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

5. Protein Techniques

Peptidases

Biochemistry

5. Protein Techniques

Peptidases

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Multiple Choice

What would the resulting peptide fragments be if the following peptide were treated with excess Pepsin?
H—E—L—P—M—E—P—L—E—A—S—E

H—E—L—P—M—E—P—L & E—A—S—E

H—E—L—P, M—E—P, & L—E—A—S—E

H—E, L—P—M—E—P—L—E—A—S—E

H—E, L—P—M—E, P—L—E, A—S—E

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Verified step by step guidance

Understand the specificity of Pepsin: Pepsin is an enzyme that cleaves peptide bonds preferentially at the N-terminal side of aromatic amino acids such as phenylalanine (F), tryptophan (W), and tyrosine (Y). However, it can also cleave at other sites depending on the structure of the peptide.

Identify the peptide sequence: The given peptide sequence is H—E—L—P—M—E—P—L—E—A—S—E. We need to determine where Pepsin would cleave this sequence.

Examine the peptide sequence for potential cleavage sites: Look for aromatic amino acids or other residues where Pepsin might cleave. In this sequence, there are no aromatic amino acids, so Pepsin may cleave at other sites based on the peptide's structure.

Consider the provided options: The problem provides several possible fragmentations. Compare these options with the expected cleavage pattern of Pepsin.

Select the correct fragmentation: Based on Pepsin's cleavage specificity and the provided options, choose the fragmentation that aligns with Pepsin's activity. The correct answer is: H—E, L—P—M—E, P—L—E, A—S—E.

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Related Practice

Multiple Choice

A nonapeptide was determined to have the following amino acid composition: (Lys)₂, (Gly)₂, (Phe)₂, His, Thr, Met. The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycine were recovered. Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and free Lys. 2,4-Dinitrophenyl-histidine was recovered from the pentapeptide, and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide. Digestion with the enzyme pepsin produced a dipeptide, a tripeptide, and a tetrapeptide. The tetrapeptide was composed of (Lys)₂, Phe, and Gly. The native sequence was determined to be:

*Recall: Pepsin cleaves N-terminal peptide bond of F, Y, W & L residues.*

Open Question

The following reagents are often used in protein chemistry. Match the reagent with the purpose for which it is best suited. Some answers may be used more than once or not at all and more than one reagent may be suitable for a given purpose.

Open Question

Draw out each of the peptide fragments that would be generated if the peptide is treated with trypsin.

Open Question

Draw out the resulting peptide fragments that would be generated if the peptide is treated with chymotrypsin.

Multiple Choice

Which is the expected result of chymotrypsin cleavage of the following peptide?

Lys—Gly—Phe—Thr—Tyr—Pro—Asn—Trp—Ser—Tyr—Phe

Multiple Choice

You perform multiple tests to derive the amino acid sequence of a purified peptide (see results below). Which of the following peptides listed best represents the sequence of the unknown peptide?

Open Question

A) The octapeptide AVGWRVKS was digested with the enzyme trypsin. Would ion exchange or size-exclusion chromatography be most appropriate for separating the fragments? Explain.

a. Ion-Exchange chromatography.

b. Size-exclusion chromatography.

B) Suppose the same peptide was digested with chymotrypsin. Which would be the optimal separation technique? Explain.

a. Ion-Exchange chromatography.

b. Size-exclusion chromatography.

Multiple Choice

*Recall: Pepsin cleaves N-terminal peptide bond of F, Y, W & L residues.*

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