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Biochem Chap 3


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a protein containing a carbohydrate group
A lipid protein aggregate that serves to carry water-insoluble lipids in the blood. The protein component alone is an apolipoprotein
prosthetic group
a metal ion or an organic compound (other than an amino acid) that is covalently bound to a protein and is essential to its activity
conjugated protein
a protein containing one or more prosthetic groups
oligomeric protein
a multisubunit protein having two or more identical polypeptide chains
carboxyl terminal residue
the only amino acid residue in a polypeptide chain with a free α-carboxyl group; defines the carboxyl terminus of the polypeptide
amino terminal residue
the only amino acid residue in a polypeptide chain with a free α-amino group; defines the amino terminus of the polypeptide
a long chain of amino acids linked by peptide bonds; the molecular weight is generally less than 10,000
a few amino acids joined by peptide bonds
peptide bond
a substituted amide linkage between the α-amino group of one amino acid and the α-carboxyl group of another, with the elimination of the elements of water
a macromolecule composed of one ore more polypeptide chains, each with a characteristic sequence of amino acids linked by peptide bonds
two or more amino acids covalently joined by peptide bonds
isoelectric point (pI)
the pH at which a solute has no net electric charge and thus does not move in an electric field. Also called isoelectric pH.
a substance that can act as either a base or an acid
capable of donating and accepting protons, thus able to serve as an acid or a base
a dipolar ion, with spatially separated positive and negative charges
the nonuniform distribution of electrons in a molecule; polar molecules are usually soluble in water
absolute configuration
the configuration of four different substituent groups around an asymmetric carbon atom, in relation to D- and L-glyceraldehyde
optical activity
the capacity of a substance to rotate the plane of plane-polarized light
chiral center
an atom with substituents arranged so that the molecule is not superimposable on its mirror image
R Group
1) An abbreviation denoting any alkyl group
2) Occasionally, used in a more general sense to denote virtually any organic substituent (e.g. the R groups of amino acids)
amino acids
α-Amino substituted carboxylic acids, the building blocks of proteins
The individual polypeptide chains in a multisubunit
protein may be identical or different. If at least two
are identical the protein is said to be oligomeric, and
the identical units (consisting of one or more polypeptide chains) are referred to as protomers.
homologous proteins
The members of closely related protein families are called homologous proteins, or homologs.
types of homologs
orthologs and paralogs
Homologs from different species are called orthologs
If two proteins within a family (that is, two homologs) are present in
the same species, they are referred to as paralogs.
lateral gene transfer
the rare transfer of a gene or group of genes from one organism to another
the entire protein complement encoded by an organism’s DNA
Enzymes called proteases catalyze the hydrolytic cleavage of peptide bonds. (used in protein sequencing)
primary structure
A description of all covalent
bonds (mainly peptide bonds and disulfide bonds) linking amino acid residues in a polypeptide chain is its primary structure.The most important element of primary structure is the sequence of amino acid residues
secondary structure
refers to particularly stable arrangements of amino acid residues giving rise to recurring structural patterns.
tertiary structure
describes all aspects of the three-dimensional folding of a polypeptide.
quaternary structure
When a protein has two or more
polypeptide subunits, their arrangement in space is referred to as quaternary structure.

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