bio130 exam Flashcards
animal cell specific organelles
ECM, lysosome
extracellular matrix is
specialized material outside of the cell
organelles not found in animal cells
cell wall, vacuole, chloroplast
2 types of vacuole purpose
degradation, storage
what’s considered in the cytoplasm vs cytosol
(cytoplasm) everything in the cell excl. nucleus vs (cytosol) aqueous part of cytoplasm + ribosomes + cytoskeleton
main biochemical property of all lipids in the bilayer
amphipathic
phosphoglycerides are defined by…
their glycerol group
structure of phosphoglycerides
some group, phosphate, glycerol, hydrocarbon tail (saturated or unsaturated)
length of phosphoglyceride
14-24 carbon atoms
kink in unsaturated hydrocarbon tail is caused by
C=C cis-double bond
liposomes and thier purpose
artificial lipid bilayers used to study lipid/membrane protein properties
method to manipulate membrane without causing damage?
laser tweezers
laser tweezers are used in combination with what technique usually
live cell imaging
possible movement for individual phospholipid
lateral diffusion, rotation, flexion, flip-flop
which phospholipid movement is the rarest (unfacilitated)
flip-flop
what affects membrane fluidity
temperature, phospholipid composition (saturation, tail length, sterol presence)
what sterols are used in animals vs plants to control membrane rigidity
animals: mainly cholesterol
plants: plant sterols, some cholesterol
max cholesterol:phospholipid ratio
1:1
increase in sterol means…
dec mobility of phospholipid tails, membrane less permeable to polar molecules
structure of sterol
hydrophilic head group, right planar steroid ring structure, nonpolar hydrocarbon tail
scramblase?
catalyzes flip flop of random phospholipids from 1 leaflet to another
where does scramblase act
in the ER
why does scramblase act
phospholipids are synthesized in the cytosolic leaflet of the ER - flip flopping balances the 2 leaflets out
the leaflets of the lipid bilayer are different in that…
noncytosolic face vs cytosolic face
flippase?
catalyzes flip flop of specific phospholipids to the cytosolic leaflet. can bind cytosolic proteins
what does phosphatidylserine do
binds protein kinase C
where does flippase act
golgi membrane
where is membrane built and sent (pathway)
ER -> golgi -> transport vesicle -> plasma membrane
how are glycolipids and glycoproteins formed
adding sugar groups to lipids/proteins on the luminal/noncytosolic face of the Golgi
luminal face property (flip flopping)
consistent, no flip flopping (??)
types of membrane proteins
integral (transmembrane, monolayer-associated, lipid-linked), peripheral (protein-attached, lipid-attached)
integral membrane proteins are
directly attached to the lipid bilayer or attached to a lipid which is inserted into the lipid bilayer
how to (destroy lipid bilayer) extract integral membrane proteins
detergenr
how can peripheral membrane proteins be bound
bound to other proteins, lipids, non-covalent interactions
types of transmembrane proteins
single pass (single alpha helix), multipass (many alpha helices, beta barrel)
structure of single alpha helix single pass protein
has a section of 20-30 hydrophobic amino acids
transmembrane protein orientation particularities (movement vs phospholipids)
they have specific orientations b/c they can’t flip flop (unlike phospholipids)
how are membrane proteins identified (techniques)
x-ray crystallography, hydrophobicity plots
what does x-ray crystallography do
determines 3D structures
what can hydrophobicity plots tell you
segments of 20-30 hydrophobic AAs can span the lipid bilayer as an alpha helix
how are proteins anchored onto a cytosolic face (monolayer-associated)
by an amphipathic alpha helix
how are GPI anchor lipid linked membrane proteins made
synthesized in ER lumen, ends up on noncytosolic face of cell surface
how are fatty acid/prenyl anchored lipid-linked membrane proteins made
cytosolic enzymes add the anchor, direct protein to cytosolic face
what do you need to be careful of when destroying and reassembling the membrane
proteins may get put back in the wrong orientation
FRAP stands for
fluorescence recovery after photobleaching
how does FRAP work
protein fused to GFP/fluorescent antibody, photobleach an area, measure recovery time
artificial bilayer permeability
impermeable to most water soluble molecules
