Proteins

• Proteins


  Macromolecules that are one of the four major components of cells, along with lipids, carbohydrates, and nucleic acids
• DNA


  Codes for proteins
• Proteins


  • They are closely connected to DNA, which provides the instructions for their synthesis
  • They come in many different types and structures, with diverse functions in the body
• Amino acids


  The small building blocks that make up proteins
• There are 20 different amino acids
• Polypeptide


  Another term for a protein, a chain of amino acids
• Proteins


  • They can vary in length, from a few amino acids to thousands
  • They can have different orders of the same amino acids, creating different proteins
  • They can be modified after synthesis, such as by adding carbohydrates
• Categories of amino acids


  • Essential amino acids
  • Non-essential amino acids
• Essential amino acids


  Amino acids that must be obtained from the diet, as the body cannot synthesize them
• Non-essential amino acids


  Amino acids that the body can synthesize from other amino acids, so they do not need to be obtained from the diet
• There are 9 essential amino acids and 11 non-essential amino acids
• Eating a limited diet lacking certain essential amino acids


  Can lead to problems in making all the proteins the body needs
• Essential amino acids


  Amino acids that must come from the diet because the body cannot synthesize them from other amino acids
• Non-essential amino acids


  Amino acids that can be synthesized by the body from other amino acids, so they do not need to come from the diet
• Non-essential amino acids can comprise 11 of the total 20 amino acids
• Amino acid


  The basic building block of proteins, consisting of a central carbon atom bonded to a hydrogen atom, an amino group, a carboxyl group, and a variable side chain (R group)
• Amino acid structure


  • Contains an amino group (NH2), a carboxyl group (COOH), and a variable R group
  • The R group is what makes each amino acid unique
• Peptide bond


  The covalent bond that forms between the carboxyl group of one amino acid and the amino group of another, linking them together
• Formation of a peptide bond


  1. The carboxyl group of one amino acid reacts with the amino group of another

  2. This releases a water molecule (H2O)

  3. The remaining atoms form a peptide bond, linking the two amino acids
• Dipeptide


  Two amino acids linked together by a peptide bond
• Polypeptide


  A long chain of many amino acids linked by peptide bonds
• Condensation reaction


  The reaction that forms a peptide bond, releasing water
• Hydrolysis reaction


  The reverse of a condensation reaction, where a peptide bond is broken by the addition of water
• Proteins in food are broken down into amino acids by hydrolysis in the digestive system, so they can be absorbed into the bloodstream
• Protein


  Macromolecule made up of amino acids
• Digestion of protein


  1. Protein too big to be absorbed, broken down by hydrolysis in intestine

  2. Amino acids absorbed into bloodstream

  3. Amino acids can be used to synthesize new proteins or broken down for energy
• Proteins are made of amino acids
• Amino acid structure


  Contains amino group, carboxyl group, R-group, and hydrogen
• Linking of amino acids

  1. Condensation reaction forms peptide bond

  2. Hydrolysis breaks peptide bond
• Proteins are sensitive to pH and temperature
• Denaturation


  Disruption of 3D structure of protein due to changes in pH or temperature, can be reversible (renaturation)
• High temperature


  Increases kinetic energy, disrupts hydrogen bonds and causes denaturation
• Acidic pH


  Protons interfere with hydrogen bonding and cause denaturation
• Molecular diagrams


  • Amino acid
  • Polypeptide
  • Ribose
  • Phospholipid
• Collagen is the most abundant structural protein in the human body, found in ligaments and skin
• Proteins


  Complex macromolecules composed of one or more chains of amino acids
• Proteins


  • Play essential roles in many biological processes, including structural support, catalysis and signalling pathways
• Amino acids


  The monomers that are used to make proteins
• Amino acids


  • 20 unique amino acids
• Alpha (α) carbon


  The central carbon that is covalently bonded to four different chemical groups