Membranes
Membrane Mechanisms
Fluid Mosaic Structure
Membrane Proteins
Membrane Lipids
Diffusion
Osmosis
Facilitated Diffusion
Concentration Gradient
Amphipathic Proteins
Amphipathic Lipids
Fluidity
Most lipids and proteins are able to shift sideways
Some lipids flip-flop to the other side of the membrane
Phospholipids yeet around and proteins shuffle
Factors affecting fluidity
saturation of hydrocarbon tails
cholesterol within cell membranes
a layer of phospholipids
Proteins bobbing in the phospholipids layer
Integral proteins
Peripheral proteins
Transmembrane proteins
Partially-penetrating-the-membrane proteins
Hydrophilic channels
Loosely-bound to the surface of membrane
On the Cytoplasm side: bound to cytoskeleton
On the extracellular side: materials outside the cell
Requires no ATP because molecules naturally want to find equilibrium
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Small molecules of gas can flow through membrane and squeeze through the lipid bilayer
The passive diffusion of water molecules across the membrane in order to try and reach equilibrium
Transport proteins help move substances
Still requires no ATP
Can be a protein channel where the substance moves straight through
Can be a "pac-man" like shape wher the molecule enters the opening of a protein and once in the middle the other side opens
When water is in a sugar solution, the water molecules cluster around the sugar molecules in order to dissolve the sugar
Represents the need for water to balance out the ratio of sugar molecules on both sides of the membrane
Osmoregulation regulates the amount of the solution in the cell and is vital for the cell's health
The direction a molecule takes in order to satisfy equilibrium
Movement from more concentrated to less concentrated
Occurs naturally without ATP
Each substance reacts in it's own environment regardless of other substances, everything will go down their own concentration gradient
Selective permeability controls what enters and leaves the lipid bilayer
When temperature decreases the lipid's movement decreases and can even solidify
However if lipids are moving too much the the proteins cannot carry out their function and become inactive
Evolution
Organisms can evolve to survive in their temperatures since the number of unsaturated vs. saturated fats in their lipid bilayers can adapt.
For example, an animal that in the cold has lots of unsaturated lipids in its bilayer so it is still fluid even if it moves slower