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General Biology Key Concepts

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  • Five fundamental characteristics of living organisms
    Cells, Replication, Information processing, Energy use, and Evolution.
  • Cell theory
    All organisms are made of membrane-bound cells, and all cells come from preexisting cells.
  • Basic atomic structure
    Atoms have a nucleus with protons (+) and neutrons (neutral), surrounded by electrons (-).
  • Isotopes
    Atoms of the same element with different numbers of neutrons and different atomic masses.
  • Valence electrons and valence
    Electrons in the outermost shell; valence is the number of unpaired valence electrons.
  • Covalent bond
    A chemical bond formed by sharing unpaired valence electrons between two atoms.
  • Difference between nonpolar and polar covalent bonds
    Nonpolar bonds share electrons equally; polar bonds share unequally due to electronegativity differences.
  • Water polarity and hydrogen bonding
    Water is polar with partial charges; hydrogen bonds form between water molecules.
  • Amino acid structure
    Consists of an amino group, carboxyl group, central carbon, and a unique side chain (R-group).
  • Protein secondary structure
    Formed by hydrogen bonds between amino and carbonyl groups; includes α-helix and β-pleated sheets.
  • Types of R-group interactions in protein tertiary structure
    Hydrogen bonds, hydrophobic interactions, van der Waals, covalent (disulfide), and ionic bonds.
  • Carbohydrate molecular formula
    General formula is (C H2O)n, where n varies from 3 to over 1000.
  • Energy storage in carbohydrates
    Electrons in C–H and C–C bonds have higher potential energy than in C=O and C–O bonds.
  • Lipids and their insolubility
    Carbon-containing compounds insoluble in water due to high proportion of nonpolar C–H bonds.
  • Fatty acid saturation effects
    Double bonds create kinks preventing tight packing; saturated fats are solid, unsaturated fats are liquid at room temperature.
  • Phospholipid bilayer structure
    Amphipathic lipids with hydrophilic heads and hydrophobic tails form bilayers spontaneously in water.
  • Diffusion and osmosis
    Diffusion is movement from high to low concentration; osmosis is diffusion of water across selectively permeable membranes.
  • Membrane protein types
    Integral (transmembrane) proteins span the membrane; peripheral proteins bind to membrane surfaces.
  • Active vs passive transport
    Passive transport moves substances down concentration gradients without energy; active transport requires energy to move substances against gradients.
  • Fluid-mosaic model of membranes
    Membranes are dynamic mosaics of phospholipids and proteins, allowing fluidity and selective permeability.
  • Cytoskeleton filament types and functions
    Actin filaments resist tension, intermediate filaments maintain cell shape, microtubules resist compression and assist intracellular transport.
  • Cellular respiration overview
    Glucose is oxidized to CO2; energy released is used to produce ATP via glycolysis, citric acid cycle, and electron transport chain.
  • Fermentation purpose
    Regenerates NAD+ from NADH allowing glycolysis and ATP production to continue without oxygen.
  • Photosynthesis overall reaction
    Converts CO2 and H2O into carbohydrates and O2 using light energy.
  • Calvin cycle phases
    Fixation of CO2, reduction of 3PGA to G3P, and regeneration of RuBP.
  • Cell cycle checkpoints
    G1, G2, and M phase checkpoints ensure cell size, DNA integrity, and chromosome alignment before division.
  • Mitosis vs meiosis key differences
    Mitosis produces identical diploid cells; meiosis produces haploid cells with genetic variation through two divisions.