Membrane Structure Flashcards
organs definition
specialized structure in the body that perform specific life processes
organelles definition
specialized structures inside the cell that perform specific cellular processes
often surrounded by a membrane
cell fractionation
a method of separating cell parts to study their function
homogenization definition
the disruption of cell membrane without damaging organelle
centrifuge
instrument that spins a high speeds to spearate contents by density
4 ways to rupture the plasma membrane
- break cells with high frequency
- use a mild detergent
- use high pressure by forcing cells through a small hole
- shear cells between a close fitting rotating plunger
steps to cell fractionation
- homogenize
- centrifuge
- decant supernatant
- repeat centrifugation at higher speeds to separate into smaller components
pellet
larger, more dense components of tissue
supernatant
lighter suspended in liquid above the pellet in tissue
plasma membrane
aka cell membrane all cells and organelles are surrounded by it
what is the membrane composed of?
- phspholipids
- membrane proteins (integral, peripheral)
- carbohydrates
- cholesterol
what is each layer called in a phospholipid bilayer
leaflet
what environment is the phospholipid bilayer in?
water is on both sides -> cell is in water environment and the cell interior is also a water environment (polar)
how is the phospholipid arraged in the phospholipid bilayer
- hydrophobic tails face inward forming a hydrophobic core
- hydrophilic heads face outwards
what are the two locations classification of membrane proteins
integral, peripheral
what are the classification of integral proteins
- polytopic transmembrane, sinlge-pass, multi-pass
-monotopic
what are the classifications of peripheral proteins
- extracellular
- intracellular
what does polytopic mean?
faces both sides of membrane
transmembrane definition
spans entire phospholipid bilayer
single pass protein definition
crosses membrane once
multi-pass protein definition
crosses membrane several times
monotopic definition
associated with membrane on one side, does not span entire bilayer
how are non peripheral mombrane proteins bound?
non-covalently to either surface of the membrane
does NOT enter the leaflet
functions of membrane proteins
- receptor
- enzymatic activity
- recognition
- attachment
- transport
- cell adhesion
types of transmembrane proteins
- receptor protein
- channel protein
- gated channel protein
- transport protein
- glycroprotein protein
receptor protein
has a binding site to fit the molecule which acts as a chemical signal/messenger,
result of binding in receptor protein
causes a conformational change in receptor protein, which results in a relaying message to the interior of the cell
enzymatic activity
protein has a binding sit for molecule, binding results in a chemical reaction that changes the substrate to a new product
recognition protein
glycoprotein, surface carbohydrate groups help identifycell (eg antigens)
what does an attachment protein attach to?
interior cytoskeleton, exterior extacellular matrix (ECM)
what does the attachment protein do?
provide structural support
where does the extracellular cell face?
exterior/outside of the cell
what do extracellular proteins attach to?
the extracellular matrix, ECM
what is the fuction of ECM(extracellular matrix)
- supports cell structure
- anchors cell
- separates tissues
- functions in cell signalling
components of ECM
a matrix of glycoproteins secreted by cells, it varies with type of tissue
where are intracellular proteins attached?
inner membrane surface
what do intracellular cytoskeleton protein attach to?
cytoskeleton of cell
describe the intracellular cytoskeleton
a network of fibers extending throughout the cytoplasm
what does it mean by the intracellular cytoskeleton being dynamic
can be quickly dismantled and reassembled in a new location
what are the functions of the cytoskeleton
- mechanical support to cell
- cell motility
how does cytoskeleton support cell structure?
- anchorage for organelles
- maintain cell shape
critical for animal cells as there is no cell wall
what does motility of a cell mean in regards to the cytoskeleton
movement of cell -> change in cell location
movement of parts, vesicles, chromosomes, etc
what are the components of the cytoskeleton
- micro filament - actin
- intermediate filament
- microtubules - tubulin
types of transport proteins
channel, carrier/pump
types of channel transport protein
ungated, gated
describe the channel proteins
- act like tunnels
- molecules move through protein passively
what types of particles to channel proteins move?
small molecules or charged ions
describe an ungated channel protein
always opened aka leak channels
describe a gated channel protein
has open and closed conformations changes stimulated by changes in external environment,
describe the carrier/pump proteins
- acts like turnstile
- undergoes conformational change to allow molecules through
what does it mean by cell adhesion proteins
structures that connect cell to cell, in animal cells
what are the types of cell adhesion proteins
- channel-forming
- ocluding junction
- anchoring junction
describe the channel forming protein
provides channel between adjacent cells for passage of small molecules and ions
describe the occluding junction protein
fuses membranes of adjacent cells, forms impermeable barrier between cells
what is another name for anchoring proteins
desmosome
describe the anchoring/desmosome proteins
desmosomes bind to desmosomes on adjacent cell
what does a desmosome do?
helps resist shearing force when cells are under mechanical stress
where are desmosomes attached?
cytoskeleton
what is the name of occluding proteins?
tight junctions
what is the name of channel forming proteins?
gap junctions
example of gap junction attachements
muscle tissue
example of tight junction attachment
intestinal lining
example of desmosome
bladder tissue
functions of integral proteins
receptor, enzymatic activity, recognition, attachment, transport, cell adhesion
peripheral protein functions
recognition
attachment
glycoprotein makeup
carbohydrate + protein
glycolipid makeup
carbohydrate + lipid (phospholipid)
where are carbohydrates relative to the cell
extracellular
what are the function of cell surface carbohydrates?
- identifies the cell, helping other cells recognize it
- acts as a signal for communication
what is membrane fluidity affected by?
- saturation of fatty acid
- hydrophobic restrictions
- cholesterol and temperature
what are the types of movement within the membrane?
- lateral diffusion
- rotation
- swing
- flexion
what is lateral diffusion movement within a membrane?
movement accross the same leaflet (phospholipids transpose with neigboring molecules)
what is rotation movement within a membrane?
when a individual molecule rotates quickly around its axis
what is swing movement within a membrane?
from side to side
what is flexion movement within a membrane?
contraction movement
transverse diffusion aka…
flip flop
transverse diffusion
movement from one leaflet to another
what enzyme facilitates transverse diffusion
flippase
why is transverse diffusion rare?
the hydrophilic head of phospholipid must go cross the hydrophobic core to get the leaflet
properties of cholesterol
large molecular size and non polar
what is the impact of cholesterol having a large molecular size
can interrupt intermolecular forces of attraction
what is the impact of cholesterol being non polar
stabilizes hydrophobic interactions
what does cholesterol do at a low temperature?
the phospholipid moves around less, squeezes phospholipids and increases fluidity -> large molecular size
what does cholesterol do a high temperature?
pulls together the bilayer -> non polar
