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lec 14 Flashcards

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1
Q

membrane compositions

A

phospholipids, proteins, sugars, cholesterol and submembrane meshwork

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2
Q

which organisms have a plasma membrane (PM)?

A

eukaryotes

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3
Q

some principal function of cell membranes

A
  1. compartmentalization
    - allows for&raquo_space; efficiency of func
  2. defense
    - barrier
  3. selective permeability
  4. attachment and movement of cell/organelle
  5. response to signals
    - receptors bind to ligands
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4
Q

main components of membrane structure

A
  1. amphipathic lipid bilayer
  2. membrane, proteins, sugars and cholesterol
  3. cytosolic submembrane protein meshwork
    - peripheral proteins and cytoskeletal components
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5
Q

amphipathic lipid bilayer

A

fundamental structure of biological membrane
- double layer of phospholipids
provides hydrophobic barrier to most molecules
- allows a select few to diffuse across (O2, CO2, H2O, urea, etc)

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6
Q

permeability of lipid bilayer and simple diffusion kinetics

A
  1. hydrophobic molecules can dissolve in the lipid bilayer and cross the membrane easily
  2. uncharged polar molecules
    - small can cross the membrane slowly
    - large cross the membrane slower
  3. charged/strongly polar molecules cannot cross
    - ex. ions
    > enables the maintenance of gradients/membrane potentials
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7
Q

ion gradients cause membrane depolarization in what?

A

synaptic signaling

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8
Q

membrane gradient in cellular respiration

A

ATP synthase

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9
Q

what type of phospholipids are in eukaryotics?

A

most are in eukaryotic membranes
- phosphoglycerides

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10
Q

characteristics of phosphoglycerides

A
  1. polar phosphate head group
  2. glycerol backbone
  3. fatty acid tails
    - can be saturated and/or unsaturated and can vary in length
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11
Q

there are 4 major classes of phospholipids

A
  1. defined by different polar phosphate head groups
  2. each class can have a lot of variation in fatty acid tails
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12
Q

different leaflets (sides) of membranes have different phospholipid compositions

A

ER membrane proteins that function to position specific phospholipids into specific leaflets of the membrane go to
1. cytosolic side (facing cytosol)
2. non-cytosolic side (facing away from the cytosol)

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13
Q

membrane proteins

A

provides the bulk of a specific membrane function
- variation = primary determinant of cellular identity
proteins can associate with membranes
- transmembrane proteins
> single and multiple passes
> barrel/channel
- single sheath proteins
- anchored proteins
> lipid, sugar and protein anchors

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14
Q

sugars

A

on glycoproteins and glycolipids
func: cell recognition
- sugar side chains on the proteins and lipids are recognized selectively by other cells
differences in cell-surface sugars
- molecular basis for different blood groups
always on the non cytosolic face of membranes

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15
Q

cholesterol

A

sterol, with a polar head group, rigid ring structure, and nonpolar hydrocarbon chain
eukaryotic plasma membrane have&raquo_space; amounts of cholesterol
func: provide rigidity to membrane
- crucial for maintaining fluidity at &laquo_space;temp

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16
Q

submembrane protein meshwork

A

always on cytosolic side of membranes
gives structural support to membranes
connects plasma membrane with the rest of the cell

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17
Q

membranes within the eukaryotic cell

A
  1. plasma membrane
  2. nuclear envelope
  3. endoplasmic reticulum
  4. golgi apparatus
  5. mitochondria and chloroplasts
  6. endosomal sys and lysosomes
  7. peroxisomes
  8. vacuoles
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18
Q

nucleus func

A
  1. store/protect and transcribe DNA
  2. RNA processing and export
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19
Q

endoplasmic reticulum func

A
  1. protein and lipid synthesis
  2. N-linked glycosylation and lipid mod of proteins
  3. detoxification of dangerous material
  4. calcium sequestration
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20
Q

golgi apparatus func

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A

post-translational mod of proteins and lipids
- O-linked glycosylation
- mod of oligosaccharides originally added during N-linked glycosylation in ER

21
Q

protein sorting/packaging

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A

into vesicles for transport to endosomes, lysosomes, or plasma membrane

22
Q

mitochondria func

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A
  1. store, protect, and express their DNA
  2. cellular power plant
    - generate most of the cell’s ATP (chemical energy)
23
Q

chloroplast func

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A
  1. store, protect, and express their DNA
  2. site of photosynthesis
    - harness light energy and convert it to ATP to fix carbon
24
Q

