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

Amino Acid Groups

Biochemistry

3. Amino Acids

Amino Acid Groups

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Multiple Choice

Which of the following is true of amino acids?

All standard amino acids contain both an amino group ($-\mathrm{NH}_2$) and a carboxyl group ($-\mathrm{COOH}$) attached to the same carbon atom.

Amino acids do not have chiral centers.

The side chain (R group) is always a methyl group ($-\mathrm{CH}_3$).

All amino acids are nonpolar and hydrophobic.

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Verified step by step guidance

Step 1: Begin by understanding the structure of standard amino acids. Standard amino acids are the building blocks of proteins and share a common structure: a central carbon atom (called the alpha carbon) bonded to four groups: an amino group ($-\mathrm{NH}_2$), a carboxyl group ($-\mathrm{COOH}$), a hydrogen atom, and a variable side chain (R group).

Step 2: Evaluate the statement 'All standard amino acids contain both an amino group ($-\mathrm{NH}_2$) and a carboxyl group ($-\mathrm{COOH}$) attached to the same carbon atom.' This is true because the alpha carbon is the central point where these groups are attached in all standard amino acids.

Step 3: Analyze the statement 'Amino acids do not have chiral centers.' This is false because most amino acids (except glycine) have a chiral alpha carbon, meaning the alpha carbon is bonded to four different groups, making it asymmetric.

Step 4: Examine the statement 'The side chain (R group) is always a methyl group ($-\mathrm{CH}_3$).' This is false because the R group varies among amino acids and determines their unique properties. For example, alanine has a methyl group ($-\mathrm{CH}_3$) as its R group, but other amino acids have different side chains, such as hydroxyl ($-\mathrm{OH}$) in serine or benzyl in phenylalanine.

Step 5: Assess the statement 'All amino acids are nonpolar and hydrophobic.' This is false because amino acids can be polar, nonpolar, charged, hydrophilic, or hydrophobic depending on the nature of their R group. For instance, lysine is positively charged and hydrophilic, while leucine is nonpolar and hydrophobic.