Term
| How are the amino acid residues joined to their neighbors in proteins (which are polymers of amino acids)? |
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Definition
| they are joined by a specific type of covalent bond |
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Term
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Definition
| the side chains of amino acids that differentiate amino acids from one another; vary in size, structure, & electric charge; influence the solubility of the amino acids in water |
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Term
| What type of center is the alpha carbon in an amino acid? |
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Definition
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Term
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Definition
| two forms of stereoisomers that are nonsuperposable mirror images of each other |
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Term
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Definition
| molecules that rotate plane-polarized light; all molecules with a chiral center are optically active |
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Term
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Definition
| how the absolute configurations of simple sugars & amino acids are specified; based on the absolute configuration of the three-carbon sugar glyceraldehyde |
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Term
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Definition
| the system of specifying configuration around a chiral center which is used in the systematic nomenclature of organic chemistry & describes more precisely the configuration of molecules with more than one chiral center |
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Term
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Definition
| the tendency to interact with water at biological pH; how amino acids are grouped into five main classes based on their R groups |
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Term
| 4 amino acids which have side chains that tend to cluster together within proteins, stabilizing protein structure by means of hydrophobic interactions |
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Definition
1. alanine
2. valine
3. leucine
4. isoleucine |
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Term
| What amino acid has the simplest structure? |
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Definition
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Term
| Which sulfur-containing amino acid has a slightly nonpolar thioether group in its side chain? |
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Definition
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Term
| Which amino acid has an aliphatic side chain with a distinctive cyclic structure? |
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Definition
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Term
| 3 amino acids with aromatic side chains that are relatively nonpolar |
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Definition
1. phenylalanine
2. tyrosine
3. tryptophan |
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Term
| Which amino acid comes from cysteine being readily oxidized into two cysteine molecules (residues) joined by a disulfide bond? |
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Definition
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Term
| 3 amino acids in which the R groups have significant positive charge at pH 7.0 |
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Definition
1. lysine (has a second primary amino group at the epsilon position on its aliphatic chain)
2. arginine (has a positively charged guanidinium group)
3. histidine (has an aromatic imidazole group) |
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Term
| 2 amino acids that have R groups with a net negative charge at pH 7.0 |
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Definition
1. aspartate
2. glutamate
(they both have a second carboxyl group) |
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Term
| What is 4-hydroxyproline derived from? |
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Definition
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Term
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Definition
| a constituent of myosin which is a contractile protein of muscle |
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Term
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Definition
| an amino acid found in the blood-clotting protein prothrombin & in certain proteins that bind Ca2+ |
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Term
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Definition
| a derivative of four Lys residues; found in the fibrous protein elastin |
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Term
| What are ornithine & citrulline key intermediates in? |
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Definition
| the biosynthesis of arginine & in the urea cycle |
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Term
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Definition
| a dipolar ion which can act as either an acid or base; forms when an amino acid lacking an ionizable R group is dissolved in water at a neutral pH |
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Term
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Definition
| substances having a dual acid-base nature |
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Term
| isoelectric point (isoelectric pH) (pI) |
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Definition
| the characteristic pH at which the net electric charge is zero of an amino acid |
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Term
| 2 polymers of amino acids |
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Definition
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Term
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Definition
| a substituted amide linkage through which two amino acids are covalently joined to yield a dipeptide |
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Term
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Definition
| when many amino acids are joined |
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Term
| What is the difference between the amino-terminal residue of a peptide & the carboxyl-terminal residue of a peptide? |
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Definition
amino-terminal = the amino acid residue at the end with a free alpha-amino group
carboxyl-terminal = the residue at the other end from the amino-terminal residue which has a free carboxyl group |
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Term
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Definition
| proteins that have two or more polypeptides associated noncovalently; the opposite of the proteins that consist of a single polypeptide chain |
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Term
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Definition
| the identical units in an oligomeric protein |
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Term
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Definition
| proteins that contain permanently associated chemical components in addition to amino acids |
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Term
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Definition
| the non-amino acid part of a conjugated protein |
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Term
| What is the difference between the conjugated proteins lipoproteins, glycoproteins, & metalloproteins? |
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Definition
lipoproteins = contain lipids
glycoproteins = contain sugar groups
metalloproteins = contain a specific metal
*they differ on the basis of the chemical nature of their prosthetic groups* |
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Term
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Definition
| when cells are broken open & their proteins are released into a solution |
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Term
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Definition
| subjecting the crude extract to treatments that separate the proteins into different fractions based on a property such as size or charge |
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Term
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Definition
| a procedure that separates proteins from small solutes by taking advantage of the proteins' larger size |
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Term
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Definition
| the most powerful method for fractionating which takes advantage of differences in protein charge, size, & binding affinity |
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Term
| ion-exchange chromatography |
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Definition
| exploits differences in the sign & magnitude of the net electric charge of proteins at a given pH |
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Term
| What is the difference between cation exchangers & anion exchangers? |
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Definition
cation = groups on the synthetic polymer of a column matrix with bound anionic groups
anion = groups on the synthetic polymer of the column matrix with bound cationic groups |
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Term
| In cation-exchange chromatography, does the matrix have positively or negatively charged groups? |
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Definition
| the solid matrix has negatively charged groups |
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Term
| size-exclusion chromatography |
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Definition
| AKA gel filtration; separates proteins according to size |
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Term
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Definition
| based on binding affinity |
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Term
| How are chromatographic methods typically enhanced? |
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Definition
| HPLC (high-performance liquid chromatography) |
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Term
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Definition
| a technique for the separation of proteins based on the migration of charged proteins in an electric field |
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Term
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Definition
| a procedure used to determine the isoelectric point of a protein |
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Term
| two-dimensional electrophoresis |
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Definition
| the process of combining isoelectric focusing & SDS electrophoresis to permit the resolution of complex mixtures of proteins |
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Term
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Definition
| the total units of enzyme in a solution |
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Term
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Definition
| the number of enzyme units per milligram of total protein |
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