Explain how non-competitive inhibitors work and how they affect the Michaelis-Menten kinetics of an enzyme.
Non-competitive inhibitors function to bind to a site somewhere on an enzyme (called an "allosteric site") away from the active site. Because non-competitive inhibitors do not occupy and block the active sites of enzymes, the substrate of the enzyme is still allowed to dock into the active site and associate with the enzyme. However, when a non-competitive inhibitor is present, it will alter the enzyme's conformation in such a way that the enzyme will function sub-optimally (i.e., the reaction will not occur as fast). This decreases the maximum velocity (Vmax) of the enzyme catalyzed reaction. However, since the binding of the substrate to the enzyme active site is not interfered with, the affinity for the enzyme and substrate (Km) remains the same and does not change in the presence of a non-competitive inhibitor. The bottom line: Non-competitive inhibitors bind to a site away from the active site on an enzyme and decrease Vmax, but do not change Km.
In which phase of the cell cycle does DNA replication occur?
BLUF: DNA replication occurs during the S phase of the cell cycle. More detailed explanation: The cell cycle consists of two phases: Interphase (where the cell spends most of its life and is not dividing) and the M Phase (where the cell is dividing). Interphase is further broken up into 3 sub-phases: G1 Phase, S Phase, and then G2 Phase. During G1 phase, the cell is preparing and synthesizing all the material it needs for replications. During S phase, the DNA is replicated. During G2 phase, the replicated DNA is double checked for errors before entering the M phase. Significance: DNA replication during S phase allows for the proper amount of genetic material to be in each cell after mitosis has ended and division has occurred.
Which nerve innervates the diaphragm and from which spinal vertebrae does this nerve originate?
The phrenic nerve innervates the diaphragm and it arises from the the C3, C4, and C5 cervical vertebrae in your neck/upper back. A good way to remember this is with the following rhyme: "C3, 4, 5 keeps the diaphragm alive."