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Nutrition and Metabolism

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Presentation on theme: "Nutrition and Metabolism"— Presentation transcript:

1 Nutrition and Metabolism

2 Metabolism Recall: metabolism = all chemical reactions occurring in the body. Reactants = substances that “enter” a chemical reaction Products = substances that are formed by a chemical reaction Metabolic pathways = specific series of reactions in the body Begin with specific reactants and make specific produts. Occur over many steps. Each step is triggered by a catalyst called an enzyme.

3 Metabolism cont’d Enzymes
Protein molecules which function as catalysts to speed up rate of chemical reactions In a reaction using an enzyme, the “reactant” is called a substrate.

4 Digestive Enzymes - Overview
Much of digestion relies on the use of specific digestive enzymes. Many cause hydrolytic reactions to occur. Substrate is broken down by a reaction with water. Large nutrients get broken into smaller molecules. Digestive enzymes need an optimal pH to work properly. Maintains shape of the enzyme.

5 Major Digestive enzymes
Salivary amylase Catalyzes the reaction: starch + H2O  maltose Starch is broken down into a smaller sugar – maltose. Maltose is made up of two glucose Occurs in the mouth

6 Major Digestive Enzymes cont’d
Pepsin Catalyzes the reaction: protein + H2O  peptides Only active when pH < 2 Occurs in the stomach in presence of HCl (strong acid).

7 Major Digestive enzymes cont’d.
Pancreatic amylase Catalyzes the reaction: starch + H2O  maltose Occurs in duodenum (part of the small intestine) pH must be a little basic (over 7). Completes digestion of starches to disaccharides Disaccharides are molecules made up of 2 sugar molecules.

8 Disaccharide examples

9 Major Digestive enzymes cont’d.
Trypsin Catalyzes the reaction: protein + H2O  peptides Occurs in duodenum Produced by pancreas as trypsinogen – an inactive form (switched off). Activated (switched on) in duodenum by another enzyme called enterokinase.

10 Major Digestive Enzymes cont’d
Lipase Catalyzes the reaction: fats + H2O  glycerol + 3 fatty acids Occurs in duodenum

11 Major Digestive enzymes cont’d.
Peptidases Catalyze reaction: peptides + H2O  amino acids Occurs in small intestine Maltase Catalyzes reaction: maltose + H2O  2 Glucose Each disaccharide has its own enzyme (like maltase) Examples include lactase and sucrase Lactase = enzyme that breaks down lactose; sucrase = enzyme that breaks down sucrose.

12 Major Digestive enzymes cont’d.
Table 14.3

13 Digestive Enzymes – Conditions Required
Environmental conditions must be optimum Changes to conditions harm the enzymes. Conditions include: Warm temperature Most function well at normal body temperature Extreme heat causes irreversible shape change – denaturing. Correct pH Each enzyme has its own optimal pH Most function at near neutral pH (7). Others prefer acidic (lower pH) or basic (higher pH) conditions.

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