Which of the following valves has two leaflets and is closed during the systolic phase of the cardiac cycle?

a. Releases hydrogen ions: Releasing hydrogen ions (H⁺) into the solution would lower the pH, making the solution more acidic. This is not the correct way to normalize a slightly acidic pH of 7.30.

b. Blinds hydrogen ions: This is likely a typographical error, and it should be "binds hydrogen ions." Binding hydrogen ions (H⁺) would reduce the concentration of free hydrogen ions in the solution, thereby raising the pH and making the solution less acidic. This is the correct mechanism to normalize the pH of 7.30 to a more neutral level.

c. Creates additional hydrogen ions: Creating additional hydrogen ions would further lower the pH, making the solution more acidic. This is not how a buffer system would normalize a slightly acidic pH.

d. Destroys excess hydrogen ions: While this option might seem correct, it is not typically how chemical buffer systems operate. Buffer systems usually bind (or release) hydrogen ions rather than destroy them.

a. Lipase: Lipase is the enzyme responsible for breaking down fats into fatty acids and glycerol during digestion.

b. Maltase: Maltase is an enzyme that breaks down maltose into glucose molecules. It is involved in carbohydrate digestion.

c. Protease: Proteases are enzymes that break down proteins into amino acids. They are not involved in fat digestion.

d. Lactase: Lactase is an enzyme that breaks down lactose, the sugar found in milk, into glucose and galactose. It is involved in carbohydrate digestion.