Zoology Biomolecules ONE-SHOT Gun - Class 11 JKBOSE Zoology

Biomolecules: Structure, Types, and Functions

Definition and Core Concept of Biomolecules

Biomolecules are chemical compounds found in living organisms that play essential roles in life processes and structural organization. They are primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Biomolecules support daily physiological activities and provide structural integrity to living things.

• Examples include carbohydrates, proteins, lipids, and nucleic acids.
• Biomolecules are involved in processes such as respiration, nutrition, transport, and excretion.

Metabolites: Primary and Secondary

Metabolites are compounds produced during metabolic reactions in living cells. They are classified based on their necessity for…

Biomolecules: Structure, Types, and Functions

Definition and Core Concept of Biomolecules

Biomolecules are chemical compounds found in living organisms that play essential roles in life processes and structural organization. They are primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Biomolecules support daily physiological activities and provide structural integrity to living things.

• Examples include carbohydrates, proteins, lipids, and nucleic acids.
• Biomolecules are involved in processes such as respiration, nutrition, transport, and excretion.

Metabolites: Primary and Secondary

Metabolites are compounds produced during metabolic reactions in living cells. They are classified based on their necessity for growth and development.

• Primary Metabolites: Essential for daily physiological activities, growth, and development (e.g., glucose, amino acids, chlorophyll, heme, nucleic acids).
• Secondary Metabolites: Not directly involved in growth or development but serve other functions (e.g., rubber, gum, plant drugs).

Carbohydrates: Structure, Types, and Examples

Carbohydrates are organic compounds containing carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio. They serve as energy sources and structural components.

• General formula: For glucose, $C_6H_{12}O_6$ (1:2:1 ratio).
• Types of Carbohydrates:
  • Monosaccharides: Single sugar unit (e.g., glucose, fructose).
  • Oligosaccharides: 2–9 sugar units joined by glycosidic bonds (e.g., sucrose, lactose, maltose).
  • Polysaccharides: 10 or more sugar units, often insoluble in water and not sweet (e.g., starch, glycogen, cellulose).
• Polysaccharide Types:
  • Homopolysaccharides: Composed of the same type of monosaccharide units (e.g., starch, glycogen, cellulose).
  • Heteropolysaccharides: Composed of different types of monosaccharide units.

Proteins and Amino Acids: Structure and Levels

Proteins are polymers of amino acids linked by peptide bonds. They perform diverse functions such as transport, defense, hormonal regulation, and catalysis.

• Amino acids: Organic compounds with a central (alpha) carbon attached to an amino group, carboxyl group, hydrogen, and a variable R group.
• Types of Amino Acids:
  • Essential: Not synthesized by the body, must be obtained from diet.
  • Non-essential: Synthesized by the body.
• Levels of Protein Structure:
  • Primary: Linear sequence of amino acids (N-terminal with amino group, C-terminal with carboxyl group).
  • Secondary: Folding of the polypeptide chain (alpha-helix, beta-pleated sheet) stabilized by hydrogen bonds.
  • Tertiary: Further folding into a compact, globular structure with pockets (active sites).
  • Quaternary: Association of multiple polypeptide chains (e.g., hemoglobin with alpha and beta chains).

Nucleic Acids: DNA, RNA, and Nucleotides

Nucleic acids include DNA and RNA, which store and transmit genetic information. Both are polymers of nucleotides.

• DNA: Double-stranded, contains deoxyribose sugar (deoxyribonucleic acid).
• RNA: Single-stranded, contains ribose sugar (ribonucleic acid).
• Nucleotide Structure:
  • Phosphate group (PO₄)
  • Pentose sugar (ribose in RNA, deoxyribose in DNA)
  • Nitrogenous base (purines: adenine, guanine; pyrimidines: cytosine, thymine in DNA, uracil in RNA)
• Nucleoside: Composed of a pentose sugar and a nitrogenous base (no phosphate group).
• Nucleotide Types: Named based on the nitrogenous base (e.g., adenylic acid, guanylic acid, cytidylic acid, uridylic acid, thymidylic acid).
• Function: Responsible for heredity and genetic material transfer from parents to offspring.

Lipids: Types, Structure, and Examples

Lipids are organic compounds insoluble in water, including fats, oils, waxes, and some hormones. They serve as energy reserves and structural components.

• Types of Lipids:
  • Simple Lipids: Fats and oils (e.g., triglycerides), waxes.
  • Compound Lipids: Contain additional groups (e.g., phospholipids, glycolipids).
  • Lipid Derivatives: Not detailed in the transcript.
• Fatty Acids: Long hydrocarbon chains with a terminal carboxyl group (COOH).
  • Saturated Fatty Acids: Only single bonds between carbons.
  • Unsaturated Fatty Acids: One or more double bonds between carbons.
  • Examples: Palmitic acid (16 carbons), arachidonic acid (20 carbons).
• Glycerol: Trihydroxy propane (three-carbon chain with three hydroxyl groups).
• Formation of Lipids:
  • Monoglyceride: Glycerol + 1 fatty acid.
  • Diglyceride: Glycerol + 2 fatty acids.
  • Triglyceride: Glycerol + 3 fatty acids (joined by ester bonds).
• Phospholipids: Diglyceride + phosphate group; major component of cell membranes.

Enzymes: Structure, Function, and Mechanism

Enzymes are mostly tertiary-structured proteins that act as biological catalysts, speeding up chemical reactions by lowering activation energy.

• Active Site: Pocket or crevice on the enzyme where the substrate binds.
• Enzyme Action Mechanism:
  1. Substrate binds to enzyme's active site, forming enzyme-substrate complex.
  2. Enzyme changes shape to fit substrate tightly.
  3. Enzyme breaks substrate's chemical bonds, forming enzyme-product complex.
  4. Product is released, and enzyme is free to catalyze another reaction.
• Effect on Activation Energy: Enzymes lower the activation energy required for a reaction, increasing the rate of product formation.
• Example: Without enzyme, CO₂ + H₂O → H₂CO₃ forms 200 molecules/hour; with enzyme (carbonic anhydrase), 600,000 molecules/second.

Factors Affecting Enzyme Activity

Enzyme activity is influenced by several factors, each with an optimal value for maximum efficiency.

• pH: Each enzyme has an optimum pH where activity is highest. Deviations reduce activity and can denature the enzyme.
• Temperature: Optimum temperature (e.g., 37°C for many human enzymes) yields maximum activity. Higher or lower temperatures decrease activity; above 40°C, many enzymes denature.
• Substrate Concentration: Increasing substrate increases reaction rate until all enzyme molecules are saturated (Vmax), after which rate remains constant.
• Inhibitors: Substances that reduce or block enzyme activity.
  • Competitive Inhibitors: Resemble substrate and compete for active site (e.g., malonate inhibits succinate dehydrogenase by mimicking succinate).

Enzyme Cofactors and Holoenzymes

Some enzymes require non-protein components (cofactors) for activity. Enzymes with both protein and non-protein parts are called holoenzymes.

• Apoenzyme: Protein part of the enzyme.
• Cofactor: Non-protein part, essential for activity.
  • Types of Cofactors:
    • Prosthetic Group: Organic compound tightly bound to apoenzyme (e.g., heme).
    • Coenzyme: Organic compound loosely and temporarily bound (e.g., not specified in transcript).
    • Metal Ion: Metallic ion associated with enzyme (e.g., zinc in carboxypeptidase).
• Holoenzyme: Complete, active enzyme with both apoenzyme and cofactor.

Summary Table: Types of Biomolecules and Key Features