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General Biology: Chemical Context of Life

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  • What is matter and what is it composed of?

    Matter is anything that takes up space and has mass. It is composed of elements, which are substances that cannot be broken down by chemical reactions.

  • What are essential elements in living organisms?

    About 25 of the 92 natural elements are essential to life. Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter.

  • What is the structure of an atom?

    An atom consists of a nucleus containing protons and neutrons, surrounded by a cloud of electrons.

  • Define atomic number and mass number.

    Atomic number is the number of protons in the nucleus. Mass number is the sum of protons and neutrons.

  • What are isotopes?

    Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are radioactive and used as biological tracers.

  • What is potential energy in atoms?

    Potential energy is the energy matter has due to its location or structure. Electrons have different potential energy levels called electron shells.

  • What are valence electrons and their importance?

    Valence electrons are electrons in the outermost shell. They determine an atom's chemical behavior and bonding.

  • Describe covalent bonds.

    Covalent bonds form by sharing valence electrons between atoms. They can be nonpolar (equal sharing) or polar (unequal sharing).

  • What are ionic bonds?

    Ionic bonds form when atoms transfer electrons, creating charged ions that attract each other.

  • Explain hydrogen bonds.

    Hydrogen bonds occur between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom, often oxygen or nitrogen.

  • What are Van der Waals interactions?

    Weak attractions between molecules due to transient 'hot spots' of positive or negative charge caused by asymmetric electron distribution.

  • Why are weak chemical bonds biologically important?

    They reinforce molecular shapes, help molecules adhere, and enable specific molecular recognition.

  • What are the four emergent properties of water?

    1. Cohesion and adhesion
    2. Ability to moderate temperature
    3. Expansion upon freezing
    4. Versatility as a solvent

  • How does water's polarity affect its properties?

    Water's polarity allows it to form hydrogen bonds, leading to cohesion, temperature moderation, and solvent abilities.

  • What is cohesion in water?

    Cohesion is the attraction between water molecules via hydrogen bonds, enabling transport in plants and surface tension.

  • How does water moderate temperature?

    Water absorbs and releases heat with little temperature change due to hydrogen bond formation and breaking.

  • Why does ice float on water?

    Ice is less dense because hydrogen bonds form a stable, ordered lattice, allowing life to survive under frozen surfaces.

  • Define hydrophilic and hydrophobic substances.

    Hydrophilic substances have an affinity for water; hydrophobic substances do not and repel water.

  • What is a polymer and a monomer?

    A polymer is a long molecule made of repeating units called monomers.

  • Describe dehydration synthesis and hydrolysis.

    Dehydration synthesis forms covalent bonds between monomers by removing water. Hydrolysis breaks bonds by adding water.

  • What are carbohydrates and their types?

    Carbohydrates include monosaccharides (single sugars), disaccharides (two sugars), and polysaccharides (many sugars).

  • What is the difference between saturated and unsaturated fats?

    Saturated fats have no double bonds and are solid at room temperature; unsaturated fats have one or more double bonds and are liquid.

  • What are phospholipids?

    Phospholipids have two hydrophobic fatty acid tails and a hydrophilic phosphate head, forming cell membranes.

  • Describe the four levels of protein structure.

    Primary: amino acid sequence
    Secondary: coils and folds
    Tertiary: 3D shape from side chain interactions
    Quaternary: multiple polypeptide chains

  • What causes sickle-cell disease at the protein level?

    A single amino acid substitution in hemoglobin changes its primary structure, affecting protein function.

  • What are nucleic acids composed of?

    Nucleic acids are polymers of nucleotides, each with a nitrogenous base, pentose sugar, and phosphate group.

  • Difference between DNA and RNA?

    DNA has deoxyribose sugar, is double-stranded, and uses bases A, T, C, G. RNA has ribose sugar, is single-stranded, and uses A, U, C, G.

  • Name the seven key functional groups in organic molecules.

    Hydroxyl, Carbonyl, Carboxyl, Amino, Sulfhydryl, Phosphate, and Methyl groups.