biology (check answers)

1. How do endothermic and exothermic reactions differ?

a. Endothermic reactions release energy and are spontaneous.
b. Exothermic reactions release energy and are spontaneous.
c. Endothermic reactions give off heat and light.
d. Photosynthesis is exothermic.


2. Which is NOT a description of activation energy?

a. The energy absorbed by the reactants.
b. The energy needed to get an endothermic reaction to proceed.
c. The "push" to start a chemical reaction.
d. The energy transfer between the products and reactants.


3. An animal's stomach contains enzymes that break down food into smaller molecules that the animal's cells can use. Enzymes perform this function by:

a. participating in chemical reactions
b. increasing the temperature
c. changing the ionic concentration
d. lowering the pH


4. Milk you buy at the store has been “Pasteurized.” This means the milk was warmed up to around 150 F/65 C to kill harmful bacteria. This process probably works because:

a. it speeds up the metabolism of the bacteria and this increases their death rate
b. it causes the bacteria’s carbohydrates to under go hydrolysis, thus killing the bacteria
c. the bacteria’s enzymes will denature at the high temperature, thus killing the bacteria
d. it causes the bacteria to build many polymers, which kills the bacteria


5. In a test tube, a student used the enzyme catalase to break down some H2O2 (Hydrogen Peroxide). After the reaction, she discovered another bottle of H2O2 that needed to be broken down also. Will she be able to use the enzyme again?

a. No, because enzymes get broken down when they do chemical reactions
b. Yes, because enzymes are carbohydrates and does not break them down
c. No, because the enzymes denature after doing chemical reactions
d. Yes, because enzymes are not used up by the reactions they help speed up


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