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chapter 3 lecture

Chapter Three: Biological Macromolecules

Introduction to Biological Macromolecules

  • The chapter discusses biological macromolecules, specifically emphasizing their significance in the composition and functions of living organisms.

  • Begins with the concept of lactose intolerance as an example of the importance of biological molecules and enzymes in everyday life.

    • Lactose intolerance occurs when individuals cannot digest milk or milk-based products due to a deficiency of the enzyme lactase, which is classified as a protein.

    • Most of the world’s population exhibits some form of lactose intolerance.

Organic Compounds

  • Definition of organic compounds: Molecules that are carbon-based (composed mainly of carbon atoms).

  • Contrast with inorganic compounds: Any compound that lacks carbon is not considered organic.

    • Key Point: Carbon is capable of forming four covalent bonds, allowing for diverse molecular arrangements.

  • Structure of simple organic compounds: Example given is methane (CH₄), which is the simplest organic molecule, consisting of one carbon atom bonded to four hydrogen atoms.

Hydrocarbons

  • Hydrocarbons: Organic compounds made solely of carbon and hydrogen.

    • Examples include methane, propane, and butane, highlighting how carbon chains can vary in length and complexity (linear, branched, or cyclic).

Isomers

  • Isomers: Compounds that have the same molecular formula but different structural arrangements, leading to different properties.

    • An example of isomers is butane and isobutane (C₄H₁₀).

Functional Groups

  • Six key functional groups in organic chemistry that are important for the properties and reactions of organic molecules:

    1. Hydroxyl

    • Structure: -OH (water-loving, hydrophilic)

    1. Carbonyl

    • Structure: C=O

    1. Carboxyl

    • Structure: -COOH (both hydroxyl and carbonyl groups, acidic behavior)

    1. Amino

    • Structure: -NH₂ (can act as a base)

    1. Phosphate

    • Structure: -PO₄³⁻ (important in energy transfer)

    1. Methyl

    • Structure: -CH₃ (nonpolar, affects molecular shape but not reactive)

Macromolecules (Polymers)

  • Macromolecules, also known as polymers, are large molecules composed of smaller building blocks (monomers).

  • Four major classes of biological macromolecules:

    1. Carbohydrates

    2. Lipids

    3. Proteins

    4. Nucleic acids

  • Important to understand the monomeric units that compose each type of macromolecule.

Carbohydrates

  • Monosaccharides (simple sugars): The building blocks of carbohydrates. Examples include glucose (C₆H₁₂O₆) and fructose.

    • When two monosaccharides combine, they form disaccharides (e.g., sucrose, lactose).

    • Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).

    • Functions: Energy storage and structural components.

Lipids

  • Definition: A group of hydrophobic (water-fearing) molecules, primarily composed of carbon and hydrogen, involved in energy storage.

  • Types of lipids:

    1. Fats (Triglycerides)

    • Composed of glycerol and fatty acids.

    • Formation: Glycerol + 3 Fatty Acids via dehydration reaction.

    1. Phospholipids

    • Major components of cell membranes. Composed of glycerol, two fatty acids, and a phosphate group.

    • Structure: Hydrophilic heads and hydrophobic tails, forming a phospholipid bilayer in water.

    1. Steroids

    • Characterized by a four-ring structure (e.g., cholesterol, sex hormones).

  • Saturated vs. Unsaturated Fats:

    • Saturated fats: No double bonds, solid at room temperature, generally unhealthy.

    • Unsaturated fats: Contain one or more double bonds, liquid at room temperature, healthier options.

  • Trans fats: Artificially hydrogenated fats associated with health risks.

Proteins

  • Most diverse macromolecule category, composed of 20 different amino acids (monomers).

  • Proteins have various roles, including acting as enzymes, transport molecules, structural components, and antibodies.

    • Example: Enzymes (like lactase) facilitate biochemical reactions.

  • Formation of proteins:

    • Amino acids link via peptide bonds during dehydration reactions, forming dipeptides or polypeptides.

    • Importance of structure: Primary (sequence of amino acids), secondary (alpha-helix or beta-pleated sheets), tertiary (3D shape), and quaternary (multiple polypeptides combined).

Nucleic Acids

  • DNA and RNA as fundamental molecules that carry genetic information and play roles in heredity and protein synthesis.

  • Structure includes nucleotides as monomer units.

Conclusion

  • Key takeaways on biological macromolecules encompass their structures (monomers and polymers), their functions, and the significance of their arrangements and interactions in biological systems. Further details on nucleic acids will be covered in a separate session.

Polycythemia Acids

Basic Concepts

  • Definition of Polycythemia: The condition is related to the amino acid sequence programmed by discrete units of inheritance known as genes.

Genes and DNA

  • Definition of a Gene: A gene is a unit of heredity consisting of DNA, which is known as deoxyribonucleic acid, a type of nucleic acid.

  • Role of DNA:

    • DNA is inherited from an organism's parents.

    • DNA provides instructions for its own replication.

    • DNA directs the synthesis of proteins through RNA.

DNA and RNA Relationship

  • Direct Action: DNA does not build proteins directly; it requires ribonucleic acid (RNA) as an intermediary.

  • Process of Protein Synthesis:

    1. DNA is transcribed into RNA in the cell's nucleus.

    2. RNA is then translated into proteins in the cytoplasm.

Types of Nucleic Acids

  • Nucleic Acids: Composed of monomers called nucleotides.

  • Components of Nucleotides:

    • Five Carbon Sugar:

    • In RNA: Ribose

    • In DNA: Deoxyribose

    • Phosphate Group

    • Nitrogenous Base

Nitrogenous Bases

  • DNA Nitrogenous Bases:

    • Adenine (A)

    • Thymine (T)

    • Cytosine (C)

    • Guanine (G)

  • RNA Nitrogenous Bases:

    • Adenine (A)

    • Cytosine (C)

    • Guanine (G)

    • Uracil (U) replaces Thymine in RNA.

Nucleic Acid Structure

  • Polynucleotide Formation:

    • A nucleic acid polymer (polynucleotide) is formed when the phosphate group of one nucleotide bonds to the sugar of another nucleotide through dehydration reactions.

    • This results in a sugar-phosphate backbone with nitrogenous bases protruding out.

  • RNA Structure:

    • Typically a single polynucleotide strand.

  • DNA Structure:

    • Always forms a double helix with two polynucleotide strands that wrap around each other.

    • The strands are associated through hydrogen bonding between complementary bases.

    • Adenine pairs with Thymine.

    • Cytosine pairs with Guanine.

    • In RNA, Thymine is replaced by Uracil, so the pairing is:

      • Adenine pairs with Uracil.

      • Cytosine pairs with Guanine.

Lactose Intolerance and Genetics

  • Lactose Intolerance:

    • Most people stop producing the enzyme lactase in early childhood, which leads to difficulty digesting milk due to the absence of this enzyme.

  • Lactose Tolerance as a Mutation:

    • Represents a relatively recent mutation in the human genome, offering a survival advantage for cultures consuming milk and dairy products year-round.

Genetic Mutations

  • Research Findings:

    • Three new mutations were identified across 43 ethnic groups in East Africa that keep the lactase gene permanently activated.

    • The mutations vary from one another and differ from the European lactase mutation.

    • These mutations appeared approximately 7,000 years ago, coinciding with the domestication of cattle in East Africa.

Conclusion

  • This module discussed key concepts related to nucleic acids, the relationship between DNA and RNA, and highlighted the genetic implications of lactose tolerance in human populations.

  • Ready to proceed with the quiz once the understanding of these topics is confirmed.