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Molecular Biology > Intracellular compartments and protein sorting 1 (lecture 10) > Flashcards

Intracellular compartments and protein sorting 1 (lecture 10) Flashcards

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1
Q

What is the Plasma membrane

A
  • Outer boundary of cells,bilary
    • fxn: protective barrier, has transporter, signaling
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2
Q

Nucleus

A
  • Contains the genome
  • principle site for DNA and RNA synthesis
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3
Q

Cytoplasm

A
  • Consists of cytosol and cytoplasmic organelle
  • intermediary metabolism
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4
Q

Enoplasmic Reticulum (ER)

A
  • Ribosomes attached to it (rough ER), no ribosomes (smooth ER)
  • Protein synthesis, lipid synthesis, protein folding, storage of calcium
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5
Q

Golgi apparatus

A
  • Stacks of disc-like compartments
  • site of post-translational changes on proteins and lipids, trafficking
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6
Q

Mitochondria

A
  • Outer and inner membrane and matrix
  • Makes ATP, signaling, cell differentiation and cell death
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7
Q

Lysosomes

A
  • Contain digestive enzymes that degrade organelles and biomolecules
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8
Q

Peroxisomes

A
  • Small vesicular compartments that contain enzymes used in oxidation reactions
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9
Q

What intracellular compartment makes up the majority of the cell

A

Cytosol

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10
Q

The cell can be divided into what 3 topological categories

A
  • Nucleus and cytosol (communicate through nuclear pore complex)
  • Organelles in secretory and endocytic pathways (ER, Golgi apparatus, endosomes, and lysosomes) (communicate through vesicles)
  • Mitochondria
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11
Q

Nucleus and cytosol communicate through _____ complex

A
  • nuclear pore complex
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12
Q

Organelles in secretory and endocytic pathways (ER, Golgi apparatus, endosomes, and lysosomes) communicat through

A

Vesicles

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13
Q

membrane ____ and ____ allows the lumen of the cell compartments to communicate with each other and with the cell exterior

A

Budding and fusion

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14
Q

Protein trafficking

A
  • Gated transport
  • Transmembrane transport
  • Vesicular transport
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15
Q

Gated transport: between ____ and ___ through nuclear pore complexes (active transport and free diffusion)

A

Nucleus and cytosol

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16
Q

Transmembrane transport: membrane _______ directly transport specific proteins from cytosol across an organelle membrane

A

Protein translocators

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17
Q

Vesicular transport: membrane-enclosed transport intermediates move proteins between various compartments via

A

vesicles

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18
Q

Protein transfer/transport to various compartments guided by ____

A

sorting signals

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19
Q

Sorting signals on proteins are a stretch of amino acids, typically ____ residues long

A

15-60

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20
Q

Sorting signals may be localized on ___ or ___ terminus or _____

A

N or C terminus, within protein sequence

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21
Q
A
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22
Q

multiple scattered sequences in protein may form

A

signal patch

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23
Q

____ may remove signal after protein reaches final destination

A

signal peptidase

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24
Q

Protein signal sequences are both necessary and sufficient for _____

A

protein targeting

25
Q

_________ properties of the protein signaling sequence are more important than the actual sequence

A

physical properties (charge,hydrophobicity)

26
Q

Protein signal sequences are recognized by ______

A

complementary receptors

27
Q

what is the protein signal sequence for importing into nucleus

A
  • Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val
    • (note that there are 5 positive charges)
28
Q

Nuclear transport is ____, _____ and _____

A

gated, bidirectional, and selective

29
Q

Proteins needed in nucleus (e.g. histones, DNA and RNA polymerases, topoiserases, gene regulatory proteins) are imported from ____ where they are synthesized

A

cytoplasm

30
Q

____ and ____ molecues synthsized in nucleus are exported to cytosol

A

tRNA and mRNA

31
Q

Nuclear pore complexes (NPCs) perforate ____ in eukaryotes

A

Nuclear envelope

32
Q

What si the moleuclar mass of nuclear pore complexes (NPCs)

A

125 million Daltons

33
Q

Nuclear Pore Complexes (NPCs) are composed of ____ different proteins or ____-

A

30, nucleoporins

34
Q

Nuclear Pore coplexes (NPCs) are arranged in ____- symmetry with one or more ______

