Overview
This lecture covers fundamental concepts in life and physical sciences for the AIT's version 7 exam, focusing on biological organization, cell and molecular biology, genetics, infectious agents, disease transmission, and microscopes.
Levels of Biological Organization
- Life is organized from cells → tissues → organs → organ systems → organisms.
- Cells are the basic unit of life; all living things are made up of cells.
- Tissues are groups of similar cells performing a function.
- Organs are made of tissues; organ systems are groups of organs working together.
Cell Structure and Function
- Modern cell theory: all organisms are made of cells, cells are the basic unit of life, and cells come from pre-existing cells.
- Prokaryotes (bacteria, archaea) lack a nucleus and membrane-bound organelles.
- Eukaryotes (plants, animals, fungi, protists) have nuclei and membrane-bound organelles.
- Key organelles: nucleus (stores DNA), ribosomes (protein synthesis), mitochondria (ATP production), Golgi apparatus (packaging), ER (protein/lipid synthesis), lysosomes (digestion), chloroplasts (photosynthesis in plants), vacuoles (storage).
Cell Division: Mitosis vs. Meiosis
- Mitosis produces two identical diploid cells for growth and repair.
- Meiosis produces four genetically unique haploid cells for sexual reproduction.
- PMAT (Prophase, Metaphase, Anaphase, Telophase) sequence applies; meiosis performs PMAT twice.
- Crossing over during Prophase I and independent assortment contribute to genetic diversity in meiosis.
Genetics and Inheritance
- DNA is made of nucleotides: sugar, phosphate, and a base (A, T, G, C).
- Genes are DNA segments coding for proteins; chromosomes are DNA/protein structures.
- Regulatory genes control the expression of other genes.
- RNA types: mRNA (carries info), tRNA (brings amino acids), rRNA (makes ribosomes).
- Protein synthesis: transcription (DNA→mRNA) then translation (mRNA→protein at ribosome).
- Alleles are gene variants; dominant alleles mask recessive ones.
- Punnett squares predict genotype/phenotype ratios for single (monohybrid) and two-trait (dihybrid) crosses.
- Incomplete dominance: blended traits.
- Codominance: both traits expressed equally.
Biomolecules
- Carbohydrates (monomer: monosaccharide): energy and structure.
- Lipids (no true monomer): long-term energy storage, cell membranes, hormones.
- Proteins (monomer: amino acids): structure, enzymes, signaling, immunity.
- Nucleic acids (monomer: nucleotide): genetic information (DNA, RNA).
Infectious Agents and Disease
- Pathogenic agents: viruses (non-living, need host), bacteria (prokaryotic), fungi (eukaryotic), protozoa, helminths (worms), ectoparasites.
- Virulence: severity of the pathogen.
- Bacterial cell wall (gram-positive: thick; gram-negative: thin + outer membrane), bacteria shapes: cocci (spheres), bacilli (rods).
- Fungi: cell wall made of chitin, reproduce via spores, can cause superficial or deep infections.
- Protozoa cause diseases like malaria and giardiasis.
- Helminths and ectoparasites can cause disease and irritation.
Disease Transmission
- Infectious diseases spread via direct (contact/droplet) and indirect (airborne, fomite, vector) transmission.
- Non-infectious diseases arise from genetic, environmental, or lifestyle factors (e.g., diabetes, heart disease, cancer).
Microscopes
- Magnification: makes objects appear larger; resolution: distinguishes close objects.
- Light microscopes for cells; transmission electron microscope (TEM) for internal structures; scanning electron microscope (SEM) for surface details.
Key Terms & Definitions
- Cell — Basic structural and functional unit of life.
- Prokaryote — Cell without nucleus or membrane-bound organelles.
- Eukaryote — Cell with nucleus and membrane-bound organelles.
- Gene — DNA segment that codes for a protein.
- Allele — Variant form of a gene.
- Phenotype — Observable physical trait.
- Genotype — Genetic makeup of an organism.
- Pathogen — Disease-causing agent.
- Vector — Organism that transmits pathogens.
- Fomite — Inanimate object that transmits disease.
- Virulence — Severity or harmfulness of a pathogen.
Action Items / Next Steps
- Review diagrams for mitosis vs. meiosis, Punnett squares, organelles, and disease transmission.
- Practice using Punnett squares for monohybrid and dihybrid crosses.
- Memorize key biomolecule classes and their functions.
- Complete assigned readings on cell theory, inheritance, and infectious agents.