61 terms

Chapter 2: Chemistry

Raw materials and fuel for our bodies What is life: Phelan - Chapter 2
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acid
Any fluid with a pH below 7.0, indicating the presence of more H+ ions than OH- ions. [Lat., acidus, sour]
amino acid
One of 20 molecules built of an amino group, a carboxyl group, and a unique side chain; proteins are constructed of combinations of these. [Gk., Ammon, name of ancient Libyan god, near whose temple a compound known as "sal ammoniacus," or "ammonium salt," was prepared]
amino group
A nitrogen atom bonded to three hydrogen atoms.
atom
A particle of matter than cannot be further subdivided without losing its essential properties. [Gk., atomos, indivisible]
atomic mass
The mass of an atom; the combined mass of the protons, neutrons, and electrons in an atom (the mass of the electrons is so small as to be almost negligible).
atomic number
The number of protons in the nucleus of an atom of a given element.
base(chemistry)
Any fluid with a pH above 7.0, that is, with more OH- ions than H+ions.
base(genetics)
One of the nitrogen-containing side-chain molecules attached to a sugar molecule in the sugar-phosphate backbone of DNA and RNA.
carbohydrate
One of the four types of biological macromolecule, containing mostly carbon, hydrogen, and oxygen; the primary fuel for cellular activity and form much of the cell structure in all life forms. [Lat., carbo, charcoal + hydro-, pertaining to water]
carboxyl group
A carbon atom bonded to two oxygen atoms.
cellulose
A complex carbohydrate, indigestible by humans, that serves as the structural material for a huge variety of plant structures; it is the single most prevalent organic compound on earth. [Lat., cellula, dim. of cella, room]
chitin
(pron. KITE)-in A complex carbohydrate, indigestible by humans, that forms the rigid outer skeleton of most insects and crustaceans. [Gk., chiton, undershirt]
cholesterol
One of the sterols, lipids important in regulating growth and development; cholesterol is an important component of most cell membranes, helping the membrane to maintain its fl exibility. [Gk., chole, bile + stereos, solid + -ol, chemical suffix for an alcohol]
complex carbohydrate
A carbohydrate that contains multiple simple carbohydrates linked together; types of complex carbohydrates include starch, which is the primary form of energy storage in plants, and glycogen, which is the primary form of short-term energy storage in animals.
compound
A substance composed of atoms of different elements in specific ratios, held together by ionic bonds. [Lat., componere, to put together]
covalent bond
A strong bond formed when two atoms share electrons; the simplest example is the H2 molecule, in which each of the two atoms in the molecule shares its lone electron with the other atom. [Lat., con-, together + valere, to be strong]
denaturation
The disruption of protein folding, in which secondary and tertiary structure are lost, caused by exposure to extreme conditions in the environment such as heat or extreme pH (that is, a strong acid or a strong base); this process causes proteins to lose their function
deoxyribonucleic acid (DNA)
A nucleic acid, DNA carries information about the production of particular proteins in the sequences of its nucleotide bases.
disaccharides
Carbohydrates formed by the union of two simple sugars, such as sucrose (table sugar) and lactose (the sugar found in milk). [Gk., di-, two + sakcharon, sugar]
double bond
The sharing of two electrons between two atoms; for example, the most common form of oxygen is the O2 molecule, in which two electrons from each of the two atoms of oxygen are shared.
double helix
The spiraling ladder-like structure of DNA composed of two strands of nucleotides; the bases protruding from each strand like "half-rungs" meet in the center and bind to each other (via hydrogen bonds), holding the ladder together. [Gk., heligmos, wrapping]
electron
A negatively charged particle that moves around the atomic nucleus.
element
A substance that cannot be broken down chemically into any other substances
enzyme
A protein that initiates and accelerates a chemical reaction in a living organism; enzymatic proteins take part in chemical reactions on the inside and outside surfaces of the plasma membrane. [Gk., en, in + zume, leaven]
fatty acid
A long hydrocarbon (a chain of carbon-hydrogen Molecules); fatty acids form the tail region of triglyceride fat molecules.
glycerol
A small molecule that forms the head region of a triglyceride fat molecule. [Gk., glukus, sweet + -ol, chemical suffix for an alcohol]
glycogen
A complex carbohydrate consisting of stored glucose molecules linked to form a large web, which breaks down to release glucose when it is needed for energy. [Gk., glukus, sweet + Gk., genos, race, descent]
hydrogen bond
A type of weak chemical bond formed between the slightly positively charged hydrogen atoms of one molecule and the slightly negatively charged atoms of another (often oxygen or nitrogen atoms); hydrogen bonds are important in building multi-atom molecules, such as complex proteins, and are responsible for many of the unique and important features of water.
hydrophilic
Attracted to water, as, for example, polar molecules that readily form hydrogen bonds with water.
hydrophobic
Repelled by water, as, for example, non-polar molecules that tend to minimize contact with water.
ion
An atom that carries an electrical charge, positive or negative, because it has either gained or lost an electron or electrons from its normal, stable configuration.
ionic bond
A bond created by the transfer of one or more electrons from one atom to another; the resulting atoms, now called ions, are charged oppositely and so attract each other to form a compound.
