3.6.5 Explain the use of 3.6.5 Explain the use of lactase in the production of lactase in the production of

lactose-free milk. lactose-free milk.

• Lactose is a disaccharide (glucose + Lactose is a disaccharide (glucose + Galactose) milk sugar Galactose) milk sugar

• Around Around 90%90% of all humans show some of all humans show some kind of lactose intolerance. kind of lactose intolerance.

• People who are lactose intolerant can People who are lactose intolerant can drink milk if it is lactose free.drink milk if it is lactose free.

• LactLactasease is an enzyme extracted from is an enzyme extracted from yeast that can digest the milk sugar to yeast that can digest the milk sugar to glucose and galactose.glucose and galactose.

Enzyme ImmobilizationEnzyme Immobilization::

• Enzyme is attached to an inert, Enzyme is attached to an inert, insoluble material such as alginate insoluble material such as alginate (alginic acid)(alginic acid)

• Allows enzyme to remain in place Allows enzyme to remain in place throughout reactionthroughout reaction

• Provides increased resistance to pH Provides increased resistance to pH and temperature changesand temperature changes

• First the Lactase is First the Lactase is immobilized in alginate immobilized in alginate beads.beads.

• Next the beads are placed Next the beads are placed in a container over which in a container over which milk can be passed.milk can be passed.

• The milk is collected and re-The milk is collected and re-circulated (pump) to circulated (pump) to convert any remaining convert any remaining lactose to glucose and lactose to glucose and galactose. galactose.

• The circulation is The circulation is maintained until all lactose maintained until all lactose has been converted.has been converted.

It is possible to make the It is possible to make the process more efficient by process more efficient by immobilizing the lactose on a immobilizing the lactose on a recoverable surface such as recoverable surface such as alginate.alginate.

• This model of an This model of an industrial process industrial process allow the lactase to allow the lactase to be recovered and re-be recovered and re-used (cheaper).used (cheaper).

• Efficient conversion Efficient conversion of lactose to glucose of lactose to glucose and galactose.and galactose.

• High % lactose High % lactose conversion is conversion is achieved.achieved.

• All these factors All these factors reduce cost reduce cost particularly on the particularly on the downstream downstream processing and processing and purification.purification.

6.1.2 Explain the need for 6.1.2 Explain the need for enzymes in digestion enzymes in digestion

• Enzymes are biological catalysts that Enzymes are biological catalysts that increase the rate of reaction increase the rate of reaction

• Digestive enzymes are secreted into the Digestive enzymes are secreted into the lumen of the gut lumen of the gut

• Digestive enzyme increase the rate of Digestive enzyme increase the rate of reaction of the hydrolysis of insoluble food reaction of the hydrolysis of insoluble food molecules to soluble end products molecules to soluble end products

• Digestive enzymes increase the rate of Digestive enzymes increase the rate of reaction at body temperaturereaction 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, 6.1.3 State the source, substrate, products and optimum pH conditions products and optimum pH conditions for one amylase, one protease and for one amylase, one protease and one lipase one lipase

Pancreatic amylase Pancreatic amylase

• Source the Source the Pancreas Pancreas

• Optimal pH 7.5-7.8 Optimal pH 7.5-7.8 • Substrate is starch Substrate is starch

(amylose) (amylose) • End product is the End product is the

disaccharide disaccharide maltose maltose

• Action: hydrolysis Action: hydrolysis of 1-4 glycosidic of 1-4 glycosidic bonds bonds

Conditions:

Pepsin is a protease produced Pepsin is a protease produced in the stomachin the stomach

• Source is the Source is the stomach stomach

• Optimal pH is 2 Optimal pH is 2 • Substrate is a Substrate is a

polypeptide chains polypeptide chains of amino acids of amino acids

• End product is small End product is small polypeptides polypeptides

• Action is the Action is the hydrolysis of peptide hydrolysis of peptide bonds within the bonds within the polypeptide chain polypeptide chain (endopeptidase). (endopeptidase).

Conditions:

Pancreatic lipases Pancreatic lipases

• Source is the pancreas Source is the pancreas • The optimal pH is 7.2 The optimal pH is 7.2 • The substrate is a The substrate is a

triglyceride lipid triglyceride lipid • The product is glycerol and The product is glycerol and

fatty acid chains fatty acid chains • The action of pancreatic The action of pancreatic

amylases also requires the amylases also requires the presence of bile salts that presence of bile salts that emulsify the lipid. This emulsify the lipid. This emulsification has two emulsification has two effects: effects:

Conditions:

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.7.6.1 Metabolic pathways.

• Chemical changes in living things Chemical changes in living things often occurring with a number of often occurring with a number of intermediate stages. intermediate stages.

• Each stage has its own enzyme.Each stage has its own enzyme.

• Catabolic pathways breakdown Catabolic pathways breakdown moleculesmolecules

• Anabolic pathways build up moleculesAnabolic pathways build up molecules

Linear Chain Pathways:Linear Chain Pathways: • Enzyme (1) is specific to Enzyme (1) is specific to

substrate 1. This is changed substrate 1. This is changed to product 1. to product 1.

• Enzyme (2) is specific to Enzyme (2) is specific to product1 which becomes the product1 which becomes the substrate and converted to substrate and converted to product 2. product 2.

• Enzyme (3) is specific to Enzyme (3) is specific to products which becomes the products which becomes the substrate and converted t o substrate and converted t o product 3. product 3.

• Product 3 is called the 'End Product 3 is called the 'End product'. product'.

• e.g. Glycolysis e.g. Glycolysis

Cyclic PathwaysCyclic Pathways: :

• The initial substrate is fed into the The initial substrate is fed into the cycle.cycle.

• Enzyme (1) combines the Enzyme (1) combines the regenerated 'intermediate 4' with regenerated 'intermediate 4' with the initial substrate to catalyses the initial substrate to catalyses the production of intermediate 1.the production of intermediate 1.

• Enzyme (2) is specific to Enzyme (2) is specific to intermediate 1 and converts intermediate 1 and converts intermediate 1 to intermediate 2intermediate 1 to intermediate 2

• Enzyme (3) is specific to Enzyme (3) is specific to intermediate 2 and catalyses it intermediate 2 and catalyses it conversion to product and conversion to product and intermediate 3. intermediate 3.

• Enzyme (4) is specific to Enzyme (4) is specific to intermediate 3 and catalyses its intermediate 3 and catalyses its conversion to intermediate 4.conversion to intermediate 4.

• The difference is the regeneration The difference is the regeneration of the intermediate, in this case of the intermediate, in this case intermediate 4.intermediate 4.Examples Krebs cycle and Calvin

cycle.