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MBB-231 > Midterm 2 > Flashcards

Midterm 2 Flashcards

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1
Q

What distinct compartments are part of the golgi complex?

A
  • the cis face (CGN) of the Golgi faces the ER
  • the trans face (TGN) is on the opposite side of the stack
  • Medial cisternae are sacs between CGN and TGN
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2
Q

What are the functions of the cis Golgi network?

A

Functions to sort proteins for the ER or the next Golgi station

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3
Q

What are the functions of the trans Golgi Network?r

A

Functions in sorting proteins either to the membrane or various intracellular destinations

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4
Q

What happens in the medial cisternaie?

A

This is where processing takes place

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5
Q

What is the process of oligosaccharide glycosylation in the ER?

A
  • biosynthesis of core oligosaccharide for N-linked glycosylation of certain asparagine residues
  • initial processing of core oligosaccharide
  • identification and removal of misfolded proteins
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6
Q

What is the process for oligosaccharide glycosylation in the CGN?

A
  • attachment of N-acetylgalactosamine to serine or threonine

- first stem of phosphorylation of lysosomal proteins

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7
Q

What is the process for oligosaccharide glycosylation in the medial cisternae?

A
  • removal of mannose
  • second step of phosphorylation of lysosomal proteins
  • attachment of N-acetylglucosamine
  • addition of sialic acid
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8
Q

What is the process of oligosaccharide glycosylation in the TGN?

A

-attachment of surface to tyrosine

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9
Q

What is the general processing of an oligosaccharide (in terms of Golgi and ER)?

A
  • First N-linked in the ER

- then goes through further processing in the Golgi Complex

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10
Q

Where are o-linked oligosaccharide abundant?

A

In the extra cellular matrix (ECM)

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11
Q

What does oligosaccharide coating a cell do to it?

A

it protects the cell

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12
Q

What are some known functions of glycosylation?

A
  • participate in sorting in TGN
  • protrusions from membrane can limit the approach of other macromolecules to the protein surface
  • serve as recognition molecules in cell-cell interaction
  • regulatory roles
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13
Q

What is the vesicular transport model?

A

Cargo is shuttled from the CGN to the TGN in vesicles (antegrade transport)

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14
Q

What is the cisternae maturation model?

A

Each cistern “matures” as it moves from the cis face to the trans face

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15
Q

What is the current model for movement of materials through the golgi complex?

A

Similar to cisternal maturation model but with vesicles retrograde where Golgi cisternae serve as primary anterograde carriers (combination of the the two)

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16
Q

What is the role of the COPII coated vesicles?

A

Move materials from the ER “forward” to the ERGIC and Golgi complex

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17
Q

What is the role of COPI coated vesicles?

A

Move materials from ERGIC and Golgi “backward” to ER, or from trans Golgi to cis Golgi cisternae

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18
Q

What is the role of Clathrin-coated vesicles?

A

Move materials from the TGN to endosomes, lysosomes and plant vacuoles

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19
Q

What does the KDEL sequence do?

A

Keeps the protein in the ER and it is not secreted out

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20
Q

What is a synaptic vesicles?

A

In neurons they store various neurotransmitters that are released at the synapse

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21
Q

What is the role of lysosomes?

A

-can hydrolysis virtually every type of biological macromolecule

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22
Q

What are lysosomal proteins tagged with in the cis-Golgi?

A

Phosphorylation mannose residues

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23
Q

What are tagged lysosomal enzymes recognized by?

A

By mannose 6-phosphate receptors which are bound by coat proteins

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24
Q

Where are mannose 6-phosphate residues added?

