6 questions AAMC 4 biology

[2010premed]

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• At the end of his initial hospital stay, a few E. coli cell remained in the patient’s colon, even though he was taking antibiotics. These cell were most likely present because:

• the antibiotics cause drug-resistance mutations to occur in the bacterial DNA
• the patient’s colon cell became increasingly resistant to the antibiotics during his hospitalization
• chance mutations in a few E. coli before the treatment made these cells and their descendants antibiotic-resistant

answer: C

To me, all the choices are possible

• Which of the following slkyl halides can be used in an acetoacetic ester synthesis to make 4-methyl-2-pentanone?

A: Isopropyl iodide

I guessed this answer b/c of the structure, but I have no clued what the mechanism should be. Should I know any more info for this question?

• How can 3-ethyl-2-pentanone be synthesized starting with acetoacetic ester?

A: by successive alkylations with ethyl iodide.

Again I guessed right, what should I know for this question?

• I found this in an explanation. “Vasodilation increases blood flow to both the muscle during exercise and the skin during blushing. Vasoconstriction restricts blood flow to an organ and can increase blood pressure, whereas vasodilation has the opposite effect.

I thought that blood flow was always constant, and I also thought that vasodilation would decrease blood pressure, because it would increase the velocity (b/c of a smaller are) and therefore exert a smaller pressure on the walls.

• What is a danger of using the drug in treatment 1?

A: it may decrease endogenous antibacterial activities… ok this one is based on a passage. But how does giving an infected patient anti-inflammatory drugs have the potential of reducing their ability to fight an infection??

• Fever in septic shock leads to which of the following compensation mechanisms?

A; dilation of capillary beds in the skin

What is the relationship between respiration rate, fluid loss, and dissipation of heat?

 

[vsl5]

• At the end of his initial hospital stay, a few E. coli cell remained in the patient's colon, even though he was taking antibiotics. These cell were most likely present because:

• the antibiotics cause drug-resistance mutations to occur in the bacterial DNA
• the patient's colon cell became increasingly resistant to the antibiotics during his hospitalization
• chance mutations in a few E. coli before the treatment made these cells and their descendants antibiotic-resistant

answer: C

To me, all the choices are possible

C is right because antibiotics do not cause mutations, they select for them. B is wrong because colon cells are not the target of antibiotics and therefore should be resistant (otherwise you'd kill your colon cells).

• Which of the following slkyl halides can be used in an acetoacetic ester synthesis to make 4-methyl-2-pentanone?

A: Isopropyl iodide

I guessed this answer b/c of the structure, but I have no clued what the mechanism should be. Should I know any more info for this question?

http://en.wikipedia.org/wiki/Acetoacetic_ester_synthesis

• How can 3-ethyl-2-pentanone be synthesized starting with acetoacetic ester?

A: by successive alkylations with ethyl iodide.

Again I guessed right, what should I know for this question?

see previous question. You need a strong base to deprotonate the alpha carbon on the 2-pentanone after the 1st rxn with ethyl iodide.

• I found this in an explanation. "Vasodilation increases blood flow to both the muscle during exercise and the skin during blushing. Vasoconstriction restricts blood flow to an organ and can increase blood pressure, whereas vasodilation has the opposite effect.

I thought that blood flow was always constant, and I also thought that vasodilation would decrease blood pressure, because it would increase the velocity (b/c of a smaller are) and therefore exert a smaller pressure on the walls.

Vasodilation increases blood flow to muscles and vasoconstriction of other blood vessels ensures that blood goes mainly to muscles during exercise. Vasodilation does decrease bp. The problem with your thinking is that the circulatory system is not ideal and does not follow bernoulli's equation.

• What is a danger of using the drug in treatment 1?

A: it may decrease endogenous antibacterial activities… ok this one is based on a passage. But how does giving an infected patient anti-inflammatory drugs have the potential of reducing their ability to fight an infection??

I didn't read the passage so I'll explain the question you asked. Anti-inflammatory drugs work by suppressing the immune system (eg. cortisol) and the immune system is require to fight infections

• Fever in septic shock leads to which of the following compensation mechanisms?

A; dilation of capillary beds in the skin

What is the relationship between respiration rate, fluid loss, and dissipation of heat?

Fever leads to increase body temp. In order to maintain homeostasis, the body reacts by trying to decrease body temperature. By dilating the capillary beds of the skin, more warm blood flows to the large surface areas of the skin allowing more efficient heat exchange (eg by convection and sweating).

 

[Rabolisk]

For the first one, antibiotics aren't meant to target colon cells, but rather bacteria. Antibiotics don't "cause" mutation, but rather kills all bacteria that haven't mutated by chance.

For the next two questions, you shouldn't have to guess. Read the passage and understand the reactions...

Vasoconstriction increases pressure because it reduces the cross-sectional area of the arteriole. To compensate for that, higher blood pressure must be supplied to maintain blood flow.


Inflammation is a response to infections and other tissue damage. If you inhibit this process, you inhibit the immune system's first response, thus reducing the body's ability to fight an infection.

Dilation of blood vessels leading to the skin results in increased heat loss. The body wants to be in its normal temperature range. Fever results in increased temperature, so the body wants to give off the heat and cool itself. Another mechanism is sweating.

 

[2010premed]

Thanks guys!