Question

how do enzymes affect chemical reactions in the body?
they increase the energy needed
they slow down the reaction rate
they lower the amount of energy needed
they change the final products
what happens to the enzyme after it catalyzes a reaction?
it is destroyed
it combines with the product
it can be used again
it changes shape permanently
why cant humans digest milk after weaning (without lactase persistence)?
milk proteins become toxic
stomach acid becomes too strong
lactase enzyme is no longer produced
intestines lose absorption ability

Explanation:

• Enzymes are biological catalysts. Catalysts lower the activation energy (the amount of energy needed) for a reaction. They do not increase the energy needed, slow down the reaction rate (they speed it up), or change the final products.
• Enzymes are not consumed in the reaction they catalyze. So, after catalyzing a reaction, they can be used again. They are not destroyed, do not combine with the product (except transiently during the reaction mechanism), and do not change shape permanently (any shape change during the reaction is usually reversible).
• Lactase is the enzyme that breaks down lactose (the sugar in milk). In humans without lactase persistence, the lactase enzyme is no longer produced (or produced in very low amounts) after weaning. Milk proteins do not become toxic, stomach acid does not become too strong, and intestines do not lose absorption ability in a general sense related to this.

Answer:

• For the first question: They lower the amount of energy needed.
• For the second question: It can be used again.
• For the third question: Lactase enzyme is no longer produced.