Biomolecules Lesson : Types, Functions & Structure Explained

Lesson Overview

• What Are Biomolecules?
• What Are the Four Biomolecules?
• Structure and Composition of Biomolecules
• What Are the Functions of Biomolecules?
• Biomolecules Chart

Biomolecules are fundamental to life, playing a key role in cellular functions and processes. This lesson will introduce you to the types, functions, and structures of biomolecules. Understanding these molecules is essential for grasping how living organisms grow, develop, and maintain vital biological activities.

What Are Biomolecules?

Biomolecules are organic molecules essential for life. They are the building blocks of cells and play a crucial role in biological processes, such as energy production, genetic information storage, and structural support. These molecules contain carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur in various combinations.

Examples of Biomolecules

Carbohydrates – Provide energy

• Example: Glucose (C₆H₁₂O₆), Starch, Cellulose

Proteins – Support structure and function

• Example: Hemoglobin, Enzymes (Amylase), Collagen

Lipids – Store energy and form cell membranes

• Example: Fats, Phospholipids, Cholesterol

Nucleic Acids – Store genetic information

• Example: DNA, RNA, ATP

Fig: Examples of Biomolecules

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What Are the Four Biomolecules?

The four main biomolecules are carbohydrates, proteins, lipids, and nucleic acids. Each has a distinct function and chemical structure.

Carbohydrates 

Carbohydrates are organic molecules made of carbon (C), hydrogen (H), and oxygen (O) in a 1:2:1 ratio. They serve as the primary source of energy in living organisms and also provide structural support in plants.

Examples of Carbohydrates

• Simple Sugars (Monosaccharides): Glucose, Fructose, Galactose
• Double Sugars (Disaccharides): Sucrose, Lactose, Maltose
• Complex Carbohydrates (Polysaccharides): Starch, Glycogen, Cellulose

Fig: A diagram of glucose molecules

Proteins 

Proteins are large biomolecules made of amino acids that perform structural, enzymatic, and transport functions. They are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes sulfur (S).

Examples of Proteins

• Structural Proteins: Collagen (skin), Keratin (hair, nails)
• Enzymes (Catalysts): Amylase (digests starch), Pepsin (breaks down proteins)
• Transport Proteins: Hemoglobin (carries oxygen in blood)
• Defensive Proteins: Antibodies (fight infections)

Fig: A labeled diagram of an amino acid

Lipids 

Lipids are hydrophobic (water-insoluble) molecules made of carbon (C), hydrogen (H), and oxygen (O), with some containing phosphorus (P). They are essential for energy storage, insulation, and cellular membrane formation.

Examples of Lipids

• Fats and Oils: Triglycerides (Butter, Olive Oil)
• Phospholipids: Form the cell membrane
• Steroids: Cholesterol, Estrogen, Testosterone

Fig: A phospholipid bilayer diagram showing its role in cell membranes

Nucleic Acids – The Genetic Blueprint

Nucleic acids store and transmit genetic information. They are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P). The two main types are DNA and RNA.

Examples of Nucleic Acids

• DNA (Deoxyribonucleic Acid): Stores genetic instructions
• RNA (Ribonucleic Acid): Helps make proteins
• ATP (Adenosine Triphosphate): Provides energy for cellular activities

Fig: A DNA double helix diagram showing its structure and function

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Structure and Composition of Biomolecules

Biomolecules are complex organic compounds that are essential for life. They are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S), forming macromolecules with unique structures and functions. The four major biomolecules-carbohydrates, proteins, lipids, and nucleic acids-have distinct compositions and structural variations that determine their biological roles.

Structure of Carbohydrates

• Monosaccharides: Single sugar units like glucose (C6H12O6).
• Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose = glucose + fructose).
• Polysaccharides: Long chains of monosaccharides forming storage molecules (starch, glycogen) or structural components (cellulose, chitin).

Fig: A labeled diagram of glucose and polysaccharide chains.

Structure of Proteins

• Primary Structure: Linear sequence of amino acids.
• Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding.
• Tertiary Structure: 3D folding due to interactions between amino acid side chains.
• Quaternary Structure: Multiple polypeptide chains combined (e.g., hemoglobin).

Fig: A diagram showing the four levels of protein structure.

Structure of Lipids

• Triglycerides: Three fatty acids attached to a glycerol backbone.
• Phospholipids: Two fatty acids, glycerol, and a phosphate group (forms cell membranes).
• Steroids: Four fused carbon rings (cholesterol, hormones).

Fig: A diagram of the structure of lipids.

Structure of Nucleic Acids

• DNA (Deoxyribonucleic Acid): Double-helix structure with complementary base pairing (A-T, G-C).
• RNA (Ribonucleic Acid): Single-stranded molecule with uracil (U) replacing thymine (T).
• ATP (Adenosine Triphosphate): Energy carrier with high-energy phosphate bonds.

Fig: A labeled DNA double-helix structure showing base pairing.

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What Are the Functions of Biomolecules?

The four main biomolecules have distinct functions necessary for life. Let's understand.

Functions of Carbohydrates

Carbohydrates serve as the primary source of energy and contribute to structural support in cells. Their main functions include:

• Energy Production: Glucose is broken down in cellular respiration to produce ATP.
• Energy Storage: Glycogen (animals) and starch (plants) store excess glucose.
• Structural Role: Cellulose forms the cell walls of plants, providing rigidity.
• Cell Communication: Glycoproteins on cell membranes help in cell recognition.

Proteins Function in the Body

Proteins have diverse functions due to their complex structures. Their key roles include:

• Enzymatic Activity: Enzymes like amylase and DNA polymerase speed up biochemical reactions.
• Structural Support: Collagen provides strength to skin, bones, and tendons.
• Transport and Storage: Hemoglobin transports oxygen in the blood.
• Immune Response: Antibodies help defend the body against infections.
• Cell Signaling: Hormones like insulin regulate blood sugar levels.

Functions of Lipids

Lipids store energy, protect organs, and form essential components of cell membranes. Their main functions include:

• Energy Storage: Fats provide long-term energy reserves.
• Cell Membrane Structure: Phospholipids form the lipid bilayer of cell membranes.
• Insulation and Protection: Fat deposits help regulate body temperature and cushion organs.
• Hormone Production: Steroids like estrogen and testosterone regulate body functions.

Nucleic Acids Contribution to Life

Nucleic acids store and transmit genetic information, guiding cell functions. Their major roles include:

• Genetic Storage: DNA holds instructions for protein synthesis.
• Protein Synthesis: RNA helps translate DNA into functional proteins.
• Cell Division and Inheritance: DNA replication ensures genetic information is passed to new cells.
  
  

Biomolecules Chart

Biomolecule	Elements	Monomer	Polymer	Function	Examples
Carbohydrates	C, H, O	Monosaccharide	Polysaccharide	Energy, structure	Glucose, Starch, Cellulose
Proteins	C, H, O, N, S	Amino Acid	Polypeptide	Enzymes, structure, transport	Hemoglobin, Collagen, Enzymes
Lipids	C, H, O (P)	Fatty Acids & Glycerol	Triglycerides, Phospholipids	Energy storage, membranes	Fats, Oils, Waxes, Cholesterol
Nucleic Acids	C, H, O, N, P	Nucleotide	DNA & RNA	Genetic info, protein synthesis	DNA, RNA, ATP