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Cell Bio > Exam 2 > Flashcards

Exam 2 Flashcards

(85 cards)

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1
Q

Phospholipids

A

most common amphipathic lipid
glycerol backbone + 2 fatty acids + phosphate + polar head
- ALWAYS face cystolic side

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2
Q

Sterols

A

4 planar rings + phytyl tail + hydroxyl group (polar head)
Controls membrane fluidity
- cholesterol

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3
Q

Van der Waals forces in lipid bilayer

A

interactions between the hydrophobic tails

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4
Q

Ceramides

A

hydroxyl groups
decrease membrane fluidity
makes membranes more permeable to small molecules

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5
Q

Sphingomyelin

A

Neuron insulator
Lipids rafts

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6
Q

Glycolipids

A

Sugars
Non-cystolic side of membrane

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7
Q

Membrane fluidity - fatty acyl tail length

A

Shorter tails –> more fluid
- fixed in an organism

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8
Q

Membrane fluidity
Saturation level

A

More desaturation –> more fluidity
Double bonds induce kinds into the tails

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9
Q

Membrane fluidity
Cholesterol

A

More cholesterol –> less fluidity
eukaryotes

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10
Q

FRAP

A

Measures membrane fluidity
1. label membrane with fluorescence
2. ‘Bleach’ label in small area with laser
3. Monitor signal return

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11
Q

Flippases

A

Maintain membrane asymmetry and transport specific phospholipids across cell membranes

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12
Q

Integral proteins

A

Part of protein is imbedded in the bilayer

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13
Q

Transmembrane proteins

A

most common bilayer protein
- amphipathic alpha-helixes
- every 3-4 AA is hydrophilic
- good channels

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14
Q

Beta-barrels

A

Transmembrane protein
Made from beta-sheets
Form large openings (porins)

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15
Q

Lipid-linked protein

A

Found on signaling proteins
cystolic side

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16
Q

How do we study the bilayer

A

Mostly nonpolar so hard to study
Detergents ‘solubilize’ them

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17
Q

Cell cortex

A

Found in animals and protists
- Meshwork inside PM
Actin and spectrin fibers attach to membrane anchors (integrins)

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18
Q

Glycocalyx

A

Carb layer made from glycoproteins
- outside PM
- forms protective layer
-important for cell/cell binding and recognition
review white blood cell example

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19
Q

What molecules can freely diffuse across the lipid bilayer

A

Hydrophobic molecules (O2, CO2, N2)
Small uncharged polar molecules (H20, NH3, urea, glycerol)

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20
Q

What can’t freely cross the bilayer?

A

Polar things bigger than glucose
Anything with a charge

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21
Q

Transport proteins

A

Aka carrier proteins
- very specific: precise binding sites for transported solutes
- active or passive transport
Ex: uniporter

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22
Q

Channel proteins

A

Not necessarily specific for solutes
-transport many molecules at a time
-passive only

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23
Q

Coupled transporter

A

Harnesses the electrochemical gradient of one solute to drive another solute across a membrane against its gradient

