Microbiology: Biomolecules and Metabolism Ch.2

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Fundamental Chemistry for Microbiology

Overview of Key Concepts

This section introduces the essential chemical principles underlying microbiology, focusing on the structure and function of biomolecules. Understanding these concepts is crucial for comprehending microbial cell structure, metabolism, and genetic processes.

Chemical Bonding: Atoms combine via covalent, ionic, and hydrogen bonds to form molecules essential for life.
Water: The universal solvent, critical for biochemical reactions and cellular structure.
Acids, Bases, and pH: pH affects enzyme activity and microbial growth.
Biological Molecules: Includes carbohydrates, lipids, proteins, and nucleic acids.

Fundamental Chemistry for Microbiology diagram

Biomolecules

Classification and Importance

Biomolecules are organic compounds that form the structural and functional basis of all living organisms, including microbes. The four major classes are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates: Provide energy and structural support.
Lipids: Form cell membranes and store energy.
Proteins: Catalyze reactions and provide cellular structure.
Nucleic Acids: Store and transmit genetic information.

Biomolecules: lipids, nucleic acids, carbohydrates, proteins

Carbohydrates

Carbohydrates are composed of carbon, hydrogen, and oxygen. They are classified as monosaccharides, disaccharides, and polysaccharides based on their complexity.

Monosaccharides: Simple sugars (e.g., glucose, fructose) that serve as energy sources.
Disaccharides: Formed by joining two monosaccharides via a glycosidic bond (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen) with structural or storage functions.

Formation of a disaccharide: glucose + fructose = sucrose

Examples and Applications

Glucose: Primary energy source for cells.
Fructose: Found in fruits; used in metabolism.
Sucrose: Table sugar; a disaccharide of glucose and fructose.

Table sugar (sucrose) Fruit bowl containing fructose

Polysaccharides

Cellulose: Structural component in plant cell walls; composed of β-glucose monomers.
Starch: Storage form of glucose in plants; consists of amylose (unbranched) and amylopectin (branched).
Glycogen: Storage form of glucose in animals; highly branched structure.

Cellulose structure in plant cell walls Comparison of starch, glycogen, and cellulose structures Amylose and amylopectin structure

Lipids

Lipids are hydrophobic molecules that include fats, phospholipids, and steroids. They are essential for membrane structure and energy storage.

Fats (Triglycerides): Composed of glycerol and three fatty acids; store energy.
Phospholipids: Major component of cell membranes; consist of a hydrophilic head and hydrophobic tails.
Steroids: Include cholesterol (in animals) and ergosterol (in fungi); important for membrane fluidity and signaling.

Triglyceride structure Phospholipid structure Phospholipid and fatty acid molecules Phospholipid molecule: hydrophilic head and hydrophobic tail Lipid bilayer structure Fatty acid molecule and micelle Hydrophobic vs. hydrophilic Hydrophobic leaf surface Hydrophilic paper surface Steroid structures: cholesterol and ergosterol

Proteins

Proteins are polymers of amino acids linked by peptide bonds. They perform a wide range of functions, including catalysis, structural support, and regulation.

Amino Acid Structure: Each amino acid has a central carbon, an amino group, a carboxyl group, and a variable side chain (R group).
Peptide Bond Formation: Amino acids are joined by dehydration synthesis, forming peptide bonds.
Protein Structure: Proteins have four levels of structure—primary, secondary, tertiary, and quaternary.

Peptide bond formation Amino acid structure Protein structure: amino acids, peptides, proteins Primary structure of protein Secondary structure: helix Tertiary structure Quaternary structure

Classification of Proteins

Type of protein	Fibrous	Globular	Conjugated
Shape	Collagen, Keratin	Enzymes, Antibodies, Hormones	Haemoglobin

Protein classification table

Nucleic Acids

Nucleic acids are polymers of nucleotides that store and transmit genetic information. The two main types are DNA and RNA.

Nucleotide Structure: Each nucleotide consists of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.
DNA: Double-stranded; contains deoxyribose and bases adenine, guanine, cytosine, and thymine.
RNA: Single-stranded; contains ribose and bases adenine, guanine, cytosine, and uracil.

Nucleotide structure Pentose sugars: deoxyribose and ribose Nitrogenous bases: purines and pyrimidines DNA base pairing and hydrogen bonds DNA structure and base pairs DNA vs. RNA structure

Key Differences Between DNA and RNA

Strandedness: DNA is double-stranded; RNA is single-stranded.
Base Composition: DNA contains thymine; RNA contains uracil.
Function: DNA stores genetic information; RNA is involved in protein synthesis and regulation.

ATP: The Universal Energy Molecule

ATP (Adenosine Triphosphate) is the primary energy carrier in cells. The hydrolysis of its high-energy phosphate bonds releases energy for cellular functions.

Structure: Composed of adenine, ribose, and three phosphate groups.
Function: Provides energy for metabolic processes.

Essentials of Metabolism

Key Concepts

Metabolism encompasses all chemical reactions in a cell, divided into catabolism (breakdown of molecules) and anabolism (synthesis of molecules). Enzymes are biological catalysts that speed up metabolic reactions.

Enzyme: A protein that accelerates biochemical reactions.
Metabolism: The sum of all chemical reactions in an organism.
Catabolism: Breakdown of complex molecules into simpler ones, releasing energy.
Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.

Summary

Understanding the chemistry of biomolecules and metabolism is foundational for studying microbiology. These concepts explain how microbes grow, reproduce, and interact with their environment.

Additional info: Expanded explanations and examples were added to ensure completeness and academic quality for exam preparation.