Microbiology Study Guide: Biomolecules, Cells, Genomes, Growth, and Control

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Biomolecules in Microbiology

Macromolecules, Polymers, and Monomers

Macromolecules are large, complex molecules essential for life, including nucleic acids, proteins, carbohydrates, and lipids. They are often polymers, which are chains of repeating units called monomers.

Macromolecule: A large molecule composed of thousands of atoms.
Polymer: A molecule made from repeating monomer units.
Monomer: The basic building block of a polymer.
Examples:
- Nucleic acids: monomer = nucleotide; polymer = DNA or RNA
- Proteins: monomer = amino acid; polymer = polypeptide/protein
- Carbohydrates: monomer = monosaccharide; polymer = polysaccharide

Dehydration Synthesis and Hydrolysis

Biological polymers are formed and broken down by specific chemical reactions.

Dehydration Synthesis (Condensation): Joins monomers by removing a water molecule.
Hydrolysis (Decomposition): Breaks polymers into monomers by adding water.
Equation:

Nucleic Acids: DNA and RNA

Nucleic acids store and transmit genetic information. DNA and RNA are polymers of nucleotides.

Nucleotide: Consists of a sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base.
DNA: Contains deoxyribose, bases A, T, C, G; double-stranded, antiparallel, complementary base pairing (A-T, C-G).
RNA: Contains ribose, bases A, U, C, G; single-stranded.
5' phosphate and 3' OH ends: Directionality of DNA strands.
Base Pairing: Hydrogen bonds between complementary bases.
Antiparallel: Strands run in opposite directions.

Proteins and Amino Acids

Proteins are polymers of amino acids, responsible for structure and function in cells.

Amino Acid: Contains a central carbon, amino group, carboxyl group, and side chain (R group).
Peptide: Short chain of amino acids.
Polypeptide: Longer chain; folds into a protein.
Protein Structure:
- Primary: Sequence of amino acids
- Secondary: Alpha helices and beta sheets
- Tertiary: 3D folding
- Quaternary: Multiple polypeptides
Protein Folding: Essential for function; improper folding leads to denaturation.
Denaturation: Loss of structure and function due to heat, pH, or chemicals.

Carbohydrates

Carbohydrates provide energy and structural support.

Monosaccharide: Simple sugar (e.g., glucose).
Disaccharide: Two monosaccharides (e.g., lactose, sucrose).
Polysaccharide: Many monosaccharides (e.g., cellulose, glycogen, starch).
Functions: Energy storage (glycogen, starch), structure (cellulose).

Lipids

Lipids are hydrophobic molecules important for membranes and energy storage.

Triglyceride: Glycerol + 3 fatty acids; energy storage.
Phospholipid: Glycerol + 2 fatty acids + phosphate; forms cell membranes.
Steroid: Four fused rings; hormones and membrane structure.
Hydrophobic: Repels water.
Hydrophilic: Attracts water.

Functions of Biomolecules

Nucleic Acids: Genetic information storage and transfer.
Proteins: Enzymes, structure, transport, signaling.
Carbohydrates: Energy, structure.
Lipids: Membranes, energy storage, signaling.

Microbiologists and Science Identity

Colonialism and Science

European colonialism influenced the development and spread of Western science, shaping global scientific practices and access.

Colonialism: Expansion and control by European powers.
Impact: Western science became dominant; marginalized other knowledge systems.
Current Effects: Inequities in scientific funding, access, and recognition.
Decolonizing Science: Suggestions include recognizing diverse contributions, promoting inclusion, and valuing local knowledge.

Science Identity and Inclusion

Science Identity: How individuals see themselves as scientists.
Importance of Inclusion: Diverse perspectives improve science and innovation.

Cells and Microbial Classification

Microbes and Pathogens

Microbes are microscopic organisms, some of which cause disease (pathogens).

Microbe: Microscopic organism (bacteria, archaea, fungi, protists, viruses).
Pathogen: Microbe that causes disease.
Size: Most microbes range from 0.2 to 10 micrometers.

Importance of Microbes

Essential for nutrient cycling, digestion, biotechnology, and disease.

Microbial Classification

Microbes are classified by cellular structure and genetic relationships.

Three Domains: Bacteria, Archaea, Eukarya
Four Kingdoms (Eukarya): Animal, Plant, Fungi, Protist
Groups: Cellular (bacteria, archaea, fungi, animal, helminth, protist, algae, protozoan), Acellular (virus, viroid, prion)

Cell Theory

All living things are composed of cells.
Cells are the basic unit of life.
Cells arise from pre-existing cells.

Prokaryotic vs. Eukaryotic Cells

Prokaryotes: No nucleus, simple structure (bacteria, archaea).
Eukaryotes: Nucleus, complex organelles (fungi, animals, plants, protists).

Bacterial vs. Archaeal Cells

Bacteria: Peptidoglycan cell wall, diverse metabolism.
Archaea: Unique cell wall (no peptidoglycan), extremophiles.

Cell Structures and Functions

Cell/Plasma Membrane: Controls entry/exit of substances.
Mitochondria: Energy production (eukaryotes).
Nucleoid: DNA region in prokaryotes.
Nucleus: DNA storage in eukaryotes.
Chromosome DNA: Genetic material.
Ribosomes: Protein synthesis.
Endoplasmic Reticulum: Protein/lipid synthesis.
Golgi Complex: Protein modification and sorting.
Cell Wall: Structure and protection.

