Many of the important reactions that take place in the cell occur in the cytoplasm. It includes the organelles and a jelly-like fluid called the cytosol. The cytoplasm is the interior of the cell that surrounds the nucleus. Fasteners: Some receptors help bind the cell to its neighbors.Communicators: Some receptors help the cell communicate with other cells and the environment.Markers: These receptors act as name badges, informing the immune system that they are part of the organism and not foreign invaders.Gatekeepers: Some receptors allow certain molecules through and stop others.The plasma membrane contains a range of receptors, which carry out a number of tasks, including being: Phospholipids make most of this membrane and prevent water-based substances from entering the cell. To ensure each cell remains separate from its neighbor, a special membrane, known as the plasma membrane, envelops the cell. Nuclear pores within the membrane allow small molecules and ions to cross back and forth, while larger molecules need to transport proteins to help them through. The nucleus sends out messages to tell the cell to grow, divide, or die.Ī membrane called the nuclear envelope separates the nucleus from the rest of the cell. The nucleus contains the majority of the cell’s DNA, and the mitochondria house a small amount. Skeletal muscle cells, for instance, have two. The nucleus represents the cell’s headquarters. Below are some of the most important: Nucleus These are known as organelles or mini-organs. Share on Pinterest Alexander Spatari/Getty ImagesĮxperts estimate that there are around 200 cell types in the human body.Ĭell types can look different, and carry out distinct roles within the body.įor instance, a sperm cell resembles a tadpole, a female egg cell is spherical, and nerve cells are essentially thin tubes.ĭespite their differences, cells often share certain structures.
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