive exocytosis
• regulated exocytosis

Question 25

what is constitutive exocytosis?

Answer 25

releases extracellular matrix proteins

Question 26

what is regulated exocytosis?

Answer 26

releases hormones and neurotransmitters - signal saying what to do (will make it a short period of time then it'll stop)

Question 27

what is endocytosis?

Answer 27

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

Question 28

what is phagocytosis?

Answer 28

- cell “eating” - uptake of “food” particles - forms a phagocytic vacuole which is “digested” by the lysosomes - in humans, this occurs in macrophages - opens and closes to bring food inside the cell in a vacuole

Question 29

what is pinocytosis?

Answer 29

- Cell “drinking” - up-take of extracellular fluid containing various solutes such as protein and sugars - up-take vesicle is formed with the the aid of a coat protein - up-take is non-selective

Question 30

what is receptor-mediated endocytosis?

Answer 30

- a specialized form of pinocytosis - allows the cell to take up the 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 31

what are lysosomes?

Answer 31

- lysosomes are membrane-bound organelles made by the rER and Golgi body containing hydrolytic enzymes - The interior of a lysosome 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 32

how do we use lysosomes to break down products inside the cell?

Answer 32

- Lysosomes digest and recycle unwanted cellular materials this process is called autophagy and is important for cell health - Lysosomal digestion is also important in programmed cell death in which whole cells “intentionally” die.

Question 33

what happens when there is defects in lysosomal enzymes?

Answer 33

- Defects in lysosomal enzymes can result in lysosomal storage diseases

Question 34

why are vacuoles important in plants?

Answer 34

- can perform lysosome-like functions - large central vacuole absorbs water allowing plant cells to grow without a large increase in cytoplasm - Usually largest compartment in a plant cell

Question 35

food vacuoles are involved in...

Answer 35

phagocytosis

Question 36

what are the different types of endocytosis?

Answer 36

- phagocytosis - pinocytosis - receptor-mediated endocytosis

Question 37

for vesicles to form in pinocytosis what do we need?

Answer 37

coated protein pit

Question 38

what is pinocytosis?

Answer 38

- Cell “drinking” - uptake of extracellular fluid containing various solutes such as protein and sugars - up-take vesicle is formed with the aid of a coat protein - up-take is non-selective

Question 39

what are receptors in terms of proteins?

Answer 39

Receptors are proteins that will detect and bind to molecule/solute of interest

Question 40

what fuses with lysosomes?

Answer 40

Phagocytic vacuoles fuse with lysosomes

Question 41

what is autophagy?

Answer 41

Lysosomes digest and recycle unwanted cellular materials this process is called autophagy and is important for cell health

Question 42

what are vacuoles?

Answer 42

large vesicles derived from the rER and the golgi