Unit 4 Cells 4 3 Cell Membrane https

Unit 4: Cells 4. 3 Cell Membrane https: //www. youtube. com/watch? v=6 fhbb. Fd 4 ic. Y

Cell membrane/Plasma Membrane The cell membrane is made up of a phospholipid bilayer, proteins, and cholesterol

Phospholipid Bi-layer Made up of 2 parts: 1. Phosphorus head Polar: will form weak bonds with other polar substances

Phospholipid Bi-Layer 2. Lipid Tails Non-polar: will form weak bonds with other nonpolar substances. Water inside and outside the cell will repel these tails causing them to be on the inside of the membrane. Substances that will dissolve in lipids, like cholesterol, will pass freely through the membrane.

Draw the Phospholipid Bilayer

Other Molecules- Proteins There are two main types of proteins within the phospholipid bilayer: Channel/Integral: they go all the way through the membrane Surface/Peripheral: on only one side of the membrane

Functions of Proteins: Marker Proteins/Cell Signaling: tell us what type of cell it is. Ex: liver cell, lung cell, skin cell, etc. Receptor Proteins: bind to specific substances and act like signals molecules on the outside of the cell. Carrier/Transport Proteins: aid in the movement of substances in and out of the cell. Enzymes: aid in the chemical reactions of the cell.

Other Molecules- Cholesterol is an additional type of lipid found in the cell membrane Cholesterol helps to strengthen the bilayer and regulate proteins

The Fluid Mosaic Model Together, the bi-layer and proteins make up the fluid mosaic model. The cell membrane is not rigid like an egg shell, it is fluid, like the surface of a soap bubble. The proteins are not stationary, they move around the membrane freely. The bi-layer is NOT bonded together, there are only weak attractions. This means that the membrane can be flexible and change shape.

Function of the Cell Membrane

Four Functions of the Cell Membrane: 1. Separation of internal and external environment 2. Cell Signaling 3. Selective transport 4. Excretion of Waste