The Cell Membrane (Plasma Membrane)

The Cell Membrane Surrounds all living cells Controls how substances can move in and out of the cell The membranes that surround the nucleus and other organelles are almost identical to the cell membrane It is semi-permeable meaning it allows only certain substances through it Protects the cell from the outer environment

The Structure of the Cell Membrane Contain: Phospholipids Proteins Carbohydrates

Phospholipids Cell membrane is made of two layers composed mainly of molecules called phospholipids Glycerole and Phosphate -charged  -hydrophilic + - Fatty Acids -uncharged  -hydrophobic

Phospholipids Arranged in two layers, each has the charged part facing either the watery exterior or interior environment Uncharged fatty parts are sandwiched between Cholesterol is spaced throughout each layer to prevent the phospholipids from moving around too much

Proteins Transport protein allows substances in and out of the cell Identifier protein describes the type of cell it is Marker protein tell if there is an important spot nearby These proteins are imbedded in the layers

Carbohydrate Chains Glycoproteins: proteins with carbohydrates Glycolipids: phospholipids with carbohydrates Function as protection

Fluid Mosaic Model of a Cell Membrane The phospholipids, proteins, and cholesterol can move amongst themselves somewhat like particles floating on a thin layer of oil Fluid refers to the ability of the membrane “peas” to move Mosaic refers to “little peas” working together

Special Properties of the Cell Membrane Substances can pass into or out of the cell or organelles with help from the protein molecules Some proteins molecules form a tunnel that helps move substances across the membrane Proteins regulate the chemical reactions that take place