Introduction to Cell Biology

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms.
• Central concepts in biology include cell theory, gene theory, evolution, homeostasis, and thermodynamics.
• All living organisms share key characteristics, such as cellular organization, metabolism, homeostasis, heredity, response to stimuli, growth and reproduction, and adaptation through evolution.

Cell Biology

• Cell biology studies the structure, function, and behavior of cells.
• The cell is the basic unit of life, responsible for carrying out all essential processes in living organisms.
• Cells are broadly classified into two types: prokaryotic and eukaryotic.
  • Prokaryotic cells (bacteria and archaea) lack a nucleus and other membrane-bound organelles.
  • Eukaryotic cells (protists, fungi, plants, and animals) possess a nucleus and complex organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.
• Key cellular structures and their functions:
  • Plasma membrane: Separates the cell from its external environment and regulates the transport of substances into and out of the cell.
  • Nucleus: Contains the cell's genetic material (DNA) and controls cell growth, metabolism, and reproduction.
  • Mitochondria: The powerhouses of the cell, responsible for generating energy (ATP) through cellular respiration.
  • Endoplasmic reticulum (ER): Involved in protein and lipid synthesis, and calcium storage.
    • Rough ER contains ribosomes for protein synthesis.
    • Smooth ER is involved in lipid metabolism and detoxification.
  • Golgi apparatus: Modifies, sorts, and packages proteins and lipids for transport within the cell or secretion outside the cell.
  • Lysosomes: Contain enzymes that break down cellular waste and debris.
  • Cytoskeleton: Provides structural support, facilitates cell movement, and enables intracellular transport.
• Cellular processes include:
  • Cell division: The process by which cells multiply (mitosis and meiosis).
  • Cellular respiration: The process by which cells convert glucose into ATP (energy).
  • Photosynthesis: The process by which plants and some bacteria convert light energy into chemical energy (glucose).
  • Protein synthesis: The process by which cells create proteins from amino acids based on the genetic code.
  • Membrane transport: The movement of substances across the cell membrane (passive and active transport).

Genetics

• Genetics is the study of heredity and variation in living organisms.
• Genes are the units of heredity, composed of DNA, and contain the instructions for building proteins.
• DNA (deoxyribonucleic acid) is the molecule that carries genetic information.
  • DNA is a double-stranded helix composed of nucleotides.
  • Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).
• RNA (ribonucleic acid) is involved in protein synthesis.
  • RNA is typically single-stranded and contains ribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil).
• Key genetic concepts:
  • Genotype: The genetic makeup of an organism.
  • Phenotype: The observable characteristics of an organism.
  • Alleles: Different versions of a gene.
  • Dominant allele: An allele that masks the effect of a recessive allele.
  • Recessive allele: An allele whose effect is masked by a dominant allele.
  • Homozygous: Having two identical alleles for a gene.
  • Heterozygous: Having two different alleles for a gene.
• Mendelian genetics:
  • Gregor Mendel's laws of inheritance:
    • Law of segregation: Each individual has two alleles for each trait, and these alleles separate during gamete formation.
    • Law of independent assortment: Genes for different traits are inherited independently of each other.
• Molecular genetics:
  • DNA replication: The process by which DNA is copied.
  • Transcription: The process by which RNA is synthesized from a DNA template.
  • Translation: The process by which proteins are synthesized from an RNA template.
• Mutations: Changes in the DNA sequence that can lead to genetic variation.
• Genetic engineering: The manipulation of genes for practical purposes.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Key concepts in ecology:
  • Ecosystem: A community of living organisms interacting with their physical environment.
  • Population: A group of individuals of the same species living in the same area.
  • Community: A group of different species living in the same area and interacting with each other.
  • Biosphere: The part of Earth where life exists.
• Ecological levels of organization:
  • Individual
  • Population
  • Community
  • Ecosystem
  • Biome
  • Biosphere
• Types of ecosystems:
  • Terrestrial ecosystems (forests, grasslands, deserts, tundra)
  • Aquatic ecosystems (freshwater and marine)
• Trophic levels:
  • Producers (autotrophs): Organisms that produce their own food through photosynthesis or chemosynthesis.
  • Consumers (heterotrophs): Organisms that obtain energy by consuming other organisms.
    • Primary consumers (herbivores): Eat producers.
    • Secondary consumers (carnivores): Eat primary consumers.
    • Tertiary consumers: Eat secondary consumers.
  • Decomposers: Organisms that break down dead organic matter.
• Food chains and food webs:
  • Food chain: A linear sequence of organisms through which nutrients and energy pass.
  • Food web: A complex network of interconnected food chains.
• Ecological interactions:
  • Competition: When organisms compete for the same resources.
  • Predation: When one organism (the predator) kills and eats another organism (the prey).
  • Symbiosis: A close and long-term interaction between two different species.
    • Mutualism: Both species benefit.
    • Commensalism: One species benefits and the other is neither harmed nor helped.
    • Parasitism: One species benefits and the other is harmed.
• Biogeochemical cycles:
  • The cycling of essential elements (e.g., carbon, nitrogen, water) through the biotic and abiotic components of ecosystems.
• Human impacts on ecosystems:
  • Habitat destruction
  • Pollution
  • Climate change
  • Overexploitation of resources