A

In the cis-Golgi

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25
What is autophagy?
A pathway that allows cytotoxic proteins and organelles to be delivered to the lysosomal interior for degradation
26
How does autophagy occur?
- a double membrane structure envelops an organelle to produce a double-membrane sequestering vesicle called an autophagosome - the autophagosome fuses with a lysosome, generating an autolysosome, in which both the inner membrane of the autophagosome and the enclosed contents are degraded
27
What is the docking stage?
A v-SNARE in the vesicle membrane interacts with the t-SNARES
28
What is exocytosis?
The discharge of a secretory vesicle or granule after fusion with plasma membrane
29
What is endocytosis?
Primarily a process by which the cell internalizes cell-surface receptors and bound extracellular ligands
30
What two categories can endocytosis be broken into?
- bulk-phase endocytosis (non specified) | - receptor-mediated endocytosis (specified)
31
What are AP2 adaptors and what is their role in endocytosis?
- adaptors on coated vesicle that face the cytosol - AP2 adaptors engage cytoplasmic tails of specific receptors to select bound cargo molecules, and bind and recruit the clathrate molecules of the overlying lattice - helps select cargo
32
What is Dynamin?
- a G protein required for the release of a clathrin-coated vesicle from the membrane where it forms - acts as an enzyme that uses the energy from GTP to provide mechanical force
33
What occurs in G1?
- RNA and protein synthesis | - there is a restriction point that a cell needs to pass in order to enter S phase and continue through the cell cycle
34
What occurs in S phase?
- DNA synthesis doubles the amount of DNA in the cell | - RNA and protein are also synthesized
35
What occurs in G2 phase?
-RNA and protein synthesis continue
36
What are the phases of M phase?
- Prophase - Prometaphase - Metaphase - Anaphase - Telophase - Cytokinesis
37
When does centrosome duplication occur?
-during S-phase
38
What occurs in Prophase?
- protein synthesis stops - internal membrane systems that normally associate with microtubules disperse - endocytosis and exocytosis stop
39
What occurs in Prometaphase?
- the definitive mitotic spindle is formed and chromosomes are moved by microtubules into the center of the cell - a single kinetochore is attached to microtubules from both spindle poles
40
What occurs in Metaphase?
- chromosomes align at the metaphase plate | - chromatids are in a “tug-of-war” between two equally strong centrosomes
41
What are the three types of microtubules involved in mitosis?
- Kinetochore microtubules - Astral microtubules - Polar microtubules
42
Where are kinetochore microtubules connected?
-to the chromosomes
43
Where are astral microtubules located?
-project toward the cell cortex and interact with it thereby orienting the spindle of division
44
What do polar microtubules do?
-interact with microtubules from the opposite pole of the cell
45
What occurs in Anaphase?
-the two sister chromatids of each chromosome abruptly separate and move toward opposite poles
46
When is the spindle assembly checkpoint?
-at the metaphase/anaphase transition to check for misaligned chromosomes
47
What occurs in Telophase?
-the daughter cells return to interphase
48
What occurs in cytokinesis?
-the cytoplasm is partitioned into two cells
49
What the Ran-GAP?
- GTPase Activating Protein | - turns it off
50
What is Ran-GEF?
- Guanine-nucleotide Exchange Factor | - exchanges GDP for GTP
51
Explain the nuclear import cycle.
- Importin recognizes and binds to NLS (nuclear localization signal) on cargo protein in cytosol - Importin and cargo protein go into nucleus - Ran-GEF binds to complex and releases cargo protein - Ran-GEF and Importin go out of nucleus - Ran-GAP occurs and GTP is transferred to a GDP and Pi and releases Importin - Importin is now free to recognize another NLS sequence - Ran-GDP can diffuse into nucleus to go through GEF again
52
Explain the nuclear export sequence
- Exportin binds to Ran-GTP(GEF) and NES (nuclear export signal) of cargo protein - transfers out of the nucleus - GAP changes GTP to GDP and Ran releases the exportin and and cargo protein - exportin and the cargo protein dissociate - Ran-GDP is now able to diffuse into nucleus - Exportin goes back into the nucleus to pick up more cargo
53
What are the microtubule motor proteins?
- kinesin | - dynein
54
What do MAPs (microtubule-associated proteins) do?
-generally increase the the stability of microtubules and promote their assembly
55
What are the roles of cytoplasmic dynein?
- position the spindle and move chromosomes during mitosis | - position the centrosome and golgi complex and moving organelles, vesicles and particles through cytoplasm
56
What are two MTOCs?
- centrosome | - basal body
57
What is a MTOC?
Any structure used by cells to nuclear and organize microtubules
58
What are centrosomes made of?
Gamma tubulin
59
What does the GTP cap do?
- adds stability to the microtubule | - GDP in beta tubulin causes a bend in the microtubule where when it stays as GTP and is not hydrolyzed it is straight
60
What is a catastrophe? (In regards to microtubules)
-GTP is hydrolyzed and the MT depolymerizes rapidly
61
What are two MAPs and what do they do?
- MAP2- promotes the formation of looser bundles in dendrites - Tau- causes MTS to form tight bundles in axons
62
What are three actin polymerization regulating proteins?
- thymosin - profilin - cofilin
63
What does thymosin do?
- sequesters G-actin preventing polymerization’ | - When it binds to G-actin then G-actin is unable to polymerize on the growing end
64
What is profilin?
- acts as an adenine exchange factor, promotes polymerization - positive regulator
65
What is cofilin?
- binds ADP-actin and severs filaments - can take off G-actin one by one - can sever the filament - negative regulator
66
What causes phagocytosis?
- actin is involved in phagocytosis | - actin binding protein networks exert a force
67
What is processivity?
-an enzyme’s ability to catalyze consecutive reactions without releasing its substrate
68
What are the steps of the contractile cycle?
- ATP binds to the cleft in the myosin head, releasing myosin from actin - ATP hydrolysis to ADP+Pi causes weak binding to actin - Pi release causes tight binding and power stroke backwards - Actin is pulled backwards and ADP is released freeing the ATP binding cleft - ATP binds to the cleft in the myosin head, releasing myosin
69
What are the components of the thin filament of sarcomeres?
- Actin - Tropomyosin - Troponin
70
How does calcium trigger contraction?
- motor neuron excitation signal - signal transduction pathway leads to Ca2+ release from the ER - Ca2+ binds to troponin causing conformation shift - Troponin conformation shift moves tropomyosin out of place - myosin binding site on actin is exposed - when excitation signaling ceases, Ca2+ are pumped back into ER and muscle relaxes

MBB-231 (4 decks)

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