3.6.5 Explain the use of lactase in the production of lactose-free milk.
Lactose is a disaccharide (glucose + Galactose) milk sugar • Around 90% of all humans show some kind of lactose intolerance. • People who are lactose intolerant can drink milk if it is lactose free. • Lactase is an enzyme extracted from yeast that can digest the milk sugar to glucose and galactose.
Enzyme Immobilization: • Enzyme is attached to an inert, insoluble material such as alginate (alginic acid) • Allows enzyme to remain in place throughout reaction • Provides increased resistance to pH and temperature changes
It is possible to make the process more efficient by immobilizing the lactose on a recoverable surface such as alginate. • First the Lactase is immobilized in alginate beads. • Next the beads are placed in a container over which milk can be passed. • The milk is collected and re-circulated (pump) to convert any remaining lactose to glucose and galactose. • The circulation is maintained until all lactose has been converted.
This model of an industrial process allow the lactase to be recovered and re-used (cheaper). • Efficient conversion of lactose to glucose and galactose. • High % lactose conversion is achieved. • All these factors reduce cost particularly on the downstream processing and purification.
6.1.2 Explain the need for enzymes in digestion • Enzymes are biological catalysts that increase the rate of reaction • Digestive enzymes are secreted into the lumen of the gut • Digestive enzyme increase the rate of reaction of the hydrolysis of insoluble food molecules to soluble end products • Digestive enzymes increase the rate of reaction at body temperature
The enzyme-catalyzed reaction has a lower activation energy. This lower activation energy would correspond to body temperature but is only possible in the presence of an enzyme
6.1.3 State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase
Pancreatic amylase • Source the Pancreas • Optimal pH 7.5-7.8 • Substrate is starch (amylose) • End product is the disaccharide maltose • Action: hydrolysis of 1-4 glycosidic bonds Conditions:
Pepsin is a protease produced in the stomach • Source is the stomach • Optimal pH is 2 • Substrate is a polypeptide chains of amino acids • End product is small polypeptides • Action is the hydrolysis of peptide bonds within the polypeptide chain (endopeptidase). Conditions:
Pancreatic lipases Conditions: • Source is the pancreas • The optimal pH is 7.2 • The substrate is a triglyceride lipid • The product is glycerol and fatty acid chains • The action of pancreatic amylases also requires the presence of bile salts that emulsify the lipid. This emulsification has two effects: 1) Increases the surface area of the lipid for the digestion of fat 2) Exposes the glycerol 'head' structure to the enzyme Action: hydrolysis of ester bonds between the glycerol molecules and the fatty acid chains.
7.6.1 Metabolic pathways. • Chemical changes in living things often occurring with a number of intermediate stages. • Each stage has its own enzyme. • Catabolic pathways breakdown molecules • Anabolic pathways build up molecules
Linear Chain Pathways: • Enzyme (1) is specific to substrate 1. This is changed to product 1. • Enzyme (2) is specific to product1 which becomes the substrate and converted to product 2. • Enzyme (3) is specific to products which becomes the substrate and converted t o product 3. • Product 3 is called the 'End product'. • e.g. Glycolysis
Cyclic Pathways: • The initial substrate is fed into the cycle. • Enzyme (1) combines the regenerated 'intermediate 4' with the initial substrate to catalyses the production of intermediate 1. • Enzyme (2) is specific to intermediate 1 and converts intermediate 1 to intermediate 2 • Enzyme (3) is specific to intermediate 2 and catalyses it conversion to product and intermediate 3. • Enzyme (4) is specific to intermediate 3 and catalyses its conversion to intermediate 4. • The difference is the regeneration of the intermediate, in this case intermediate 4. Examples Krebs cycle and Calvin cycle.