Final answer:
Yes, proteins or enzymes that are bound to Guanosine triphosphate (GTP) are often active, playing a vital role in cell signaling and various cellular responses until GTP is hydrolyzed to GDP, rendering the protein inactive.
Step-by-step explanation:
When bound to Guanosine triphosphate (GTP), a protein or enzyme in a cell is typically considered to be active. This is true for various proteins involved in cell signaling, including G-proteins, which become activated upon binding GTP. These activated proteins can then go on to transmit signals within the cell to elicit various responses, such as the activation of other enzymes or opening of channels. Eventually, GTP is hydrolysed to GDP, and the protein becomes inactive again, ready for another cycle of activation.
For example, a G-protein linked receptor is activated when a ligand binds to it. The inactive G-protein associated with the receptor exchanges the bound GDP for GTP, thus becoming activated. This activated G-protein can then activate other signaling pathways within the cell. Over time, the GTP bound to the G-protein is hydrolyzed back to GDP, and the G-protein returns to its inactive state.