lipid
One of four types of macromolecules, lipids are insoluble in water and greasy to the touch; they are important in energy storage and insulation, membrane formation, and regulating growth.
macromolecule
A large molecule, made up of smaller building blocks or subunits; four types of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids.
mass
The amount of matter in a given sample of a substance.
molecule
A group of atoms held together by covalent bonds. [Lat., dim. of moles, mass]
monosaccharides
The simplest carbohydrates and the building blocks of more complex carbohydrates; monosaccharides, which cannot be broken down into other monosaccharides, include glucose, fructose, and galactose; also known as simple sugars. [Gk., monos, single + sakcharon, sugar]
neutron
An electrically neutral particle in the atomic nucleus. [Lat., neutro, in neither direction]
nucleic acid
One of the four types of biological macromolecules, the nucleic acids DNA and RNA store genetic information in unique sequences of nucleotides.
nucleotide
A molecule containing a phosphate group, a sugar molecule, and a nitrogen-containing molecule; nucleotides are the individual units that together, in a unique sequence, constitute a nucleic acid.
nucleus (chemistry)
The central and most massive part of an atom, usually made up of two types of particles, protons and neutrons.
peptide bond
A bond in which the amino group of one amino acid is bonded to the carboxyl group of another; two amino acids so joined form a dipeptide, several amino acids so joined form a polypeptide. [Gk., peptikos, able to digest]
pH
A logarithmic scale that measures the concentration of hydrogen ions (H+ ) In a solution, with decreasing values indicating increasing acidity; water, in which the concentration of hydrogen ions (H+ ) equals the concentration of hydroxyl ions (OH- ), is pH = 7, the midpoint of the scale. [abbreviation for "power of hydrogen"]
phospholipid
A lipid that is the major component of the plasma membrane; phospholipids are structurally similar to fats, but contain a phosphorus atom and have two, not three, fatty acid chains.
polysaccharides
Complex carbohydrates formed by the union of many simple sugars. [Gk., polus, many + sakcharon, sugar]
primary structure
The sequence of amino acids in a polypeptide chain.
protein
One of the four types of biological macromolecules; constructed of unique combinations of 20 amino acids that result in unique structures and chemical behavior, proteins are the chief building blocks of tissues in most organisms. [Gk., proteion, of the first quality]
proton
A positively charged particle in the atomic nucleus; it is identical with the nucleus of the hydrogen atom, which lacks a neutron, and has atomic number 1. [Gk., protos, first]
quaternary structure
Two or more polypeptide chains bonded together in a single protein; hemoglobin is an example of a protein molecule with this structure. [Lat., quaterni, four each]
ribonucleic acid (RNA)
A nucleic acid, RNA serves as a middleman in the process of converting genetic information in DNA into protein; messenger RNA (mRNA) takes instructions for production of a given protein from DNA to another part of the cell, whereas transfer RNA (tRNA) interprets the mRNA code and directs the construction of the protein from its constituent amino acids.
saturated fat
A fat in which each carbon in the hydrocarbon chain forming the tail region of the fat molecule is bound to two hydrogen atoms; saturated fats are solid at room temperature.
secondary structure
The corkscrew-like twists or folds formed by hydrogen bonds between amino acids in a polypeptide chain.
simple sugars
Monosaccharide carbohydrate, generally containing three to seven carbon atoms, which store energy in their chemical bonds and which biological cells can break down; cannot be broken down into other simple sugars; include glucose, fructose, and galactose.
starch
A complex polysaccharide carbohydrate consisting of a large number of monosaccharides linked in line; in plants, starch is the primary form of energy storage.
sterol
A lipid important in regulating growth and development; the sterols include cholesterol and the steroid hormones testosterone and estrogen, and are all modifications of a basic structure of four interlinked rings of carbon atoms. [Gk., stereos, solid + -ol, chemical suffix for an alcohol]
substrate
The molecule on which an enzyme acts; the active site on the enzyme binds to the substrate, initiating a chemical reaction; for example, the active site on the enzyme lactase binds to the substrate lactose, breaking it down into the two simple sugars glucose and galactose. [Lat., s u b, under + stratus, spread]
tertiary structure
The unique and complex three-dimensional shape formed by multiple twists of the secondary structure of the protein as amino acids come together and form hydrogen bonds or covalent sulfur-sulfur bonds. [Lat., tertius, third]
trans fat
An unsaturated fat that has been partially hydrogenated (meaning that hydrogen atoms have been added to make the fat more saturated and to improve a food's taste, texture, and shelf-life); the added hydrogen atoms are in a trans orientation, which differs from the cis ("near") orientation of hydrogen atoms in the unsaturated fat. [Lat., trans, on the other side of]
triglyceride
A fat having three fatty acids linked to the glycerol molecule. [Gk., tri- three + glukus, sweet]
unsaturated fat
A fat in which at least one carbon in the hydrocarbon chain forming the tail region of the fat molecule is bound to only one hydrogen atom; unsaturated fats are liquid at room temperature.
wax
A lipid similar in structure to fats but with only one long-chain fatty acid linked to the glycerol head of the molecule; because the fatty acid chain is highly non-polar, waxes are strongly hydrophobic.
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