cell membrane general permeability
molecules can cross via facilitated transport/membrane transport proteins
what molecules can diffuse faster across lipid bilayer
more hydrophobic or non-polar molecules
rank the following from easiest to cross membrane to hardest: small nonpolar vs uncharged polar vs ions vs large uncharged polar
small nonpolar, small uncharged polar, large uncharged polar, ions
what molecules are impermeable to membrane
ions
2 main classes of membrane transport proteins
channel, transporter
how do channel proteins bind to their transported molecules
bind weakly to transported molecules
how does channel protein selectivity work
selected based on size and electric charge of solute
channel vs transporter protein (conformation)
channel doesn’t change in conformation during transport, transporter changes a lot
how does transporter protein selectivity work
solute needs to fit into the binding site
types of passive transport
channel-mediated, transporter-mediated (uniport)
types of active transport
gradient-driven pumps, ATP-driven pumps (both types of transporters)
concentration gradient vs resting membrane potential in strength
concentration gradient is usu larger than resting membrane potential
electrochemical gradient =
concentration gradient + membrane potential
how are gated ion channels activated
require some signal to open channel
what has a role in generating resting membrane potential in animal cells
non-gated ion channels, na+/k+ pump or h+ pump
types of gated ion channels
mechanically, ligand (intracellular, extracellular), voltage
uniport proteins transport __ solutes w/ [transport method]
transport 1 solute w/ passive transport/down gradient
what happens to uniport proteins when EC gradient shifts
transport reverses
example of uniport
glucose transporter (GLUT uniporter)
types of active transport pumps
gradient-driven, atp-drive, light-driven
gradient driven pumps… (how do they work)
1 solute goes down its gradient to generate energy for the 2nd solute going against its gradient
types of gradient pumps
symport, antiport
example of symporter and how it works
na+ down gradient into cytosol, glucose against gradient
example of antiporter and how it works
na+ down gradient into cytosol, h+ against gradient
why is moving h+ important
cytosol ph needs to be regulated for enzymes
why is moving na+ out of cell important
pumped into cell for gradient-driven pumps, sent back out to extracellular space with na+-k+ pumps
types of atp-driven pumps
p-type, abc transporter, v-type proton
what’s special about p-type pumps
pump is phosphorylated during the pumping cycle
what type of pump is na+ k+ pump
p type
ratio of na+ and k+ in na+/k+ pump
3 na out, 2 k in
___ pump in animals and __ pump in plants (for membrane potential)
na+-k+, h+
na+ EC gradient equivalent for plants
h+ EC gradient
how does ABC transporter work
uses 2 atp to pump small molecules
how does v-type proton pump work
uses atp to pump h+ into organelles to acidify lumen
how does f-type atp synthase work
uses h+ gradient to drive synthesis of atp
where are v-type proton pumps found
lysosome, plant vacuole
where are h-type atp synthases found
mitochondria, chloroplast, bacteria
apical, lateral, basal domains are
apical: membrane covering microvillus
lateral: membrane in extracellular fluid in b/w epithelial cells
basal: membrane in extracellular fluid opposite of apical domain
where is glucose concentration high (in intestine)
inside epithelial cell
basolateral domain
basal + lateral domains
proteins involved in glucose control
na+driven glucose symport, na+ k+ pump, passive glucose uniport
transcellular transport of glucose requires…
asymmetric distribution of membrane proteins
how is asymmetry of membrane proteins in epithelial cells maintained
tight junctions
basolateral plasma membrane has what proteins
GLUT2 uniporter, na+ k+ pump
membrane potential defn
difference in electrical charge on 2 sides of membrane, from POV of inside of the cell
role of k+ leak channels
flow of k+ to extracellular space
na+ k+ pump generates ___% of membrane potential
10
net ion of na+ k+ pump
1+ ion pumped out (into extracellular space)
animal cell resting membrane potential (give range)
-20mV to -200mV
cytosol na+, k+, cl- content compared to extracellular space
cytosol: low na+, low cl-, high k+
extracelular space: opp.
