Endomembrane system and bulk transport processes

Question 1

what does the membrane system include

Answer 1

1. nuclear envelope
2. endoplasmic reticulum
3. golgi apparatus
4. vesicles
5. lysosomes
6. vacuoles
7. plasma membrane
8. a membrane system interconnected by direct physical contact or transfer by vesicles

Question 2

3 stages on how to move proteins out the cell

Answer 2

1. synthesis
   - endoplasmic reticulum
2. tag and package
   - Golgi apparatus
3. deliver
   - vesicles transport proteins
   - vesicles can fuse with membrane of organelles/cells

Question 3

6 functions of smooth endoplasmic reticulum

Answer 3

1. metabolism of carbohydrates
2. lipid synthesis for membrane
3. detoxification of drugs and poisons
4. storage of calcium ion (used as a signal in the cell)
5. extensive sER in cells in these processes
6. the amount of sER can decrease of be increased to meet demand

Question 4

4 functions of the rough endoplasmic reticulum

Answer 4

1. rough appearance due to ribosomes
2. involved in protein synthesis
3. secreted and membrane-bound proteins enter the lumen (interior) of the rER
4. 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 5

function of free ribosomes

Answer 5

synthesis of cytoplasmic proteins

Question 6

3 characteristics of golgi complex

Answer 6

1. series of membrane sacs and associated vesicles
2. receives, modifies, sorts and ships proteins arriving from the rER
3. has polarity
   - vesicles from the endoplasmic reticulum arrive at the cis face
   - processed vesicles leave at the trans face

Question 7

3 functions of the golgi complex

Answer 7

1. glycosylation
   - the addition (or modification) of carbohydrates to proteins which is important for secreted or cell surface proteins
   - golgi also produces many polysaccharides which may also be secreted from the cell
2. sorting proteins
   - adds molecular markers to direct proteins to the correct vesicles before budding from the trans face
3. directing vesicle trafficking
   - adds molecular tags (short proteins exposed on vesicle surface) to vesicles leaving the trans face to direct them to lysosomes, or secretory pathways or to plasma membrane to add membrane proteins.
   - acts as docking sites when they reach their target

Question 8

what are vesicles

Answer 8

membrane bound, cytoplasm/ fluid filled organelles

Question 9

3 types of vesicles

Answer 9

1. transport vesicles
2. secretory vesicles
3. vacuoles

Question 10

what is exocytosis

Answer 10

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

Question 11

2 types of exocytosis

Answer 11

1. constitutive exocytosis
2. regulated exocytosis

Question 12

what is the constitutive exocytosis

Answer 12

releases extracellular matrix proteins

Question 13

what is regulated exocytosis

Answer 13

releases hormones and neurotransmitter

Question 13

what is endocytosis

Answer 13

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

Question 14

2 types of endocytosis

Answer 14

1. phagocytosis
2. pinocytosis

Question 15

what is phagocytosis

Answer 15

uptake of ‘food’ particles by forming a phagocytic vacuole which is digested by the lysosomes

Question 16

what is pinocytosis

Answer 16

uptake of extracellular fluid containing various solutes such as proteins and sugars by forming a vesicle with the aid of a coat protein - non selective

Question 17

what is receptor medicated endocytosis

Answer 17

a specialised form of pinocytosis which 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 18

what are lysosomes

Answer 18

membrane bound organelles made by rER and golgi body containing hydrolytic enzymes, they have acidic interior which is required for the enzymes to be active

Question 19

3 functions of lysosomes

Answer 19

1. digest and recycle unwanted cellular material (autophagy - self eating)
2. important in programmed cell death - cell intentionally dies due to being damaged
3. degrade proteins, lipids, carbohydrates and nucleic acids, and release broken down products into the cell

Question 20

what are vacuoles

Answer 20

large vesicles that are derived from the rER and golgi

Question 21

3 function of vacuoles in plant cells

Answer 21

1. can preform lysosome-like functions
2. large central vacuole absorbs water allowing plant cells to grow without a large increase in cytoplasm
3. turgor pressure