Vesicular Targeting, Lysosomes & Endosomes (15)

Question 1

what facilitates movement of vesicles?

Answer 1

microtubules & motor PROs

Question 2

when does the vesicle attach to motor PROs?

Answer 2

when the coat is shed, there is a PRO on the vesicle enabling motor PRO attachment

Question 3

Rab PRO

Answer 3

integral membrane PRO

GTP binding PRO

direct vesicles to where they need to go in the cell & then tethering PROs attach to Rabs bringing them closer to the target membrane

Question 4

T-SNARE

Answer 4

located on the receiving/target membrane (diff ones on diff target membranes)

Question 5

V-SNARE

Answer 5

located on the vesicle, type of V-SNARE is determined by the type of COP PRO on the vesicle

Question 6

SNARE PROs

Answer 6

family of diff PROs each with a diff location/target

Question 7

when are V-SNAREs incorporated in the vesicle?

Answer 7

incorporated in the membrane during budding

Question 8

docking

Answer 8

T-SNARE on the receiving membrane has an affinity for the V-SNAREon the vesicle

Question 9

how do vesicles fuse with their target membranes?

Answer 9

SNARE PROs intertwine & pull membranes together allowing them to fuse

Question 10

nerve cells membrane fusion

Answer 10

nerve cells releasing neurotransmitters synaptic vesicle dock to presynaptic membrane in nerve cells

vesicles are dumped & fuse with postsynaptic membrane (neuron, muscle etc.)

Question 11

what happens to SNARES once the vesicle has fused?

Answer 11

recycled through interactions with COP I

Question 12

when do V & T SNARES interact?

Answer 12

during tethering

Question 13

what do lysosomes breakdown?

Answer 13

organic substances: 
	NAs
	PROs
	GAGs (glycosaminoglycans) 
	Glycogen
	Oligosaccharides 
	Sphingolipids 
	Phospholipids 
	Triglycerides

Question 14

what happens to the compounds that lysosomes breakdown?

Answer 14

various transporters dump subunits into the cytoplasm to be reused

Question 15

PROs (enzymes) destined for the lysosome are tagged with ____

Answer 15

phosphorylated mannose (6) residues

Question 16

what is the role of clathrin?

Answer 16

Coat PRO, clathrin facilitates the vesicles budding from the Golgi which then travel to a phagosome or other vesicle, clathrin will shed facilitating fusion (primary lysosome)

Question 17

primary lysosome

Answer 17

Non-functional lysosome, enzymes haven’t been activated

Question 18

secondary lysosome

Answer 18

enzymes are activated & are capable of hydrolysis

Question 19

what does the lysosomal membrane contain?

Answer 19

Proton pump maintaining the pH inside by pumping protons inside

2 groups of acidic, highly glycosylated PROs line the interior protecting the inner lining from the enclosed enzymes

Question 20

When do lysosomal enzymes have optimal activity?

Answer 20

at an acidic pH

Question 21

heterophagy

Answer 21

degradation of foreign material brought into the cell by phagocytosis

Primary lysosome fuses with the phagosome & digests the contents

Introduce the enzymes converting it into a secondary lysosome

Question 22

what are purposes of heterophagy?

Answer 22

nutrition: products move into the cytoplasm
defense: microorganisms are killed

Question 23

what type of cell acts as a defense mechanism in heterophagy?

Answer 23

white blood cells destroying microbes

Question 24

phagolysosome

Answer 24

lysosome + phagosome

Question 25

autophagy

Answer 25

digestion of intracellular components that have damage or no longer needed Isolation envelope forms around components, fuses with primary lysosome, dump enzymes, lower the pH & contents are degraded

Question 26

autophagolysosome

Answer 26

lysosome + autophagic vacuole

Question 27

autolysis

Answer 27

rupture of lysosome within cytoplasm kills the cell

Question 28

when does autolysis occur?

Answer 28

when infection cannot be resolved programmed cell death during development, ex: selective removal of cells removing webbing b/w fingers & toes

Question 29

extracellular digestion

Answer 29

lysosomes may discharge their enzymes to the outside of a cell by exocytosis

Question 30

when does extracellular digestion occur?

Answer 30

acrosome in sperm fertilization sperm will hit the egg, release lyssomes with digestive enzymes allowing the sperm to enter the egg & fuse with the membrane& fertilize

Question 31

how do phagocytosed bacteria escape destruction?

Answer 31

Fusion of primary & phagosome is inhibited Bacterium prevent proton pumps from working, pH is not where it needs to be & enzymes are unable to perform their function Bacteria escape secondary lysosome by producing phospholipase to destroy lysosomal membrane (lysosome bursts and bacteria move out)

Question 32

What are ways that lysosomes fail to carry out their functions?

Answer 32

Phagocytosed bacteria escape Lysosome with a missing acid hydrolase

Question 33

what occurs in lysosomes with a missing acid hydrolase?

Answer 33

Lysosomes don’t have necessary enzymes to break down the materials so they accumulate

Question 34

endocytosis

Answer 34

cellular uptake of particles & macromolecules

Question 35

what are the types of endocytosis?

Answer 35

Phagocytosis: uptake of particulate matter ``` Bulk phase (pinocytosis): cell drinking, uptake of extracellular fluids without recognition by surface of PM Brings anything in that’s around the area where endocytosis occurs ``` Receptor-mediated endocytosis: uptake of specific macromolecules Brought to endosomes

Question 36

what are professional phagocytes in phagocytosis?

Answer 36

macrophages neutrophils

Question 37

how do lysosomes kill ingested microbes?

Answer 37

Contain lysozyme, an enzyme that degrades bacterial cell walls Acidic pH kills some bacteria alone Oxidases on inner surface of phagosome produce hydrogen peroxide that kills some bacteria

Question 38

what type of endocytosis has coat PROs?

Answer 38

receptor-mediated

Question 39

early endosomes

Answer 39

located near the periphery of the cell, aggregation of endocytotic vesicles

Question 40

late endosome

Answer 40

interior of the cell, sort materials & send them off to fuse with a primary lysosome (activating the secondary lysosome

Question 41

where do late endosomes receive material from?

Answer 41

Receive materials from: early endosomes & Golgi

Question 42

what type of endosome can develope into lysosomes?

Answer 42

late endosome

Question 43

coated pits

Answer 43

sites on membrane where receptors for receptor-mediated endocytosis are concentrated coated with clathrin PRO (on the cytoplasmic side)

Question 44

what are the steps in the endocytosis pathway?

Answer 44

1. Clathrin coat is removed from coated vesicle to yield uncoated vesicle Strips receptors & sending them back to be recycled 2. Uncoated vesicle fuses with early endosome 3. Transport or carrier vesicle buds off from early endosome 4. Transport vesicle fuses with late endosome 5. Transport vesicle bud off from late endosome & contain either: a. Ligand only b. Receptor only c. Receptor ligand complex

Question 45

How do endosomes deal with receptors & ligands? (4)

Answer 45

Receptor returned to PM & ligand delivered to lysosome for degradation Nutrition Both receptor & ligand returned to PM where ligand is released Both receptor & ligand are destroyed in a lysosome Receptor & ligand delivered to opp side of cell & ligand released into extracellular space Transcytosis

Question 46

Transcytosis

Answer 46

where receptor & ligand are taken in from one side & sent out the other

Question 47

when does transcytosis occur in humans?

Answer 47

Infant's intestines take up antibodies from mom's milk. The infant takes the antibodies in with receptors & prevents digestion by sending them out the other side