Evolutionary Biology

• Evolutionary biology is the study of the processes that have shaped the diversity and adaptation of life over time.
• Key concepts in evolutionary biology:
  • Evolution: The change in the genetic makeup of a population over time.
  • Natural selection: The process by which organisms with advantageous traits are more likely to survive and reproduce.
  • Adaptation: A trait that enhances an organism's survival and reproduction in its environment.
  • Speciation: The process by which new species arise.
• Mechanisms of evolution:
  • Mutation: A change in the DNA sequence.
  • Gene flow: The movement of genes between populations.
  • Genetic drift: Random changes in allele frequencies due to chance events.
  • Natural selection: Differential survival and reproduction of individuals based on their traits.
• Evidence for evolution:
  • Fossil record: The preserved remains or traces of ancient organisms.
  • Comparative anatomy: The study of similarities and differences in the anatomy of different species.
  • Embryology: The study of the development of embryos.
  • Molecular biology: The study of DNA and protein sequences.
• Patterns of evolution:
  • Divergent evolution: The process by which two or more species evolve from a common ancestor and become increasingly different.
  • Convergent evolution: The process by which unrelated species evolve similar traits due to similar environmental pressures.
  • Coevolution: The process by which two species evolve in response to each other.
• Speciation:
  • Allopatric speciation: Speciation that occurs when populations are geographically isolated.
  • Sympatric speciation: Speciation that occurs within the same geographic area.
• Phylogeny: The evolutionary history of a group of organisms.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, archaea, viruses, fungi, and protists.
• Key concepts in microbiology:
  • Microorganisms are ubiquitous and play essential roles in ecosystems, industries, and human health.
  • Bacteria and archaea are prokaryotic cells, while fungi and protists are eukaryotic cells.
  • Viruses are acellular entities that require a host cell to replicate.
• Microbial structure and function:
  • Bacteria:
    • Cell wall (peptidoglycan in bacteria)
    • Cell membrane
    • Cytoplasm
    • DNA (nucleoid)
    • Ribosomes
    • Plasmids
    • Flagella
    • Pili
  • Archaea:
    • Similar structure to bacteria but with distinct cell wall and membrane components.
  • Fungi:
    • Cell wall (chitin)
    • Cell membrane
    • Cytoplasm
    • Nucleus
    • Organelles
  • Protists:
    • Diverse group of eukaryotic microorganisms.
    • Vary in structure and function.
  • Viruses:
    • Nucleic acid (DNA or RNA)
    • Protein coat (capsid)
    • Envelope (in some viruses)
• Microbial metabolism:
  • Autotrophs: Produce their own food through photosynthesis or chemosynthesis.
  • Heterotrophs: Obtain energy by consuming organic compounds.
  • Aerobes: Require oxygen for growth.
  • Anaerobes: Do not require oxygen for growth.
  • Fermentation: Metabolic process that converts sugars to acids, gases, or alcohol.
• Microbial genetics:
  • Genetic material: DNA or RNA.
  • Reproduction:
    • Bacteria and archaea: Binary fission.
    • Fungi: Sexual and asexual reproduction.
  • Genetic transfer:
    • Conjugation
    • Transformation
    • Transduction
• Microbial ecology:
  • Microorganisms in soil, water, and air.
  • Roles in nutrient cycling, decomposition, and bioremediation.
• Medical microbiology:
  • Pathogenic microorganisms: Bacteria, viruses, fungi, and protists that cause diseases.
  • Immune response: The body's defense mechanisms against pathogens.
  • Antibiotics: Drugs that kill or inhibit the growth of bacteria.
  • Vaccines: Preparations that stimulate the immune system to protect against specific pathogens.
• Industrial microbiology:
  • Use of microorganisms in food production, pharmaceuticals, and biofuels.