The phospholipid bilayer's function is to maintain a barrier between the cell and its external environment and to store and transport a variety of proteins that are essential to the cell's function. It controls what ente... More »

In a phospholipid bilayer, the polar head of each layer points outwards, while the long nonpolar lipid chains of each layer points towards the middle. A phospholipid bilayer membrane is a specific type of lipid bilayer w... More »

In a cell, proteins are made in the cell's ribosomes. Ribosomes string together long chains of amino acids to synthesize proteins. The mRNA (messenger ribonucleic acid), tRNA (transfer ribonucleic acid) and the amino aci... More »

The cell membrane is the barrier between a cell and its environment. Some cells also have a cell wall, which provides further protection and some support for the cell. More »

In a phospholipid bilayer, the polar head of each layer points outwards, while the long nonpolar lipid chains of each layer points towards the middle. A phospholipid bilayer membrane is a specific type of lipid bilayer w... More »

A generalist species is one that can live in a wide variety of habitats and have a varied diet, while specialist species are adapted to a particular environment or a specific diet. Koalas and tiger salamanders are exampl... More »

Because they are the energy-producing organelles in plant and animal cells, a high number of mitochondria implies that the cell requires a great deal of energy to perform its specific function. Skeletal muscle cells, for... More »