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The Chemistry of Life

What are the most common elements in humans?

Oxygen, Carbon, Hydrogen, and Nitrogen


a substance that cannot be broken down to other substances by chemical means


a substance consisting of two or more different elements combined in a fixed ratio


anything that takes up space and has mass

trace elements

elements required by an organism in minute quantities


smallest unit of matter that still retains the properties of an element

subatomic particles

particles that compose an atom


a subatomic particle with a neutral charge, weighs 1 dalton/amu, and is found in the nucleus


a subatomic particle with a positive charge, weighs 1 dalton/amu, and is found in the nucleus


a subatomic particle with a negative charge, weighs 0 dalton/amu, and is found orbiting the nucleus

atomic nucleus

the dense core of an atom packed with neutrons and protons

atomic number

the number of protons in an atom of an element

mass number

the sum of the protons and neutrons in the nucleus of an atom

atomic mass

the total mass of an atom


one of the atomic forms of an element, with each form varying in neutron amount and atomic numbers

radioactive isotope

an isotope in which the nucleus decay spontaneously


the capacity to cause change

potential energy

the energy that matter possesses because of its location or structure

energy levels

the different states of potential energy that electrons have in an atom

electron shells

the average distances of electrons from the nucleus, which correlates to electrons' energy levels

valence electrons

the outermost electrons of an atom

valence shell

the outermost electron shell

chemical bonds

the attractive forces that hold atoms together

covalent bond

the sharing of a pair of valence electrons by two atoms


two or more atoms held closely together by covalent bonds


the attraction of an atom for the electrons of a covalent bond

nonpolar covalent bond

a covalent bond where the electrons are shared equally

polar covalent bond

a covalent bond where the electrons are not shared equally; on atom is more electronegative than the other


a charged atom


a positively charged atom


a negatively charged atom

ionic bond

the attraction between cations and anions

ionic compounds

compounds formed by ionic bonds; aka salts

hydrogen bond

a weak bond formed when a hydrogen atom covalently bonded to on electronegative atom is also attracted to another electronegative atom

van der Waals interactions

weak attractions between molecules or parts of molecules that are brought about by localized charge fluctuations


the binding together of like molecules, often by hydrogen bonding


the clinging of one substance to another

surface tension

a measure go how difficult it is to stretch or break the surface of a liquid

kinetic energy

the energy of motion


a measure of the total amount of kinetic energy due to molecular motion in a body of motion


the intensity of heat due to the average kinetic energy of the molecules

specific heat

the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1°C

Heat of vaporization

the quantity of heat a liquid must absorb for 1 g of it to be converted from liquid to gas

evaporative cooling

when liquid evaporates, and the surface of the liquid than remains behind cools down


a liquid that is completely homogenous mixture of two or more substances


the dissolving agent of a solution


the substance that is dissolved

aqueous solution

a solution where water is the solvent


any substance that has an affinity for water


substances that do not have an affinity for water

hydration shell

the sphere of water molecules around each dissolved ion


a stable suspension of fine particles in a liquid


the number of moles of solute per liter in a solution


a substance that increases the hydrogen ion concentration of a solution


a substance that reduces the hydrogen ion concentration of a solution

hydrogen ion

a single proton with a charge of 1+

How are isotopes used in biology?

Radioactive isotopes are used to date fossils and label chemical substances in metabolic processes

What happens when electrons change levels?

Electrons absorb or lose energy when they change energy levels.

What is the significance of valence numbers?

Valence numbers determine the chemical behavior of an atom.

Why is H bonding so important to water's properties?

Properties such as cohesion, adhesion, surface tension, and high specific heat would onto exist without hydrogen bonding.

Why is cohesion important to living things?

Cohesion helps to transport water and nutrients to plants.

Why is moderation of temperature important to living things?

Moderation of temperature prevents living organisms from overheating and stabilizes temperature in bodies of water.

Why is expansion when freezing important to living things?

Expansion when freezing prevents large bodies of water from completely freezing over, thus protecting underwater sea life.

Why is versatile solvent important to living things?

Versatile solvent means water is strong enough to dissolve necessary enzymes into bodily fluids, such as blood and saliva, without dissolving cell membranes.

What happens when hydrogen bonds break?

Heat is absorbed when hydrogen bonds break.

What happens when hydrogen bonds form?

Heat is released when hydrogen bonds break.

shape of a molecule

very important to its function, depends on the shape of the valence shells

organic chemistry

the branch of chemistry that specializes in carbon compounds


organic molecules consisting only of carbon and hydrogen


compounds that have the same numbers of atoms of the same elements, but different structures and properities

structural isomers

isomers that differ in the covalent arrangements of their atoms

geometric isomers

isomers with the same covalent partnerships, but they differ in their spatial arrangements


molecules that are mirror images of each other

functional groups

the components of organic molecules most commonly involved in chemical reactions


-OH; hydrogen atom bonded to oxygen atom, which is bonded to the carbon skeleton; alcohols


>CO; carbon atom joined to an oxygen atom by a double bond; Ketones if carbonyl is within a carbon skeleton, Aldehydes if the carbonyl is at the end of the carbon skeleton


