Important Molecules Flashcards
How are peptide bonds formed?
peptide bonds are formed by linking a carboxyl group of one amino acid with a a-amino group of another amino acid
What is a residue?
an individual amino acid part of a polypeptide chain
What is the “backbone” of a polypeptide chain?
N-C-C-N-C-C
What is an amino terminus?
the first end made during polypeptide synthesis
What is a carboxyl terminus?
the last end made during polypeptide synthesis
In the oligopeptide Phe-Glu-Gly-Ser-Ala, which residue has a free a-amino group, and which residue has a free a-carboxyl group?
Phe - amino group
Ala - carboxyl group
What is a protease?
a proteolytic enzyme that cleaves peptide bonds
What is cystine?
dimer of cysteine, residue that results from one cysteine residue besoms disulfide-bonded to another cysteine residue
What is a denatured protein?
non-functional protein that is improperly folded. the protein’s shape is disrupted without breaking peptide bonds.
How does urea affect protein?
urea disrupts hydrogen bonding by extremes of pH, extremes of temperature, and changes in salt concentration
Primary Structure
simplest level of protein structure, the same as sequence
Secondary Structure
initial folding of a polypeptide chain into shapes stabilized by hydrogen bonds between backbone NH and CO groups
Parallel B-pleated sheets vs anti-parallel B-pleated sheets?
parallel sheets have polypeptide chains running in the same direction, anti-parallel have sheets running in the opposite direction
If a single polypeptide folds once and forms a B-pleated sheet with itself, would this be a parallel or anti-parallel B-pleated sheet?
Anti-parallel
Tertiary Structure
protein folding that concerns interaction between amino acid residues located more distantly from eachother
Which of the following may be considered an example of tertiary protein structures?
I. van der Waals interactions between two Phe R-groups located far apart on a polypeptide
II. Hydrogen bonds between backbone amino acids
III. Covalent disulfide bonds between cysteine residues located far apart on a polypeptide
I and III
What is a polypeptide subunit?
a single polypeptide chain that is part of a large complex containing many subunits
Quaternary Structure
highest level of protein structure, the arrangement of subunits in a multisubunit complex
What is the difference between a disulfide bridge involved in a quaternary structure and one involved in tertiary structure?
quaternary disulfides are bonds that form between chains that aren’t linked by peptide bonds. tertiary disulfides are bonds that form between residues in the same polypeptide.
Why do fatty acids end in a carboxylic acid?
the chains are synthesized two carbons at a time for acetate
How does the shape of an unsaturated fatty acid differ from that of a saturated fatty acid?
an unsaturated fatty acid is bent or kinked the double bond
If fatty acids are mixed into water, how are they likely to associate with each other?
the long hydrophobic chains will interact with each other to minimize contact with water, exposing the charged carboxyl group the aqueous environment
Would a saturated or an unsaturated fatty acid residue have more van Der Waals interaction with a neighboring alkyl chain in a bilayer membrane?
a saturated fatty acid would have more van Der Waals interactions. the bent shape of the unsaturated fatty acid means that it doesn’t fit in as well and has less contacted with neighboring groups
What are the structural determinants of membrane fluidity?
degree of saturation, tail length, and amount of cholesterol
How do double bonds affect membrane fluidity?
double bonds tend to increase membrane fluidity
How does length affect membrane fluidity?
decreasing the length of a fatty acid tails increase fluidity
How does cholesterol affect membrane fluidity?
increases fluidity at low temps, decreases fluidity at high temps; keeps fluidity at an optimum level
How are linked phosphates able to provide so much energy?
linked phosphates act as a compressed spring waiting to fly open and provide energy