A

ocagonal symmetry, aqueous pores

35
Q

Nuclear envelope has ______ Nuclear pore comlexes (NPCs)

A

3000-4000

36
Q

Nuclear Pore Complexes transport molecules in ______

A

both directions

37
Q

Nuclear pore complexes (NPCs) transport molecuels in both directions. By means of ____ of small molecules and _____

A

Passive diffusion, facilitated transport

38
Q

Nuclear pore complexes (NPCs) faciliate tansport by

A

binding of particles to fibrils extending from NPC

39
Q

____ are sorting signals that direct molecules to the nucleus

A
  • Nuclear Localization Signals (NSL)
40
Q

Nuclear localization signals (NLS) are short sequences rich in _____ amino acids ____ and ____

A

postitivley charged amino acids lysine and arginine

41
Q

Nuclar locatlization signals (NLS) are located on many different sites on protein- form ____ or ____ on surface

A

loops or pathes

42
Q

Nuclear Localization Signals (NLS) result in ____ import of proteins into nucleus

A

selective

43
Q

Nuclear localization signals (NLS) are recognized by

A

nuclear import receptors (NIRS)

44
Q

Nuclar import receptors (NIRs) are ______ that bind to ____ on protein and to ______ present on fibrils that extend into cytoplasm

A

soluble cytosolic proteins, NLS, NPC proteins

45
Q

NPC proteins have _____ which serve as binding sites for import receptors

A

Phenylalanine glycine (FG) repeats

46
Q

Nuclear import receptors plus cargo traverse NPC by ___, ___, and ___ to adjacent Phenylalanine glycine (FG) repeats

A

binding, dissociating, and re-binding

47
Q

Once cargo is released inside the nucleus the NIR

A

return to cytoplasm

48
Q

Nuclear import receptors (NIRs) can either do ____ binding or ____ binding to cargo protein with help of adapter protein

A

direct or indirect binding

49
Q

Nuclear export works similar to import but

A

in opposite direction

50
Q

Nuclear export relies on _____ on molecules that need to go out of nucleus

A

nuclear export signals (NES)

51
Q

For nuclear export Nuclear export signals (NES) on molecules need complementary

A

nuclear export receptors (NER)

52
Q

NER binds to cargo present in nucleus and ____ proteins

A

NPC

53
Q

Gradient of ____ conformational states drive nuclear transport in appriate direction

A

Ran

54
Q

RAN-GTP binds to complex of ____ and ____. The binding causes release of cargo. Ran-GTP and ____ then leave the nucleus and return to cytoplasm. In the cytoplasm Ran-GTP is hydrolyzed by _____. The _____ is released from Ran-GDP and is ready for another cycle

A

import receptor and cargo, import receptor, Ran-GAP. Import receptor

55
Q

Shuttle protein contain both ____ and ___. This allows them to shuttle back and forth between ___ and ___

A

NLS and NES. nucleus and cytosol

56
Q

Steady state locatlization is dependent upon

A

relative rate of transport

57
Q

If the rate of import is greater than export, the shuttle protein is considered ____

A

nuclear

58
Q

Gene regulatory protein can regulate transport by turning ____ and ____ on and off. The mechanisms include ____, ____, and ______

A

NLS and NES. phosphorylation, proteolysis, and binding to inhibitory proteins

59
Q

Feedback regulation of cholesterol biosynthesis

A

SREBP (sterol response element binding protein), a latent transcription regulator that controls expression of cholesterol biosynthetic enzymes, is initially synthesized as an ER membrane protein. It is anchored in the membrane by interaciton wiht another ER memabre protein, called SCAP (SREBP cleavage activation protein), which binds cholesterol. If the cholesterol binding site on SCAP is empty (at low cholesterol concentrations), SCAP changes conformation and is packaged together with SREBP to free its cytosolic domain form the membrane. The cytosolic domain then moves into the nucleus, where it binds to the promoters of genes that encode proteins involved in cholesterol biosynthesis and activates their transcription. In this way, more cholesterol is made when its concentration falls below a threshold.

Molecular Biology (14 decks)

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