Structure of Plasma Membrane Flashcards
the plasma membrane is part of____. what is that?
endomembrane system. eg er, nuclear membrane, golgi apparatus and lysosomes
how many membrane does mitochondria and chloroplasts have?
2 (inner and outer membrane)
fx of mito and chloro outer membrane
has pores that allow small molecule to pass easily
fx of mito and chloro inner membrane
loaded w proteins that make up the electron transport chain and help generate energy for the cell
diversity of cell membrane but
share common chemical composition
membrane function
- compartmentalization
- scaffold for biochemical activity
- providing a selectively impermeable barrier
- transporting solute
- responding to external signals
- intracellular interaction
- energy transduction
explain compartmentalization
-membranes are continuous, unbroken sheet
-membrane-bound compartments possessed markedly different contents
-allow specialized activities to proceed without external interference and enable cellular to be regulated independently
explain scaffold for biochemical activities
-membranes are not stable as long as reactants are present in the solution, their interaction are dependants on random collision
-provide an extensive scaffolding within which component can be ordered for effective interaction
explain providing selectively impermeable barrier
preven unrestricted exchange of molecules from one side to another side
provide the means of communication between compartments they separate
explain transporting solute
-transport substances from one side to the other
-allow cell to accumulate substances such as sugar and amino acid (to fuel metabolism and buid macromolecules)
-transport specific ions to create gradient (nerve and muscle cell)
explain responding to external signal
posses receptor that combine w ligand that have complementary structure and cause membrane to generate a signal that stimulates/inhibits internal activities
explain intercellular interaction
plasma membrane mediates the interaction between a cell and its neighbors by recognizing, signalling to adhere when appropriate and to exchange materials and information
explain energy transduction
membranes are involved in the process of energy conversion such as photosynthesis, respiration
explain davson danielli sandwich model
-1935
-made up of a phospholipid bilayer sandwiched between two protein layers
Singer and Nicolson
-1972
-proposed that membrane proteins are dispersed and individually inserted into the phospholipid bilayer
the chemical composition of cellular membrane
plasma membrane encloses cell and organelles
the core of the membrane consists of lipids arranged in a bimolecular layer
lipid-protein is held tgt in a thin sheet by non-covalent bonds
chemical composition memrane
- all membranes composed of lipids proteins and carbohydrates
- the lipid bilayer gives the membrane its basic structure and serves as impermeable to most water-soluble molecules
- the proteins carry out most of the other functions of the membrane and give different membranes their individual characteristics
- the ration of lipid to protein depends on
-type of cellular membranes
-type of organism
-type of cell
eg: mitochondria high ration protein: lipid
myelin sheath of nerve has thick layer of lipid
5. carbohydrates are attached to protein or lipid
membrane lipid is amphipathic.
true both hydrophilic and phobic regions
how lipid assemble
-lipid molecule spontaneously aggregate to bury their hydrophobic hydrocarbon tails in the interior and expose their hydrophilic heads to water.
-2 forms: spherical micelles or bilayer
-spherical micelles tails inward
-bilayer hydrophobic tails sandwiched between the hydrophilic head grups
types of membrane lipid . how many
3 (phosphoglyceride, sphingolipids, cholesterol)
the most abundant membrane lipid
phosphoglyceride
phosphoglyceride contains
a phosphate group, a glycerol backbone and two fatty acyl chains
who attached to the phosphatidic acid (phosphate grp)
choline, ethanolamine, serine or inositol
-this group are small and hydrophilic and formed highly water soluble domain tgt with PO-
jnis2 saturated
fully saturated, monounsaturated, polyunsaturated
the plasma membrane of cell is a bilayer of
phosphoglyceride molecules
phosphoglyceride composed of 2 major region
a hydrophilic head and hydrophobic tail
susunan warna dri atas - biru, oren, hijau, purple.
biru choline
oren phosphate
hijau glycerol
purple hydrophobic tails
why the tail sometimes slightly bent
-unsaturated
-a double bond in one of tge hydrocarbon tails causes a slight kink on this molecule so it appears bent
sphingolipid consist of
sphingosine linked to fatty acid
phosphate and carbohydrate of sphingolipid attached to
ceramide domain
all sphingolipids have 2 long hydrophobic hydrocarbon chains at one end and a hydrophilic region at the other
cholesterol fx
to stabilize lipid bilayer . dont want too dynamic bcs not stable
smaller and less amphipatic than other lipids
cholesterol
how carbohydrate molecules are oriented
oriented w their small hydrophilic hydroxyl group toward the membrane surface and the remainder embedded in the lipid bilayer
how the hydrophobic rings interfere the movements of the fatty acid tails of the phospholipid
they are flat and rigid
the lipid bilayer is asymmetrical
cell membranes present a very different face to the interior of the cell/organelle than they show to the exterior (diff phospholipid and glycolipid in the two different faces) to perform diff functions
lipid bilayer consists of how many leafltes
2 . they have distinct composition
-independent monolayers having diff physical and chemical properties
importance of lipid bilayer
-determine the physical state of the membrane
-influence the activity of particular membrane proteins
-provide the precursors for highly chemical messenger that regulates cellular fx
-provide flexibility and deformability of membrane; shape can change during locomotives, cell division
-form extensive interconnected network
-ability to self assemble
3 classes of membrane protein
-integral protein
-peripheral
-lipid-anchored
integral protein
-amphipatic
-pass thru lipid bilayer and have domains that protrude from both the extracellular and cytoplasmic sides
-some have only one segment others are multispanning
-amino acid residues in transmembrane domains form van der waals interactions with the fatty acyl chains of the bilayer
peripheral protein
-located entirely outside of the lipid bilayer, on the cytoplasmic or extracellular side
-associated w the surface of the membrane by noncovalent electrostatic bonds
-always associated w integral protein
lipid anchored protein
-located entirely outside of the bilayer on either cytoplasmic or extracellular surface
-covalently linked to a lipid molecule in the bilayer
-2 types
2 types of lipid anchored protein
- GPI-anchored proteins are peripheral proteins containing glycosylphosphatidylinositol linkage
- protein present on the cytoplasmic side is anchored to membrane by one or more long hydrocarbon chains embedded in the inner leaflet
integral protein function
-RECEPTORS that bind specific substances at the membrane surface
-CHANNELS/TRANSPORTER involved in the movement of ions and solutes across the membrane
-CARRIERS that transfer electrons during photosynthesis and respiration
peripheral protein fx
-provide MECHANICAL SUPPORT to the membrane
-as ANCHOR for integral protein
-those on the internal plasma membrane surface function as ENZYMES, SPECIALIZED FACTORS THAT TRANSMIT TRANSMEMBRANE SIGNAL
-have dynamic relationship w membrane. recruited or released
bond in membrane proteins
- integral van der waals
- peripheral nonvovalent weak electrostatic bond
- lipid anchored covalent
fx of membrane protein
- TRANSPORT particular nutrients, metabolites and ions across the lipid bilayer
- as ANCHOR to attach macromolecules on either side
-as RECEPTOR that detect chem signal in cell’s environment and relay them to the cell interior
work as ENZYME to catalyze specific reactions
example of transporter protein and explain fx
transporter
eg na+ pump
fx actively pump na+ out of cells and k+ in
example of anchors protein and explain fx
integrin
fx link intracellular actin filaments to extracellular matrix protein
example of receptot protein and explain fx
PDGF
binds extracellular PDGF and generates intracellular signal that cause the cell to grow and divide
