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General Biology: The Chemical Context of Life

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  • What is matter?

    Matter is anything that takes up space and has mass.

  • Define element and compound.

    An element is a substance that cannot be broken down by chemical reactions. A compound consists of two or more elements in a fixed ratio with different properties from its elements.

  • Which four elements make up 96% of living matter?

    Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter.

  • What subatomic particles compose an atom?

    Atoms are composed of protons (positive charge), neutrons (no charge), and electrons (negative charge).

  • What does atomic number represent?

    Atomic number is the number of protons in an atom's nucleus and equals the number of electrons in a neutral atom.

  • How is atomic mass approximated?

    Atomic mass is approximated by the sum of protons and neutrons in the nucleus (mass number).

  • What are isotopes?

    Isotopes are atoms of the same element with different numbers of neutrons.

  • What determines an atom's chemical behavior?

    The distribution of electrons in electron shells, especially the number of valence electrons, determines chemical behavior.

  • What are valence electrons?

    Valence electrons are electrons in the outermost shell involved in chemical bonding.

  • Define covalent bond.

    A covalent bond is a chemical bond formed by sharing a pair of valence electrons between two atoms.

  • Difference between single and double covalent bonds?

    A single bond shares one pair of electrons; a double bond shares two pairs.

  • What is electronegativity?

    Electronegativity is an atom's attraction for electrons in a covalent bond.

  • Difference between nonpolar and polar covalent bonds?

    Nonpolar covalent bonds share electrons equally; polar covalent bonds share electrons unequally due to differing electronegativities.

  • What causes partial charges in polar molecules?

    Unequal sharing of electrons causes partial negative (δ–) and partial positive (δ+) charges, creating polarity.

  • Define ionic bond.

    An ionic bond forms when one atom transfers electrons to another, creating oppositely charged ions that attract.

  • What are cations and anions?

    Cations are positively charged ions; anions are negatively charged ions.

  • What is a hydrogen bond?

    A hydrogen bond is a weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

  • Why are hydrogen bonds important in biology?

    They stabilize DNA, help protein folding, and contribute to water's unique properties.

  • What are Van der Waals interactions?

    Weak attractions due to temporary partial charges from uneven electron distribution in molecules close together.

  • How does molecular shape affect function?

    Molecular shape, determined by orbital positions and bonding, affects how molecules recognize and respond to each other.