Biomolecules: Carbohydrates, Proteins, Lipids, Nucleic Acids & Enzymes

TAKEAWAYS:

• Biomolecules are organic compounds essential for life, including carbohydrates, proteins, lipids, and nucleic acids.
• Carbohydrates provide energy, proteins build tissues, lipids store energy and insulate, and nucleic acids carry genetic information.
• Enzymes are biological catalysts that speed up chemical reactions in cells.
• Biomolecules are tested in NEB exams through definitions, functions, and practical applications.

What are Biomolecules?

Biomolecules are organic compounds found in living organisms. They are essential for life because they perform vital functions like:

• Providing energy (carbohydrates, lipids).
• Building and repairing tissues (proteins).
• Storing and transmitting genetic information (nucleic acids).

Biomolecules are made up of smaller units called monomers, which join together to form polymers. For example:

• Carbohydrates are made of monosaccharides (simple sugars).
• Proteins are made of amino acids.
• Nucleic acids (DNA and RNA) are made of nucleotides.

1. Carbohydrates: The Energy Molecules

Carbohydrates are the primary source of energy for living organisms. They are classified into three types:

A. Monosaccharides (Simple Sugars)

• Examples: Glucose, Fructose, Galactose.
• Function: Provide quick energy.
• Structure: Single sugar unit (C₆H₁₂O₆).
• Example: Glucose is the main energy source for cells.

B. Disaccharides (Double Sugars)

• Examples: Sucrose (Glucose + Fructose), Lactose (Glucose + Galactose), Maltose (Glucose + Glucose).
• Function: Provide energy and are used for storage.
• Example: Sucrose is table sugar.

C. Polysaccharides (Complex Carbohydrates)

• Examples: Starch (plants), Glycogen (animals), Cellulose (plant cell walls).
• Function:
  • Starch: Energy storage in plants.
  • Glycogen: Energy storage in animals.
  • Cellulose: Provides structural support in plants.

2. Proteins: The Building Blocks of Life

Proteins are made up of amino acids and perform many functions, such as:

• Building muscles and tissues.
• Acting as enzymes (biological catalysts).
• Transporting molecules (e.g., hemoglobin in blood).

classDiagram
  class Protein {
    +String primaryStructure
    +String secondaryStructure
    +String tertiaryStructure
    +String quaternaryStructure
    +function() catalyze()
  }
  class AminoAcid {
    +String name
    +String sideChain
    +function() bond()
  }
  Protein "1" *-- "n" AminoAcid : contains
  Protein <|-- Enzyme : "is a"
  Protein <|-- Hemoglobin : "is a"

Structure of Proteins

Proteins have four levels of structure:

1. Primary: Sequence of amino acids.
2. Secondary: Folding into alpha-helices or beta-pleated sheets.
3. Tertiary: 3D shape of a single protein.
4. Quaternary: Multiple protein chains (e.g., hemoglobin).

Examples of Proteins

• Enzymes: Catalase (breaks down hydrogen peroxide).
• Hormones: Insulin (regulates blood sugar).
• Structural Proteins: Collagen (found in skin and bones).

3. Lipids: The Energy Reservoirs

Lipids are hydrophobic (water-repelling) molecules that include:

• Fats and Oils: Store energy.
• Waxes: Protect surfaces (e.g., plant leaves).
• Steroids: Hormones like cholesterol.

Types of Lipids

Functions of Lipids

• Provide twice the energy of carbohydrates per gram.
• Insulate the body (e.g., fat under the skin).
• Protect organs (e.g., fat around kidneys).

4. Nucleic Acids: The Genetic Material

Nucleic acids store and transmit genetic information. There are two types:

1. DNA (Deoxyribonucleic Acid): Stores genetic instructions.
2. RNA (Ribonucleic Acid): Helps in protein synthesis.

Structure of Nucleic Acids

• Made of nucleotides, which consist of:
  • A phosphate group.
  • A sugar (deoxyribose in DNA, ribose in RNA).
  • A nitrogenous base (Adenine, Thymine, Cytosine, Guanine in DNA; Uracil replaces Thymine in RNA).

Functions of Nucleic Acids

• DNA: Stores genetic code for inheritance.
• RNA: Transfers genetic information to make proteins.

5. Enzymes: Biological Catalysts

Enzymes are proteins that speed up chemical reactions without being used up. They work by:

• Lowering the activation energy of reactions.
• Being specific to their substrates (like a key fits a lock).

Factors Affecting Enzyme Activity

Examples of Enzymes

• Amylase: Breaks down starch into sugars.
• Pepsin: Digests proteins in the stomach.
• DNA Polymerase: Helps in DNA replication.

Comparison of Biomolecules

Solved Example: Identifying Biomolecules

Question: Which biomolecule is responsible for storing genetic information in cells? Solution:

• DNA is the biomolecule that stores genetic information.
• It is made of nucleotides and has a double-helix structure.
• Answer: DNA.

NEB Board-Style Questions

Short Answer Questions

1. Define monosaccharides and give two examples.
2. What is the primary function of lipids in the human body?
3. How do enzymes speed up chemical reactions?
4. Name the four levels of protein structure.

Long Answer Questions

5. Explain the structure and function of carbohydrates with examples.
6. Describe the role of nucleic acids in heredity and protein synthesis.
7. How do enzymes work? Discuss the factors affecting enzyme activity.

Exam Tip

• Memorize the classification and functions of biomolecules.
• Draw diagrams of glucose, DNA structure, and enzyme activity graphs.
• Compare carbohydrates, proteins, and lipids in tables.
• Practice identifying biomolecules in given scenarios (e.g., "Which biomolecule is used for long-term energy storage?").

Final Note: Biomolecules are the foundation of life. Understanding their structure and function will help you score well in NEB exams and build a strong biology knowledge base! 🚀