Q of the Day

Question 1

Organic chemistry

Answer 1

Diastereomers

The molecule on the left has the chlorines in the cis configuration, while the one on the right has them arranged trans. Cis and trans are a type of diastereomer

Tautomers are a form of constitutional isomer in which the bonding between the atoms is changed. The molecules depicted have the same bonding arrangment, so they are not tautomers. Also, by far the most common tautomer on the MCAT is the ketone / enol tautomer, which this is not.

Conformers can be freely interconverted by rotation around a single bond, with no bond-breaking. Here, there’s no way to convert between cis and trans without breaking bonds.

Question 2

Which of the following correctly indicates the order and relevant connection between the listed terms:

I. Zygote → Blastula → Gastrula
II. Morula → Inner Cell Mass → Placenta
III. Gastrula → Ectoderm → Neural Tissue

A) I only

B) I and II only

C) I and III only

D) II and III only

Answer 2

C) I and III only

Question 3

Which of the following correctly indicates stages in the development of a plasma cell the location where those stages occur:

A) bone marrow: B-cell, lymph node: plasma cell

B) bone marrow: T-cell, thymus: plasma cell

C) lymph node: B-cell, bone marrow: plasma cell

D) thymus: T-cell, lymph node: plasma cell

Answer 3

A) bone marrow: B-cell, lymph node: plasma cell

Plasma cells, also called plasma B cells, or effector B cells, originate in the bone marrow. They act as antigen presenting cells after leaving the bone marrow. After taking up an antigen, they typically make their way to a lymph node where they present the antigenic material to a T-cell and become activated. Some develop into plasma cells, secreting antibodies. Others develop into memory B cells.