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Histology Block 1 > 3.ER, Golgi Apparatus, and Lysosomes > Flashcards

3.ER, Golgi Apparatus, and Lysosomes Flashcards

1
Q

recognize the golgi apparatus and lysosome in microscopic preparations

A

a

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2
Q

explain the golgi’s role in sorting proteins and membranes into 3 major cellular pathways

A

a

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3
Q

to explain the function of lysosomes, endocytic pathways

A

a

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4
Q

to learn the major steps of vesicular trafficking leading to fusion

A

a

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5
Q 
keywords:
transport vesicles
vesicle budding
vesicle tethering
vesicle docking
vesicle priming
vesciel fusion
protein/vesicle sorting
coat proteins
slavaging
recycling
lysosomal hydrolases
constituitve and regulated secretory pathway
A

a

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6
Q

What are the principal functions of the RER

A
  • new proteins translocated into the RER cisternae
  • N-linkages formed: mannose rich oligosaccharides are added to specific asparagine residues (CSF CONCEPT!!!)
  • proteins are folded, guided by chaperones (CSF CONCEPT!!!)
  • disulfide bonds form between cysteine residues (CSF CONCEPT!!!)
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7
Q

what are the functions of the cis golgi network. define retrograde and anterograde

A
  • vesicles with COPII coat protein move from RER to golgi apparatus
  • retrograde = toward the nucleus; anterograde means away from the nucleus
  • mannose 6-phosphate is added to future lysosomal enzymes
  • N-linked glycosaccharides are trimmed and other sugars are added

“Your cister wants to go to your room, take your stuff, and cut your hair”

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8
Q

what are the functions of the medial golgi cisternae?

A
  • new glycosylation occurs on Oh groups of lipids, serine, and threonine
  • N-linked oligosaccharides on proteins are modified further (** only trimmed, do not have sugars added)
  • glycoproteins and gycolipids are sorted into specific vesicles

“Medial acts like your mother and wants to prune your room and sort your stuff”

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9
Q

what are the functions of the trans golgi?

A
  • sialic acid added as terminal sugar in some oligosaccharides
  • sulfation of tyrosine residues and some sugars occurs
  • specific vesicles with different destinations are separated and sorted

“trans gets modifications SSS: sialic, sulfation, and sorted” which guide them to new stages and new destinations

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10
Q

the golgi apparatus is prominent in cells that do what?

A

secrete proteins

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11
Q

what are the 2 methods of transporting maturing proteins?

give examples

A

-vesicles do transport
in the vesicular transport model:
-vesicle buds off and moves in anterograde motion to the medial, then the trans, and then heads to plasma membrane and fuses to be released with the protein and the receptor.
-vesicle never moves backwards bc is tagged with signal sequence

ex: lysosomal proteins

or

-stack moves from cis to trans direction
(ex: pro collagen)
-cisternal maturation model:
-dynamic process where vesicles from ER buds off each of the cis, median, and trans golgi. These vesicles travel retrograde motion and
-vesicles from trans fuse with former medial to form new trans
-vesicles from medial fuse with former cis to form new medial
-vesicles from former cis fuse with RER to form new cis
-

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12
Q

movement from cis to trans golgi would be called?

A

anterograde

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13
Q

how are proteins targeted for the lysosome?

A

add phosphate to 6th sugar of mannose

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14
Q 
what is I cell disease?
why does it happen
what organs are affected
prevalence?
genetics?
A

Lysosomal storage disease

-waste products accumulate in the cell into masses called inclusion bodies.
why?
bc lysosomal proteins (made in RER) are not phosphyorylated at mannose 6 in cis golgi
therefore
not delivered to late endosomes bc receptor involved in sorting in the trans golgi only recognizes phsophorylated mannose
so
proteins go to constitutive secretory pathway

-organs: cloudy cornea, enlarged liver and/or spleen, restricted joint movement, corse facial features

autosomal recessive
-usually die young

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15
Q

what does the golgi look like under the microscope?

