Biological molecules - Proteins and Enzymes Flashcards
What is the function of haemoglobin as a protein
Transports oxygen
What is the function of antibodies as a proein
Defends the body against infection
What is the function of enzymes as a protein
Biological catalysts
What is the function of actin + myolin as a protein
involved in muscle contraction
How are dipeptides formed
A condensation reaction between 2 amino acids forms a peptide bond
How are polypeptides formed
Many peptode bonds between many amino acids
What is the primary structure
Number and sequence of amino acids in a polypeptide chain
What is the secondary structure
- The folding of the polypeptide chain into an alpha helix or a beta pleated sheet
- Structure is maintained by hydrogen bonds between the NH group of one amino acid and the C=O bond
What is the tertiary structure
The further folding of the polypeptide chain into a specific 3D shape
What are the 3 different types of bonds between R groups in the tertiary structure
- Hydrogen Bonds which are weak bonds but many together are strong
- Ionic Bonds, also weak bonds which form between oppositely charged R groups
- Disulphide Bridges - Covalent bonds which form between sulphur containing R groups
What is the quaternary structure
More than one polypeptide chain joined together
Biuret test
- Add Biuret solution to a sample
- For positive test result there will be a colour change from blue to purple/lilac
Describe the induced fit model
- Enzyme-substrate complex formed between substrate and enzyme active site
- Binding substrate induces the change in shape of the active site so it becomes complementary to the substrate
- This puts pressure on the bonds in the substrate which cause them to break more easily
- When producs leave, the active site returns to its previous shape allowing it to bind to another substrate
Effect of temperature on rate of enyme activity
- As temperature increases to optimum, enzyme and substrate molecules have more KE and are more likely to form enzyme-substrate complexes
- Beyond optimim - hydrogen bonds holding tertiary structure start to break which changes shape of active site so no longer specific
Effect of pH on rate of enyme activity
- Up to optimum - rate of enzyme activity increases
- After optimum - Hydrogen nd ionic bonds in the tertiary structure are broken. Active site changes shape. No enzyme substrate complexes are formed
Effect of substrate concentration on rate of enyme activity
- As substrate conc increases the rate of reaction increases and then plateaus
- RoR is low at low substrate concentrations as the substrate is the limiting factor
- As substrate conc increases the substrate is no longer the limiting factor and therefore RoR increases
- At high substrate cones all enzyme sites are filled so no more enzyme substrate complexes can form. The concentration of enzymes is now the limiting factor
Effect of enzyme concentration on rate of enzyme activity
- The more enzymes in a solution, the more likely they are to collide with a substrate and form an enzyme substrate complex
- Increasing the enzyme concentration increases the rate of reaction
- If the amount of the substrate becomes limiting, increasing enzyme concentration will have no effect on the rate of reaction
What are the 2 types of inhibitors
- Competitive inhibitors
- Non-competitive inhibitors
Effect of a competitive inhibitor rate of enzyme activity
- They have similar structures to the substrates
- They fit into the active site but do not react
- They prevent the normal substrate from binding and hence slow the rate of reaction as less enzyme substrate complexes can be formed
Effect of a non-competitive inhibitor on rate of enzyme activity
- They bind to a site on the enzyme other than the active site
- They alter the shape of the active site so that the substrate cannot fit
- No more enzyme substrate complexes can be formed and the rate of reaction is decreased
