Plasma Membrane Structure

​When you view a plasma membrane using a microscope, it just looks like a line. However, the plasma membrane consists of many smaller structures that work together to help it perform its function.

Every organism is composed of cells, and a plasma membrane surrounds every cell. Your body contains trillions of cells, so it also contains trillions of plasma membranes. The plasma membrane:

• holds the cytoplasm and other organelles inside the cell

• controls what materials enter and leave the cell

Plasma Membrane

The plasma membrane, also called the cell membrane, surrounds every cell of every organism on Earth. A plasma membrane consists of three major components:

• phospholipid bilayer

• cholesterol

• proteins

​The head of a phospholipid contains the element phosphorus, which is where the word phosphate comes from. The phosphate head is attracted to water. Biologists use the word hydrophilic which means water-loving, to describe the head of a phospholipid.

Phospholipids

A phospholipid is a molecule that makes up the majority of the plasma membrane. A phospholipid contains two regions:

• phosphate head

• lipid tail

Label these regions on the diagram in Plasma Membrane Structure Notes.

​The tail region of a phospholipid consists of two strands of lipids. A lipid is a type of molecule found in living things that repels water. Fats, oils, and wax are examples of lipids. Lipids feel greasy on your skin. Biologists refer to lipids as water-fearing, or hydrophobic because they repel water.

​The phospholipids in the cell membrane are arranged in a bilayer. A bilayer is composed of two layers.


Together, the parts of the word mean two sheets. A phospholipid bilayer is two sheets of phospholipids.

​Let's go inside of the plasma/cell membrane!

​Semipermeable means that some things are able to pass through the cell membrane while others cannot.

You can observe the green virus on the left side of the gif not being allowed to enter the cell.

THIS IS HAPPENING INSIDE OF YOUR BODIES AS WE SPEAK!

​The plasma membrane is semipermeable. Semipermeable means that only some substances can pass through.

​If it were possible to allow a whole twix into your cell membrane, which one would you grant access to?