endosomal sys and lysosome func

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A
  1. deliver molecules to lysosomes for degradation
  2. send vesicles back to plasma membrane to recycle membrane components
25
peroxisome func
1. detoxification - metabolism of reactive oxygen species (ROS) 2. lipid synthesis 3. breakdown of long chain fatty acids
26
vacuole func
in all plants, fungal cells, bacterial cells, and some protist 1. water storage 2. maintaining pH and turgor 3. exporting harmful materials/waste products
27
intracellular transport
A. vesicular transport within the endomembrane system - outward and inward flow - movement within the cytosol B. protein-mediated transport within the cytosol (non vesicular) ex: nuclear-encoded mitochondrial proteins
28
vesicular transport within the endomembrane system
targeted, specific transport of molecules out of, into or within the cell
29
outward flow
1. of newly synthesized proteins translated on bound ribosomes 2. vesicular trafficking from ER outward a. starts with export from the nuclear envelope and then translation on bound ribosomes at ER b. vesicular budding c. processing in golgi d. transport from golgi to plasma membrane, lysosome or back to the ER
30
inward flow
endocytosis 1. phagocytosis - uptake of solid 2. pinocytosis - uptake of liquid 3. receptor-mediated endocytosis
31
movement within the cytosol
autophagy (self eating) membrane contained movement to lysosome to digest components that are not working properly/breaking down
32
where does the outward flow occur?
in nucleus-ER complex ribosomes 1. free (cytosolic) and bound (to the ER) 2. can cycle back and forth between being free and bound 3. bind to the ER when translating peptide with ER signal seq 4. return to free state when finished translating
33
ER func
1. lipid biosynthesis - phospholipids, steroids, lipoproteins 2. membrane-bound translation of mRNA - ER signal seq on nascent peptides (N-terminal leader peptide) binds to SRP > directs nascent peptide, ribosome, and mRNA complex to the ER complex = binding SRP-receptor on ER membrane 3. integration of membrane lipids and proteins into the membrane
34
what kinds of proteins are translated on bound ribosomes?
proteins are destined for: 1. extracellular space 2. plasma membrane 3. lysosome 4. ER 5. golgi proteins have ER signal seq that instruct delivery into the ER - trafficked in vesicles to golgi and onto the final destination - entry into the ER is crucial for entry into the intravascular trafficking sys
35
what kinds of proteins are translated on free ribosomes?
proteins are destined for: 1. cytosol - glycolysis enzymes, actin, tubulin, IFs 2. nucleus - histone proteins, transcription factors 3. mitochondria - some electron transport chain proteins 4. chloroplast or peroxisomes *2-4: proteins have signal seq that are recognized by the transcript proteins that take them to the final destinations not vesicle-mediated transport - no ER signal seq
36
how do proteins know where to go?
signal peptide = continuous stretch of amino acids - important during or immediately following translation
37
signal peptide/seq
short seq that functions as an address - helps determine the eventual location of the protein in the cell binds to dedicated transport protein at N-terminus (common), C- terminus or internal
38
most outward flow of material goes through the golgi apparatus
for proteins with ER signal peptides leave ER in vesicles that travel to the golgi apparatus - proteins can be further processed > post-translational mods and targeting information after processing - proteins = transported within the vesicles to the final destination
39
transport
motor binding proteins bind to specific motor proteins
40
vesicular budding, transport targeting and fusion
1. vesicle bud off of a membrane by coat proteins 2. vesicles = transported to the next membrane with the motor-binding proteins and molecular motors that move along the cytoskeleton 3. vesicles = specifically targeted to the next membrane by Rabs 4. Vesicles fuse to the destination membrane due to lipid constituents and SNARES
41
coat proteins
form vesicles from organelle membranes 3 families 1. COPII: from ER to golgi 2. COPI: retrograde flow from medial to cis golgi or golgi to the ER 3. clathrin: from golgi to endosome or plasma membrane or inward from plasma membrane to endosome
42
dynamin helps pinch off clathrin-coated vesicles
dynamin assembles into a ring around the neck of the forming bud and other proteins - destabilize interacting lipid bilayers > Newly formed vesicles can pinch off from the membrane specific mutations in dynamin - can block/enhance pinching-off process
43
vesicular protein signatures help direct vesicular transport
protein signature = cytosolic side of a vesicle 1. peripheral proteins 2. cytosolic side of a transmembrane protein peripheral proteins make up the submembrane meshwork on the cytosolic side of the vesicle
44
motor binding proteins can be
1. peripheral 2. transmembrane
45
transportation of vesicles
vesicle protein signature - includes motor binding proteins > bind to molecular motor proteins = aid in transport of vesicles along the cytoskeleton many different proteins can func as motor binding proteins
46
targeting and fusion of vesicles
cytosolic protein signature includes proteins that target and fuse with specific target membrane
47
targeting/tethering
Rab on vesicle bind to Rab effector proteins on target membrane to tether 2 together
48
fusion
SNARE proteins bind and start the fusion of 2 lipid bilayers "lipid signatures" of outer and inner leaflets of the membrane - outer/inner fuses with the outer/inner > due to phospholipid similarities
49
can different Rabs target vesicles to different cellular locations?
yes

molecular bio (10 decks)

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