The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be.

The membrane lipid molecules are amphipathic. The most numerous are the phospholipids. When placed in water they assemble spontaneously into bilayers, which form sealed compartments that reseal if torn. There are three major classes of membrane lipid molecules—phospholipids, cholesterol, and glycolipids.

phospholipids

What is the most common phospholipid in cell membranes? Phosphatidylcholine, and it is build from five parts: they hydrophilic head, which consists of a choline linked to a phosphate group; two hydrocarbon chains, which form the hydrophobic tails; and a molecule of glycerol, which links the head to the tails.

Biological membranes have three primary functions: (1) they keep toxic substances out of the cell; (2) they contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products, that mediate cellular and extracellular activities to pass between organelles and between the …

Terms in this set (6)

• Molecule Transport. Helps MOve food, water, or something across the membrane.
• Act as enzymes. Controls metabolic processes.
• Cell to cell communication and recognition. so that cells can work together in tissues.
• Signal Receptors.
• intercellular junctions.
• Attatchment to the cytoskeleton and ECM.

Terms in this set (5)

• protects the cell by acting as a barrier.
• regulates the transport of substances in and out of the cell.
• receives chemical messengers from other cell.
• acts as a receptor.
• cell mobility, secretions, and absorptions of substances.

The cell membrane, therefore, has two functions: first, to be a barrier keeping the constituents of the cell in and unwanted substances out and, second, to be a gate allowing transport into the cell of essential nutrients and movement from the cell of waste products.

Functions of the Plasma Membrane

• A Physical Barrier.
• Selective Permeability.
• Endocytosis and Exocytosis.
• Cell Signaling.
• Phospholipids.
• Proteins.
• Carbohydrates.
• Fluid Mosaic Model.

The plasma membrane, or the cell membrane, provides protection for a cell. It also provides a fixed environment inside the cell, and that membrane has several different functions. One is to transport nutrients into the cell and also to transport toxic substances out of the cell.

Membranes are thin layers of epithelial tissue usually bound to an underlying layer of connective tissue. Membranes cover, protect, or separate other structures or tissues in the body. The four types of membranes are: 1) cutaneous membranes; 2) serous membranes; 3) mucous membranes; and 4) synovial membranes.

The main functions of the cell wall are to provide structure, support, and protection for the cell. The cell wall in plants is composed mainly of cellulose and contains three layers in many plants. The three layers are the middle lamella, primary cell wall, and secondary cell wall./span>

The most common example is the phospholipid bilayer cell membrane that surrounds every cell in our bodies. Another example of a selectively permeable membrane is the inner membranes of an egg. Phospholipids are molecules composed of a hydrophilic, or water-loving, head and a hydrophobic, or water-fearing, tail./span>