Idea that the plasma membrane is a mosaic of components, mainly phospholipids, cholesterol, and proteins which flow freely in the membrane plane
Because the plasma membrane is fluid, if you stick a fine enough needle through it, the membrane will simply flow around it
Phospholipid
A lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group
Phospholipid bilayer
Two layers of phospholipids with their tails pointing inward to form a semi-permeable membrane
Cholesterol
A lipid made up of four fused carbon rings, is found along phospholipids at the core of the membrane
Membrane proteins may extend partway through the membrane, cross it entirely, or be loosely attached to its inside or outside face
Carbohydrates
Only attached to the outside layer of the plasma membrane, hanging on to lipids or proteins
50 / 40 / 10 ratio of proteins to lipids to carbohydrates in the human cell's plasma membrane
Amphipathic
Structures that have both hydrophobic and hydrophilic regions
The head of the phospholipid (phosphate and R) is hydrophilic, due to a partial negative charge, and so readily interacts with water
The tail of the phospholipid (long, nonpolarfatty acid strings) is hydrophobic, because of its nonpolarity, and interacts poorly with water but well with each other, so the tails stick together on the inside of the membrane
A phospholipid bilayer is good at protecting the cell because the hydrophilic ends interact well with their surroundings, but it's hard for things to penetrate it because of the inner layer of hydrophobic tails
Phospholipid molecule
Liposome
A hollow droplet of bilayer membrane made naturally in an aqueous solution when phospholipids have bulkier tails
Micelle
A small, single-layered sphere of phospholipids with small tails formed naturally in an aqueous solution
Integral membrane proteins
Proteins that have at least one hydrophobic part that anchors it to the hydrophobic core of the phospholipid bilayer
Transmembrane proteins
Proteins that pass through the phospholipid bilayer completely and stick out on both ends
The parts of integral membrane proteins that are inside of the membrane are generally hydrophobic, and the parts inside of the cell or touching the cytoplasm are generally hydrophyllic
Transmembrane proteins can cross the membrane just once, or up to 12 times, like when hydrophobic amino acids are arranged in an alpha helix
Peripheral membrane proteins
Found on the inside or outside of the phospholipid membrane, attached either to integral membrane proteins or phospholipids. They tend to be more loosely attached
Glycoprotein
Carbohydrates found on the outside surface of cells bound to proteins in the membrane
Glycolipid
Carbohydrates bound to the outside surface of cells bound to lipids
Carbohydrates and membrane proteins form distinctive cellular markers that immune cells use to know which cells to attack
At cooler temperatures, the straight tails of saturated fatty acids pack closely together to form a dense and fairly rigid membrane
At cooler temperatures, the kinky tails of unsaturated fatty acids cannot pack together as tightly, so membranes made up of unsaturated fatty acids stay liquid for longer
Most cell membranes have a mix of saturated and unsaturated fatty acid tails; some have two saturated tails, others have one saturated and one unsaturated
Cholestorol
Lipid embedded within the phospholipids of a membrane to help extend its range of fluidity (reduces fluidity at high temperatures, and keeps the phospholipids from packing too close together at lower temps)