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General Biology Key Concepts

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  • Predominant atoms in a typical cell and their valences

    HONC: Hydrogen (1), Oxygen (2), Nitrogen (3), Carbon (4)

  • Covalent bond

    Sharing of one pair of electrons between outer shells of two nonmetal atoms; strongest bond type.

  • Ionic bond

    Transfer of electrons where an electronegative atom steals electrons from a bonding partner (metal + nonmetal); second strongest bond.

  • Polar covalent bond

    Electrons shared unequally between atoms with different electronegativities, creating a dipole.

  • Hydrogen bond

    Dipole-dipole interaction requiring a hydrogen donor (H) and acceptor (O or N); third strongest bond.

  • Van der Waals interactions

    Weak, brief partial charge interactions promoting weak attraction between nonpolar molecules over short distances.

  • Why is water an ideal biological solvent?

    Due to its polarity and ability to form hydrogen bonds that continuously break and reform.

  • pH scale meaning

    Describes proton concentration in solution; pH < 7 acidic (high H+), pH > 7 basic (low H+).

  • Role of buffers in biological systems

    Buffers prevent major pH changes by accepting or donating protons; consist of weak acid + conjugate base or weak base + conjugate acid.

  • Major classes of macromolecules

    Proteins, nucleic acids, carbohydrates, lipids.

  • Building blocks of proteins

    Amino acids.

  • Dehydration and hydrolysis reactions

    Dehydration forms bonds by removing water; hydrolysis breaks bonds by adding water.

  • Four R group classifications of amino acids

    Nonpolar, polar uncharged, charged acidic (-), charged basic (+).

  • Primary protein structure

    Sequence of amino acids in a polypeptide chain from N-terminus to C-terminus.

  • Secondary protein structure

    Local folding into alpha helices and beta sheets stabilized by hydrogen bonds in the polypeptide backbone.

  • Tertiary protein structure

    Overall 3D shape of a single polypeptide chain.

  • Quaternary protein structure

    Organization of multiple polypeptide chains into a protein complex.

  • Denaturation of proteins

    Loss of protein structure and function due to disruption of weak bonds by heat, pH, salt, or solvents.

  • Monosaccharide general formula

    \(C_nH_{2n}O_n\)

  • Difference between cellulose and starch

    Cellulose: linear, structural support, insoluble; Starch: branched, energy storage, partially soluble.

  • DNA vs RNA differences

    DNA: double-stranded, thymine, deoxyribose; RNA: single-stranded, uracil, ribose.

  • Phosphodiester bond

    Covalent bond linking nucleotides by connecting 5' phosphate to 3' OH via dehydration reaction.

  • Saturated vs unsaturated fatty acids

    Saturated: no double bonds, solid at room temp; Unsaturated: one or more double bonds, liquid at room temp.

  • Phospholipid structure

    Glycerol + 2 fatty acids + phosphate head; amphipathic with hydrophilic head and hydrophobic tails.

  • 1st and 2nd laws of thermodynamics

    1st: Energy conserved; 2nd: Entropy increases in energy transfers.

  • Free energy (G) and spontaneity

    Negative ∆G: spontaneous, exergonic; Positive ∆G: non-spontaneous, endergonic.

  • Cellular respiration overall reaction

    \(C_6H_{12}O_6 + 6O_2 \to 6CO_2 + 6H_2O\), releases energy (∆G = -686 kcal/mol).

  • Photosynthesis overall reaction

    \(6CO_2 + 6H_2O \to C_6H_{12}O_6 + 6O_2\), requires energy (∆G = +686 kcal/mol).

  • Enzyme function

    Lower activation energy to speed reactions without changing ∆G; specific to substrates; not consumed.

  • Passive vs active transport

    Passive: no energy, down gradient; Active: requires energy, against gradient.