3. Organic compounds (A) always contain nitrogen. (B) are synthesized only by animal cells. (C) always contain carbon. (D) always contain oxygen.

5. The cholesterol associated with animal cell membranes (A) is attached to membrane proteins and extends into the watery environment surrounding the cell. (B) helps to keep phospholipids from being too close to one another. (C) is an abnormality resulting from a diet high in cholesterol. (D) helps solidify the membranes when the room temperature is below freezing.

3. Organic compounds
(A) always contain nitrogen.
(B) are synthesized only by animal cells.
(C) always contain carbon.
(D) always contain oxygen.

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