Question

Multiple or none of the answers may be correct:

The affinity of a protein for a ligand

	a.	Changes as a function of the ligand concentration
	b.	Is described by the Kd
	c.	Is governed at the molecular level by weak interactions between the protein’s amino acids and the functional groups on the ligand
	d.	Is a measure of the tightness of the binding interaction

The following statements about enzyme inhibitors are TRUE:

	a.	Mixed inhibitors bind at a second site
	b.	Competitive inhibitors bind at the active site
	c.	Suicide inhibitors irreversibly (covalently) attach to the active site
	d.	Uncompetitive inhibitors bind at the active site

The following statements about protein secondary structure are TRUE:

	a.	Beta sheets may have parallel or anti-parallel strands
	b.	Alpha helices are always right-handed
	c.	Beta sheets form hydrogen bonds between the carbonyl groups on one strand and the carbonyl groups on the opposite strand
	d.	Alpha helices are always stabilized by interactions between parallel helices

Answer 1

affinity of a protien for a ligand does not change with concentration is does not descriced by Kd and is not governed at the molecular level by weak interactions between the protein’s amino acids and the functional groups on the ligand.

1-D

mixed inhibitors bind to a allosteric sites i.e a site different from the active site

Competitive inhibition is a form of enzyme inhibition where binding of the inhibitor to the active site on the enzyme prevents binding of the substrate and vice versa.

2--B

The β-sheet (also β-pleated sheet) is a common motif of regular secondary structure in proteins. Beta sheets consist of beta strands (also β-strand) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation. The supramolecular association of β-sheets has been implicated in formation of the protein aggregates and fibrils observed in many human diseases, notably the amyloidoses such as Alzheimer's disease.

3-C