Proteins

• Proteins are polymers consisting of many amino acids
• Each amino acid is represented by a circle and is a monomer that forms the protein
• When many amino acids are combined, it is called a polypeptide
• The bond that connects individual amino acid residues is a peptide bond
• Structure of an amino acid:
• Chiral carbon with a hydrogen attached
• Amine group attached
• R group
• Carboxyl group
• Condensation reaction between two amino acids:
• Lose water and connect the two amino acids into one molecule
• Form a peptide bond, also known as a dehydration reaction
• Resulting in a dipeptide
• Levels of protein structure:
• Primary structure: based on the sequence of amino acids in the protein
• Secondary structure: describes the localized shape of a protein

  • Alpha helix: stabilized by hydrogen bonds between NH group and carbonyl group
  • Beta pleated sheet: stabilized by hydrogen bonds between carbonyl group and NH group
• Tertiary structure: represents the three-dimensional complete folding pattern of the protein
• Quaternary structure: formed by combining multiple subunits

  • Hemoglobin is an example with two alpha subunits and two beta subunits
• Proteins play many roles in biology, such as making up channels, being part of structure, serving as enzymes for important biological processes, and being involved in protecting the body
• Proteins are constantly being made in a process known as protein synthesis
• Proteins need modifications to be functional, including adding chemical groups like phosphorylation and folding
• Proteins need to be folded correctly to be functional
• Shape and function in biology are closely related
• Proteins are made up of amino acids, which are the building blocks held together by peptide bonds
• The sequence of amino acids in a protein is critical to its structure and function
• Amino acids have a carboxyl group, an amino group, and an R group (side chain)
• Proteins have different levels of structure:

  • Primary structure: sequence of amino acids
  • Secondary structure: folding of amino acids into alpha helix or beta pleated sheet due to hydrogen bonds
  • Tertiary structure: 3D folding of a functional protein due to interactions involving R groups like hydrophobic and hydrophilic interactions, ionic bonds, Van der Waals interactions, disulfide bonds, and hydrogen bonds
  • Quaternary structure: protein consisting of more than 1 polypeptide chain with interactions between subunits like hydrogen bonds or disulfide bonds
• Protein folding involves interactions like hydrogen bonds and R group interactions based on the protein's amino acids
• Proteins can have help in the folding process from chaperonins, which provide an ideal environment for proteins to fold correctly
• Protein misfoldings can lead to diseases
• Proteins need an ideal environment for functioning, including specific temperature and pH ranges
• Exposure to conditions outside the ideal range can denature proteins, disrupting their shape and preventing correct functioning
• Denaturing a protein may or may not be reversible, depending on the cause and extent of disruption to the protein's structure
• The environment a protein is in is crucial for its functioning
• Proteins are polymers of amino acids and are the most diverse type of biomolecule in the body
• Different kinds of proteins include:

  • Enzymes that catalyze chemical reactions
  • Receptors that control signaling in the body
  • Hemoglobin, which carries oxygen throughout the bloodstream
  • Muscle and organ tissue, which give the body structure and mobility
• Amino acids polymerize by forming peptide bonds with one another
• Peptide bond formation is a dehydration reaction where a water molecule is lost as two amino acids come together to form a peptide bond
• If two amino acids combine, it forms a dipeptide. Between three and ten amino acids form an oligopeptide, and more than ten form a polypeptide
• Each protein has an N-terminus (ends with the amino group) and a C-terminus (ends with the carboxyl group)