AP Biology Unit 1

• Polar molecule


  Molecule with unequal distribution of charge, with opposite partial charges at the ends
• Chemical formula


  Represents the proportion of atoms per element that make up a chemical compound using symbols from the periodic table
• Water is polar because the hydrogens carry partial positive charges, and oxygen has a partial negative charge
• Hydrophilic substance


  Substance with an affinity for water, which means it attracts water
• Hydrophobic substance


  Substance that avoids water or does not have an affinity for water
• Lipids


  Hydrophobic because they have relatively nonpolar bonds
• Hydrogen bonding


  A type of chemical intermolecular bond that occurs when a hydrogen atom bonds to a highly electronegative atom, including oxygen, nitrogen, and fluorine
• Hydrogen bonds are generally weaker than covalent bonds, but they are still relatively strong and play an important role in many chemical and biological processes
• Hydrogen bonding is critical in biology, as it occurs in many different types of molecules, including water, DNA, and proteins
• Hydrogen bonding is responsible for many molecular properties, such as the shape and function of proteins, the stability of many chemical compounds, and the formation of intermolecular interactions in crystalline solids
• Cohesion


  The attraction of water molecules, due to strong hydrogen bonding forces
• Adhesion


  When one substance is attracted to another, such as water adhering to other molecules and surfaces
• Surface tension


  The difficulty to break the surface of the water because of cohesive forces
• Specific heat


  The amount of heat energy it takes to raise or lower the temperature of one gram of a substance by one degree Celsius
• Water has a high specific heat, so it can absorb or release a large amount of heat with only a slight change in its own temperature, so large bodies of water take a while to evaporate
• Evaporative cooling


  The process where the surface of an object becomes cooler during evaporation, as the molecules with the highest kinetic energy are most likely to evaporate, leaving behind molecules with lower average kinetic energy and thus reducing temperature
• Dissociation of water


  The breaking down of H2O molecules into ions - specifically, one hydrogen ion (H+) and one hydroxide ion (OH-)
• Acid


  A substance that donates protons or hydrogen ions to an aqueous solution, thereby increasing the hydronium ion concentration
• Base


  A substance that can accept protons or donate a pair of valence electrons. In the context of biology, bases often refer to substances that can accept hydrogen ions and have a pH value greater than 7
• The counterbalance of hydronium and hydroxide results in water having a neutral pH of 7.0, meaning it is neither acidic nor basic
• pH scale


  Ranges from 0 (very acidic) to 14 (very basic), with 7 being neutral. Each level is a ten-fold change because the pH scale is logarithmic
• Most biological fluids are in the pH range of 6-8
• pH = -log [H+]
• Covalent Bonds

  Chemical bonds formed by sharing pairs of electrons between atoms
• Dipole Moment


  A measure of the polarity of a molecule, indicating how much positive and negative charge is separated within the molecule
• Electronegative Atom


  An atom that has a high affinity for electrons, meaning it has a tendency to attract shared electrons in a covalent bond towards itself
• Evaporative Cooling


  A process where the surface of an object becomes cooler during evaporation because the molecules with the highest kinetic energy are most likely to evaporate, leaving behind molecules with lower average kinetic energy and thus reducing temperature
• Hydrogen


  The first element on the periodic table, a colorless, odorless, tasteless gas that's highly flammable and combines with oxygen to form water
• Hydrogen bonding


  A special type of intermolecular attraction between the hydrogen atom in a polar bond (particularly H-F, H-O, and H-N) and an electronegative atom nearby
• Hydrogen Ions


  Single protons with no electrons that play crucial roles in chemical reactions, especially those involving acids and bases
• Hydronium Concentration


  The measure of the amount of hydronium ions (H3O+) in a solution, used to determine the acidity or alkalinity (pH) of a solution
• Hydrophilic Substance


  A substance that has an affinity for water; it can dissolve in or mix well with water
• Hydrophobic Substance


  A substance that does not have an affinity for water; it does not dissolve in or mix well with water
• Lipids


  A group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, phospholipids; they are an important part of living cells and serve as energy storage
• Logarithmic


  (In the context of biology) A scale where each increment increases by a factor of 10, used to represent data that covers a large range of values in a compact way
• Neutral pH


  A pH value of 7, indicating neither acidity nor basicity; pure water has a neutral pH
• Oxygen


  A chemical element with symbol O and atomic number 8, essential for life on earth as it's part of the air we breathe and water we drink
• Partial Negative Charge


  When an atom in a molecule attracts electrons more strongly than other atoms, causing the electrons to spend more time near that atom and giving it a slight negative charge
• Partial Positive Charge


  When an atom shares its electron unequally with another atom in covalent bonding, the atom that pulls less strongly on shared electrons has partial positive charge due to lack of electron density
• pH Scale


  Measures how acidic or basic an aqueous solution is, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral