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Biochemistry: Amino acids and protein structure · Amino Acid Structure and Properties

How amino acids are built, how their side chains and charges behave, and why those properties shape proteins and health.

For learning, not medical advice: for your own health, ask a doctor or another qualified professional.

Biochemistry · 25 questions

Try 3 questions

1. What distinguishes one of the 20 standard amino acids from another?

  1. Its side chain (R group)
  2. Its carboxyl group
  3. Its amino group
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Answer: Its side chain (R group)

All share the same backbone: an alpha carbon bearing an amino group, a carboxyl group and a hydrogen; only the side chain differs.

2. Why is every standard amino acid except glycine chiral?

  1. Its alpha carbon bears four different groups
  2. Its side chain always contains a ring
  3. Its amino group is always charged
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Answer: Its alpha carbon bears four different groups

A carbon with four different substituents has non-superimposable mirror images; glycine's side chain is a second hydrogen, so its alpha carbon is not a stereocenter.

3. Which configuration do the amino acids built into human proteins have?

  1. The D configuration
  2. An equal mix of L and D
  3. The L configuration
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Answer: The L configuration

Ribosomes incorporate only L-amino acids; D forms do occur in nature, for example in bacterial cell walls, but not in our ribosome-made proteins.

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