Biology Solomon, 8Th Edition Chapter 3

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organic compound

Back 1

A compound consisting of a backbone made up of covalently bonded carbon atoms.

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hydrocarbon

Back 2

Organic compounds consisting only of carbon and hydrogen.
They can exist as unbranched or branched chains, or as rings.

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isomer

Back 3

Compounds with the same molecular formulas but different structures and thus different properties.

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functional group

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Groups of atoms that determine the types of chemical reactions and associations in which the compound participates.
Most functional groups readily form associations, such as ionic and hydrogen bonds, with other molecules.

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hydroxyl group

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Polar, hydrophilic functional group. (abbreviated: R--OH

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aldehyde group

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Polar, hydrophilic functional group. Carbonyl group carbon is bonded to at least one H atom.
(abbreviated: R--CHO)

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ketone group

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Polar, hydrophilic functional group. Carbonyl group carbon is bonded to two other carbons.

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carboxyl group

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Weakly acid; can release an H+.
(abbreviated: R--COOH) in its non-ionized form.
(abbreviated: R--COO-) in its ionized form.
Essential constituents of amino acids.

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amino group

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Weakly basic; can accept an H+.
(abbreviated R--NH2) in its non-ionized form includes a nitrogen atom covalently bonded to two hydrogen atoms.
(abbreviated R--NH3+) in its ionized form and has 1 unit of positive charge.
Amino groups are components of amino acids and of nucleic acids.

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phosphate group

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Weakly acidic; one or two H+ can be released. Phosphates are constituents of nucleic acids and certain lipids.
(abbreviated: R--PO4H2). The attraction of electrons by the oxygen atoms can result in the release of one or two hydrogen ions, producing ionized forms with 1 or 2 units of negative charge.

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sulfhydryl group

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Helps stabilize internal structure of proteins.
(abbreviated: R--SH). Consists of an atom of sulfur covalently bonded to a hydrogen atom and found in molecules called thiols.

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macromolecule

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A very large organic molecule (consisting of thousands of atoms), such as a protein or nucleic acid.

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polymer

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Macromolecule produced by linking small organic compounds called monomers.
examples include: proteins, nucleic acid, polysaccharides.

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monomer

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A molecule that can link with other similar molecules; two monomers join to form a dimer, whereas many form a polymer.
Monomers are small (e.g., sugars or amino acids), or large (e.g., tubulin or actin proteins).

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hydrolysis reaction

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("to break with water"). A reaction in which a covalent bond between two subunits is broken through the addition of the equivalent of a water molecule; a hydrogen atom is added to one subunit and a hydroxyl group to the other.

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condensation reaction

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A reaction in which two monomers are combined covalently through the removal of the equivalent of a water molecule. This process requires energy and is regulated by different enzymes.

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carbohydrate

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Compound containing carbon, hydrogen, and oxygen, in the approximate ratio of C:2H:O
e.g., sugars, starch, and cellulose.

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monosaccharide

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A sugar that cannot be degraded by hydrolysis to a simpler sugar.
(e.g., glucose or fructose).

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simple sugar

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Monosaccharides are simple sugars and are the most basic units of biologically important carbohydrates.

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pentose sugars

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A sugar molecule containing five carbons.

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ribose

Back 21

The five-carbon sugar present in RNA and in important nucleoside triphosphates such as ATP.

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deoxyribose

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Pentose sugar lacking a hydroxyl (--OH) group on carbon-2'; a constituent of DNA.

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hexose sugars

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A monosaccharide containing six carbon atoms.
(e.g., glucose, fructose, galactose)

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glucose

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The most abundant monosaccharide used as an energy source in most organisms. Glucose is also used in the synthesis of other types of compounds such as amino acids and fatty acids. Glucose is so important in metabolism that mechanisms have evolved to maintain its concentration at relatively constant levels in the blood of humans and other complex animals. (A hexose aldehyde sugar that is central to many metabolic processes).

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a-glucose

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Glucose in solution (as in the cell) typically exists as a ring of five carbons and one oxygen. It assumes this configuration when its atoms undergo a rearrangement, permitting a covalent bond to connect carbon 1 to the oxygen attached to carbon 5. When glucose forms a ring, two isometric forms are possible. When it is on the side (with respect to the plane of the ring) opposite the --CH2OH side group, the compound is designated alpha glucose (a-glucose).

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B-glucose

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When glucose forms a ring, two isometric forms are possible, differing only in orientation of the the hydroxyl (--OH) group attaced to carbon 1. When this hydroxyl group is on the same side of the plane of the ring as the --CH2)H side group, the glucose is designated beta glucose (B-glucose).

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fructose

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Fructose, or fruit sugar, is a simple monosaccharide found in many foods. It is one of the three important dietary monosaccharides along with glucose and galactose.

