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In the alveoli, oxygen from the air is absorbed into the blood. Carbon dioxide, a waste product of metabolism, travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli.
Best Answer: Plasma membrane- The membrane enclosing a cell is made up of two lipid layers called a bilipid membrane. The lipids that are present in the plasma membrane are called phospholipids.. These lipid layers are made up of a number of fatty acid building blocks. The fatty acid that makes up this membrane has two different parts to it- a small water loving head- hydrophilic head.