The -SH (sulfhydryl) groups of cysteines can form , which stabilize protein tertiary structure.

Answer: Disulfide bridges Two -SH groups can be oxidized to form a covalent S-S disulfide bridge between cysteine residues.

Which functional group accepts a proton, conferring basic character?

Answer: Amino -NH₂ + H⁺ → -NH₃⁺. Amino groups are basic.

Which group in the diagram is responsible for the chemical diversity that distinguishes one amino acid from another?

Answer: R group (orange) All 20 standard amino acids share NH2, COOH, H, and a central C-alpha; only the R (side chain) varies, dictating polarity, charge, and chemistry.

AP Biology · Topic 1.4

Properties of Biological Macromolecules Practice

Part of Chemistry of Life.(SYI-1.D)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$The -SH (sulfhydryl) groups of cysteines can form _______, which stabilize protein tertiary structure.$
- A
  $Disulfide bridges$
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- B
  $Phosphodiester bonds$
- C
  $Peptide bonds$
- D
  $Hydrogen bonds with water$
Why
$Two -SH groups can be oxidized to form a covalent S-S disulfide bridge between cysteine residues.$
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Sample 2difficulty 2/5
$Which functional group accepts a proton, conferring basic character?$
- A
  $Carboxyl$
- B
  $Sulfhydryl$
- C
  $Phosphate$
- D
  $Amino$
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Why
$-NH₂ + H⁺ \to -NH₃⁺. Amino groups are basic.$
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Sample 3difficulty 2/5
$A student examines the structure of a generic amino acid. The teacher explains that 20 different amino acids share three common groups but differ in only one part. Identifying that part is critical for understanding why some amino acids are hydrophobic while others are charged or polar.$
$Which group in the diagram is responsible for the chemical diversity that distinguishes one amino acid from another?$
- A
  $Amino group (blue)$
- B
  $R group (orange)$
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- C
  $Alpha hydrogen (green)$
- D
  $Carboxyl group (red)$
Why
$All 20 standard amino acids share NH2, COOH, H, and a central C-alpha; only the R (side chain) varies, dictating polarity, charge, and chemistry.$
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Sample 4difficulty 2/5
$Lactase hydrolyzes lactose into$
- A
  $Glucose + fructose$
- B
  $Sucrose + water$
- C
  $Two glucose molecules$
- D
  $Glucose + galactose$
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Why
$Lactose = glucose-galactose disaccharide. Lactase hydrolyzes the glycosidic bond.$
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Sample 5difficulty 2/5
$Which functional group ionizes to release a proton, conferring acidic character?$
- A
  $Amino (-NH₂)$
- B
  $Methyl (-CH₃)$
- C
  $Carboxyl (-COOH)$
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- D
  $Hydroxyl (-OH)$
Why
$-COOH \to -COO⁻ + H⁺ readily, making it an acid; this is the basis of amino-acid carboxyl behavior.$
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