Plasma Membrane Transport Mechanisms

Simple Diffusion: Movement down concentration gradient.
Facilitated Diffusion: Uses transport proteins.
Osmosis: Water movement.
Active Transport: Requires energy.
Endocytosis/Exocytosis: Bulk transport (eukaryotes).

Cell Walls: Medical Relevance

Gram-positive: Thick peptidoglycan, stains purple.
Gram-negative: Thin peptidoglycan, outer membrane, stains pink.
Archaea: Unique cell wall.
Fungi: Chitin cell wall.
Algae: Cellulose or silica cell wall.
Medical Relevance: Cell wall differences affect antibiotic susceptibility.

Prokaryotic Cell Structures

Plasmids: Small, circular DNA.
Capsules: Protection, adherence.
Flagella: Motility.
Pili/Fimbriae: Attachment.
Inclusion Bodies: Storage.
Endospore: Dormant, resistant structure.
Sporulation: Formation of endospore.
Germination: Return to active growth.

Eukaryotic Cell Structures

Lysosomes: Digestion.
Flagella/Cilia: Movement.
Chloroplasts: Photosynthesis.

Endosymbiotic Theory

Explains origin of mitochondria and chloroplasts from prokaryotic ancestors.

Genomes and DNA

Genome Structure

The genome is the complete set of genetic material in an organism.

Genome: All genetic material.
Chromosome: Main DNA molecule.
Chromosomal DNA: DNA in chromosomes.
Extrachromosomal DNA: DNA outside chromosomes (e.g., plasmids).
Plasmid: Small, circular DNA in bacteria.
Cellular vs. Viral Genomes: Cellular genomes are DNA; viral genomes can be DNA or RNA.

Genotype and Phenotype

Genotype: Genetic makeup.
Phenotype: Observable traits.
Relationship: Genotype determines phenotype via gene expression.

Microbial Growth and DNA Replication

Reproduction and Cell Division

Asexual Reproduction: Offspring from one parent (binary fission, mitosis).
Sexual Reproduction: Offspring from two parents (meiosis).
Interphase: Cell growth and DNA replication.
Mitosis: Division of nucleus.
Cytokinesis: Division of cytoplasm.
Meiosis: Produces haploid gametes.
Haploid: One set of chromosomes.
Diploid: Two sets of chromosomes.
Binary Fission: Prokaryotic cell division.

DNA Replication

Origin of Replication: Starting point.
Replication Fork: Area where DNA is unwound.
Replication Bubble: Region of active replication.
Enzymes: DNA polymerase, helicase, ligase, topoisomerase.
Okazaki Fragments: Short DNA segments on lagging strand.
Semiconservative Replication: Each new DNA has one old and one new strand.
Telomeres/Telomerase: Protect chromosome ends (eukaryotes).
Equation:

Microbial Growth and Biofilms

Generation Time: Time for population to double.
Planktonic: Free-floating microbes.
Biofilm: Community of microbes in extracellular matrix.
Health Risks: Biofilms resist antibiotics and cause persistent infections.

Growth Curve Phases

Lag Phase: Adaptation, no growth.
Log Phase: Rapid growth.
Stationary Phase: Growth equals death.
Death Phase: Decline in population.

Microbial Culture Methods

Closed System: Limited nutrients (batch culture).
Open System: Continuous nutrients (chemostat).

Microbial Environmental Preferences

Obligate Aerobe: Requires oxygen.
Obligate Anaerobe: No oxygen.
Facultative Anaerobe: With or without oxygen.
Aerotolerant Anaerobe: Tolerates oxygen.
Microaerophile: Low oxygen.
Neutrophile: Neutral pH.
Acidophile: Acidic pH.
Alkaliphile: Basic pH.
Psychrophile: Cold-loving.
Psychrotroph: Tolerates cold.
Mesophile: Moderate temperature.
Thermophile: Heat-loving.
Halophile: Salt-loving.
Halotolerant: Tolerates salt.
Non-halophile: No salt tolerance.

Control of Microbial Growth

Definitions and Methods

Sterilization: Complete removal of all microbes.
Disinfection: Removal of pathogens.
Disinfectant: Chemical for surfaces.
Antiseptic: Chemical for living tissue.
Microbicidal: Kills microbes.
Microbiostatic: Inhibits growth.

Physical vs. Chemical Methods

Physical: Heat, filtration, radiation.
Chemical: Surfactants, alcohols, peroxygens, halogens, alkylating agents.

Heat, Filtration, and Radiation

Heat: Denatures proteins (autoclave uses steam under pressure).
Filtration: Removes microbes from liquids.
Radiation: Damages DNA.

Autoclave

Uses steam at 121°C and pressure to sterilize.

Chemical Agents

Surfactants: Disrupt membranes.
Alcohols: Denature proteins.
Peroxygens: Oxidize cell components.
Halogens: Oxidize and disrupt proteins.
Alkylating Agents: Modify DNA and proteins.

Choosing Control Methods

Depends on item type, required sterility, and safety.