Intracellular Compartments and Transport Flashcards

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1
Q

Advantages of organelles

A

“House” chemical reactions: sequester damaging molecules, keep reactions together
Membrane: create gradient for H+ motive force, regulation

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2
Q

Organelle anchorage

A

Held in place by cytoskeleton

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3
Q

Cytosol

A

Contains many metabolic pathways

Protein synthesis

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4
Q

Nucleus

A

Main genome

DNA and RNA synthesis and maintenance

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5
Q

Nucleolus

A

Storage of ribosomal RNA and euchromatin

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6
Q

Endoplasmic reticulum

A

Synthesis of most lipids (smooth)

Synthesis of proteins for distribution to many organelles and to the plasma membrane (rough)

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7
Q

Golgi apparatus

A

Modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle

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8
Q

Lysosomes

A

Intracellular degradation

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9
Q

Endosomes

A

Sorting of endocytosed material

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10
Q

Mitochondria

A

ATP synthesis by oxidative phosphorylation

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11
Q

Chloroplasts

A

ATP synthesis and carbon fixation by photosynthesis

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12
Q

Peroxisomes

A

Oxidation of toxic molecules

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13
Q

Cajal

A

Area of nucleus where RNA is processed

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14
Q

P bodies

A

RNA turnover

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15
Q

Endomembrane system

A

Nucleus, plasma membrane, ER, golgi, endosomes, lysosomes/vacuoles, vesicles
Originally formed from invaginations of plasma membrane

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16
Q

Protein sorting

A

Transport through nuclear pores (nucleus proteins)
Transport across membranes
Transport by vesicles

17
Q

Signal sequences

A

Targeting motif

Directions to where the protein is supposed to go

18
Q

How to determine where protein goes

A

Look at signal sequence
Label w/ fluorescent antibody and see where it goes (stain organelles or proteins in organelles)
Mutate sequence and see what happens (determine correct sequence as signaling)

19
Q

Nuclear envelope

A

Outer membrane: contiguous with ER

Inner membrane: nuclear lamina

20
Q

Nuclear localization signal (NLS)

A

Allows nuclear protein to be transported through pores into nucleus

21
Q

Nuclear pores

A

Openings into nucleus: selective gates
Protein with NLS is attached to transport protein
Protein swings from tangle to tangle until it reaches nucleus

22
Q

Mitochondrial and chloroplast protein import

A

Signal sequence is recognized by receptor
Receptor diffuses- forms contact site
Unfolded protein snakes through
Protein is folded in matrix

23
Q

ER Transport

A

Proteins destined for golgi, lysosome, plasma membrane, endosomes, or secretion enter the ER first
2 types of proteins: water-soluble (lumen or secreted) or transmembrane
Proteins are imported as they are translated
Polypeptide being synthesized directs its ribosome to ER by its signal sequence

24
Q

Directing an ER polypeptide to the ER

A
  1. Signal recognition particle (SRP) binds to ER signal sequence
  2. SRP binds to SRP receptor in ER membrane
  3. Translocation channel opens
  4. Polypeptide snakes through channel
25
Q

Soluble protein going to ER

A
  1. Signal sequence is cleaved off and polypeptide is released in lumen and folded
26
Q

Transmembrane protein going to ER

A
  1. During translocation, a stop transfer sequence goes through the translocator
  2. Those sequences diffuse through the membrane and the signal sequence is cleaved off
27
Q

Both soluble and transmembrane portions of protein going to ER

A
  1. Start transfer sequence is internal to polypeptide
  2. Polypeptide threads through until stop transfer sequence reaches translocator
  3. Transmembrane domains diffuse into membrane- neither start nor stop transfer sequence is cleaved
28
Q

ER protein folding and modification

A

Oxidation of thiols and cysteines to fold proteins

Chaperones assist in protein folding

29
Q

Unfolded protein response

A

Too many unfolded proteins- more chaperones and ER are made

If problem isn’t fixed, apoptosis is triggered

30
Q

Vesicular transport

A
  1. ER buds off
  2. Buds fuse with cis side of golgi
  3. Travels through cisternae (folds of golgi)
  4. Reaches trans side of golgi
  5. Secretory pathway- transport vesicles take products and release them into extracellular space
  6. Endocytic pathway: vesicle pinches off and fuses with early endosome
  7. Changes to early endosome (especially increasing acidification) turn it into a late endosome, which fuses with lysosome
31
Q

Clathrin

A

Basket shaped protein that forms coat around vesicle

32
Q

Vesicle budding

A
  1. Adaptin recognizes receptor that needs to be endocytosed (change in shape of receptor by binding to cargo is recognized)
  2. Adaptin recruits clathrin
  3. Clathrin forms invagination
  4. Dynamin pinches off vesicle
  5. Clathrin and adaptin dissociate
33
Q

Vesicle recognition and docking

A
  1. Rab (specific for cargo and target organelle) is recognized by tethering protein
  2. V-SNARE interacts with t-SNARE to pull vesicle close to target
  3. Membrane mixing- cargo is delivered
34
Q

Secretory pathway

A

Delivery of cargo from ER to golgi to the cell surface for exocytosis
Cargo can be signaling proteins, extracellular matrix, etc.
Sometimes stored in secretory vesicles until needed (ex- insulin, neurotransmitters)

35
Q

Pinocytosis

A

Cell drinking
Ingestion of plasma membrane, fluid, and small molecules
Carried out by clathrin-coated pits and vesicles (fuse with endosomes)

36
Q

Phagocytosis

A

Cell eating
Ingestion of large particles into phagosomes
Fuses with lysosome- form phagolysosomes
Performed by phagocytic cells

37
Q

Receptor-mediated endocytosis

A
  1. LDL receptors bind to LDL
  2. Vesicle budding
  3. Uncoating of clathrin
  4. Fusion with endosome
  5. Transfer of LDL to lysosome and budding off of transport vesicles carrying receptors
  6. Return of LDL receptors to plasma membrane
38
Q

Autophagy

A

Self eating
Organelles and large portions of cytoplasm are engulfed by autophagosome (triggered by cell starvation or because organelles are old and no longer functioning)
Lysosomes break down contents of autophagosomes

39
Q

V-type transporter

A

Similar to f-type ATPase, but runs in opposite direction

Gives lysosome an acidic interior