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Membrane Structure & Function - Coggle Diagram
Membrane Structure & Function
Cellular membranes are fluid mosaics
Fluid mosaic
Plasma cell membrane made of many things
Made of lipids, proteins, cholesterol, & carbohydrates
Membrane proteins are also
amphipathic
Fluidity of membranes
Phospholipids
Phospholipids are
amphipathic
Amphipathic
- both hydrophilic and hydrophobic (polar/non-polar)
Unsaturated versions prevent packing**
Made of phosphate head (polar) and a fatty acid tail (non polar)
Cholesterol
Can increase and decrease fluidity
Plants use something similar for movement, but they do not have cholesterol
"Fluidity buffer"
High temps makes it less fluid, at low temps the fluidity increases
Membrane proteins
Embedded in the membrane
Different cells contains different sets of membrane proteins
Integral proteins
- penetrate the hydrophobic interior of the lipid bilayer
Transmembrane proteins
- spans the membrane,
Peripheral proteins
- not embedded in the lipid bilayer at all
Carbohydrates
Carbohydrates allow for cell to cell recognition to happen by binding to the molecules
Usually short, branched chains of fewer than 15 sugar units
If they are covalently bonded to the lipid they form
glycolipids
If they are covalently bonded to proteins, they form
glycoproteins
On the extracellular side, they vary from species to species
Membranes selective permeability
Selective permeability
Allows certain things in
Has to be small, non-polar, & uncharged
"Gatekeeper"
Proteins
Transport proteins
- helps transport things across the membrane
Channel proteins
- Hydrophilic channel that helps certain ions or molecules through a tunnel
Aquaporins
- a type of channel protein that facilitates osmosis
Carrier proteins
- holds molecules and changes shape to the molecule to carry them across
Ions and polar molecules use proteins to get through the membrane
Cell transport
Passive transport
High
concentration to
low
concentration
Goes down the concentration gradient
No ATP required
Facilitated diffusion
-has help with a protein
Concentration gradient
- region along which the density of a chemical substance increases or decreases
Diffusion
- the movement of particles on a concentration gradient
Osmosis
- the diffusion of water through a semi permeable membrane
Only water is diffused
Water always follows the higher concentration of solute
"Wants to dilute"
From
hypotonic
to
hypertonic
Ion channels
- channel proteins that transports ions
Gated channels
- opens and closes in response to a stimulus
Tonicity
- The ability of a solution surrounding a cell to cause that cell to gain or loose water
Hypotonic
- Less/lower concentration
Hypertonic
-More concentration
Isotonic
- equal levels of tonicity of a cell and a solution
Plant cells are more
hypertonic
making them become
turgid
(
very firm
) which is healthy, in an
isotonic
solution, they become
flaccid
(
limp
)
Plasmolysis
- In a
hypertonic
solution the cell membrane pulls away from the cell wall. This causes wilting
Osmoregulation
- control of solute concentration & water balance
Active transport
Goes from
low
concentration to
high
concentration
Sodium-potassium pump
is a transport system that exchanges Na+ for K+
Requires ATP
Goes against the concentration gradient (why it needs energy)
Membrane potential
- electric voltage through your body across membranes
Electrochemical gradient
- drives the diffusion of ions across a membrane
Electrogenic pump
- a transport protein that generates voltage across a membrane
Proton pump
- actively transports H ions out of the cell
Cotransport
- a transport protein can couples the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient
Bulk transport
Exocytosis
- Cellular secretion of certain molecules by fusion of vesicles with the plasma membrane
Endocytosis
- The cell takes in molecules & particle matter by forming vesicles from the plasma membrane