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disaccharide

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(two sugars). A sugar produced by covalently linking two monosaccharides.
(e.g., maltose or sucrose).

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glycosidic linkage

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Covalent linkage joining two sugars; includes an oxygen atom bonded to a carbon of each sugar.

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maltose

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Maltose, or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4)bond. Maltose is the disaccharide produced when amylase breaks down starch. It is found in germinating seeds such as Barley as they break down their starch stores to use for food.

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sucrose

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Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. The molecule is a disaccharide derived from glucose and fructose with the molecular formula C12H22O11.

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polysaccharide

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A macromolecule consisting of repeating units of simple sugars, usually glucose. The polysaccharides are the most abundant carbohydrates and include starches, glycogen, and cellulose. Polysaccharide may be a single long chain or a branched chain, and they vary in their properties. Those that can be easily broken down to their subunits are well suited for energy storage.

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starch

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The typical form of carbohydrate used for energy storage in plants, is a polymer consisting of a-glucose subunits.

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glycogen

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Sometimes referred to as animal starch, is the form in which glucose subunits, joined by a 1-4 linkages, are stored as an energy source in animal tissues. Glycogen is similar in structure to plant starch but more extensively branched and more water soluble. In vertebrates, glycogen is stored mainly in liver and muscle cells.

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cellulose

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The most abundant carbohydrate; it accounts for 50% or more of all the carbon in plants. Cellulose is a structural carbohydrate. Cellulose is an insoluble polysaccharide composed of many joined glucose molecules. The bonds joining these sugar units are different from those in starch.

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chitin

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A nitrogen-containing structural polysaccharide that forms the exoskeleton of insects and the cell walls of many fungi.

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glycoprotein

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A protein with covalently attached carbohydrates.

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glycolipid

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A lipid with covalently attached carbohydrates, compounds on the surfaces of animal cells that allow cells to recognize and interact with one another.

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lipid

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Any of a group of organic compounds that are insoluble in water but soluble in nonpolar solvents; lipids serve as energy storage and are important components of cell membranes.

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triacylglycerol

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The main storage lipid of organisms, consisting of a glycerol combined chemically with three fatty acids; also called triglyceride.

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triglyceride

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Triglycerides are formed by combining glycerol with three molecules of fatty acid. It is the main constituent of vegetable oil and animal fats.

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glycerol

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A three-carbon alcohol that contains three hydroxyl (--OH) with a hydroxyl group on each carbon; a component of triacylglycerols and phospholipids, as well as monoacylglycerols, and diacylglycerols.

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fatty acid

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A lipid that is an organic acid containing a long hydrocarbon chain, with no double bonds (saturated fatty acid), one double bond (monounsaturated fatty acid), or two or more double bonds (polyunsaturated fatty acid); components of triacylglycerols and phospholipids, as well as monoacylglycerols and diacylglycerols.

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ester linkage

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Covalent linkage formed by the reaction of a carboxyl group and a hydroxyl group, with the removal of the equivalent of a water molecule ; the linkage includes an oxygen atom bonded to a carbonyl group.

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saturated

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A lipid that is an organic acid containing a long hydrocarbon chain, with no double bonds. Saturated fatty acids contain the maximum possible number of hydrogen atoms. Animal fat and solid vegetable shortening (examples) tend to be solid at room temperature.

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unsaturated

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Unsaturated fatty acids include one or more adjacent pairs of carbon atoms joined by a double bond. Therefore, they are not fully saturated with hydrogen.

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phospholipid

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Consists of a glycerol molecule attached at one end to two fatty acids and at the other end to a phosphate group linked to an organic compound such as choline. The organic compound usually contains nitrogen.

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amphipathic

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Phospholipids belong to this group of lipids, in which one end of each molecule is hydrophilic and the other end is hydrophobic. The two ends of a phospholipid differ both physically and chemically.

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carotenoid

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The orange and yellow plant pigments. Carotenoids are classified with the lipids because they are insoluble in water and have an oily consistency. These pigments, found in the cells of plants, play a role in photosynthesis.

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isoprene units

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Five-carbon hydrocarbon monomers that make up certain lipids such as carotenoids and steroids.

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B-carotene

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β-Carotene is an organic compound and classified as a terpenoid. It is a strongly-colored red-orange pigment abundant in plants and fruits. As a carotene with beta-rings at both ends, it is the most common form of carotene. It is a precursor (inactive form) of vitamin A

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steroid

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Consists of carbon atoms arranged in four attached rings; three of the rings contain six carbon atoms, and the fourth contains five. The length and structure of the side chains that extend from these rings distinguish one steroid from another--they are synthesized from isoprene units.

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cholesterol

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An essential structural component of animal cell membranes, but when excess cholesterol in blood forms plaques on artery walls, the risk of cardiovascular disease increases.

