Biology Flashcards
What composes the general amino acid structure?
-tetrahedral alpha carbon
-alpha amino group (NH2)
-alpha-carboxyl group (COOH)
-variable R group/side chain
What are peptide bonds?
A peptide bond (amide bond) is formed by the carboxyl group of one amino acid bonding to the amino group of another amino acid, with the loss of H2O.
What is the sequence of the backbone of a polypeptide chain?
N-C-C-N-C-C
What is proteolysis/proteolytic cleavage?
Proteolytic cleavage is a specific means of cleaving peptide bonds. It is essentially hydrolysis of the protein by another protein, since water gets released every time a peptide bond breaks. The protein (acting as an enzyme) that does the cutting is proteolytic cleavage or protease.
What are the two common types of covalent bonds between amino acids in proteins?
peptide bonds = link amino acids into polypeptide chains
disulfide bridges = links cysteine R-groups
What is a disulfide bridge?
The thiol (sulfhydryl, SH) of one cysteine will bind to the the thiol of another cysteine to make a covalent sulfur sulfur bond called a disulfide bridge. Once bonded, the cysteine is then called a cystine.
What does a denatured protein mean?
Improperly folded proteins that are non-functional. It refers to the disruption of a protein’s shape without breaking peptide bonds.
What are the ways a protein can be denatured?
-urea: disrupts hydrogen bonding interactions)
-by extremes in temperature
-by changes in salt concentration (tonicity)
What is the primary structure of proteins?
The Amino Acid Sequence –> This is the simplest level of protein structure and it refers to the order of the amino acids in the polypeptide chain.
What is the secondary structure of proteins?
Hydrogen Bonds Between Backbone Groups –> This refers to the intial folding of polypeptide chains into shapes stabilized by the hydrogen bonds between the backbones of NH and CO groups. There are common styles of protein folding, with two of them being an alpha helix and a beta pleated sheet (two types)
What is the tertiary structure of proteins?
Hydrophobic/Hydrophilic Interactions –> The next level of protein folding is when the residues from more distantly located amino acids, where they arrange with hydrophobic and hydrophilic interactions with the solvent water.
What is the quaternary structures of proteins?
Various Bonds Between Separate Chains –> The highest level of protein folding is the interactions between polypeptide subunits. (Think the four subunits of hemoglobin and the 12 subunits of RNA polymerase II)
What is a subunit?
A single polypeptide chain that is part of a large complex containing many subunits (a multisubunit complex)
What is the only bonding that is not present for quaternary structure in protein folding?
Peptide bonds! The only forces stabilizing quaternary structures - noncovalent interactions, van der Waals, hydrogen bonds, disulfide bonds, and electrostatic interactions.
Why are carbohydrates generally the principle energy source for cellular metabolism?
Carbohydrates can be broken down to CO2 by oxidation (i.e. burning, or combustion)
