Biomolecules Notes

Introduction

Biomolecules are organic molecules that are essential for life. They are involved in the structure, function, and regulation of the body's tissues and organs. In the NEET Chemistry syllabus, understanding biomolecules is crucial as it forms the basis for many biological processes. This study note will cover the major classes of biomolecules, their structure, function, and importance.

Classes of Biomolecules

Biomolecules can be broadly classified into four major categories:

1. Carbohydrates
2. Proteins
3. Lipids
4. Nucleic Acids

Each class has unique structures and functions, which will be discussed in detail.

Carbohydrates

Structure and Classification

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically with a hydrogen:oxygen atom ratio of 2:1. They are classified based on their structure and complexity:

1. Monosaccharides: Simple sugars with a single polyhydroxy aldehyde or ketone unit.
   • Example: Glucose ($C_6H_{12}O_6$), Fructose ($C_6H_{12}O_6$)
2. Disaccharides: Composed of two monosaccharide units linked by a glycosidic bond.
   • Example: Sucrose (Glucose + Fructose), Lactose (Glucose + Galactose)
3. Polysaccharides: Long chains of monosaccharide units.
   • Example: Starch, Glycogen, Cellulose

Functions

• Energy Source: Glucose is a primary energy source for cells.
• Structural Role: Cellulose in plant cell walls.
• Storage: Glycogen in animals and starch in plants.

Proteins

Structure

Proteins are polymers of amino acids linked by peptide bonds. They have four levels of structure:

1. Primary Structure: Sequence of amino acids in a polypeptide chain.
2. Secondary Structure: Local folding into structures such as $\alpha$-helices and $\beta$-sheets.
3. Tertiary Structure: Overall 3D shape of a single polypeptide chain.
4. Quaternary Structure: Arrangement of multiple polypeptide chains.

Functions

• Enzymes: Catalysts for biochemical reactions (e.g., amylase).
• Transport: Hemoglobin transports oxygen in the blood.
• Structural: Collagen provides structural support in connective tissues.

Lipids

Structure

Lipids are a diverse group of hydrophobic molecules, primarily composed of carbon, hydrogen, and oxygen. Main types include:

1. Triglycerides: Glycerol + 3 fatty acids.
2. Phospholipids: Glycerol, 2 fatty acids, and a phosphate group.
3. Steroids: Four fused carbon rings (e.g., cholesterol).

Functions

• Energy Storage: Triglycerides store energy.
• Membrane Structure: Phospholipids form cell membranes.
• Signaling: Steroids act as hormones (e.g., testosterone).

Nucleic Acids

Structure

Nucleic acids are polymers of nucleotides, each consisting of a nitrogenous base, a pentose sugar, and a phosphate group. There are two types:

1. DNA (Deoxyribonucleic Acid): Double-stranded helix, stores genetic information.
   • Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
2. RNA (Ribonucleic Acid): Single-stranded, involved in protein synthesis.
   • Bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G)

Functions

• Genetic Information: DNA stores and transmits genetic information.
• Protein Synthesis: RNA translates genetic information into proteins.

Enzyme Action

Mechanism

Enzymes are biological catalysts that speed up biochemical reactions. They work by lowering the activation energy of a reaction. The enzyme-substrate complex forms when the substrate binds to the enzyme's active site, leading to the formation of products.

Factors Affecting Enzyme Activity

• Temperature: Optimal temperature increases activity, while extreme temperatures denature enzymes.
• pH: Each enzyme has an optimal pH.
• Substrate Concentration: Increased concentration increases activity up to a saturation point.

$$ E + S \rightarrow ES \rightarrow E + P $$

Conclusion

Understanding biomolecules is essential for grasping the biochemical processes that sustain life. This study note has covered the major classes of biomolecules, their structures, functions, and significance in biological systems. Mastery of these concepts is crucial for excelling in the NEET Chemistry syllabus.