Welcome to the Proteins 1 debriefing.

Answer the questions in the spaces provided. Click on the check buttons when you are finished with each problem.


1. In a momentous discovery, planetary scientists discover a microbe living on Mars. When its chemical composition is analyzed, a novel amino acid based around the molecule morpholine is discovered. Its structure is shown below. Which group would you place this amino acid in?

Hydrophobic

The C-N and C-S bonds in the ring are polar, so morpholine is not hydrophobic.

Polar

True, morpholine is polar, but the N in the ring has a free pair of electrons. What did Lewis say free electron pairs make an atom behave like?

Acidic

While the H on the ring makes morpholine look like a Bronsted-Lowry acid, its pKa is too high for morpholine to act that way.

Basic
Correct! The N in the ring has a free electron pair and can act like a Lewis base.
The N in the ring has a free electron pair and can act like a Lewis base.

2. Shown below is the structure of a tetrapeptide, four amino acids linked by peptide bonds. What is its name? Enter the three-letter amino acid abbreviations in the spaces below and click the Check button when you are done. Click on the Protein 1 icon to see the structures of the amino acids.

1.
2.
3.
4.
At least one of the amino acids you entered was wrong.
Remember, amino acid sequences are named from the N-terminus to the C-terminus.
Correct! You have entered the correct amino acids in the correct N-terminal to C-terminal direction.

3. Sickle cell anemia is the result of a single amino acid substitution in the oxygen-carrying molecule of red blood cells, hemoglobin. This change is from Glu6 of the ß chain of hemoglobin to Val. As the image below shows, this amino acid is on the surface of hemoglobin and exposed to the water molecules surrounding it (the a chains are in blue, the ß chains are in yellow, and the two ßGlu6 amino acids are in cyan). Do you think this change makes hemoglobin more or less soluble in water?

More soluble
Less soluble
Use the table of amino acid structures to see what Val and Glu are like. What will replacing Glu with Val do to hemoglobin's solubility?
Correct! Replacing Glu with Val slightly decreases hemoglobin's solubility.

Congratulations!

You have completed the Protein 1 module.

Click on the hemoglobin image to learn more about sickle cell anemia. Click on the Proteins 1 icon to return to the Biomolecules gateway page.