AQA A Level Chemistry : Year 2 - Amino acids and Proteins, Exams of Chemistry

Download AQA A Level Chemistry : Year 2 - Amino acids and Proteins and more Exams Chemistry in PDF only on Docsity! 1 Give 4 roles of proteins - correct answer Hormones Enzymes Structural components (e.g muscles) Antibodies What is the primary structure of a protein? - correct answer The sequence of amino acids in the molecule What is a protein? - correct answer A sequence of amino acids joined by peptide links (bonds) AQA A Level Chemistry : Year 2 - Amino acids and Proteins 2 What is the name of the bond between amino acids? - correct answer Peptide bond How many naturally occurring amino acids are there? - correct answer 20 What is the general structure of an amino acid? - correct answer Central carbon group -COOH group -NH2 group -H -R group What is the only part of an amino acid that varies? - correct answer -R group (side chain) 5 What is the general structure of an amino acid zwitterion? - correct answer Central carbon group -COO^- group -NH3^+ group -H group -R group Why do amino acids have high melting points? - correct answer There are strong ionic bonds between the negative COO- group and positive NH3+ group Require high amount of energy to break What is the bonding in a solid amino acid? - correct answer Ionic 6 Why are amino acids weakly basic and weakly acidic? - correct answer Zwitterion contains weakly basic COO- group and weakly acidic NH3+ group Why are proteins polyamides? - correct answer Condensation reaction between -COOH group of one amino acid and -NH2 group of another amino acid Bond- peptide link What are the 5 groups of amino acids? - correct answer 1. Non-polar aliphatic (i.e. straight chain) R group 2. Non-polar aromatic R group 3. Polar, uncharged R grou[ 4. Acidic R group 5. Basic R group 7 What happens when an amino acid is in alkaline solution? (high pH) - correct answer -COOH group deprotonated to form -COO- group What happens when an amino acid is in acidic solution? (low pH) - correct answer -NH2 group protonated to form -NH3+ group If an amino acid contains more than one -NH2 or -COOH group, will these also be protonated/deprotonated ? - correct answer Yes On a diagram of a zwitterion or (de)protonated amino acid where should 10 What are the 5 interactions which contribute to the tertiary structure of the protein? - correct answer 1. Hydrogen bonding between polar R groups 2. Disulphide bridges between cysteine amino acid residues 3. Salt bridges between RCOO- and RNH3+ groups 4. Hydrophobic/philic interactions (polar/non-polar side chains) 5. Steric hindrance (side chains too long to pack closely together) What are enzymes? - correct answer Biological catalysts 11 What is a substrate? - correct answer The reactant in the reaction that an enzyme catalyses How do enzymes work? (6 steps) - correct answer 1. Enzyme has specific active site 2. Substrate binds to active site 3. Enzyme-substrate complex forms 4. Bonds in substrate strained 5. Product-substrate complex forms 6. Product does not fit so dissociated from enzyme What does the active site of an enzyme contain? - correct answer Amino acid residues which can interact with and hold the substrate 12 Amino acid residues which catalyse the reaction Explain the lock and key mechanism - correct answer Enzyme active site has a specific shape Substrate is complementary to that site What does stereospecific mean? - correct answer The enzyme active site is complementary to only one enantionmer What are enzyme inhibitors? - correct answer Molecules which fit to active site and block it Block enzyme activity