Biochemistry Proteins and Amino Acids Quiz

Proteins: Essential Biomolecules

• Proteins are essential for nearly all cellular processes.
• Proteins are the most abundant biological macromolecules in cells.
• The word "protein" comes from the Greek word "proteios," meaning "of first importance."

Amino Acids: The Building Blocks of Proteins

• All proteins are composed of amino acids, which are the monomers of proteins.
• Amino acids have a common structure, consisting of:
  • An amino group (-NH2)
  • A carboxylic acid group (-COOH)
  • A hydrogen atom bonded to the same carbon atom as the amino and carboxyl groups
• Amino acids are both weak acids and weak bases.
• Amino acids are distinguished by their unique side chains (R groups).

Ionization of Amino Acids

• Amino acids are ionized under physiological pH conditions.
• The amino group can be protonated (gaining a proton) to form a positively charged NH3+ group.
• The carboxylic acid group can be deprotonated (losing a proton) to form a negatively charged COO- group.
• The degree of protonation and deprotonation depends on the pH of the environment.

Protonation and pH: Understanding pKa

• pH measures the concentration of protons (H+) in a solution.
• Lower pH indicates higher proton concentration.
• pKa is a measure of the acidity of a specific compound, indicating its tendency to give away a proton.
• Lower pKa indicates a stronger acid, which readily releases protons.

Key Relationship: pH and pKa

• The protonation state of an amino acid is determined by comparing the pH of the environment and the pKa of the amino acid.
• If pH < pKa: The amino acid is protonated, as there are more protons available in the environment.
• If pH > pKa: The amino acid is deprotonated, as there are fewer protons available in the environment.

Proteins and Amino Acids

• Proteins are essential for almost all processes that occur within a cell.
• Proteins are the most abundant biological macromolecules found in cells.
• The word "protein" comes from the Greek word "Proteios" meaning "of first importance."
• All proteins are composed of monomers called amino acids.

Amino Acid Structure

• All amino acids share a common structure:
  • an amino group (-NH2)
  • a carboxyl group (-COOH)
  • a hydrogen atom bonded to the same carbon atom as the amino and carboxyl groups
• The variable part of the amino acid is the side chain (R group) which is unique to each amino acid.
• Under physiological conditions, amino acids are ionized.
• The amino group (base) can be protonated (gain a proton) resulting in a positive charge, forming -NH3+.
• The carboxyl group (acid) can be deprotonated (lose a proton) resulting in a negative charge, forming -COO-.
• The protonation and deprotonation of amino acids depends on the pH of their environment.

pH and pKa

• pH is a measure of the concentration of protons (H+) in an environment.
• The lower the pH, the higher the concentration of protons.
• pKa is a measure of the acid strength of a molecule.
• pKa is a material property (constant) meaning it doesn’t change for a given molecule.
• The lower the pKa, the stronger the acid and the easier it is for an amino acid to release protons.

pH and Protonation

• Compare the pH of the environment to the pKa of the amino acid to determine its ionization state.
• If the pH is less than the pKa (pH < pKa), the amino acid will be protonated.
• If the pH is greater than the pKa (pH > pKa), the amino acid will be deprotonated.