Correct answers are in bold, but be sure to read why the other answers are not correct.

1. Molecules such as ethanol can diffuse passively out of the gut and into the bloodstream, and this does not require energy. If energy is not required, then what drives the diffusion process?
   1. the high concentration of ethanol in the bloodstream
      Sorry, try again. The higher concentration of ethanol must be in the gut, right after drinking it. The ethanol moves down its concentration gradient into the bloodstream, and the concentration gradient is the driving force. No energy is required.
   2. the high concentration of ethanol in the gut
      You are right! The higher concentration of ethanol must be in the gut, right after drinking it. The ethanol moves down its concentration gradient into the bloodstream, and the concentration gradient is the driving force. No energy is required.
   3. the high pressure in the gut
      Wrong answer. There is no pressure forcing the ethanol from the gut into the bloodstream. The higher concentration of ethanol is in the gut, right after drinking it. The ethanol moves down its concentration gradient into the bloodstream, and the concentration gradient is the driving force. No energy is required.
   4. the high pressure in the bloodstream
      Sorry, that is incorrect. There is no pressure forcing the ethanol from the bloodstream into the gut. The higher concentration of ethanol is in the gut, right after drinking it. The ethanol moves down its concentration gradient into the bloodstream, and the concentration gradient is the driving force. No energy is required.
2. Females have a higher concentration of alcohol in their blood after drinking the same number of drinks as a male. Differences in ethanol metabolism can account for some of the different blood concentrations. What is the other reason?
   1. Females have more fat in their bodies relative to water; since ethanol distributes into water spaces the blood alcohol concentration will be higher
      Yes, you are correct! More fat means less water in the female body. Alcohol is dissolved in water and reaches higher concentrations in the smaller volume of water (including the bloodstream) present in the female body.
   2. Females have more water in their bodies relative to fat; since ethanol distributes into water spaces the blood alcohol concentration will be higher
      Close, but not quite. The second half of this statement is true, but females have more fat relative to water in their bodies, so there is a smaller space into which the ethanol will distribute.
   3. Females have more fat in their bodies relative to water; since ethanol distributes into water spaces the blood alcohol concentration will be lower
      Close, but not quite. The first half of this statement is true, but ethanol distributes into a smaller space (water) compared to males. This produces a higher concentration of alcohol in the blood, which is mostly water.
   4. Females have more water in their bodies relative to fat; since ethanol distributes into water spaces the blood alcohol concentration will be lower
      Sorry, this is incorrect. Females have more fat relative to water in their bodies so ethanol distributes into a smaller space (water) compared to males. This produces a higher concentration of alcohol in the blood, which is mostly water.
3. Ethanol, an alcohol, is a molecule that has both a polar end (OH group) and a non-polar end containing a chain of 2 C atoms. Which of the following describes the solubility of alcohol molecules with longer C atom chains?
   1. they become more soluble in water because they are more polar
      Incorrect. They become less soluble in water. As chain length of carbons in the alcohol increases the molecule becomes increasingly non-polar or hydrophobic (water fearing).
   2. they become less soluble in water because they are more polar
      Half right. They do become less soluble in water. As chain length of carbons in the alcohol increases the molecule becomes increasingly non-polar or hydrophobic (water fearing).
   3. they become more soluble in water because they are more non-polar
      Half right. They become less soluble in water. As chain length of carbons in the alcohol increases the molecule becomes increasingly non-polar or hydrophobic (water fearing).
   4. they become less soluble in water because they are more non-polar
      Great! They become less soluble in water. As chain length of carbons in the alcohol increases the molecule becomes increasingly non-polar or hydrophobic (water fearing).
4. In general it takes at least 1-1.5 hours to metabolize one drink of alcohol (one beer, glass of wine, or 1 shot of hard liquor). If someone drinks more than one drink of alcohol in this time period, which of the following explains why the person would become intoxicated?
   1. The person can’t “pee”, so the alcohol accumulates in the bloodstream and the brain
      Nope. Actually alcohol promotes urination, but the alcohol in the kidney moves back into the blood down its concentration gradient. The alcohol accumulates in the bloodstream (and the brain) because the alcohol molecules outnumber the enzyme molecules. They just can’t keep up to perform the metabolism. As alcohol levels rise in the blood (and brain), the person gets intoxicated.
   2. The enzymes that metabolize alcohol start working overtime but can’t get rid of the alcohol
      Not quite. The enzymes don’t work overtime—they become outnumbered by the alcohol molecules and just can’t keep up to perform the metabolism. As alcohol levels rise in the blood (and brain), the person gets intoxicated.
   3. The enzymes that metabolize alcohol become “saturated” and alcohol accumulates in the bloodstream and the brain
      Correct! The alcohol accumulates in the bloodstream (and the brain) because the alcohol molecules outnumber the ADH enzyme molecules. The ADH molecules just can’t keep up to perform the metabolism. As alcohol levels rise in the blood (and brain), the person gets intoxicated.
   4. The enzymes that metabolize alcohol basically stop working due to the excess alcohol in the bloodstream and the brain
      Sorry, you are incorrect. The enzymes keep working, but they can’t keep up with all the extra alcohol molecules around. As alcohol levels rise in the blood (and brain), the person gets intoxicated.
5. The oxidation of alcohol occurs without combination of alcohol and oxygen. Which of the following best describes the oxidation of alcohol?
   1. alcohol donates 2 electrons to an acceptor molecule
      Correct-but there’s more! Oxidation of ethanol involves the donation of 2 electrons in the form of H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.
   2. alcohol accepts 2 electrons from a donor molecule
      No-you got it backwards. Oxidation of ethanol involves the donation of 2 electrons in the form of H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.
   3. alcohol donates 2 H atoms to an acceptor molecule
      Correct-but there’s more! Oxidation of ethanol involves the donation of 2 electrons in the form of 2 H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.
   4. alcohol accepts 2 H atoms from a donor molecule
      No-you got it backwards. Oxidation of ethanol involves the donation of 2 electrons in the form of 2 H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.
   5. A and C
      Great! Oxidation of ethanol involves the donation of 2 electrons in the form of 2 H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.
   6. B and D
      No-you got it backwards. Oxidation of ethanol involves the donation of 2 electrons in the form of 2 H atoms to an acceptor molecule (sometimes this is oxygen, but not always). The acceptor molecule becomes reduced, because its charge is now reduced by the acceptance of the 2 electrons.