Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

4. Protein Structure

Isoelectric Point of a Peptide

Biochemistry

4. Protein Structure

Isoelectric Point of a Peptide

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Multiple Choice

Draw in the R-groups for the following peptide & calculate the pI: ATLDAG.

7.41

6.9

9.25

3.7

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Identify the amino acids in the peptide sequence ATLDAG. The sequence consists of Alanine (A), Threonine (T), Leucine (L), Aspartic acid (D), Alanine (A), and Glycine (G).

Draw the R-groups for each amino acid in the peptide. Alanine has a methyl group (CH3), Threonine has a CH(OH)CH3 group, Leucine has a CH2CH(CH3)2 group, Aspartic acid has a CH2COOH group, and Glycine has a hydrogen atom (H) as its R-group.

To calculate the isoelectric point (pI) of the peptide, identify the ionizable groups. These include the N-terminus, the C-terminus, and the side chain of Aspartic acid (D).

Determine the pKa values for the ionizable groups: the N-terminus (around 9.0), the C-terminus (around 2.0), and the side chain of Aspartic acid (around 3.9).

Calculate the pI by averaging the pKa values of the groups that are closest in pH when the peptide is neutral. For this peptide, average the pKa of the C-terminus and the side chain of Aspartic acid, as these are the groups that will be neutral at the pI.