Molecule structure and functions
Joanna George-Johnson, Contributor

A teacher explains an accounts problem to a student at Bridgeport High School. - Anthony Minott/Freelance Photographer

Last time we looked at water and carbohydrates, this week we will look at proteins, lipids and DNA.

Deoxyribonucleic acid DNA

This molecule is termed the genetic material. The reason is that this molecule contains a specific sequence that is unique to each of us that determines all of our physical characteristics.

Structure of DNA

DNA contains mainly the following elements: carbon, oxygen, hydrogen and nitrogen. The full structure looks like a twisted ladder (at this level, detailed knowledge of DNA is not necessary).

Function

DNA determines all the physical characteristics of the organism.

Proteins

This is a very abundant molecule in most organisms. It is especially abundant in animals, and performs a myriad of functions.

Structure of Proteins

All proteins contain the elements carbon, hydrogen, oxygen and nitrogen. They are made up of sub-units called amino acids. The diagram below shows the structure of a typical amino acid.

Amino acids have the ability, like monosaccharides, to join together in long chains called polypeptides. The polypeptide chain will then bend and form into a specific shape to form the particular protein molecule.

Functions

Proteins carryout many functions within an organism. Here are a few of them:

• Build muscle and tissues
• Speed up reactions in the body (enzymes)
• Provide structure and elasticity to animal cells (collagen cartilage)
• Carry oxygen all over the body. (haemoglobin in the red blood cells)
• Hair and nails are all types of proteins
• Responsible for transport across the cell membranes
• Proteins can be sourced by eating meats and peas and beans

Lipids (fats)

Lipids are found in all organisms and serve very important functions. Some lipids are solid at room temperature and are called fats, and others are liquid at room temperature and are called oils. Oils are mainly found in plants and fish. Fats are not generally found in plants.

Structure of Lipids

All lipids have the same elements as carbohydrates, that is, carbon, hydrogen and oxygen. The difference is that the elements are in a different ratio to that of carbohydrates, and they are also arranged differently.

Unlike carbohydrates and proteins, lipids are not formed from sub-units. They are made of two main molecules coming together. The molecules are glycerol and fatty acids.

The difference in the fatty acid chains is what makes the difference between one lipid and another.

Functions

Lipids' main function is energy storage. They also form a major part of cell membranes. They help to cushion vital organs.

Questions

1. Give two sources of lipids.

2. Determine what type of molecule is a) lipids b) proteins.

3. In what metabolic process is the energy from lipids released?

Joanna George-Johnson teaches at Ardenne High School.
Email: Masterbio@gmail.com.