Proteins

• Proteins are usually very large molecules
• Each organism has many different type of proteins
• The shape of any proteins differs from all other types of protein.
• What is an amino acid?

  The basic monomer units which combine to make a polymer called a polypeptide
• What is the structure of a protein?

  Central Carbon atom combined to a amino group, a carboxyl group, a hydrogen atom and a R group
• How many different types of amino acids naturally occur?

  20
• How is a peptide bond formed?

  2 amino acids, condensation reaction, bond formed between the carbon of one amino acid and the nitrogen atom of the other.
• How can a peptide bond be broken?

  Hydrolysis reaction with water.
• What is the primary structure of a protein?

  amino acid order to form a polypeptide chain.
• What is the secondary structure of a protein?

  The secondary structure is the folding or twisting patterns of the polypeptide chain, including alpha helices and beta sheets.

  O- and H+ ions readily form weak H bonds
• What is the tertiary structure of a protein?

  Beta sheets and Alphas helices can twist and fold further to form more complex structures.

  Held together by ionic and hydrogen bonds and disulfide bridges.
• What is the quaternary structure of a protein?

  Multiple polypeptide tertiary structures bonded together.

  e.g., Haemoglobin
• How do you test for proteins?

  Add biuret reagent to the sample and mix gently.

  Purple = positive

  Blue = negative
• What is an enzyme?

  An enzyme is a protein that acts as a catalyst in biological reactions, speeding up the rate of the reaction without being consumed in the process.
• What is the function of an active site?

  Enzyme-substrate binding
• What factors effect enzyme controlled reactions?

  Temperature, pH, substrate concentration, enzyme concentration, and presence of inhibitors.
• How does an increased temperature affect enzymes controlled reactions?

  Increased kinetic energy, more rapid movement, more collisions so increases the chance of them being above the activation energy and successful.
• What can a temp that is too high or too low do to enzymes?

  Denature them
• How does pH affect enzyme controlled reactions?

  Alters amino acid charge and affects the H+ bonding. Active site is changed, can be beneficial or negative. There will be an optimum pH
• What does the optimum value of the factor mean?

  Peak function
• How does enzyme concentration affect the enzyme controlled reaction?

  Excess of substrate and increase enzyme conc. = increased rate.

  Limited substrate and increase = no change.
• How does substrate concentration affect enzyme controlled reactions?

  If the conc. of the enzymes is fixed and the substrate concentration is increased the rate of reaction will increase.

  But once at full capacity = no change
• What is a competitive inhibitor?

  Same shape as the substrate, binds to the enzyme and stops the substrate bunding, not permanent.
• What does an increase in competitive inhibitor do?

  Decreases enzyme activity and decrease rate of reaction
• What is a non competitive inhibitor?

  Binds to anywhere other than the active site. Changes the tertiary structure of the enzyme. Enzyme unable to bind afterwards.
• what is the site called where a non-competitive inhibitor binds?

  Allosteric site
• What is the lock and key model?

  Enzymes are specific and complementary to a substrate. Substrate fits like a key. Suggests there is a fixed structure.
• What is the induced fit model?

  Enzymes are not rigidly shaped and can mould to the substrate. As it changes shape it exerts pressure on the substrate and lowers its Ea.
• What is an anabolic pathway?

  A metabolic pathway that builds larger molecules from smaller ones.
• What is a catabolic pathway?

  A catabolic pathway is a metabolic pathway that breaks down complex molecules into simpler ones, releasing energy in the process.
• What is feedback inhibition?

  Regulation of a process by its end product.
• What are the stages of holozoic nutrition?

  Ingestion, digestion, absorption, assimilation, egestion.
• Pepsin, Dipeptidase, exopeptidase, endopeptidase, are all examples of what?

  Proteases
• Amylase, maltase, sucrase, lactase are all examples of what?

  Carbohydrases
• What digestive enzyme is there for lipids?

  Lipase
• What are immobilised enzymes?

  Enzymes that are attached or confined to a solid support or matrix.
• What are the advantages of immobilised enzymes?

  Reusability, stability, and increased efficiency.
• What are the disadvantages of immobilised enzymes?

  Substrate needs to diffuse through membrane, smaller SA of enzyme, less energy.
• What is collagen?


  Fibrous proteins with long chains running parallel and bonded in cross-bridged. Found in tendons and has a strong pull in direction of the tendon