A Bag full of Jell-O
This simple, cut-away version of an animal cell (Figure \(\PageIndex1\)) shows that a cell resembles a plastic bag full of Jell-O. Its an easy structure is a plasma membrane filled with cytoplasm. Like Jell-O containing blended fruit, the cytoplasm the the cell additionally contains assorted structures, such together a nucleus and also other organelles. Her body is consisted of of trillions the cells, but every one of them execute the same straightforward life functions. They all obtain and also use energy, respond come the environment, and reproduce. How do her cells bring out these straightforward functions and keep themselves — and you — alive? to answer this questions, you have to know much more about the structures that make up cells, beginning with the plasma membrane.
You are watching: The plasma membrane consists primarily of
The plasma membrane is composed largely of phospholipids, which consist of fat acids and also alcohol. The phospholipids in the plasma membrane are arranged in two layers, dubbed a phospholipid bilayer, v a hydrophobic, or water-hating, interior and a hydrophilic, or water-loving, exterior. Every phospholipid molecule has a head and also two tails. The head “loves” water (hydrophilic) and also the tails “fear” water (hydrophobic). The water-fearing tails room on the interior of the membrane, vice versa, the water-loving heads suggest outwards, toward either the cytoplasm or the liquid that surrounds the cell. The polar head group and fatty mountain chains space attached by a 3-carbon glycerol unit. Number \(\PageIndex2\) shows a single phospholipid beside a phospholipid bilayer.
Molecules that space hydrophobic can easily pass through the plasma membrane if they are small enough due to the fact that they space water-hating choose the interior of the membrane. Molecules that room hydrophilic, top top the various other hand, can not pass through the plasma membrane — at least not without help — due to the fact that they are water-loving like the exterior of the membrane.
Additional attributes of the Plasma Membrane
The plasma membrane may have extensions, such together whip-like flagella or brush-like cilia, that give it other functions. In single-celled organisms, like those shown below, these membrane expansions may assist the organisms move. In multicell organisms, the expansions have different functions. For example, the cilia on human lung cell sweep foreign particles and mucus towards the mouth and nose.
See more: The Seven Dwarfs Names In Snow White, Unused Dwarfs