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protein

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Macromolecules composed of amino acids, are the most versatile cell components. A large, complex organic compound composed of covalently linked amino acid subunits; contains carbon, hydrogen, oxygen, nitrogen, and sulfur.

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enzyme

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An organic catalyst (usually a protein) that accelerates a specific chemical reaction by lowering the activation energy required for that reaction.

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amino acid

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An organic compound containing an amino group (--NH2) and a carboxyl group (--COOH); may be joined by peptide bonds to form a polypeptide chain.

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peptide bond

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A distinctive covalent carbon-to-nitrogen bond that links amino acids in peptides and proteins.

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dipeptide

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Formed when two amino acids combine.

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polypeptide

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A longer chain of amino acids

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globular protein

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When some polypeptide chains form long fibers. Globular proteins are tightly folded into compact, roughly spherical shapes.
A typical enzyme is a globular protein with a unique shape that allows it to catalyze a specific chemical reaction.

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primary structure

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The sequence of amino acids, joined by peptide bonds of a polypeptide chain. Primary structure is always represented in a simple linear, "beads-on-a-string" form.

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secondary structure

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A regular geometric shape produced by hydrogen bonding between the atoms of the uniform polypeptide backbone; includes the alpha helix and the beta-pleated sheet.

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alpha-helix
(a-helix)

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A regular, coiled type of secondary structure of a polypeptide chain, maintained by hydrogen bonds.

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Beta-pleated sheet
(B-pleated sheet)

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A regular, folded, sheetlike type of protein secondary structure, resulting from hydrogen bonding between two different polypeptide chains or two regions of the same polypeptide chain.

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tertiary structure

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The overall three-dimensional shape of a polypeptide that is determined by interactions involving the amino acid side chains. These include both weak interactions (hydrogen bonds, ionic bonds, and hydrophobic interactions) and strong covalent bonds.

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quaternary structure

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The overall conformation of a protein produced by the interaction of two or more polypeptide chains.

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molecular chaperones

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Proteins that help other proteins fold properly. Although not dictating the folding pattern, chaperones make the process more efficient.

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denaturation

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Changes in shape and the accompanying loss of biological activity of the protein due to its being heated, subjected to significant pH changes, or treated with certain chemicals. The structure then becomes disordered and the coiled peptide chains unfold, yielding a more random conformation. This unfolding, which is mainly due to the disruption of hydrogen bonds and ionic bonds, is typically accompanied by a loss of normal function.

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nucleic acid

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Transmit hereditary information and determine what proteins a cell manufactures. Two classes of nucleic acids are found in cells: deoxyribonucleic acid (DNA), and ribonucleic acid (RNA).

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deoxyribonucleic acid (DNA)

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Composes the genes, the hereditary material of the cell, and contains instructions for making all the proteins, as well as all the RNA the organism needs.

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ribonucleic acid (RNA)

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A family of single-stranded nucleic acids that function mainly in protein synthesis.

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ribozyme

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A molecule of RNA that has catalytic properties.

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nucleotide

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A molecule consisting of one or more phosphate groups, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base (purine or pyrimidine).

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purine

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Nitrogenous bases with carbon and nitrogen atoms in two attached rings, e.g., adenine and guanine; components of nucleic acids, ATP, GTP, NAD+, and certain other biologically active substances.

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pyrimidine

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Nitrogenous bases, each composed of a single ring of carbon and nitrogen atoms, e.g., thymine, cytosine, and uracil; components of nucleic acids.

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adenine

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A nitrogenous purine base that is a component of nucleic acids and ATP.

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guanine

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A nitrogenous purine base that is a component of nucleic acids and GTP.

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cytosine

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A nitrogenous pyrimidine base that is a component of nucleic acids.

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thymine

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A nitrogenous pyrimidine base found in DNA.

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uracil

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A nitrogenous pyrimidine base found in RNA.

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phosphodiester linkage

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Covalent linkage between two nucleotides in a strand of DNA or RNA; includes a phosphate group bonded to the sugars of two adjacent nucleotides.

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ATP
adenosine triphosphate

Back 82

An organic compound containing adenine, ribose, and three phosphate groups; of prime importance for energy transfers in cells.

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GTP
guanosine triphosphate

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An energy transfer molecule similar to ATP that releases free energy with the hydrolysis of its terminal phosphate group.

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cAMP
cyclic AMP

Back 84

A form of adenosine monophosphate in which the phosphate is part of a ring-shaped structure; acts as a regulatory molecule and second messenger in organisms ranging from bacteria to humans.

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cGMP

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A related molecule to cAMP that plays a role in certain cell signaling processes.

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nicotinamide adenine dinucleotide
NADH/NAD+

Back 86

Has a primary role in oxidation and reduction reactions in cells. It can exist in an oxidized form (NAD+) that is converted to a reduced form (NADH) when it accepts electrons (in association with hydrogen).