-in what tissues would we see a lot of the golgi?

A

like pancakes (don’t confuse with SER)

  • only observable in cells active in protein secretion
  • looks like ghost
  • adjacent to the nucleus

ex:
plasma cells secreting antibodies in connective tissue surrounding mammary gland (ANATOMY LINK)
-principal cells of the epididimus for sperm production
-chodrocytes - active in ECM production of collagen

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16
Q

what is a residual body?

  • what does the residual bodies look like under the microscope?
  • dont confuse with inclusion bodies!
A

residual bodies are where the lysosome cannot digest everything.

  • can accumulate as lypofuscin
  • usually brown under a microscope
17
Q

differentiate:
endocytosis
phagocytosis
autophagosomes

A

Endocytosis:
vesicles fuse with endosomes before merging with lysosomes

phagocytosis:
phagosome vacuoles fuse with primary lysosomes to become secondary lysosomes

autophagosomes:
nonfunction/surplus organelles become enclose in a membrane and fuse with lysosome

18
Q

describe very well receptor mediated endocytosis and fate

A

a) ligands bind with high affinity to surface proteins and clatharin and adaptor proteins
b) aggregate regions called coated pits, which is facilitated by clatharin and dynamin
c) region pinches off as a coated vesicle to make a clatharin pit
d) merge to endosomal vesicle

fates:

  • carried to late endosomes and then lysosomes for degradation
  • released internally and receptors recycled
  • vescles may move and fuse with other cell surface
19
Q

describe the structure of the lysosome
-hydrolases
-defense mechanism
pH? how is it maintained?

A

membrane: glycosylated membrane proteins
- lipid bilayer

hydrolytic enzyme mixture inside
-hydrolases are active at low pH therefore if the contents leak, it is okay?

  • pH inside is 5
  • pH maintained by Hdrogen pump (uses ATP) to pump ATP inside
20
Q

lysosomes under microscope?

A

later stages- evenly electrodense and dark

21
Q

describe a lipofuscin. where are you more likely to see it?

A

usually in neuronal cell/ cells that live long

its a non-degradable waste product that may accumulate

22
Q

describe tay-sachs disease

why does it happen
what organs are affected
prevalence?
genetics?

A

s/s: cherry red spot on retina, progressive neurodegeneration, developmental delay

  • “onion skin” lysosomes
  • 1:27 ratio in US Jews and Cajuns
    1: 250 in US pop

autosomal recessive

-deficiency in lysosomal enzyme
bc
hexosaminidase enzyme involved in hydrolysis of molecules contaiing hexose (CNS)
-inability to properly hydrolyze GM2 type ganglioside, causing lipids to accumulate over time in lysosomes

"first vowel rule for lysosomal storage diseases:
tAysachs
hex A disease
of gAngliosides (CSF connection!) 
chArry red macula
BrAiN
23
Q

what is the constitutive pathway?

A

default pathway for proteins lacking secretory signal peptide sequence

24
Q

what does a protein need to be sorted to the lysoosomal pathway?

A

6 carbon position of the mannose residue has to be phosphorylated

25
Q

why are SNARE proteins important

A

they are proteins that mediate membrane fusion, especially for exocytosis
–proteins bind and assemble core complex that drive lipid layers together, leading for fusion. sometimes preceded by rise in calcium
3 snare proteins: vSNare found mostly on vesicles, SNAP25 which is classified as t-snare because it is a major one.
soluble NSF attachment protein Receptor

26
Q

both constitutive and regulated secretion use__, but regulation___

A

SNARE proteins for fusion, but regulated also employs a calcium sensor

27
Q

goblet cells secrete mucins through which type of secretion?

what about paneth cells?

insulin?

A

both constitutive and regulated

paneth cells use regulated secretion (intestinal glands)

insulin is released by regulatory

28
Q

describe constitutive secretion and give examples of cells that use it

how can you tell a cell uses this method?

