BIOC 1303 Lecture 9: Ch. 19 Amino Acids and Proteins
28 Jun 2018
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03-59-191
Week Five: February 5 - 9, 2018
Introduction to Organic and Biological Chemistry for Health Sciences
Chapter 19 Amino Acids and Proteins
19.1 Proteins and Amino Acids
Learning Goals → Classify proteins by their functions in the cell.
→ Draw the structure for an amino acid.
Functions of Proteins Summary - Pg. 673
- Know first column
Amino Acids are Building Blocks of Proteins - Pg. 673
Five components:
1. Alpha Carbon atom in blue to which is bonded four groups:
A. H atom in black
B. Amino group in blue
C. Carboxyl group in red
D. R = a side group that gives each amino acid unique characteristics. in
turquoise.
Example:
R side chain
|
H2N—C —COOH
|
H
Nonpolar Amino Acids Summary - Side Chain R Groups - Yellow - Pg. 675
- Amino acids are classified as nonpolar when the R groups are H, alkyl, or aromatic.
Polar Amino Acids Summary Side Chain
R Groups - Yellow- Pg. 675
- Amino acids are classified as polar
when the R groups are alcohols,
thiols, or amides.
Acidic & Basic Amino Acids Side chain R groups-yellow Summary - pg 675
- Amino acids are classified as acidic when the R group is a carboxylic acid. Amino acids
are classified as basic when the R group is an amine.
Fischer Projections of
Amino Acids - Pg. 676
- All amino acids except glycine are chiral.
- Amino acids have stereoisomers.
- In biological systems, only L amino acids are used in proteins.
03-59-191
Week Five: February 5 - 9, 2018
19.2 Amino Acids as Acids and Bases
Learning Goal → Write the ionic form of an amino acid at pH values above, below and equal to its isoelectric point.
Zwitterions - Pg. 678
- Both the –NH2 and the –COOH groups in an amino acid undergo ionization in water.
- A zwitterion forms that has + and – charge.
- At the isoelectric point (pI), the + and – charges in the zwitterion are equal = NO NET
CHARGE
Example:
NH2—CH2—COOH → H3N+—CH2—COO–
Glycine Zwitterion of glycine Z
Amino Acids - Charges - Pg. 678
- If pH > pI, the amino acid is negatively charged.
Example:
+ OH–
H3N—CH2—COO– → H2N—CH2—COO–
Zwitterion
pH =6.0 pH = 10.0
pH = pI = 6.0 pH > pI
No net charge Net negative charge
Amino Acids - Charges - Pg. 698
- If pH < pI, the amino acid is positively charged.
Example:
+ H+
H3N—CH2—COO– → H2N—CH2—COOH
Zwitterion Positive Ion
pH =6.0 pH = 2.0
pH = pI = 6.0 pH < pI
No net charge Net + charge
pH and Ionization - Pg. 678
Document Summary
Introduction to organic and biological chemistry for health sciences. Learning goals classify proteins by their functions in the cell. Draw the structure for an amino acid. Amino acids are building blocks of proteins - pg. Alpha carbon atom in blue to which is bonded four groups: D. r = a side group that gives each amino acid unique characteristics. in turquoise. Nonpolar amino acids summary - side chain r groups - yellow - pg. Amino acids are classified as nonpolar when the r groups are h, alkyl, or aromatic. Amino acids are classified as polar when the r groups are alcohols, thiols, or amides. Acidic & basic amino acids side chain r groups-yellow summary - pg 675. Amino acids are classified as acidic when the r group is a carboxylic acid. Amino acids are classified as basic when the r group is an amine. All amino acids except glycine are chiral.
