1.5.2 Protein Structure

• Proteins are complex molecules composed of amino acids linked by peptide bonds.
• Arrange the levels of protein structure from simplest to most complex.

  1️⃣ Primary Structure

  2️⃣ Secondary Structure

  3️⃣ Tertiary Structure

  4️⃣ Quaternary Structure
• Match the level of protein structure with its description.

  Primary Structure ↔️ Linear sequence of amino acids

  Secondary Structure ↔️ Folding into α-helices and β-pleated sheets

  Tertiary Structure ↔️ Three-dimensional structure stabilized by bonds

  Quaternary Structure ↔️ Arrangement of multiple polypeptide chains
• Each amino acid contains an amino group, a carboxyl group, a hydrogen atom, and a unique R group.
• There are 20 common amino acids classified as acidic, basic, or neutral based on their R groups.
• Match the type of amino acid with its example.

  Acidic ↔️ Glutamic acid

  Basic ↔️ Lysine

  Neutral ↔️ Alanine
• The primary structure of a protein is the linear sequence of amino acids.
• The R groups of amino acids directly participate in forming the primary structure backbone.

  False
• R groups influence the overall three-dimensional structure of a protein but do not form peptide bonds.
• The secondary structure of a protein involves the local folding of the polypeptide chain into specific patterns.
• Match the type of secondary structure with its description.

  α-helices ↔️ Spiral structure stabilized by hydrogen bonds

  β-pleated sheets ↔️ Flat, extended structure stabilized by hydrogen bonds
• Hydrogen bonds stabilize both α-helices and β-pleated sheets in secondary structure.
• What are proteins made of?

  Amino acids
• Proteins are complex molecules made of amino acids linked by peptide bonds.
• The structure of a protein determines its function.
• Arrange the four levels of protein structure in order.

  1️⃣ Primary Structure

  2️⃣ Secondary Structure

  3️⃣ Tertiary Structure

  4️⃣ Quaternary Structure
• Match the level of protein structure with its description:

  Primary Structure ↔️ Linear sequence of amino acids

  Secondary Structure ↔️ Folding into α-helices and β-pleated sheets

  Tertiary Structure ↔️ Three-dimensional structure stabilized by bonds

  Quaternary Structure ↔️ Arrangement of multiple polypeptide chains
• What are the four components of an amino acid attached to a central carbon?

  Amino, carboxyl, hydrogen, R group
• The R group of an amino acid determines its properties.
• There are 20 common amino acids classified based on their R group properties.
• Which amino acids are examples of acidic amino acids?

  Glutamic acid, Aspartic acid
• Basic amino acids have an extra amino group and are positively charged at physiological pH.
• Match the amino acid type with its characteristics:

  Acidic ↔️ Extra carboxyl group, negatively charged

  Basic ↔️ Extra amino group, positively charged

  Neutral ↔️ Neither acidic nor basic, can be polar or nonpolar
• Why is lysine classified as a basic amino acid?

  It has an extra amino group
• The primary structure of a protein is formed by peptide bonds between amino acids.
• The R groups of amino acids directly participate in forming the polypeptide backbone.

  False
• What is the primary structure of a protein defined as?

  Linear sequence of amino acids
• Peptide bonds link amino acids in the polypeptide chain
• The R groups of amino acids directly form the polypeptide backbone

  False
• What are the two main types of secondary protein structure?

  α-helices and β-pleated sheets
• α-helices are stabilized by hydrogen bonds between amino
• β-pleated sheets are stabilized by hydrogen bonds between adjacent chains
• In which protein is α-helices commonly found?

  Keratin
• List the types of interactions that stabilize tertiary protein structure in order of decreasing strength.

  1️⃣ Disulfide Bridges

  2️⃣ Ionic Bonds

  3️⃣ Hydrogen Bonds

  4️⃣ Van der Waals Forces
• Hydrogen bonds in tertiary structure are weak bonds between electronegative atoms and hydrogen atoms
• What type of bond forms between oppositely charged R groups in tertiary structure?

  Ionic Bonds
• Weak attractions between nonpolar R groups are called Van der Waals Forces
• What covalent bond stabilizes tertiary structure by linking cysteine residues?

  Disulfide Bridges
• The folding of a polypeptide chain results in the tertiary structure
• What type of bond is formed between electronegative atoms and hydrogen atoms?

  Hydrogen bond