Answer:
Quartz falls into a group of minerals called the silicates, all of which contain the elements silicon and oxygen in some proportion.
Explanation:
Answer:
e. PhoU keeps PhoR bound to the phosphate transporter protein Pst
Explanation:
PhoU is a membrane protein known to regulate the transport of phosphate (Pi) between cellular compartments. It has been discovered that mutations in this protein cause lethality because the cell becomes incapable of controlling the intracellular levels of Pi, this being toxic for the cell. PhoR is a histidine kinase/phosphatase. When the Pi level is considered to be a limiting factor, PhoR autophosphorylates at a histidine residue and then donates its phosphoryl group to PhoB. On the other hand, when the Pi level is high, this protein removes the phosphoryl group from phospho-PhoB. Finally, the Pst is a signal transduction protein that acts as a transporter capable of switching its conformation during the transport of PI.
In the stomach, the enzyme pepsin has the function to break proteins into smaller units-polypeptides. Pepsin is synthesized and secreted in an inactive form- pepsinogen. Activation energy (the minimum amount of energy that is required to activate an enzyme) is achieved in the acidic medium (pH from 1 to 3). So, the activation of pepsin (conversion of pepsinogen to pepsin) is possible thanks to the cells in the stomach lining which produce hydrochloric acid (HCl), causing the stomach contents to have a low pH.
Antacids neutralize the acid made by the stomach, affecting the digestion.
