Hydrophilic: Definition, Function and Examples of These Hydrophilic Molecules

A hydrophilic molecule or substance is attracted to water. Water is a polar molecule that acts as a solvent and dissolves other polar and hydrophilic substances.

An agent that easily absorbs water is known or called hydrophilic.


In biology, many substances are hydrophilic , allowing them to disperse throughout a cell or organism.

All cells use water as the solvent that creates the solution known as cytosol. The cytosol contains many substances, most of which are hydrophilic in at least part of the molecule. This ensures that it can be easily transported around the cell.

Substances that are hydrophobic or water repellent are often transported through and between cells with hydrophilic proteins or structures attached to aid in their dispersion.

Hydrophilic substances diffuse into water, that is, they move from areas of high concentration to areas of low concentration.

This is caused by the attraction of water molecules to hydrophilic molecules. In areas of high concentration of the molecules, the water moves and separates the molecules.

The molecules are distributed to areas of low concentration, where more water molecules can interact.

Diffusion is a very important property of most hydrophilic substances for living organisms. Diffusion allows them to distribute substances with little or no energy on their part.

Examples of Hydrophilic

Sugar or glucose: it is a molecule that many types of cells use as an energy source. A glucose molecule is made up of hydrophobic and hydrophilic particles.

It is made up of carbon atoms, oxygen atoms, and hydrogen atoms. The bonds between carbon atoms share electrons equally, and no static electric charge is created.

However, oxygen atoms extract an uneven portion of electrons from the carbon and hydrogen atoms to which they are attached.

This property, known as electronegativity, causes electrons to be unevenly distributed, most of the time.

This causes an electric dipole to form across the bond, creating areas of positive and negative energy. Water can interact with these dipoles and dissolve glucose.

In the human body, as in many animals, the energy stored in glucose bonds is used in each cell to control cellular functions.

To transport glucose to many cells, glucose dissolved in the intestine and stored in the liver is released into the bloodstream.

Because glucose is a partially hydrophilic molecule, it dissolves equally in the bloodstream, delivering glucose to all parts of the body.

To cross the hydrophobic centers of plasma membranes, glucose is transported by special proteins.

Once in each cell, glucose can be broken down through glycolysis and respiration to provide coenzyme ATP.

ATP can provide energy to other enzymes to help them perform their various functions.

Enzymes: DNA, the information molecule that powers life on Earth, encodes a sequence of amino acids. These amino acids are characterized by being in some cases hydrophilic or, on the contrary, hydrophobic.

Proteins are created by amino acid sequences, but they do not become functional until they are properly folded.

A long chain of amino acids folds due to the various interactions it has with the other amino acids in the chain, as well as interactions with the environment.

Eventually, the hydrophobic and nonpolar regions of the protein will clump together and the hydrophilic polar regions will be exposed to the environment.

Proteins become functional enzymes when they are shaped correctly to accept a substrate and lower the activation energy of a chemical reaction.

If a mutation in DNA places a hydrophobic amino acid where a hydrophilic amino acid should have gone, the entire structure can suffer and the enzyme can stop working.

Since water is the solvent in all cellular cytosols, it is important that the exterior of proteins is hydrophilic, so that they can disperse and move around the cell.

Thus, a cell can create proteins in one place (usually ribosomes ) and cause them to distribute throughout the cell by diffusion.

This hydrophilic property of most proteins allows them to fill certain cells and produce a large amount of certain products necessary for the body.

Cell membranes: They are created from two sheets of molecules known as phospholipids.

Phospholipids are amphiphilic, which means that they are both attracted to water in one region of the molecule and repel water in other regions.

The head of the phospholipid molecule is the hydrophilic region. The tails are the hydrophobic region, and they point inward, towards each other.

This excludes water from the middle of the two sheets, thus creating a divider between two reservoirs of solution. If the membrane is closed, in a sphere, a cell is created.

Bacterial cells do not further divide, but eukaryotes further divide their cells into organelles. These organelles are also surrounded by phospholipids.

Although water cannot easily pass through the cell membrane, there are many built-in proteins that allow water to enter the cell. There are also proteins that carry other hydrophilic substances across the membrane.

These proteins, although they are not enzymes, are also made up of chains of amino acids. These proteins often work by using energy from ATP to move various substances across the membrane.

Without a channel through the hydrophobic membrane, hydrophilic substances could not pass through.

Protein is composed of hydrophobic and hydrophilic portions or particles. The exterior of the protein, the parts exposed to the environment and the cytoplasm, will be hydrophilic.

The interior parts of the protein that interact with lipids in the middle of the membrane will be hydrophilic.

In this way, the protein can remain embedded in the membrane simply because of the tendency of hydrophobic substances to clump together and hydrophilic substances to attract water.

The ends are pulled into the water, and the medium interacts with the hydrophobic lipids. Many macromolecules are amphiphilic in this way, to interact with various substances.