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24
Q

Na+-K+ pump

A
  1. Na+/K+ ATPase: pumps 3 Na+ out for every 2 K+ in, generating some membrane potential
  2. K+ leak ion channels: lets a litlle K+ when the membrane is depolarized
  3. Na+ coupled transporter: harnesses Na+ e-chemical gradient
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25
ATP-driven transporters
-P-type ATPases -ATP binding cassette
26
P-type ATPases
Ion transporters - Na/K pump Phosphate addition from ATP and removal causes conformational change
27
ATP binding cassete
Transport small organic molecules Have two ATP binding domains - sugars, AA
28
How do cells deal with osmotic stress?
a. animal cells- regulate intra and extracellular ion concentration b. plant cells - have walls
29
Aquaporin channels
alpha helixes that allow rapid movement of water across membranes - always open - passive
30
Cystic fibrosis ion channel
ABC-like Cl- channel allows Cl- to flow out into the lumen Drives sodium out of cell - If the Cl- channel is defective, less Na+ leaves the cell and mucus is dry and thick
31
Nuclear pore complexes
Nuclear pores are gated for molecules >30 kDa
32
Nuclear import is regulated by
Nuclear import receptors Bind to nuclear localization signals (NLS) on cargo - proline++++
33
Ran-GTP
G-protein that shuttles between the nucleus and the cytosol
34
Ran-GEF
inside the nucleus
35
Ran-GAP
Outside the nucleus
36
old NPCs become leaky
Once NPCs and incorporated in the nuclear envelope and mitosis ceases, scaffold protein subunits do not exchange but peripheral proteins do This is a problem for cells that rarely divide, as the scaffold proteins can become damaged and lead to 'leaky' NPCs
37
Protein to the mitochondria
Most have transit peptides Interact with receptors on the outer membrane --> translocated via TOM and TIM
38
Transit peptide
Signal peptide for mitochondria
39
TOM
Translocon of the outer membrane
40
TIM
Translocon of the inner membrane
41
How do peptides cross the mitochondrial membrane
a. membrane potential due to transmembrane protein + charge and membrane - charge b. ATP - causes cystolic Hsp70 to fall of - import ATPase to pull protein through
42
What do cytosolic hsp70 chaperones do.
Protect the translated protein from degradation in the cytoplasm
43
Peroxisomes function
Degradation of 'toxic' chemicals, H2O2 metabolism, lipid metabolism and more
44
Catalase
Enzyme in peroxisomes Required for aerobes to break down hydrogen peroxide into H2O and O2
45
Signal peptide
N-terminal zip code for protein entry into ER - cut off final protein by signal peptidase
46
Signal Recognition Particle (SRP)
1. The SRP directs ribosome/mRNA complex to SRP receptor and translocator on the ER membrane 2. Signal peptidases are cleaved off the final protein
47
Type 1 transmembrane proteins
Have and SP and one or more additional hydrophobic transmembrane domain (TMD) N-terminus ALWAYS faces the lumen
48
Type 2 transmembrane protein
No SP, have a non-cleavable internal start transfer sequence Orientation dictated by charges that flank the first TMD (++ --> cytosol)
49
The lumen of the endomembrane system is acidic due to
v-H+-ATPases and high levels of Ca++
50
KDEL sequence
ER resident proteins Located on the C-terminal
51
Cargo receptors
Transmembrane proteins that bind 'cargo' in the lumen and adaptins on the cytosolic side
52
Adatpins (APs)
Bind to receptor proteins on the cytosolic side of the membrane and recruit coat proteins - Different APs bind to different membranes via differential phosphoinositide accumulation
53
Coat proteins
Bind to APs and drive vesicle formation
54
Different coat proteins bind to different
APs
55
COP11
vesicles leaving the ER
56
COP1
Vesicles leaving golgi for secretion and retrograde traffic to ER
57
Clathrin
Endocytic vesicles and vesicles from the golgi to the endosome/lysosome
58
Dynamin
Uses GTP to constrict vesicular neck to pinch off vesicle
59
Kinesins
For 'secretory' (anterograde) traffic
60
Dyneins
For retrograde traffic
61
Rabs
G-proteins that ID target membranes - bind to 'tether' proteins -vesicles from different source membranes have different Rabs on their surfaces
62
SNAREs
Drive membrane fusion
63
v-SNARES
on vesicles
64
t-SNARES
On target membrane - one v-SNARE for 3 t-SNAREs - coiled-coils
65
Botulism
Cleavage of the SNAP-25 by Botox
66
N-linked glycosylation
Addition of short chain carbohydrates to an asparagine side chain - for soluble and transmembrane proteins
67
Why glycosylate proteins?
a. increase protein solubility b. prevent damage and degradation of proteins c. Can be part of the glycoalyx d. used to monitor proper protein folding in ER - prevents damaged proteins from leaving ER - If they are correctly folded, glycosylation is removed e. part of the ZIP code for delivery to the lysosome
68
Calnexin
A membrane bound chaperone that helps proteins fold
69
Glycocalyx
Carbohydrate layer outside the cell attached to the membrane protein
70
Disulfide bond formation
Disulfide bonds form spontaneously in the oxidizing environment of the ER - very little GSH to break them - only found in endomembrane system, outside cell, and in mitochondrial matrix
71
Glutathione (GSH)
Breaks disulfide bonds in cytosol
72
Protein disulfide isomerase (PDI)
Chaperone for disulfide bond formation in the ER
73
Secretory pathway
Flows from the ER to the golgi to the PM or lysososme
74
GPI-anchors
Some membrane proteins acquire a covalently attached GPI anchor in the ER - anchors protein to the luminal side of the system - most go to the PM and face the extracellular space
75
Golgi function
1. Modification of the N-linked glycoproteins, synthesis of glycolipids and O-linked proteoglycans 2. Post office - send things to lysosome, secretory pathway, or secretion
76
Endocytic pathway
Usually flows from the PM to the endosome to the lysosome
77
Phagocytosis
Large things by specialized cells
78
Cholera
CFTR (chloride channel) is opened by cAMP binding on the cytosolic side of the membrane - cholerae toxin causes cAMP to be made - leads to dehydration and death
79
Phagosome
A vesicle formed when a cell engulfs a pathogen via phagocytosis
80
Phagolysosome
A vesicle formed during the fusion of a phagosome with a lysosome for enzymatic degradation
81
Autophage
Where cells break down and recycle damaged organelles or proteins
82
Pinocytosis
Endocytosis of large things by all eukaryotic cells
83
Endosome
First place endocytosed material goes Sorts internal molecules from the plasma membrane
84
Early endosome
Fist compartment in the endocytic pathway Receives vesicles from the plasma membrane Sorts cargo for recycling or degradation
85
Late endosome
Formed from matured early endosomes Fuses with lysosomes for degradation

Cell Bio (4 decks)

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