Physical Science: An Interactive e-Learning Materials

Lesson 4: Exploring the Structure and Function of Biological Molecules

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Discussion

Structure and Functions of Biological Macromolecules

Biological macromolecules are large molecules that are important components of living systems. Performing a variety of functions, they are vital to sustaining life. The term “macromolecule” was coined in 1920 by Nobel Laureate Hermann Staudinger. Staudinger was also the first to assert that large biological molecules are made up and formed by covalently bonded sub-units.

Monomers and Polymers

Macromolecules perform a crucial role in our cell structure and processes. The majority of biological macromolecules are polymers and are made of covalently linked basic units called monomers. All the monomers that make up a polymer are typically similar or at least highly similar to one another and are bonded to form a larger unit or larger macromolecule. Monomers that link with other monomers in various combinations result in the formation of polymers, which have different structures and functions.

Biological Macromolecules

Carbohydrates

The word carbohydrate may be broken down to carbon and hydrate, and this is due to the fact that most carbohydrates follow the formula Cn(H2O)n. Another term for carbohydrate is saccharide. Carbohydrates are classified either as simple or complex. Simple sugars are monosaccharides and disaccharides. Complex sugars are polysaccharides. They are made from carbon, hydrogen, and oxygen.

Carbohydrates are the primary source of energy in the human body. The different saccharides that humans eat are converted to glucose which can be readily used by the body. The excess carbohydrates taken into the body are converted to glycogen that is stored in the liver and in muscles.

Monosaccharide (one saccharide)

Disaccharides (two saccharides)

Polysaccharides (many saccharides)

Did you know that?

Marathon runners, tri-athletes, and other runners consume carbohydrates for weeks leading up to a big event. They call it “carbo-loading”.

What’s the point? As the athletes consume massive amounts of starch and pasta, the energy begins to store up in their body, saving itself for use during the event.

2. Lipids or Fats

Lipids or fats are important nutrients in your body but eating too many unhealthy fats such as saturated fats and trans fats can lead to heart disease and obesity. Lipids also serve other functions such as material for cell membranes, insulation to maintain body temperature, aid in digestion, and as signal molecules.

There are different common classifications of lipids: triglyceride, phospholipid, wax, and steroid. The lipid family is one of the most varied in terms of structure but they share the common property - being insoluble in water.

Fat and oil are the most common examples of lipids. They are under triglycerides because they are composed of glycerol and three fatty acids.

Fat refers to solid triglyceride usually from animal sources such as meat, milk, butter, margarine, eggs, and cheese. Oil refers to liquid triglycerides from plant sources. Examples are olive oil, corn oil, sunflower oil, and soybean oil. Animal fats contain high percentages of saturated fatty acids while plant oils are mostly unsaturated fatty acids.

They are made from carbon, hydrogen, and oxygen. They are soluble (dissolve) in oil but are insoluble (don’t dissolve) in water.

3. Proteins

Proteins are composed of four elements, namely: carbon, hydrogen, oxygen, and nitrogen. Sulfur is sometimes also found in proteins. If carbohydrates are made up of saccharides, proteins are made up of amino acids.

Examples of proteins and their functions are:

Keratin

A structural protein found in hair, skin, and nails

Fibroin

Fibroin is found in silk. Silk has a smooth and soft texture. It is one of the strongest natural fibers that have high resistance to deformation. It is also a good insulating material.

Collagen

A major insoluble fibrous protein found in connective tissues such as tendons, ligaments, skin, cartilage and the cornea of the eye. It comprises as much as 30% of proteins in animals.

Enzymes

It function to catalyze chemical reactions. They either speed up a reaction, lower the needed energy for a reaction to take place, or bind substances to their specific partners. Such as lipase, pepsin, and sucrose

Myoglobin

A polypeptide that stores oxygen in muscles. It contains a heme group which has an iron where the oxygen is stored.

4. Nucleic Acids

Nucleic acids are biological macromolecules vital in the continuity of life. Nucleic acid carries the genetic material of a cell and provides instructions for the functioning of the cell. There are two main types of nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries genetic material found in all living organisms. They are made from carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Remember this mnemonic device of biomolecules: CHO, CHO, CHON, CHONP

C stands for the element Carbon

H stands for the element Hydrogen

O stands for the element Oxygen

N stands for the element Nitrogen

P stands for the element Phosphorus

CHO for Carbohydrates; Monomer is saccharides

CHO for Lipids or Fats; Monomer is fatty acid

CHON for Protein; Monomer is amino acid

CHONP for Nucleic Acid; Monomer is nucleotide

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