TOPIC 2 BIOLOGY

• What are the monomers of proteins?

  Amino acids
• Dipeptide


  Two amino acids bonded together
• Polypeptide


  A polymer (chain) of more than two amino acids bonded together
• What are proteins made of?

  One or more polypeptides
• What is the general structure of amino acids?

  A carboxyl group, an amine/amino group, a carbon-containing R group
• How many amino acids are there?

  20
• What is the difference between amino acids?

  Their R group
• How are amino acids linked?

  Condensation reaction
• What is released in a condensation reaction?

  Water molecule
• What type of bond is formed between amino acids?

  Peptide bond
• What are the 4 structural levels of proteins?


  Primary, Secondary, Tertiary, Quaternary
• What is the primary structure of a protein?

  The sequence of amino acids in the polypeptide chain
• What is the secondary structure of a protein?

  The 2D arrangement of the chain of amino acids. Alpha helix or Beta pleated sheet
• What determines the secondary structure of a protein?

  Hydrogen bonds between amino acids
• What is the tertiary structure of a protein?

  The 3D structure of a protein
• What determines the tertiary structure of a protein?

  Hydrogen bonds, ionic bonds, disulphide bridges, hydrophobic and hydrophilic interactions
• What is the quaternary structure of a protein?

  Some proteins are made of more than one polypeptide chains linked together. The quaternary structure is the way these polypeptide chains are assembled together
• What is the primary structure of proteins held together by?

  Peptide bonds between amino acids
• Ionic bonds in proteins

  Attractions between negative and positive charges on different parts of the molecule
• Disulphide bridge/bond in proteins

  Covalent bond between sulphur atoms of two cysteine amino acids
• Hydrophobic interactions in proteins

  When hydrophobic groups are close together, they tend to clump together
• Hydrophilic interactions in proteins

  Hydrophilic groups get pushed to the outside
• What do hydrophilic/phobic interactions affect tertiary structure?

  They affect how the protein folds up
• How does a proteins primary structure determine its 3D structure and properties

  The amino acid sequence of a protein determines what bonds will form and how the protein folds into its 3D structure. The 3D structure determines its properties and function in the body
• Globular proteins


  - Round, compact proteins made up of multiple polypeptide chains.

  
  

  - proteins are soluble - easily transported in fluids.
• How are the chains structured in globular proteins?

  Coiled up so that hydrophilic parts are on the outside and hydrophobic parts face inwards
• What are the two types of protein 3D structure?

  Globular

  Fibrous
• How does the structure of globular proteins make it good for their function?

  Makes them soluble, so they're easily transported in fluids
• Hydrogen bonds


  Weak bonds between a slightly positively charged hydrogen atom in one molecule and a slightly negatively charged atom in another molecule
• Example of globular protein


  Haemoglobin
• Haemoglobin strucutre

  Globular protein made of 4 polypeptide chains. It has iron-contains haem groups that bind to oxygen
• What is the function of haemoglobin?

  Carries oxygen around the body
• How is haemoglobin suited for its function?

  Its soluble so can easily be transported in the blood
• Collagen structure

  Fibrous protein made up of 3 polypeptides
• Fibrous proteins


  - Long, insoluble polypeptide chains, tightly coiled round each other to form a rope shape

  
  

  - Chains are held together by lots of bonds, making the proteins strong

  
  

  - Little tertiary/quaternary structure

  
  

  - Occasional cross linkages which forms microfibres for tensile strength

  
  

  - Insoluble
• How are fibrous proteins suited for their function?

  They are strong so are often found in supportive tissue
• How is collagen suited for its function?

  High tensile strength due to hydrogen and covalent bonds and forms the structure of bones, cartilage and connective tissue in animals
• What do enzymes do?

  Catalyse metabolic reactions
• Intracellular enzymes


  Catalyse reactions inside the cell
• Extracellular enzymes


  Secreted by cells to catalyse reactions outside of cells