Module 2: Enzymes Flashcards
What is an enzyme?
Tertiray globular protein that is a biological catalyst, which can speed up reactions by lowering activiation energy
How do enzymes show specificity?
Have a specific shape so the substrate has a specific shape for the enzyme active site
Define catabolism
Break down complex molecules into smaller ones, releasing energy in metabolic pathways
Define anabolism
Build up molecules from simple ones - components synthesised and assembled into cells to form tissues, organs and whole organisms
Define metabolism
Almost all reactions in living organisms are catalysed by enzymes
Define intracellular enzymes. Give an example
Catalyse reactions in a metabolic pathway within cells e.g. catalase to break down hydrogen peroxide into oxygen and water to prevent accumulation and therefore poisoning of the body.
Define extracellular enzymes. Give examples
Secreted from cells and used outside of cells e.g. trypsin (protease) catalyses the break down of proteins into small peptide chains, which can then be broken down into amino acids by other proteases. Prouced by the pancreas and released into the small intestines. The amino acids released are absorbed by the intestine lining.
Starch broken down partially into maltose by amylase - produced by salivary glands and pancreas - mouth and small intestines. Maltase breaks the maltose down into glucose in the small intestines.
Why is the active site of an enzyme so important? What would happen is it changed shape?
Provides a complementary shape for the substrate molecule. Without the specific shape reactions would not take place, because the substrate would not fit into the active site, and so an ESC would not form, and no product would form
Define activation energy
The energy needed for a reaction to start
What do enzymes do to the activation energy? Why?
Lower activation energy providing an alternative route in order to increase the rate of reaction
What is the lock and key mechanism?
The enzyme active site is complementary to the shape of the substrate, and the substrate fits into the active site perfectly, like a key has a specific shape to a lock - specificity. Temporary bonds form between the R-groups of the active site and the substrate
This forms and enzyme substrate complex where the substrate reacts and forms products in an enzyme product complex
What is the induced-fit hypothesis?
The active site changes shape slightly when the substrate reacts with the enzyme. Means the binding is more effective. R-groups of amino acids give a precise conformation. Strain put on the substrate due to binding, weakening bonds in the substrate, lowering the activation energy
What interaction occurs between the substrate and enzyme to help the reaction along?
R-groups of enzyme active site and substrate interact to form temporary bonds, which puts strain on the bonds within the substrate, helping the reaction along.
What is the effect of temperature on an enzyme?
Slow reaction at low temps = molecules have low KE, so fewer collisions between enzyme and substrate
Higher temps = more collisions occur and with more KE to break bonds in the substrate. Optimum temp occurs here and product is formed quickly and efficiently
Highest temps = molecules vibrate too much breaking the H bonds within the enzyme - denaturation - changes specific 3D shape of active site so no longer complementary with substrate - tertiary structure altered
What is the effect of pH on enzyme activity?
Change from optimum reduces rate of reaction
H ions interact with R groups of amino acids
Breaks H and ionic bonds at active site
pH very different from the optimum will denature enzyme changing the specific 3D shape of the enzyme active site - no longer complementary
