Amino acids, proteins and DNA (A-level only) common mistakes

Common mistakes

• Confusing amino acids with other biomolecules

  Students often confuse amino acids with carbohydrates or lipids.

  Fix itRemember that amino acids specifically contain both amine and carboxylic acid functional groups.

• Confusing zwitterions with charged ions

  Students often confuse zwitterions with fully charged ions.

  Fix itRemember that zwitterions have both positive and negative charges but are overall neutral, unlike fully charged ions.

• Confusing peptide bonds with other types of bonds

  Students often confuse peptide bonds with ionic or hydrogen bonds.

  Fix itRemember that peptide bonds are covalent bonds specifically formed between amino acids during protein synthesis.

• Confusing hydrolysis with condensation

  Students often confuse hydrolysis with the process of condensation, which forms peptide bonds.

  Fix itRemember that hydrolysis involves breaking bonds by adding water, while condensation involves forming bonds by removing water.

• Confusing DNA and RNA components

  Students often confuse ribose (found in RNA) with deoxyribose (found in DNA).

  Fix itRemember that DNA contains deoxyribose, which lacks one oxygen atom compared to ribose.

• Confusing condensation with hydrolysis

  Students often confuse condensation reactions with hydrolysis reactions.

  Fix itRemember that condensation reactions build larger molecules by removing water, while hydrolysis reactions break down molecules by adding water.

• Confusing hydrogen bonds with covalent bonds

  Students often describe hydrogen bonds as strong covalent bonds.

  Fix itRemember that hydrogen bonds are weak interactions, unlike covalent bonds which involve the sharing of electrons.

• Confusing DNA and RNA structures

  Students often confuse the structure of DNA with RNA, particularly regarding the presence of uracil in RNA instead of thymine in DNA.

  Fix itRemember that DNA contains thymine, while RNA contains uracil. Additionally, DNA is double-stranded, whereas RNA is typically single-stranded.