Membrane Structure Flashcards
All the cells have a membrane to
Seperate and protect it
The membrane that sorrounds the entire cells is called
The plasma membrane
Eukaryotes consist of
Cytoplasm organelles all of them are srrounded by cel membranes
Each oraganelle membrane is similar in ——& ————- to the plasma membrane
Function and structure
Plasma membrane functions
Barrier nad protector
Selectivity
Responsible for the cell comunication with the external environment
A recognistin of signaling molecules ,immune molecules, adhesion protein
B signal generation in response to chemical and electrical stimuli
Transport
Water
Through the lipid bilayer
Through ion channels
Through aquaporins
Small non polar molecules(CO2,O2,some hormons)
Through the lipid bilayer
Large polar molecues(ions ,Amino acids ,glucose)
Through transport proteins
Large materials (cellular debris)
Large amounts of small molecules
Exocytosis and endocytosis
Plasma membrane is about ——thick
——protein
——lipid
——water
——carbohydrate
5nM
60% except mitochondria(75%) myelin(18%)
40%
20%
1to10%
Membrane is
A phospholipid bilayer (fatty acids with charged phosphate head groups)
And proteins
It has a mosaic structure (fluid mosaic model)
Membranes must be ——
Involves the ———and———
Of both_____ &______
Fluid
Structure and dynamics
Lipid and proteins
Membrane fluidity is determined and regulated by
Cholesterol and unsaturated fatty acids
Membrane lipids
1
2
3
1 phospholipid
a phosphoglycerides fatty acids are atached to glycerol 3 phosphate
Pe
Ps
Pi
Pc
B sphingo myelin no glycerol
2 cholesterol(in plants stigma sterol)
3 glycolipis
Choline
I
Phosphate
I
Glycerol
I
Fatty acid
Membrane lipids are asymmetric
Ps and pe inside
Pc and s out side
We maintain the lipid asymmetry through
Actively flip loppase activity
More ps out side
Target the cell for apoptosis
Unsaturated fatty acids chains
Are in cis conformation
Forming kinks
Cholesterol functions
Provides rigidity and mechanical stability to plasma membrane
Generates natural negative curviture
Exocytosis
Lowers permeability and affects water penetration
Regulates the fluidity
Anti oxidant against radiation initiated oxidation
Raft
Composed
Function
Small islands floating freely within the plasma membrane
Cholesterol+protein receptor+glycosphingolipid
As an organizing center for signaling molecules
Membrane glycolipids
Important in
Carbohydrates atached to lipids
stability, cell-
cell recognition, crucial to the immune response, in tissue formation, and are important in signal transduction.
1.Cerebrosides: Head group is a sugar monomers
2. Gangliosides:
Head group is an oligosaccharides
Dynamics in lipid bilayers
Fast axial rotation
Fast lateral diffusion
Flip flop mechanism
Intra chain motion kink formation
Scramblase
Flippase
flopase
exchange fatty scids between the lipid bilayer
Move lipids from outer to inner
Both floppase and flippase aquire ATP and they are important for equalizing lipids during membrane generation
Types of proteins according to their location
Integral
Anchored
Peripheral
Glyco proteins
This attachement
Two types
Oligosaccharides covalently attached to proteins
Is a type of glycosylation
Which is a post transitional modification
N glycosylated( asparagine)
O glycosylated (serine and therionine)
Some membrane proteins provide extra strength to the plasma membrane by attaching
To proteins of the ECM on the outside and cytoskeleton on the inside
Cytoskeleton
Nicrotubules
Intermediate filaments
Actin
A number of long fibrous proteins that mantain cell skeleton
Important for cell division
For mechanical strength
Contraction force for movement
Membrane proteins functions
Enzymes
Receptors
Energy transducers
Adhesion/Cell-cell recognition p
Transporters
Angiotensin-converting enzyme 2 (ACE2) located in
Interacts with
Normaly binds to
Lung epithelium
Covid-19 viral Spike Glycoprotein to atach and enter the cells
Angiotensin II
Mobility of membrane proteins
- Conformational change 2. Rotational
- Lateral
Che wadaka membrane protein natwane zor bjule
Lipids
Association with other membrane proteins
Carbohydrate atachment
Association with extra membranous protein
Integral;
Glycophorins
Band 3
Peripheral:
Spectrin
Actin
Ankyrin
Protein 4.1
Protein 4.2
Trophomyo
Provide a negative charge to cell to reduce interaction with other cells and endothelium.
Exchange bicarbonate ion for chloride ion.
Cytoskeleton protein responsible for the biconcave shape of RBCs.
Participate in protein-protein interaction.
Interacts with spectrin and Bnad 3, links membrane to cytoskeleton.
Stabilizes actin-spectrin interaction
Help interaction of Band 3 protein with ankyrin Stabilizes actin filaments
ABO
By glyco proteins on cell membrane
Erythrocyte deformability
RBC change their shape under mechanical forces
Its possible bc
Cytoskeleton and membrane flexibilty
Hereditary Spherocytosis
spectrin levels is 40-50% depleted.
Hemolytic anaemia
Hereditary Elliptocytosis
where spectrin is unable to form a network with actin
Treatment with cytochalasin
Phospholipid synthesis
Fatty acids
Phosphate head groups and phosphate and water
smooth ER.
Form van der walls
Electrostatic and hydrogen bonding
Amphipathic
Liposome
Micelle
Lipid bilayer
Amphipathic
Liposome
Micelle
Lipid bilayer