membrane potential for plants (range)
-120 to -160mV
hepotocyte job
help with detox in liver cells
how much of the cell is cytosol (volume)
half the cell volume
RER vs SER amounts in liver hepatocyte vs pancreatic exocrine cell
RER + SER = ~50%
more SER in hepatocyte
there’s more membrane ___ in the cell
in the cell (vs around the cell)
role of SER
PHOSpholipid synthesis and detoxification
role of RER
synthesis of soluble proteins and transmembrane proteins
defn of organelle
a discrete structure of a euk cell specialized to carry out a particular function, typically membrane enclosed
e.g. non membrane bound organeles
nucleolus, centrosome
cytosolic protein
have no signal sequence, default location is the cytosol
signal sequence/sorting signal
a specific seq of AA that tells the cell where the protein should go
sorting receptor protein
recognize signal sequences and take proteins to their destination
post translational sorting
proteins are fully synthesized in the cytosol before sorting
post translational sorting destinations and folded or unfolded
nucleus peroxisomes (folded) mitochondria plastids (unfolded)
co translational sorting
proteins are sorted during translation which is done in the ER (proteins have an ER signal sequence)
signal sequence for nucleus and receptor
nuclear localization signal and nuclear import receptor
transcription activators
required in nucleus for euk transcription
how are proteins sorted into peroxisomes
imported through a transmembrane protein complex
most mitochondria and chloroplasts proteins are…
nuclear-encoded
how does the unfolding work for mitochondrial and chloroplast proteins
proteins are unfolded for import by hsp70 proteins
property of the ER signal sequence
hydrophobic
2 types of proteins entering the ER and where do they end up
soluble proteins (secreted outside of the cell or within lumen of organelle) and transmembrane proteins
process of cotranslational translocation for soluble proteins
N-terminal ER signal emerges, SRP recognition and elongation arrest, translocon open, synthesis resumes into ER lumen, signal peptidase cleaves ER signal sequence (sometimes)
SRP ribosome complex is made of
SRP receptor + translocon
diff b/w translocation for transmembrane protein and soluble protein
transmembrane has hydrophobic stop transfer sequence
what is the translocon
protein that lets specific proteins in
3 types of ER signal sequences and what is their primary protein structure
N-terminal, hydrophobic start, hydrophobic start (the latter 2 are membrane spanning alpha helix)
pathways of the endomembrane system
secretory, endocytic, retrieval
what does the secretory pathway involve in endomembrane system
proteins and lipids made in the ER are deliverd to other places in the cell
2 types of secretory pathway
constitutive exocytosis pathway, regulated exocytosis pathway
constitutive exocytosis pathway occurs only in
all euk cells
constitutive exocytosis pathway role
continual delivery of proteins and lipids to plasma membrane and secretion of soluble proteins
regulated exocytosis pathway occurs in…
specialized cells
regulated exocytosis pathway involved
regulated secretion stored in specialized secretory vesicles, secretion triggered by extracellular signals
path of a secreted protein
cytosolic ribosomes, co-translational translocation at ER, moved in transport vesicles to the plasma membrane, secreted
golgi apparatus
usually the first stop, receives proteins and lipids from the ER, modifies them, and dispatches them to the
where does protein glycosylation occur in
starts in ER and continues in golgi
what is protein glycosylation
attaching oligosaccharides to complete processing of proteins
endosomes are
membrane bound organelles containing material ingested by endocytosis
early endosomes
endocytic vesicles fused to early endosomes and ingested material is sorted, also lysosomal proteins are delivered to it
late endosomes
lysosomal proteins delivered from trans golgi network
example of lysosomal proteins
acid hydrolases, h+ pump
lysosomes occur when
most of the stuff has been digested, contains sufficient hydrolytic lysosomal enzymes to digest everything in it
what hapepns after lysosome maturation
lysosome fuses with endosome to reuse enzymes
how are lysosomes acidified
h+ pumps
why are lysosomes acidic
low ph for hydrolytic enzymes
what’s special about lysosomal membrane proteins on the non cytosolic face
glycosylated to protect from proteases
