Chemical and Physical Processes of Digestion

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Digestive tract

Continuous tube that winds through the body from the oral cavity to the anus

Accessory digestive glands

Exocrine gland that secrete enzyme and fluid needed for digestion

Digestion

Process of breaking down food molecules into smaller molecules with the aid of enzymes in the digestive tract

Hydrolase

An enzyme that breaks down H2O to build smaller molecules

Salivary amylase

An enzyme in the oral cavity that breaks down starch and glycogen

Bile salts

Includes bile acid and base used in emulsification of lipids

Pepsin

Enzyme that breaks down protein into amino acids. Secreted by chief cells in the pancreas.

Two factors that play key roles in the efficacy of digestive enzymes

Temperature - hot and cold, enzyme denature when heated, enzyme slow down in cold temp. pH - change in pH can lead to deactivation

Major functions of the digestive system

1. Ingestion 2. Digestion (mechanical and chemical) 3. Absorption 4. Propulsion 5. Defecation 6. Secretion

What does it mean for an enzyme to be substrate specific?

1 enzyme for 1 substrate. Based on the lock-and-key theory

Primary categories into which food molecules fall into

1. Carbohydrates 2. Proteins 3. Lipids

Carbohydrates are broken down into what building blocks?

Monosaccharides

Proteins are broken into what building blocks?

Amino acids

Lipids are broken into what building blocks?

Fatty acids and monoglycerides

Why do lipids pose special problems for digestion?

Water and oil do not mix. Lipid are fat soluble, are water insoluble, hydrophobic, lipophilic

Hydrolysis

Breaking down of a water molecule to form smaller molecules

Amylase

Enzyme that breaks down carbohydrates

Lipase

Enzyme that breaks down lipids

Optimal pH for salivary amylase? Where is salivary amylase found?

pH of 6 is optimal. Found in oral cavity

Boiling and freezing on enzyme activity

Boiling - denature, destroy, deactivate. Freezing - slows down, inactivate.

Was salivary amylase able to digest cellulose? Why or why not?

No because we do not have the enzyme cellulase

Effect of bacteria on cellulose digestion

Bacteria can digest cellulose if they have cellulase

Where is pepsin secreted?

Found in the stomach so secreted in the stomach

Optimal pH for pepsin

2

Where is lipase secreted?

From the stomach and pancreas

Optimal pH for lipase

pH of 2 for the stomach. pH of 8 for the pancreas (duodenum has basic environment)

What was the effect of bile salts on lipid digestion?

Emulsification - mechanical digestion because don't change lipid globules

IKI

Iodine Potassium Iodide. Test for starch.

Benedicts's Test

Test for reducing sugar

Spectrophotometer

Measure light absorption through liquid medium

pH meter

Measure the level of hydrogen ion

Examples of physical process of digestion

1. Chewing (mastication) 2. Emulsification (breaking fat globules into fat goblets) 3. Segmentation (longitudinal smooth muscle contracts along the esophagus and small intestine, oblique smooth muscle contracts in the stomach)

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