Biology Test 03 - Unit 2: Molecules of the Cell

Organic chemistry

The branch of chemistry that studies carbon-based compounds, especially those found in living things

Organic compound

A compound that contains carbon bonded to hydrogen; most molecules in living things are organic

Why carbon is so versatile

Carbon has 4 valence electrons, so it forms 4 covalent bonds and can build chains, branches, and rings

Hydrocarbon

A molecule made only of carbon and hydrogen atoms; hydrophobic and stores energy (example: fats' tails)

Isomers

Compounds with the same chemical formula but different structures, giving them different properties

Hydroxyl group

-OH; polar, makes molecules water-soluble; found in alcohols and sugars (carbohydrates)

Carbonyl group

C=O; found in sugars; at the end of a skeleton it's an aldehyde, in the middle it's a ketone

Carboxyl group

-COOH; acts as an acid by donating H+; found in amino acids and fatty acids

Amino group

-NH2; acts as a base by accepting H+; found in amino acids

Phosphate group

-PO4 (2-); negatively charged, stores and transfers energy; found in ATP and nucleic acids

Methyl group

-CH3; nonpolar, not reactive; affects expression of genes and shape/sex hormones

Sulfhydryl group

-SH; found in some amino acids (cysteine); forms disulfide bonds that stabilize protein shape

Dehydration synthesis

A reaction that builds polymers by removing a water molecule to join two monomers

Hydrolysis

A reaction that breaks polymers apart by adding a water molecule to split the bond between monomers

Polymer

A large molecule built from many repeating smaller units (monomers) linked by covalent bonds

Monomer

The small repeating unit that serves as the building block of a polymer

Macromolecule

A giant molecule formed by joining smaller molecules; the four classes are carbohydrates, lipids, proteins, nucleic acids

Carbohydrates

Macromolecules made of sugars; main job is quick energy and structural support (examples: glucose, starch, cellulose)

Monosaccharide

The monomer of carbohydrates; simple sugars like glucose and fructose (formula CH2O in a 1:2:1 ratio)

Disaccharide

Two monosaccharides joined by dehydration synthesis; examples: sucrose (table sugar), lactose

Polysaccharide

A carbohydrate polymer of many glucose units; starch stores energy in plants, glycogen in animals, cellulose builds plant cell walls

Lipids

Hydrophobic macromolecules (fats, oils, waxes) that store long-term energy, cushion organs, and form cell membranes; NOT true polymers

Glycerol + fatty acids

The building blocks of fats and oils; joined by dehydration synthesis to form a triglyceride

Saturated fat

A fat whose fatty acid chains have no double bonds, so they pack tightly and stay solid at room temperature (butter)

Unsaturated fat

A fat whose fatty acid chains have double bonds causing kinks, so they stay liquid at room temperature (oils)

Phospholipid

A lipid with a hydrophilic head (phosphate group) and hydrophobic tails; forms the bilayer of cell membranes

Steroid

A lipid with four fused carbon rings; cholesterol is the base for hormones like testosterone and estrogen

Protein

A polymer of amino acids; does nearly everything in the cell - enzymes, structure, transport, defense, movement

Amino acid

The monomer of proteins; has an amino group, a carboxyl group, and an R group (side chain) that determines its properties

Peptide bond

The covalent bond linking amino acids, formed by dehydration synthesis

Polypeptide

A chain of many amino acids; folds into a functional protein

Enzyme

A protein that speeds up chemical reactions by lowering activation energy; its shape determines its function

Primary structure

The sequence of amino acids in a protein; determines every higher level of folding

Denaturation

When a protein loses its shape (from heat or pH change) and stops working

Nucleic acids

Macromolecules that store and transmit genetic information: DNA and RNA

Nucleotide

The monomer of nucleic acids; made of a sugar, a phosphate group, and a nitrogenous base

DNA

Stores genetic instructions; double helix of nucleotides with bases A, T, G, C

RNA

Carries out DNA's instructions to build proteins; usually single-stranded, with base U instead of T

ATP

Adenosine triphosphate; a nucleotide that carries the cell's usable energy in its phosphate bonds