Membrane Structure Flashcards by Gashbin Maghdid

All the cells have a membrane to

Seperate and protect it

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The membrane that sorrounds the entire cells is called

The plasma membrane

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Eukaryotes consist of

Cytoplasm organelles all of them are srrounded by cel membranes

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Each oraganelle membrane is similar in ——& ————- to the plasma membrane

Function and structure

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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

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Transport
Water

Through the lipid bilayer
Through ion channels
Through aquaporins

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Small non polar molecules(CO2,O2,some hormons)

Through the lipid bilayer

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Large polar molecues(ions ,Amino acids ,glucose)

Through transport proteins

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Large materials (cellular debris)
Large amounts of small molecules

Exocytosis and endocytosis

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Plasma membrane is about ——thick
——protein
——lipid
——water
——carbohydrate

5nM
60% except mitochondria(75%) myelin(18%)
40%
20%
1to10%

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Membrane is

A phospholipid bilayer (fatty acids with charged phosphate head groups)
And proteins
It has a mosaic structure (fluid mosaic model)

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Membranes must be ——
Involves the ———and———
Of both_____ &______

Fluid
Structure and dynamics
Lipid and proteins

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Membrane fluidity is determined and regulated by

Cholesterol and unsaturated fatty acids

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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

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Choline
I
Phosphate
I
Glycerol
I
Fatty acid

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Membrane lipids are asymmetric

Ps and pe inside
Pc and s out side

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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

1. Conformational change 2. Rotational 3. 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