Amino Acids and Their Properties

The video tutorial by Nikolai covers the structure of amino acids, focusing on their central alpha carbon, amino group, carboxylic group, hydrogen group, and variable R group. It explains how pH levels affect the protonation and deprotonation of these groups, leading to different states of amino acids, such as zwitterions. The tutorial highlights the impossibility of certain conditions where both the carboxylic and amino groups are protonated or deprotonated simultaneously. It concludes with a discussion on the three possible states of amino acids at different pH levels.

What is the unique feature that differentiates each amino acid from another?

• The central alpha carbon

• The amino group

• The R group

• The carboxylic group

Which group in amino acids can gain or lose a charge depending on the pH?

• Central carbon

• Side chain

• Alpha amino group

• Alpha carboxy group

At what pH level does the alpha carboxy group retain its hydrogen?

• Above 7.0

• Above 9.0

• Below 2.0

• At neutral pH

What happens to the alpha amino group when the pH is below 9.0?

• It becomes negatively charged

• It remains unchanged

• It gains a hydrogen

• It loses a hydrogen

What is a zwitterion?

• A molecule with only positive charges

• A molecule with no charge

• A molecule with only negative charges

• A molecule with both positive and negative charges

Under what condition does an amino acid form a zwitterion?

• At any pH

• At low pH

• At high pH

• At neutral pH

Why is the molecular form shown in the video impossible?

• Because the carboxylic group cannot lose hydrogen

• Because the amino group cannot be protonated

• Because the pH cannot be both above 9.0 and below 2.0 simultaneously

• Because the R group cannot change

What charge does an amino acid have at a pH above 9.0?

• Neutral

• Negative

• Positive

• No charge

Which state is not possible for an amino acid?

• Below pH 2

• Above pH 9.0

• Simultaneously below pH 2 and above pH 9.0

• Neutral pH

What is the net charge of a zwitterion?

• Positive

• Zero

• Variable

• Negative