Biomolecules Revision Notes for Chemistry NEET

Biomolecules are essential compounds that participate in the structural and functional organization of all living beings. They include carbohydrates, proteins, nucleic acids, vitamins, and hormones. These molecules play critical roles in metabolic reactions, heredity, and cell signaling, making them crucial for a variety of biological processes. Understanding their types, structure, and function is important for grasping the biochemical foundations of life.

General Introduction and Importance of Biomolecules Biomolecules are organic compounds found in living organisms. They are primarily made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur and phosphorus. The four main categories – carbohydrates, proteins, nucleic acids, and vitamins – each perform unique and vital functions. Without biomolecules, life would not exist, as they are responsible for cell structure, energy storage, transfer of genetic information, and regulatory functions.

Carbohydrates Carbohydrates are hydrates of carbon and serve as the primary energy source for most organisms. They are classified into three main types—monosaccharides, oligosaccharides, and polysaccharides.

Classification of Carbohydrates

• Monosaccharides: Simple sugars with a single polyhydroxy aldehyde or ketone unit. Glucose and fructose are the most common examples.
• Oligosaccharides: Composed of 2–10 monosaccharide units linked by glycosidic bonds. Important ones for NEET include disaccharides like sucrose, lactose, and maltose.
• Polysaccharides: Large molecules made of many monosaccharide units. Examples are starch, glycogen, and cellulose (noting for broad understanding).

Aldoses and Ketoses Monosaccharides are further divided into:

• Aldoses: Those containing an aldehyde group (–CHO) like glucose.
• Ketoses: Those containing a ketone group (–CO–) like fructose.

Monosaccharides: Glucose and Fructose Glucose is an aldohexose and is the main source of energy in the human body. Its molecular formula is C₆H₁₂O₆. Fructose is a ketohexose, found in fruits and honey, and shares the same formula as glucose but differs in structure.

Constituent Monosaccharides of Oligosaccharides

• Sucrose: Made up of glucose and fructose molecules.
• Lactose: Composed of glucose and galactose.
• Maltose: Consists of two glucose units.

Proteins Proteins are complex biomolecules required for structure, function, and regulation of body tissues. They are polymers of α-amino acids linked by peptide bonds. The sequence and arrangement of amino acids determine each protein’s unique properties.

Elementary Idea of α-Amino Acids α-Amino acids have a central carbon (alpha carbon) attached to an amino group (–NH₂), a carboxylic group (–COOH), a hydrogen atom, and a variable side chain (R group). These molecules are building blocks for all proteins.

Peptide Bond and Polypeptides When the carboxyl group of one α-amino acid reacts with the amino group of another, a peptide bond (–CO–NH–) is formed. Chains of such amino acids connected by peptide bonds are called polypeptides. Short chains are called peptides, and long ones make up proteins.

Levels of Protein Structure

• Primary Structure: Linear sequence of amino acids in the polypeptide chain.
• Secondary Structure: Folding of the primary chain into α-helices or β-pleated sheets due to hydrogen bonding.
• Tertiary Structure: Further folding into a three-dimensional structure stabilized by various interactions (hydrogen bonds, ionic bonds, disulfide bridges).
• Quaternary Structure: Complex formed by the association of two or more polypeptide chains.

Denaturation of Proteins Denaturation causes the alteration of a protein’s structure (secondary, tertiary, or quaternary) without breaking the peptide bonds. Agents like heat, acids, or alkalis can denature proteins, leading to loss of biological activity.

Enzymes Enzymes are proteins that act as biological catalysts. They increase the rate of biochemical reactions without undergoing any permanent change themselves. Each enzyme is specific to a particular reaction due to its unique active site.

Vitamins – Classification and Functions Vitamins are organic compounds required in small amounts for normal metabolic processes. They are divided into two classes:

• Water-Soluble Vitamins: Include B-complex and vitamin C. They are not stored in the body and need to be consumed regularly.
• Fat-Soluble Vitamins: Include vitamins A, D, E, and K. They can be stored in the liver and fatty tissues.

Their functions include aiding metabolism, promoting growth and immunity, and preventing deficiency diseases (like scurvy for vitamin C and rickets for vitamin D).

Nucleic Acids – Chemical Constitution Nucleic acids are polymeric molecules crucial for storing and transmitting genetic information. There are two main types – DNA and RNA. Both are made up of nucleotides, which consist of a nitrogenous base (purines: adenine, guanine; pyrimidines: cytosine, thymine/uracil), a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a phosphate group.

DNA and RNA: Differences

• DNA (Deoxyribonucleic Acid): Double stranded, contains deoxyribose sugar and the bases A, T, G, C.
• RNA (Ribonucleic Acid): Usually single stranded, contains ribose sugar and the bases A, U, G, C (uracil replaces thymine).

Biological Functions of Nucleic Acids Nucleic acids are fundamental to heredity and cellular function. DNA stores genetic information and ensures its transfer from one generation to the next. RNA helps in protein synthesis, acting as a messenger (mRNA), adapter (tRNA), or forming part of the ribosome (rRNA).

Hormones: General Introduction Hormones are signaling molecules produced by endocrine glands, released into the bloodstream to regulate physiological processes. They control important functions like metabolism, growth, reproduction, and mood. Examples include insulin, adrenaline, and thyroxine.

NEET Chemistry Notes – Biomolecules: Key Revision Points

Use these concise NEET Chemistry Biomolecules notes to review key topics including carbohydrates, proteins, nucleic acids, vitamins, and hormones. These revision notes highlight all important concepts and exam-relevant facts in simple language, making last-minute study much easier.

With a clear focus on the syllabus structure, these Biomolecules revision points cover the essential differences, structures, and functions, helping you build strong understanding for NEET. Easy recall and smart revision can improve confidence before your Chemistry exam.