Cell membranes are composed primarily of fatty-acid-based lipids and proteins. Membrane lipids are principally of two types, phospholipids and sterols (generally cholesterol). They can also attach to the second type of protein, called the intrinsic proteins.

The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The cell membrane consists of a lipid bilayer that is semipermeable. The cell membrane regulates the transport of materials entering and exiting the cell.

The main fabric of the membrane is composed of amphiphilic or dual-loving, phospholipid molecules. The hydrophilic or water-loving areas of these molecules are in contact with the aqueous fluid both inside and outside the cell. Hydrophobic, or water-hating molecules, tend to be non- polar.

The cell membrane is composed of two layers of phospholipids, and contains a bi-layer of these phospholipids. How is the cell membrane constructed? A phospholipid is composed of a phosphate group head (of which is hydrophilic) and two fatty acid tails (of which are hydrophobic).

The cell membrane is not a solid structure. It is made of millions of smaller molecules that create a flexible and porous container. The model shows you that phospholipid molecules are shaped with a head and a tail region. The head section of the molecule likes water (hydrophilic) while the tail does not (hydrophobic).

Functions of the Plasma Membrane

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

Ribosomes are composed of two subunits, the large and the small subunit, both of which consist of ribosomal RNA (rRNA) molecules and a variable number of ribosomal proteins. Several factor proteins catalyze different steps of protein synthesis by binding transiently to the ribosome.

cell cytoplasm

phospholipid molecules

Phospholipids make up the bilayer of a plasma membrane. Phospholipids have a phosphate head and two fatty acid tails. The phospholipids tails are hydrophobic which means that they fear/dislike water.

The plasma membrane, also called the cell membrane, is the membrane found in all cells that separates the interior of the cell from the outside environment.

The components of the plasma membrane

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 …

The two main types of epithelial membranes are the mucous membranes and serous membranes.

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.

They are found in bacteria, archaea, fungi, plants, and algae. Animals and most other protists have cell membranes without surrounding cell walls.

Besides the presence of chloroplasts, another major difference between plant and animal cells is the presence of a cell wall. The cell wall surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress.

The vital parts of a cell are called “organelles.” Among the most important are the nucleus, vacuoles, and mitochondria, all of which are enclosed within the cell membrane and immersed in cytoplasm. Each organelle performs a specific task that helps keep the cell alive.

nucleus

The nucleus is called the “brain” of the cell because it holds the information needed to conduct most of the cell’s functions. These proteins are built by the cell using the information in DNA, which is held in the nucleus.