Proteins

• What elements do proteins contain?

  C, H, O, N, and sometimes S
• What are the monomers of proteins?

  Amino acids
• How many amino acids are there, and what makes them different?

  There are 20 amino acids with different R-groups
• How do plants obtain amino acids?

  Plants make amino acids using soil nitrates
• Why are some amino acids called "essential amino acids" for animals?


  Some must come from the diet
• What is formed when two amino acids join together?


  A dipeptide
• What is a chain of more than two amino acids called?


  A polypeptide
• What are proteins made up of?

  One or more polypeptide chains
• Name a structural protein and its function.

  Collagen provides structural support
• What is the role of proteins in transport?

  They act as carriers and channels
• Give an example of a storage protein.

  Milk proteins
• What is the role of enzymes in the body?

  They catalyze a range of reactions
• Name three hormones that are proteins.

  Insulin, glucagon, and adrenaline
• How do proteins contribute to protection in the body?

  Antibodies provide protection
• Why are proteins considered important building materials?

  They are essential for growth and repair
• What is the general structure of an amino acid?

  Central carbon, amine group, carboxyl group, R-group
• What makes each amino acid unique?

  The R-group gives unique properties
• What is the simplest amino acid, and what is its R-group?

  Glycine; its R-group is a hydrogen atom
• What are essential amino acids, and why are they important?

  They cannot be synthesized and must be obtained from diet
• What reaction occurs to form a dipeptide from two amino acids?

  A condensation reaction occurs
• Which group from amino acid 1 is involved in forming a dipeptide?

  The carboxyl group donates an –OH
• Which group from amino acid 2 is involved in forming a dipeptide?

  The amine group donates a hydrogen atom
• What happens to the –OH and hydrogen atom during the formation of a dipeptide?

  A water molecule is eliminated, and a peptide bond is formed
• How can a peptide bond be broken, and what controls this process?

  By hydrolysis, controlled by enzymes
• What are polypeptides?

  Long chains of amino acids joined by peptide bonds
• How many amino acids are typically found in a polypeptide?

  Hundreds of amino acids long
• What is the primary structure of a protein?

  The specific sequence of amino acids in a polypeptide
• What determines the primary structure of a protein?

  The order of DNA bases in a gene
• Do proteins always consist of a single polypeptide chain?

  No, most proteins contain several chains
• How many amino acids are there, and what does this mean for the number of possible polypeptides?

  20 amino acids mean limitless combinations
• If you have four amino acids, how many different polypeptides could you make using just these four?

  Depends on the positions in the chain
• What is the secondary structure of a protein?

  The coiling or folding of the polypeptide chain
• What are the two main three-dimensional shapes formed in the secondary structure of proteins?

  Alpha helix and beta pleated sheet
• What determines the type of secondary structure formed in a protein?

  The various R-groups present on the amino acids
• How are hydrogen bonds formed in an alpha helix?

  Between H on –NH and O on –CO groups
• What shape does the polypeptide chain form in an alpha helix?

  Coils up into a helical shape
• Why are alpha helices vulnerable to changes in pH and temperature?

  Hydrogen bonds are weak and numerous
• What is the tertiary structure of a protein?

  The overall 3D shape of a protein molecule
• What are the four types of bonding involved in a protein’s tertiary structure?

  Hydrogen, ionic, disulphide bonds, and interactions
• What is a disulphide bond, and how is it formed?

  A covalent bond formed between two cysteine molecules