Chapter 3: The Organic Molecules of Life (Essentials of Biology)

Vocabulary flashcards covering the key concepts and terms from the chapter on organic molecules, carbohydrates, lipids, proteins, and nucleic acids.

Organic molecules

Molecules that contain carbon and hydrogen; contrast with inorganic molecules (which lack a C–H combination).

Inorganic molecules

Molecules that do not contain a carbon-hydrogen (C–H) bond, such as H2O and NaCl.

Carbon atom

Central element in organic chemistry; typically forms four bonds and often shares electrons with H, N, O, or other carbons.

Hydrocarbons

Chains of carbon atoms bonded only to hydrogen atoms.

Isomer

Compounds with the same number and kinds of atoms but different arrangements, leading to different properties.

Functional group

A specific combination of bonded atoms that imparts characteristic chemical properties and reactions; often represents the reactive part of a molecule.

Monosaccharide

A single sugar molecule; 3–7 carbon backbone; examples include glucose, fructose, and galactose; ribose and deoxyribose are in RNA/DNA.

Glucose

A six-carbon monosaccharide; primary energy source for body cells.

Fructose

A six-carbon monosaccharide isomer of glucose (fruit sugar).

Galactose

An isomer of glucose found in lactose-containing foods.

Ribose

A five-carbon sugar found in RNA.

Deoxyribose

A five-carbon sugar found in DNA; lacks one oxygen atom compared to ribose.

Disaccharide

A carbohydrate formed by two monosaccharides linked together (glycosidic bond); examples include maltose, sucrose, lactose.

Maltose

Disaccharide formed from two glucose units; produced during yeast fermentation.

Sucrose

Table sugar; glucose + fructose.

Lactose

Milk sugar; glucose + galactose.

Polysaccharide

Polymers of monosaccharides; function includes energy storage (starch in plants, glycogen in animals) and structural roles (cellulose, chitin).

Starch

Plant storage polysaccharide made of glucose.

Glycogen

Animal storage polysaccharide made of glucose.

Cellulose

Plant cell-wall polysaccharide; most abundant organic molecule; digested by some microbes.

Chitin

Structural polysaccharide in crab, lobster, and insect exoskeletons.

Lipids

Insoluble in water; diverse structures and functions; mostly long nonpolar hydrocarbon chains; fats/oils store energy long-term.

Fats and oils

Lipids used for long-term energy storage.

Triglyceride

Lipid composed of glycerol plus three fatty acids; major form of stored fat.

Glycerol

Three-carbon backbone of triglycerides with three –OH groups.

Fatty acid

Long hydrocarbon chain with a carboxyl group at one end; types vary by saturation.

Unsaturated fatty acid

Fatty acid with one or more double bonds in the carbon chain; typically liquid at room temperature.

Saturated fatty acid

Fatty acid with no double bonds between carbons; usually solid at room temperature.

Trans fat

An unsaturated fat with hydrogens on opposite sides of a double bond; associated with health concerns.

Phospholipids

Membrane components with a polar (water-attracting) head and nonpolar (water-repellent) tails; form lipid bilayers.

Steroid

Lipids with four fused carbon rings; derived from cholesterol; insoluble in water and differ by functional groups.

Proteins

Macromolecules with roles in support, metabolism, transport, defense, regulation, and motion; built from amino acids.

Amino acid

Monomer of proteins; central carbon bonded to hydrogen, an amino group, a carboxyl group, and an R group; 20 different kinds.

Peptides

Two or more amino acids covalently linked by a peptide bond.

Peptide bond

Bond formed by dehydration synthesis between amino acids.

Polypeptide

A chain of many amino acids linked by peptide bonds; a protein when folded.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Localized folding patterns such as alpha helices and beta pleated sheets; stabilized by hydrogen bonds.

Alpha helix

A right-handed helical secondary structure of a polypeptide.

Beta pleated sheet

A secondary structure with strands laid out in a pleated form; stabilized by hydrogen bonds.

Tertiary structure

Overall three-dimensional shape of a single polypeptide; result of interactions among secondary structures.

Quaternary structure

Association of two or more polypeptide chains into a functional protein.

Nucleic acids

DNA and RNA; polymers of nucleotides; store genetic information and guide protein synthesis.

Nucleotide

Monomer of nucleic acids; composed of a phosphate group, a five-carbon sugar, and a nitrogenous base.

Bases

Nitrogen-containing bases in DNA and RNA: adenine (A), guanine (G), cytosine (C), thymine (T) in DNA, uracil (U) in RNA.

DNA

Deoxyribonucleic acid; stores genetic information; sugar is deoxyribose; double helix; bases pair A with T and C with G.

RNA

Ribonucleic acid; sugar is ribose; typically single-stranded; uses uracil instead of thymine.

Gene

A sequence of nucleotides that specifies the sequence of amino acids in a protein.

Complementary base pairing

A-T and C-G base pairing in DNA; in RNA, A pairs with U and C with G.

Double helix

The two-antiparallel-stranded spiral structure of DNA formed by base pairing.

Denaturation

Loss of protein structure and function due to factors like pH or temperature changes.

Sickle-cell disease

Inherited disorder caused by a single amino acid substitution in hemoglobin, leading to sickle-shaped red blood cells.