A

proteins are continuously secreted from the cell via VESICLES regardless of environment

  • no external signal needed
  • ex: proteins packaged into vesicles in the golgi and secreted via exocytosis

cell will have many golig apparati in the cytoplasm

fibroblasts, osteoblasts, and chondrocytes are some cells that perform constitutive secretion

29
Q

how do fibroblasts look special under a microscope? what does it secrete

A

they secrete collagen

-nuclei made of heterochromatin and euchromatin and abundant RER

30
Q

vesicles that transport proteins are formed by the interaction btwn proteins inserted in to the membrane and coat proteins.

describe the coat proteins

A

COPII is essential in vesicles destined to the Golgi
0also involved in forming vesicles for constitutive secretion at the golgi and sending vesicles from early to late endosome

Endoplasmic reticulum/Golgi transport mechanisms describe the two-way protein transport pathways that operate between the ER and the Golgi. The coat protein complex II (COPII) vesicles carry cargo from the ER to the Golgi, whereas the COPI vesicles return certain ER proteins from the Golgi back to the ER (retrograde)

-clathrin coat forms endosome at the plasma membrane

31
Q

general logic of vesicle targeting and fusion

A

steps: budding, tethering (pairing), docking, fusion and recycling of snare but further priming of t snare

budded vesicles contain v-SNARE and are tethered to acceptor membranes by protein complexes that include RAB GTPase and fibrous proteins.

Once the vesicle has been released from the ER, it is carried along microtubules towards the Golgi

As the COPII-coated vesicle approaches the ER–Golgi intermediate compartment (ERGIC) membrane system, it begins to shed its COPII coat.

The COPII coat is removed allowing the vesicle to be captured by tethers such as trafficking protein particle 1 (TRAPP1), which enables the SNARE proteins to engage with each other and to fuse with the early Golgi compartment.

-SNARE pairing follows, leading to membrane fusion.

(2) Function
(a) Coatomer-coated vesicles mediate the continuous constitutive protein trans-port (default pathway; bulk flow) within the cell. Specific GTP-binding proteins are present at each step of vesicle budding and fusion, and proteins called SNARES ensure that the vesicle docks and fuses only with its correct target membrane. Coated vesicle SNARES (v-SNARES) recognize and bind to com- plementary target SNARES (t-SNARES) to deliver not only cargo molecules but also membrane to the target compartment (Figure 3.7).
(b) Coatomer-coated vesicles transport proteins from the RER to the VTC (vesicular tubular structure) to the Golgi apparatus, from one Golgi cisterna to another, and from the TGN (trans golgi network) to the plasma membrane.
(i) COP-II transports molecules forward from the RER to the VTC to the cis Golgi and across the cisternae to the TGN (anterograde transport).
(ii) COP-I facilitates retrograde transport (from the VTC or any Golgi cisternal compartment or from the TGN) to the RER. It is still questionable whether or not COP-I facilitates anterograde transport, but recent findings suggest that they might move forward between Golgi regions to the TGN.

The interaction of v-SNARES with t-SNARES is essential for neurotrans-
mitter release, via exocytosis, at chemical synapses. At the presynaptic nerve terminal, one of the t-SNARES is SNAP-25, a fusion protein. Botox (botulinum neurotoxin A)
cleaves SNAP-25 and prevents the synaptic vesicles from anchoring and releasing their neurotrans- mitter, thus preventing neuromuscular transmission and contraction. This leads to a flaccid paralysis of the postsynaptic muscle.

32
Q

what are salvage mechanisms to compensate for misrouting during cargo transport

A

-cargo containing vesicles sometimes incorporate residents of donor compartments that are then wrongly delivered to the acceptor compartment. specific salvage receptors recognize these and return them to the donor compartment

33
Q

what layer do transport vesicles have?

A

lipid bilayer which contains integral or peripheral proteins

Histology Block 1 (6 decks)

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