ENZYMESENZYMES&&

Chemical Chemical DigestionDigestion

Chemical Digestion Basics

• Dehydration Synthesis vs. Hydrolysis• Anabolic – Dehydration Synthesis

– Require the removal of water to form bonds

• Catabolic – Hydrolytic Reactions– Require the addition of water to break bonds

• Carbohydrates – mono and disaccharides• Lipids (triglycerides) – glycerol + fatty acids• Proteins – amino acids

enzyme

substrate

productsenzyme

Terminology:•Enzyme•Active site•Substrate(s)•Product(s)•Reversible reactions

Factoids:

Enzymes are:• Proteins

Factoids:Enzymes:• Lower the activation

energy needed for a reaction to take place

AB

Molecule C

+

Factoids:Enzymes:• Are unchanged after catalyzing a reaction

Factoids:Enzymes:• Turnover numbers are very high• Examples:

– 1 molecule of acetylcholinesterase -> 25,000 molecules of acetylcholine in 1 second

– 1 molecule of catalase breaks down 40 million molecules of hydrogen peroxide in 1 second

Factoids:Enzymes:• Are specific in their

activity• Lock and key model

Factoids:

Enzymes:• Sometimes require a

nonprotein factor = cofactor (metallic ion) or coenzyme (vitamin)– Examples:

• Iron, zinc, copper, sodium, potassium, vitamin B

Factoids:

Enzymes:• are usually named

after the substrate on which they act

• have names ending in –ase ( with a few exceptions)

Examples: • Cellulase• Sucrase• Lipase• Lactase• Acetylcholinesterase

Factors Affecting Enzyme Activity

Temperature

pH

Pepsin – stomach enzymeTrypsin – duodenum enzyme

more H+

Concentrationof Enzyme or Substrate

Inhibitors• Competitive Inhibition• Noncompetitive

Inhibition

Enzyme Uses

Papaya and Papain

Pineapple and Bromelain

Lactose = milk sugar• Lactase – enzyme produced by

cells that line the small intestine• Symptoms• Solutions

– Avoid dairy products (calcium problem) and prepared foods containing lactose

– Determine problematic amounts of lactose or source (i.e. milk, ice cream, aged cheeses)

– Lactase additives: add to milk (lactose content reduced by 70% or buy lactose-reduced milk

Enzyme Dietary Supplements

Questions Concerning Dietary Enzyme Supplements

• Are there people who do not produce enough of certain enzymes?

• Could an increase in digestive enzymes increase the digestion of food?

• Can you increase the amount of digestive enzymes by taking oral dietary supplements?