The enzymes involved in the COX pathway are found in the membrane of rough endoplasmic reticulum. Suggest why it is advantageous for enzyme pathways to be located in cell membranes rather than in the cytosol of the cell (fluid portion of cytoplasm).
During an inflammatory response, substances produced by the COX pathway increase sensitivity to pain. Some anti-inflammatory drugs act as reversible competitive inhibitors of COX-2. Fig. 5.2 shows how raising arachidonic acid concentration affects COX-2 activity.
On Fig. 5.2, sketch the curve that would be obtained if an anti-inflammatory drug, which acts as a competitive inhibitor, is present together with arachidonic acid.
Complete the statements to show whether the maximum rate of reaction ($V_{\max}$) and the Michaelis-Menten constant ($K_m$) of COX-2 increase, decrease, or stay unchanged in the presence of a competitive inhibitor. In the presence of a competitive inhibitor: $V_{\max}$ of COX-2 ____________. $K_m$ of COX-2 ____________.
COX-2 is made of two identical polypeptides. The enzyme is produced when a gene, $PTGS2$, on chromosome 1, is activated and transcription starts. Using gene $PTGS2$ and enzyme COX-2 as examples, explain what is meant by a gene.
Some mutations in $PTGS2$ cause a higher transcription rate. These mutations have been linked to a greater risk of certain cancers. Suggest why mutations in $PTGS2$ may increase the risk of cancer.
Using Fig. 5.3 as a guide, explain why increasing the proportion of phospholipids containing arachidonic acid in a cell will raise the fluidity of the cell surface membrane.