Chemistry of Life

AP Biology Review Flashcards

Elements

Substances that cannot be broken down into smaller substances by chemical means.

Essential Elements of Life

Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N) make up 96% of the mass of all living things.

Atom

Smallest unit of an element; building blocks of the physical world.

Protons

Positively charged subatomic particles packed with neutrons in the nucleus.

Neutrons

Subatomic particles packed with protons in the nucleus; have no charge.

Isotopes

Same element with a different amount of neutrons in the nucleus; vary in mass.

Radioactive isotopes

Decay spontaneously, giving off particles and energy.

Electrons

Negatively charged subatomic particles that spin around the nucleus.

Energy level/Electron shell

An electron’s state of potential energy.

Valence electrons

Electrons in the outermost shell, or valence shell.

Atomic number

Number of protons in the nucleus.

Mass Number

Protons + neutrons; average of all isotopes.

Compound

Occurs as a result of 2 or more individual elements combining in a fixed ratio; formed by chemical reaction.

Ionic bond

Formed between a nonmetal and a metal when one or more electrons is transferred from one atom to another leading to attraction of oppositely charged ions. (cation + and anion -)

Cation

An ion with a positive charge.

Anion

An ion with a negative charge.

Covalent bond

Formed between two nonmetals when electrons are shared between atoms.

Nonpolar covalent bond

Electrons are shared equally.

Polar covalent bond

Electrons are shared unequally.

Electronegativity

An atom’s attraction for the electrons in a covalent bond.

Hydrogen bond

A hydrogen atom covalently bonds to one electronegative atom is also attracted to another electronegative atom.

Van der Waals Interactions

Attractions between molecules that are close together as a result of asymmetrical distribution of electrons.

Cohesion

Tendency for water to stick to water.

Adhesion

Tendency of water to stick to other substances.

Surface tension

Results from cohesion of water molecules.

High heat capacity

Ability of a substance to resist temperature change.

High heat of vaporization

Heat a liquid must absorb for 1g to be converted to gas.

Evaporative cooling

As a liquid evaporates, its remaining surface cools.

Solution

A liquid that is a homogenous mix of substances.

Solvent

The dissolving agent of a solution.

Solute

The substance that is dissolved.

Aqueous solution

One where water is the solvent.

Hydrophobic

Substances that do not dissolve in water.

Hydrophilic

Substances that dissolve in water.

Acidic solution

Contains a lot of H+.

Alkaline solution

Contains a lot of OH-.

Buffers

Maintain stable pH.

Organic compound

Contains Carbon.

Inorganic compound

Does not contain carbon.

Hydrocarbons

Consist of only carbon and hydrogen.

Isomers

Compounds with the same molecular formula but different structures/properties.

Functional groups

The components of organic molecules that are most commonly involved in chemical reactions.

Polymers

Most macromolecules are chains of building blocks called polymers.

Monomers

The individual building blocks of a polymer.

Carbohydrates

Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.

Monosaccharides

Most common are glucose and fructose.

Disaccharides

1 monosaccharide + 1 monosaccharide = 1 Disaccharide. Formed by dehydration synthesis (aka condensation).

Glycosidic linkage

Bond between monosaccharides in a disaccharide or polysaccharide.

Hydrolysis

Reverse of dehydration; water is used to break apart glycosidic linkage.

Polysaccharides

Repeated units of monosaccharides.

Proteins

Polypeptides that have folded into a particular shape.

Amino acids

Monomers of proteins; there are 20 kinds of naturally occurring amino acids.

R group

Also known as side chain; varies in composition, polarity, charge, shape depending on specific amino acid.

Polypeptides

Amino acid + amino acid = dipeptide; formed by dehydration synthesis; bond is called a peptide bond.

Primary structure

Linear sequence of amino acids; covalent (peptide) bonds.

Secondary structure

Protein begins to twist (alpha-helix) or zigzag (beta-pleated sheets); hydrogen bonds between carbonyl and amino group.

Tertiary structure

Covalent disulfide bridges often stabilize structure; bonds between R groups (hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic interactions).

Quaternary structure

Several different polypeptide chains sometimes interact with each other; same bonds as above, but between peptide chains rather than between R groups.

Chaperone proteins (chaperonins)

Help protein fold properly; make process more efficient.

Denature

Change in shape of a protein, which changes the function.

Enzymatic proteins

Selective acceleration of chemical reactions.

Defensive proteins

Protection against disease.

Storage proteins

Storage of amino acids.

Transport proteins

Transport of substances.

Hormonal proteins

Coordination of organism’s biological activities.

Receptor proteins

Response of cell to chemical stimuli.

Contractile/motor proteins

Movement.

Structural proteins

Support.

Lipids

Consist of carbon, hydrogen, and oxygen, but not in a fixed ratio; do not form polymers; hydrophobic due to nonpolar covalent bonds of hydrocarbon.

Triglycerides

Glycerol molecule + 3 fatty acid chains attached; formed via dehydration synthesis (bond = ester linkage).

Glycerol

A 3-carbon alcohol with a hydroxyl group attached to each carbon.

Ester linkage

Bond between glycerol and fatty acids in a triglyceride.

Saturated fatty acid

No double bond; carbon chain completely filled (“saturated”) with hydrogen; usually solid at room temp.

Unsaturated fatty acid

Double bond along carbon chain, causing a bend.

Polyunsaturated fatty acid

Multiple double bonds within the fatty acid, causing many bends.

Phospholipids

2 fatty acid “tails” + 1 negatively charged phosphate “head”.

Amphipathic molecule

Molecule that is both polar and nonpolar.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings.

Cholesterol

4-ringed molecule dispersed throughout membrane to maintain membrane stability.

Nucleic acids

Contain carbon, hydrogen, oxygen, nitrogen, and phosphorous; monomer = nucleotides.

Nucleotides

Consist of a nitrogenous base, a pentose sugar, and a phosphate group.

Nucleoside

Portion of nucleotide without the phosphate group.

DNA

Deoxyribonucleic acid; sugar = deoxyribose; contains genetic/hereditary information; directs synthesis of messenger RNA (mRNA), and through mRNA, controls protein synthesis.

RNA

Ribonucleic acid; sugar = ribose; essential for protein synthesis.

Pyrimidines

Nitrogenous bases with a single 6-membered ring (ex. cytosine, thymine [only DNA], uracil [only RNA]).

Purines

Nitrogenous bases with a 6-membered ring fused to a 5-membered ring (ex. adenine, guanine).

Phosphodiester bond

Links adjacent nucleotides together (covalent bond between the -OH group on the 3’ carbon of one nucleotide and the phosphate on the 5’ carbon on the next).