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

3. Amino Acids

Essential Amino Acids

Biochemistry

3. Amino Acids

Essential Amino Acids

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Multiple Choice

Which of the following aromatic amino acids is classified as nonessential in humans?

Tryptophan

Phenylalanine

Histidine

Tyrosine

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Verified step by step guidance

Step 1: Begin by understanding the classification of amino acids. Amino acids are categorized as essential or nonessential based on whether the human body can synthesize them. Essential amino acids must be obtained through the diet, while nonessential amino acids can be synthesized by the body.

Step 2: Review the aromatic amino acids. Aromatic amino acids contain a side chain with an aromatic ring structure. The primary aromatic amino acids in humans are phenylalanine, tyrosine, tryptophan, and histidine.

Step 3: Recall the metabolic relationship between phenylalanine and tyrosine. Tyrosine is synthesized in the human body from phenylalanine through the action of the enzyme phenylalanine hydroxylase. This makes tyrosine a nonessential amino acid, as it can be produced internally.

Step 4: Compare the other options. Tryptophan, phenylalanine, and histidine are essential amino acids because the human body cannot synthesize them and they must be obtained through dietary sources.

Step 5: Conclude that tyrosine is the correct answer, as it is classified as a nonessential aromatic amino acid in humans due to its synthesis from phenylalanine.