Chapter 5 Key Terms Flashcards
alpha (a) helix
A spiral shape constituting one form of the secondary structure of proteins, arising from a specific hydrogen-bonding structure.
amino acid
An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins.
antiparallel
The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.
beta (b) pleated sheet
One form of the secondary structure of proteins in which the polypeptide chain folds back and forth. Two regions of the chain lie parallel to each other and are held together by hydrogen bonds.
carbohydrate
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).
catalyst
A chemical agent that changes the rate of a reaction without being consumed by the reaction.
cellulose
A structural polysaccharide of cell walls, consisting of glucose monomers joined by β-1, 4-glycosidic linkages.
chaperonin
A protein molecule that assists the proper folding of other proteins.
chitin
A structural polysaccharide of an amino sugar found in many fungi and in the exoskeletons of all arthropods.
cholesterol
A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
condensation reaction
A reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water; also called a dehydration reaction.
dehydration reaction
A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule.
denaturation
In proteins, a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. In DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme conditions of pH, salt concentration, and temperature.
deoxyribonucleic acid (DNA)
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell’s proteins.
deoxyribose
The sugar component of DNA, having one less hydroxyl group than ribose, the sugar component of RNA.
disaccharide
A double sugar, consisting of two monosaccharides joined by dehydration synthesis.
disulfide bridge
A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer.
double helix
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
fat (triacylglycerol)
A biological compound consisting of three fatty acids linked to one glycerol molecule.
fatty acid
A long carbon chain carboxylic acid. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat.