Biomolecules: Structure, Function, and Biological Importance

Organic Molecules & Biomolecules

Definition and Classification

Organic molecules are compounds found in or derived from living organisms, primarily composed of carbon and hydrogen arranged in rings or chains. Biomolecules (macromolecules) are a subset of organic molecules essential for life and are present in all living organisms.

• Biomolecules include carbohydrates, proteins, nucleic acids, and lipids.

• Macromolecules are large molecules made up of smaller subunits.

• Organic molecules are the chemical foundation of biological structure and function.

Additional info: Biomolecules are crucial for cellular structure, metabolism, and genetic information storage.

Monomers & Polymers

Building Blocks of Biomolecules

Most biomolecules are polymers, which are long chains made by joining smaller molecules called monomers. The process of forming polymers involves specific chemical reactions.

• Monomers are the basic building blocks or subunits of polymers.

• Polymers are large molecules formed by linking monomers together.

• Polymerization occurs through dehydration synthesis, where water is removed to form a new bond.

• Polymers can be broken down into monomers by hydrolysis, where water is added to break bonds.

Example: Glucose (monomer) can be joined to form starch (polymer).

Polymers and Their Monomers

The following table summarizes the relationship between major biomolecule polymers and their monomers:

Polymer	Monomer
Carbohydrate	Monosaccharide
Protein	Amino Acid
Nucleic Acid	Nucleotide
Lipid	[None]

Additional info: Lipids are not true polymers as they are not formed by repetitive monomer units.

Dehydration Synthesis and Hydrolysis

Dehydration Synthesis

Dehydration synthesis is a chemical reaction in which two molecules are covalently bonded together with the removal of a water molecule. This process is essential for building polymers from monomers.

• Enzymes facilitate the removal of an -OH group from one monomer and an -H from another, forming water ($H_2O$).

• The remaining atoms form a covalent bond, linking the monomers.

Equation:

$ ext{Monomer}_1 + ext{Monomer}_2 \xrightarrow{Dehydration\ Synthesis} ext{Polymer} + H_2O$

Hydrolysis

Hydrolysis is a decomposition reaction where polymers are broken down into monomers by the addition of water. Enzymes catalyze this process, which is vital for digestion and cellular metabolism.

• Water is added to break the covalent bond between monomers.

• Each monomer receives a part of the water molecule (–OH and –H).

Equation:

$ ext{Polymer} + H_2O \xrightarrow{Hydrolysis} ext{Monomer}_1 + ext{Monomer}_2$

Comparison Table: Dehydration Synthesis vs. Hydrolysis

Type of Reaction	What Happens
Dehydration Synthesis	Two molecules covalently bond to form a larger molecule; water is removed.
Hydrolysis	A larger molecule is broken down into smaller ones by the addition of water.

Summary

• Biomolecules are essential organic compounds in living organisms.

• Monomers are the building blocks of polymers.

• Dehydration synthesis builds polymers; hydrolysis breaks them down.

• Major biomolecules include carbohydrates, proteins, nucleic acids, and lipids.

Additional info: Understanding these reactions is fundamental for studying metabolism, nutrition, and cellular processes in Anatomy & Physiology.