AP Biology 1.1 - 1.5

Water

H2O; held together by polar covalent bonds, electrons are unevenly shared within the molecule; can form hydrogen bonds with one another and other polar molecules

Polar molecule

molecule with an unequal distribution of charge, resulting in a positive and negative end

Nonpolar molecule

molecule that shares electrons equally and does not have oppositely charged ends

Hydrogen bonds

weak attraction between a partially positive hydrogen atom in one polar bond and a partially electronegative atom (such as oxygen); helps stabilize the structures of large biological molecules (like DNA); holds water together

Covalent bonds

bonds created by sharing electrons with other atoms

Cohesion

attraction between molecules of the same substance

Surface tension

the force that acts on the surface of a liquid and that tends to minimize the area of the surface; cohesion at the surface of water creates a strong surface layer

Surfactants

molecules that reduce surface tension of water; interfere with cohesive interations among water molecules at a surface

Amphipathic

A molecule that has both a hydrophilic and hydrophobic region

Adhesion

Attraction between different types of molecules

Capillary action

movement of water through narrow spaces due to both adhesion and cohesion

Water’s high specific heat

it takes a lot of energy to increase water’s temperature; compared to other substances, water can absorb large amounts of heat before its temperature increases significantly

Why does water heat up slowly?

water molecules form hydrogen bonds with one another; absorbed heat energy is used to disrupt hydrogen bonds before increasing molecular motion

Water’s high heat of vaporization

it takes a lot of energy to turn liquid water to a vapor

Evaporative cooling

the temperature of a surface decreases as water evaporates

Why is ice less dense than liquid water?

because hydrogen bonds form a stable crystalline lattice that spaces water molecules farther apart than liquid water as water freezes

Water is a solvent, why?

water is polar so it can easily make other hydrogen bonds and dissolve other substances

pH

measure of the hydrogen ion concentration of a solution

Acidic solution

any solution in which the hydrogen-ion concentration is greater than the hydroxide-ion concentration (below 7)

Neutral solution

any aqueous solution in which hydrogen and hydroxide are equal (7)

Basic solution

any solution in which the hydroxide-ion concentration is greater than the hydrogen-ion concentration (above 7)

Buffer

helps organisms resist sudden changes in pH by accepting or releasing hydrogen

Six elements most important to life

Carbon, Nitrogen, Oxygen, Phosphorus, Hydrogen, and Sulfur

Organic molecules

carbon-based molecules that typically contain carbon bonded to hydrogen; like carbohydrates, lipids, proteins, and nucleic acids

Monomers

small molecular subunits that can be joined together to form larger polymers

Polymers

large molecules made of repeating or similar monomer subunits bonded together

Dehydration synthesis

a chemical reaction in which two molecules covalently bond together with the removal of a water molecule; enzymes are required for this reaction to occur

Dehydration synthesis for carbohydrates

Monosaccharides are bonded by glycosidic bonds into polysaccharides

Dehydration synthesis for lipids

Fatty acids and glycerol are bonded with more fatty acids and glycerol by ester bonds to form glycerides (triglyceride)

Dehydration synthesis for proteins

amino acids are ponded by peptide bonds to form peptides, polypeptides, and proteins

Dehydration synthesis for nucleic acids

Nucleotides are joined by phosphodiester bonds to form DNA and RNA

Hydrolysis

breaking down complex molecules by the chemical addition of water; sped up by enzymes

Functional groups

groups of atoms attached to a molecule that give it characteristic properties; helps determine how a molecule behaves and interacts with other molecules; can affect a molecule’s polarity, solubility, and reactivity

Functional groups examples

hydroxyl, carboxyl, amino, phosphate

Carbohydrates

immediate energy, energy storage, structure, transport of sugar

Monosaccharides

monomers, simple sugars, ex: glucose, fructose, galactose

α-glucose

forms starch in plants and glycogen in animals

β-glucose

forms cellulose in plant cell walls

Disaccharides

two monosaccharides joined by a glycosidic bond; formed through dehydration synthesis; ex: sucrose, lactose, maltose

Polysaccharides

long chains of many monosaccharides; called complex carbohydrates; can be branched or unbranched; ex: starch, glycogen, cellulose

Isomers

compounds with the same formula but different structures

Branched carbohydrates

functions as energy storage; more branches means more monomers can be made available for cellular respiration, increasing ATP production (ex: glycogen)

Structural carbohydrates

have linear structure and are able to stack; provide stability, allowing for formation of rigid structures for structural support

Lipids

Function in long-term energy storage and as major components of cell membranes; includes facts, oils, waxes, phospholipids, and steroids; mostly nonpolar and hydrophobic; making them poorly soluble in water

Lipid structure

glycerol and 3 fatty acids; CHO and sometimes P

Fatty acids

molecules consisting of a long hydrocarbon chain with a carboxyl group at one end

Hydrocarbon tail

nonpolar and hydrophobic

Carboxyl group

polar and hydrophilic

Saturated fatty acids

contain only single bonds between carbon atoms in their hydrocarbon tails; are “saturated” with hydrogen because each carbon holds the maximum possible number of hydrogen atoms

Saturated fatty acids structure

Have relatively straight hydrocarbon tails, which allow them to be packed tightly together; will be solid at room temperature

Unsaturated fatty acids

contain one or more carbon-carbon double bonds (C=C) in the hydrocarbon chain

Unsaturated fatty acids structure

Double bonds create bends or “kinks” in the hydrocarbon tails; the bent tails cannot pack tightly together and will be liquid at room temperature

Monounsaturated

one double bond

Polyunsaturated

two or more double bonds

Fats

Glycerol and fatty acids; the carboxyl group of a fatty acid can form a covalent bond with the hydroxyl group (OH) of glycerol

Ester bond

The bond formed when fatty acid molecules are joined to glycerol molecules in condensation reactions to form a fat

Triglycerides

an energy-rich compound made up of a single molecule of glycerol and three molecules of fatty acid; used primarily for long-term energy storage

Phospholipids

1 glycerol + 2 fatty acids + phosphate-containing group; major component of cell membranes

Waxes

lipids made primarily of long-chain fatty acids bonded to long-chain alcohols (molecules with a long hydrocarbon chain and an hydroxide group at the end); hydrophobic and water-resistant

Wax structure

long nonpolar hydrocarbon chains; molecules pack closely together making them firm

Steriods

lipids that have different functions but are all characterized by four fused carbon rings

Cholesterol

A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids

Glucose structure

monosaccharide, C6H12O6

Triglyceride structure

glycerol + 3 fatty acids; HCO

How is a triglyceride formed?

Formed when the 3 fatty acids are linked to the glycerol backbone through dehydration synthesis to form an ester linkage

Glucose function related to structure

primary energy source and building block in living organisms because its six-carbon ring structure, hydroxyl groups, and reactive sites allow for easy water solubility, cellular transport, and chemical polymerization

Triglyceride’s function related to structure

compact, long-term energy storage and insulation units because of their hydrophobic hydrocarbon structure