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General Biology Key Concepts

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  • Hierarchy of life from least to most complex

    Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism → Populations → Communities → Ecosystems → Biosphere

  • Universal genetic code in living organisms

    All organisms share DNA with 4 bases (Adenine, Thymine, Cytosine, Guanine) encoding proteins via the same amino acid code, indicating common evolutionary origin.

  • Reductionism vs Systems Biology

    Reductionism: studying isolated parts of a system.
    Systems Biology: studying interactions and dynamics of whole biological systems.

  • Similarities between prokaryotic and eukaryotic cells

    Both have cell membrane, DNA, cytoplasm, and ribosomes.

  • Differences between prokaryotic and eukaryotic cells

    Prokaryotes lack membrane-bound nucleus and organelles; usually smaller and unicellular.
    Eukaryotes have membrane-bound nucleus and organelles; often multicellular.

  • Three domains of life

    Bacteria (prokaryotic), Archaea (prokaryotic, often extremophiles), Eukarya (eukaryotic).

  • Kingdoms within Domain Eukarya

    Animals, Plants, Fungi, Protists.

  • Characteristic of Animals kingdom

    Multicellular and ingest food.

  • Characteristic of Plants kingdom

    Multicellular autotrophs with cell walls made of cellulose.

  • Characteristic of Fungi kingdom

    Heterotrophs that absorb digested food; can be multicellular or unicellular.

  • Characteristic of Protists kingdom

    Mostly unicellular with no common structure or feature.

  • Steps of the scientific method

    Observation → Question → Hypothesis → Data Collection/Analysis → Conclusion.

  • Control group in experiments

    Group kept under baseline conditions without treatment; used for comparison to isolate effects of the independent variable.

  • Independent vs Dependent variables

    Independent: variable manipulated by researcher.
    Dependent: variable measured as response.

  • Qualitative vs Quantitative data

    Qualitative: descriptive, non-numerical (e.g., color).
    Quantitative: numerical measurements (e.g., weight).

  • Electron arrangement in atomic shells

    1st shell: max 2 electrons; 2nd shell: max 8 electrons; 3rd shell: max 8 electrons.

  • s and p orbitals shapes and electron capacity

    s orbital: spherical, holds 2 electrons.
    p orbital: dumbbell-shaped, 3 orientations, holds 6 electrons total.

  • Atomic number and atomic mass definitions

    Atomic number = protons = electrons (neutral atom).
    Atomic mass = protons + neutrons.

  • Isotopes definition

    Atoms of the same element with same protons but different neutrons, thus different atomic masses.

  • Similarity of elements in the same column of periodic table

    Same number of valence electrons, leading to similar chemical properties and family grouping.

  • Formation of covalent bonds

    Atoms share one or more pairs of valence electrons to complete outer shells.

  • Electronegativity and its effect on covalent bonds

    Electronegativity is an atom's pull on shared electrons.
    Equal electronegativity → nonpolar bond; unequal → polar bond with partial charges.

  • Most and least electronegative atoms in living cells

    Most electronegative: Oxygen (O), Nitrogen (N).
    Least electronegative: Carbon (C), Hydrogen (H).

  • Hydrogen bond formation

    Attraction between a hydrogen with partial positive charge bound to O or N and another electronegative atom with partial negative charge.

  • Chemical properties from electronic configuration

    Inert atoms have full outer shells.
    Bond capacity equals number of electrons needed to fill shell.
    Cations form by losing electrons; anions by gaining electrons.

  • Hydrophilic vs Hydrophobic compounds

    Hydrophilic: polar/ionic, dissolve in water.
    Hydrophobic: nonpolar, repel water.

  • How polar and ionic compounds dissolve in water

    Polar compounds form hydrogen bonds with water.
    Ionic compounds are surrounded by hydration shells of water molecules.

  • Emergent properties of water from hydrogen bonding

    Cohesion/adhesion, temperature moderation, expansion on freezing, and versatile solvent properties.

  • Definition of 1 mole

    1 mole = molecular mass in grams = \(6.022 \times 10^{23}\) molecules (Avogadro's number).

  • Steps to prepare molar solutions

    Calculate molecular weight, multiply by molarity and volume, weigh solute, dissolve in solvent, adjust to final volume.

  • Strong acid and strong base definitions

    Strong acid: fully dissociates to release H+ (e.g., HCl).
    Strong base: fully dissociates to release OH- or accept H+ (e.g., NaOH).

  • pH scale and calculation

    pH = -log10[H+]; acidic pH < 7, neutral = 7, basic > 7.

  • Relationship between [H+] and [OH-] in water

    [H+] × [OH-] = \(10^{-14}\); changing one affects the other inversely.

  • pH difference and [H+] concentration change

    Each pH unit change equals a 10-fold change in [H+]; e.g., pH 3 has 100 times more [H+] than pH 5.

  • Role of buffers

    Buffers resist pH changes by accepting or donating H+ ions to maintain stable conditions.

  • Why carbon is abundant in living cells

    Carbon forms 4 covalent bonds, enabling complex, stable, diverse molecules like chains, branches, and rings.

  • Carbon's electronic configuration and bonding

    Atomic number 6; 2 inner electrons, 4 valence electrons; tetravalent forming up to 4 covalent bonds.

  • Hydrocarbons and their hydrophobic nature

    Composed of C and H; C-H bonds are nonpolar due to similar electronegativities, making hydrocarbons hydrophobic.

  • Isomers definition and types

    Compounds with same formula but different structures.
    Types: Structural, Cis-Trans, Enantiomers.

  • Functional groups and their properties

    Hydroxyl (-OH): polar, alcohols.
    Carbonyl (>C=O): polar, ketone/aldehyde.
    Carboxyl (-COOH): acidic.
    Amino (-NH2): basic.
    Sulfhydryl (-SH): forms disulfide bridges.
    Phosphate (-OPO2/3-): negative, energy transfer.
    Methyl (-CH3): nonpolar, affects gene expression.