-COOH; oxygen atom double bonded to a carbon atom that is bonded to a hydroxyl group; carboxylic acids


-NH₂; nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton; amines


-SH; sulfur atom bonded to a hydrogen atom; thiols


-OPO₃²⁻; phosphorus atom bonded to four oxygen atoms, one oxygen is bonded to the carbon skeleton, two oxygen carry negative charges; organic phosphates


adenosine triphosphate; primary energy-transferring molecule in the cell

condensation reaction/dehydration reaction

two molecules are covalently bonded together through the loss of a water molecule


the reverse of a dehydration reation


simple sugars with molecular formulas with a multiple of CH₂O


two monosaccharides joined by a glycosidic linkage

glycosidic linkage

a covalent bond formed between two monosaccharides by a dehydration reaction


polymers made up of multiple monosaccharides


a storage polysaccharide of plants, entirely glucose monomers, helical, alpha


a storage polysaccharide of animals, entirely glucose monomers, helical, alpha


a structural polysaccharide of plants, straight, entirely glucose, beta


a structural polysaccharide of arthropods to build their exoskeletons


constructed from glycerol and fatty acids

fatty acid

a long carbon skeleton


three fatty acids linked to one glycerol molecule


an alcohol with three carbons, each with a hydroxyl group

saturated fatty acid

a fatty acid with no double bonds between carbons, solid at room temperature

unsaturated fatty acid

a fatty acid with one or more double bonds between carbons, liquid at room temperature


a lipid with only two fatty acids attached to glycerol, with the third hydroxyl group joined to a phosphate group


lipids characterized by a carbon skeleton consisting of four fused rings


a common component of animal cell membranes and is the precursor for which other steroids are synthesized


polymers of amino acids


one or more polypeptides folded and coiled into specific conformations

amino acids

organic molecules possessing both carboxyl and amino groups

peptide bond

the resulting covalent bond between the carboxyl group of one amino acid to the amino group of another, with the removal of a water molecule

What are the general roles of carbohydrates?

The two roles are to supply energy and help form cell structures.


a disaccharide composed of glucose and glucose


a disaccharide composed of fructose and glucose


a disaccharide composed of galactose and glucose

How does the alpha differ from the beta form of glucose?

In the alpha version, the hydroxyl group is attached to the carbon-1 in the same manner as the hydroxyl group attached to the carbon04. In the betas version, the hydroxyl group is switched.


a unit of inheritance

nucleic acids

deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)


polymers of nucleic acids


monomers of nuclide acids composed of a nitrogenous base, a pentose (five-carbon sugar), and a phosphate group.


a nitrogenous base with a six-membered ring of carbon and nitrogen atoms; cytosine, thymine, and uracil.


a larger nitrogenous base with six-membered ring fused to a five-membered ring; adenine and guanine

What types of nitrogenous bases belong to DNA or RNA?

Thymine is only found in DNA and uracil is only found in RNA. Adenine, cytosine, and guanine are found in both.

What's the difference between DNA and RNA?

DNA lacks a oxygen atom on the second carbon in its ring.

What makes fats hydrophobic?

The non-polar C-H bonds in the hydrocarbon chains of the fatty acids make fats hydrophobic.

How do phospholipids interact in an aqueous solution?

The hydrophilic heads stay on the outside of the bilayer, facing the water. The hydrophobic tails stay in the interior of the bilayer, away from the water.

List the several functions of proteins.

Proteins preform several functions including transport, storage, structural support, speeding up chemical retains, cellular communications, movement, and defense against foreign substances.

What are the three properties used to classify amino acids?

Nonpolar, polar, and electrically charged are the three properties of side chains used to classify amino acids.

What determines the primary structure of a protein?

Primary structure is determined by inherited by genetic information.

Describe the "Primary" level of protein structure.

The unique sequence of amino acids in a protein.

Describe the "Secondary" level of protein structure.

The coils and folds formed by the hydrogen bonds between repeating sections of the polypeptide backbone.

Describe the "Tertiary" level of protein structure.

Overall shape of a polypeptide, resulting from interactions between side chains.

Describe the "Quaternary" level of protein structure.

Overall protein structure that results from aggregation of the polypeptide subunits.

Describe the two functions of DNA in a cell.

DNA provides directions for its own replication and it directs RNA synthesis.


a chemical agent that speeds up the rate of a chemical reaction, without being consumed by the reaction


protein that acts as a biological catalyst

activation energy, Eₐ

the initial investment of energy for starting a reaction


the reactant an enzyme acts upon

active site

the restricted region of the enzyme that binds to the substrate

induced fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.

How is the substrate held in the active site?

The substrate is held by weak interactions, such as hydrogen and ionic bonds.

What are the effects of temperature and pH on enzyme activity?

Each type of enzyme as an optimal temperature and pH level. If they reach too far from its optimal environment, the enzyme will denature.


non-protien helpers for catalytic activity


cofactors that are organic molecules

competitive inhibitors

mimics that reduce the productivity of enzymes by blocking substrates from the active sites

noncompetitive inhibitors

mimics that do not directly compete with the substrate to bind to the enzyme at the active site

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