Chapter 5 The Plasma Membrane

What is the plasma membrane made of? Phospholipid bilayer Cholesterol Proteins Glycocalyx

What does each component do? Phospholipids- gives the membrane flexibility and allows only certain substances to pass through. Cholesterol-patches the spaces and stiffens the membrane. Proteins-carries out membrane functions. Glycocalyx- sugar chains that coats cells to lubricate, make sticky, or act as binding sites.

Integral proteins- are attached to the hydrophobic inside. Membrane proteins Integral proteins- are attached to the hydrophobic inside. Peripheral proteins- are on inside or outside and attached to integral proteins.

Types of proteins

Proteins Support-can be attached to cytoskeleton. Recognition-identification of cell. Communication-(receptors) gives cell signals. Transport- passes substances in and out. (Active and Passive)

Diffusion Movement of molecules or ions from higher to lower concentration. Concentration gradient- the difference between the highest and lowest concentration of a solute in a medium.

Osmosis The movement of water across a semi-permeable membrane from lower to higher solute.

Osmosis Hypertonic-water moves out. Hypotonic-water moves in. Isotonic-movement is even.

Passive transport Simple diffusion-no energy required, material move down the concentration gradient. Facilitated diffusion- no energy required but need an protein channel. Material moves down concentration gradient.

Active transport Requires energy. Uses ATP as energy source. Protein pumps do the job. Many pumps are specific to one or two molecules or subatances.

Sodium Potassium Pump Need high amount of potassium (K+) inside the cell and high amount of sodium (Na+ ) outside the cell. Example-nerve cells: need lots of Na to start the signal