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FEATURES OF THE CELL MEMBRANE - Coggle Diagram
FEATURES OF THE CELL MEMBRANE
CELLULAR MEMBRANE
has two leaflets- bilayer
Extracellular Leaflet
Cytosolic Leaflet
contains embedded proteins and cholesterol
maintains structure and helps in transport
Made up of phospholipids
Amphipathic
Hydrophilic
Hydrophobic
Fluid mosaic model
fluid in nature due to proteins and lipids
Different types
Lipid Anchored Proteins
protein attached to a lipid that is embedded inside the membrane
Peripheral proteins
protein that is completely unattached to the membrane
Transmembrane proteins
Proteins that are embedded onto the membrane
Integral proteins
can get harder or softer depending on the amount of cholesterol in the membrane
Membrane is semifluid
Movement of lipids
Lateral movement
Flip
uses flippase
makes use of ATP
takes a long time
Rotational
No energy requirements and takes seconds
Lipid rafts
compact arrangement of lipids- same or different, which moves along the membrane
Fluidity determinants
Double bonds
More double bonds- more fluid
Cholesterol
More cholesterol- less fluid
length of fatty acid chains
long- less fluid; due to interaction
MEMBRANE TRANSPORT
plasma membrane is selectively permeable
only allows essential molecules to enter the cell
Passive transport
does not use ATP or any energy
makes use of gradient
Electrochemical/ ionic
Transmembrane
Types
Diffusion
uses gradient
movement of solute from high to low concentration
Facilitated transport
makes use of transport proteins
Osmosis
movement of solvent from low solute to high solute concentration
Depends of tonicity
Isotonic
Equal water and solute concentrations on either
side of the membrane
Hypertonic
Solute concentration is higher on one side of the
membrane
Hypotonic
Solute concentration is lower on one side of the
membrane
Can result in entry/exit of solvent causing lysis and shrinkage resp.
Animal cell
2 more items...
Plant cell
2 more items...
Active transport
makes use of energy
moves against the gradient
Types
secondary active transport
makes use of preexisting gradient for movement of a substance against their gradient
H+/sucrose transporter
primary active transport
uses a pump
transports directly against the gradient
makes use of transport proteins
provides a passageway
Transporters
undergoes conformational change for transport
Symporter
transport 2 or more molecules in the same direction
Antiporter
transport 2 or more molecules in the opposite direction
Uniporter
transport one molecule in one direction
Channels
provides open passageway
has a gate for regulation
LIPID SYNTHESIS
takes place in the smooth endoplasmic reticulum
addition of glycerol-phosphate molecule
Polar head attachment
Fatty acid chain activated with attachment of CoA
Flippase makes sure all the leaflets have the same quantity as phospholipids are produced in the cytosolic leaflet
Lipid transport
Vesicles
Lipid Exchange Proteins
through diffusion- to the nuclear envelope as it is close to ER
PROTEIN SYNTHESIS
Transmembrane proteins
takes place initially in the ER and then transported to respective organelle
involves co/post translation process
GLYCOSYLATION
Addition of carbohydrates to lipids and proteins
Glycoproteins
Glycolipids
helps in cell recognition, prevents physical and mechanical damage
N- linked
Attachment of carbohydrate to nitrogen atom of asparagine side chain
Occurs in the ER
O- linked
Addition of sugars to oxygen atom of serine or
threonine side chains.
Occurs only in Golgi
MEMBRANE TRANSPORT METHODS
Endocytosis
Invagination of plasma membrane to engulf material from outside the cell
Pinocytosis
engulfing of small molecules/liquid substances
Receptor-mediated endocytosis
substances binds to receptors in the membrane and leads to invagination
Phagocytosis
engulfing of solid material/pathogen for degradation or nourishment
Exocytosis
Material inside the cell packaged into vesicles and
excreted into the extracellular medium
Vesicle formation makes use of protein coat for formation
protein coat is shed during transport
either goes out or inside the cell
inside the cell, vesicles fuses with lysosomes for digestion etc..