1.5.2 Protein Structure

• What type of bonds link amino acids in proteins?

  Peptide bonds
• The primary structure of a protein is the linear sequence of amino acids
• What are the two main types of folding in secondary protein structure?

  α-helices and β-pleated sheets
• The tertiary structure of a protein is stabilized by various bonds and interactions.
• The quaternary structure of a protein involves the arrangement of multiple polypeptide chains
• Which chemical groups are present in all amino acids?

  Amino and carboxyl groups
• Amino acids can be classified as acidic, basic, or neutral based on their R groups.
• The primary structure of a protein is defined as the linear sequence of amino acids
• How are peptide bonds represented in chemical notation?

  NH - CO -</latex>
• 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
• The tertiary structure of a protein is stabilized by bonds and interactions
• Which level of protein structure describes the linear sequence of amino acids?

  Primary structure
• The R group of an amino acid determines its properties and interactions.
• What are the basic building blocks of proteins?

  Amino acids
• 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 based on their R group properties.
• What determines the properties and interactions of each amino acid?

  The R group
• The R group determines the properties and interactions of each amino acid.
• Match the amino acid type with its characteristics:

  Acidic ↔️ Extra carboxyl group

  Basic ↔️ Extra amino group

  Neutral ↔️ Neither acidic nor basic
• Which amino acids are examples of acidic amino acids?

  Glutamic acid, Aspartic acid
• Lysine and Arginine are examples of basic amino acids.
• Glutamic acid is an acidic amino acid because it has an extra carboxyl group.
• Steps in forming the primary structure of a protein

  1️⃣ Amino acids link via peptide bonds

  2️⃣ Form a linear sequence of amino acids
• Do R groups directly participate in forming the polypeptide backbone of the primary structure?

  No
• R groups influence the protein's overall structure and function but not its primary structure.
• What are the two main types of secondary protein structure?

  α-helices and β-sheets
• α-helices are stabilized by hydrogen bonds between amino acids.
• The secondary structure of a protein refers to the local folding of the polypeptide chain into specific patterns
• What type of structure is an α-helix in secondary protein structure?

  Spiral structure
• β-pleated sheets are stabilized by hydrogen bonds between adjacent chains.
• Which protein is an example of a protein with α-helices?

  Keratin
• Match the secondary structure type with its description:

  α-helices ↔️ Spiral structure stabilized by hydrogen bonds

  β-pleated sheets ↔️ Flat, extended structure stabilized by hydrogen bonds
• The tertiary structure of a protein is its overall three-dimensional shape
• Arrange the following interactions in order of their strength, from strongest to weakest:

  1️⃣ Disulfide bridges

  2️⃣ Ionic bonds

  3️⃣ Hydrogen bonds

  4️⃣ Van der Waals forces
• What type of force involves weak attractions between nonpolar R groups?

  Van der Waals forces
• In enzymes, the tertiary structure creates the active site
• What is the overall three-dimensional shape of a protein referred to as?

  Tertiary structure
• The tertiary structure of a protein is stabilized by interactions between the R groups
• Match the interaction type with its description:

  Hydrogen bonds ↔️ Between polar R groups or backbone

  Ionic bonds ↔️ Between positively and negatively charged R groups

  Van der Waals forces ↔️ Weak attractions between nonpolar R groups

  Disulfide bridges ↔️ Covalent bonds between cysteine residues
• Disulfide bridges are covalent bonds between cysteine residues.