Biological molecules

Biological molecules are the building blocks of life, primarily composed of carbon, hydrogen, and oxygen, with nitrogen and other elements occasionally present. These molecules can form long chains or ring structures and often consist of repeating subunits called monomers. Through chemical bonding, monomers join to create polymers such as polysaccharides (e.g., glucose chains), proteins (chains of amino acids), and DNA (chains of nucleotide units). Polymers often exhibit unique properties distinct from their individual components, enabling them to perform specialized functions within organisms.

Monomer: Monomer is a fundamental unit. Multiple monomers join together to form a polymer. 

Polymer: A polymer is made up of multiple monomers joined together via bonds.

A condensation reaction is a chemical process where two molecules combine to form a larger molecule, with the loss of a small molecule, typically water (H₂O)

All cells share common needs for water, oxygen, minerals, and nutrients, as well as essential components like proteins, lipids, carbohydrates, and nucleic acids, which are vital for cell structure, metabolism, and overall function.

Carbohydrates:

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen atoms, usually with a ratio of hydrogen atoms to oxygen atoms of 2:1, as in water. They serve as a primary source of energy for living organisms, including humans, and play crucial roles in various physiological functions.

Carbohydrates are classified into three main groups:

Monosaccharides: These are the simplest form of carbohydrates and cannot be hydrolysed into smaller carbohydrates. Monosaccharides are the building blocks of more complex carbohydrates.  Examples include

1- Glucose
2- Fructose
3- Galactose. 

Disaccharides: Disaccharides consist of two monosaccharide units joined together by a bond formed through a dehydration reaction (also called as Condensation Reaction). Examples include the following:

1- Glucose + Glucose —–> Maltose

2-Glucose + Fructose —–> Sucrose

3- Glucose + Galactose —–> Lactose 

Disaccharides are commonly found in foods such as table sugar, milk, and malt beverages.

People who are lactose intolerant cannot digest lactose. This means that they cannot break down lactose in their body into monosaccharides glucose and galactose. If they consume lactose in any form like milk, yogurt, ice cream and etc, a lactose intolerant person will start to feel pain in the stomach. 

Polysaccharides: These are complex carbohydrates consisting of long chains of monosaccharide units. This includes hundreds and thousands of monosaccharide molecules joined together.  Two polysaccharides are discussed:

Starch: A polysaccharide found in plants, composed of glucose units. It serves as a storage form of energy in plants. Recap that the enzyme that breaks down starch is called Amylase. Amylase breaks down Starch into Maltose. Starch is also regarded as the storage form of sugar in Plants. 

Glycogen: A polysaccharide found in animals, particularly in the liver and muscles. Like starch, glycogen is composed of glucose units and serves as a storage form of energy. Glycogen is also regarded as the storage form of sugar in Animals. 

Cellulose: Cellulose consists of extended chains of glucose molecules. These molecules are organized into microscopic fibers, which are arranged in layers to form the cell wall in plant cells.

Lipids:

• Lipids include fats and oils, with fats being solid and oils being liquid at room temperature.
• Composed of carbon, hydrogen, and oxygen only.
• Consists of three molecules of fatty acids combined with one molecule of glycerol.
• Play a structural role in cell membranes and internal cellular membranes like the nuclear membrane.
• Lipid droplets stored in the cytoplasm serve as an energy source.
• It is important for insulation, energy storage, and hormone synthesis.
• Provide essential fatty acids necessary for various physiological functions.
• Act as a protective layer for organs and tissues.
• Contribute to the flavor, texture, and aroma of foods.

Proteins: 

Proteins play crucial roles in various cellular structures such as cell membranes, mitochondria, ribosomes, and chromosomes. Additionally, enzymes, a distinct group of proteins, are found in membrane systems, mitochondria, special vacuoles, and the cytoplasm’s fluid part, where they regulate chemical reactions vital for cellular function.

Despite the diversity among proteins, they all share a composition of carbon, hydrogen, and oxygen. Animal proteins typically consist of about 20 different amino acids, including alanine, leucine, valine, glutamine, cysteine, glycine, and lysine. These amino acids combine in specific sequences to form protein molecules. 

For instance, a small protein molecule may consist of a chain comprising a hundred or more amino acids arranged in a unique sequence, such as glycine–valine–valine–cysteine–leucine–glutamine–, and so forth. Each type of protein possesses its own distinctive arrangement of amino acids.