Enzymes What do you know already? What are they? Where do substrates bind? Factors affecting enzymes and how?

What are they? Biological Catalysts: Speed up reaction rates of chemical reactions in cells. These are called metabolic reactions

Enzymes are globular proteins Proteins are made up of single units called amino acids linked together to form a polypeptide chain One amino acid. The R group is a variable group that differs in different amino acids Globular proteins are Compact, Spherical, Soluble molecules

Enzymes are tertiary structure proteins These have a specific 3D shape. Why is this important in enzymes? Tertiary Structure is dependent on the bonds that form between R groups of an amino acid as the polypeptide chain folds. These bonds are disulphide bridges, hydrogen bonds, ionic bonds, hydrophobic interactions. These bonds give the enzyme a very precise 3D shape

Activation energy: The energy needed for a reaction to happen Enzymes lower the ACTIVATION ENERGY to make a reaction happen So reactions can happen at a lower temperature i.e. body temperature

How do they Work? ONLY in solution Lock and Key hypothesis – Emil Fischer (1894) Each enzyme has a specific and different shape

Lock and Key Hypothesis Active site region Complementary shape to substrate Enzyme and substrate successfully collide Substrate binds to active site Forms enzyme-substrate complex Reaction takes place  products formed Enzyme used again collides with next substrate

The lock and key hypothesis

NB enzymes don’t always break things down!

Factors Affecting enzyme activity

Temperature Frying eggs animation Hydrogen bonds break, tertiary structure changes, active site changes shape. Substrate no longer fits (Low temps inactivate enzymes) The rate of reaction doubles for each 10°C rise until the optimum is reached

pH The range of pH over which an enzyme can work is NARROW. Changes in pH affect ionic and hydrogen bonds Small deviations from the optimum are reversible and inactivate the enzyme Large deviations cause denaturation. The narrow optimum pH will vary between different enzymes

Enzyme concentration e.g. Substrate concentration

Substrate Concentration All the active sites are full all of the time Reaction is at its maximum unless more enzyme is added (Vmax) Substrate concentration limits the reaction rate

Enzymes re-cap: On a whiteboard… What do you know NOW? What are enzymes? Where do substrates bind? Factors affecting enzymes and how? DRAW GRAPHS AND USE KEY WORDS