Amino Acids

• Chemistry
• Secondary Education

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What two functional groups are present in amino acid?

Learning Objective

• describe, by drawing, the acid / base properties of amino acids and the formation of zwitterions, to include the isoelectric point

Amino acids 

Amino acids as zwitterions

• an internal transfer of a hydrogen ion from the -COOH group to the -NH2 group makes a zwitterion

What charges are found in a zwitterion?

1. positive
2. negative
3. A and B
4. zero

Zwitterions are ions.

• amino acids exist in even in the solid state
• If you dissolve the amino acid in water, a simple solution also contains this ion.
• a compound with no overall electrical charge, but which contains separate parts which are positively and negatively charged.

What happens to the hydrogen ions if you increase the pH of a solution of an amino acid by adding hydroxide ions?

1. hydrogen ion is removed from -NH3+
2. hydrogen ion is added to the -NH3+ group

Do this!

Show the equation for this reaction. 

What does the -COO- part of the zwitterion do to the hydrogen ion if you decrease the pH by adding an acid to a solution of an amino acid?

1. The -COO- releases a hydrogen ion.
2. The -COO- picks up a hydrogen ion.

Do this!

Show the equation for this reaction. 

Activity 5

Work with your study partner. 

Rate your level of understanding of the lesson.

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