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MBB-231 > Midterm 2 > Flashcards

Midterm 2 Flashcards

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
Q

What is autophagy?

A

A pathway that allows cytotoxic proteins and organelles to be delivered to the lysosomal interior for degradation

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26
Q

How does autophagy occur?

A
  • 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
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27
Q

What is the docking stage?

A

A v-SNARE in the vesicle membrane interacts with the t-SNARES

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28
Q

What is exocytosis?

A

The discharge of a secretory vesicle or granule after fusion with plasma membrane

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29
Q

What is endocytosis?

A

Primarily a process by which the cell internalizes cell-surface receptors and bound extracellular ligands

30
Q

What two categories can endocytosis be broken into?

A
  • bulk-phase endocytosis (non specified)

- receptor-mediated endocytosis (specified)

31
Q

What are AP2 adaptors and what is their role in endocytosis?

A
  • 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
Q

What is Dynamin?

A
  • 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
Q

What occurs in G1?

A
  • 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
Q

What occurs in S phase?

A
  • DNA synthesis doubles the amount of DNA in the cell

- RNA and protein are also synthesized

35
Q

What occurs in G2 phase?

A

-RNA and protein synthesis continue

36
Q

What are the phases of M phase?

A
  • Prophase
  • Prometaphase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis
37
Q

When does centrosome duplication occur?

A

-during S-phase

38
Q

What occurs in Prophase?

A
  • protein synthesis stops
  • internal membrane systems that normally associate with microtubules disperse
  • endocytosis and exocytosis stop
39
Q

What occurs in Prometaphase?

A
  • 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
Q

What occurs in Metaphase?

A
  • chromosomes align at the metaphase plate

- chromatids are in a “tug-of-war” between two equally strong centrosomes

41
Q

What are the three types of microtubules involved in mitosis?

A
  • Kinetochore microtubules
  • Astral microtubules
  • Polar microtubules
42
Q

Where are kinetochore microtubules connected?

A

-to the chromosomes

43
Q

Where are astral microtubules located?

A

-project toward the cell cortex and interact with it thereby orienting the spindle of division

44
Q

What do polar microtubules do?

A

-interact with microtubules from the opposite pole of the cell

45
Q

What occurs in Anaphase?

A

-the two sister chromatids of each chromosome abruptly separate and move toward opposite poles

46
Q

When is the spindle assembly checkpoint?

A

-at the metaphase/anaphase transition to check for misaligned chromosomes

47
Q

What occurs in Telophase?

A

-the daughter cells return to interphase

48
Q

What occurs in cytokinesis?

A

-the cytoplasm is partitioned into two cells

49
Q

What the Ran-GAP?

A
  • GTPase Activating Protein

- turns it off

50
Q

What is Ran-GEF?

A
  • Guanine-nucleotide Exchange Factor

- exchanges GDP for GTP

51
Q

Explain the nuclear import cycle.

A
  • 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
Q

Explain the nuclear export sequence

A
  • 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
Q

What are the microtubule motor proteins?

A
  • kinesin

- dynein

54
Q

What do MAPs (microtubule-associated proteins) do?

A

-generally increase the the stability of microtubules and promote their assembly

55
Q

What are the roles of cytoplasmic dynein?

A
  • position the spindle and move chromosomes during mitosis

- position the centrosome and golgi complex and moving organelles, vesicles and particles through cytoplasm

56
Q

What are two MTOCs?

A
  • centrosome

- basal body

57
Q

What is a MTOC?

A

Any structure used by cells to nuclear and organize microtubules

58
Q

What are centrosomes made of?

A

Gamma tubulin

59
Q

What does the GTP cap do?

A
  • 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
Q

What is a catastrophe? (In regards to microtubules)

A

-GTP is hydrolyzed and the MT depolymerizes rapidly

61
Q

What are two MAPs and what do they do?

A
  • MAP2- promotes the formation of looser bundles in dendrites
  • Tau- causes MTS to form tight bundles in axons
62
Q

What are three actin polymerization regulating proteins?

A
  • thymosin
  • profilin
  • cofilin
63
Q

What does thymosin do?

A
  • sequesters G-actin preventing polymerization’

- When it binds to G-actin then G-actin is unable to polymerize on the growing end

64
Q

What is profilin?

A
  • acts as an adenine exchange factor, promotes polymerization
  • positive regulator
65
Q

What is cofilin?

A
  • binds ADP-actin and severs filaments
  • can take off G-actin one by one
  • can sever the filament
  • negative regulator
66
Q

What causes phagocytosis?

A
  • actin is involved in phagocytosis

- actin binding protein networks exert a force

67
Q

What is processivity?

A

-an enzyme’s ability to catalyze consecutive reactions without releasing its substrate

68
Q

What are the steps of the contractile cycle?

A
  • 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
Q

What are the components of the thin filament of sarcomeres?

A
  • Actin
  • Tropomyosin
  • Troponin
70
Q

How does calcium trigger contraction?

A
  • 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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