Chemical Digestion Flashcards
The Digestive System
What is chemical digestion?
The chemical break down of large, complex molecules into smaller, simpler molecules which are small enough to be absorbed into the bloodstream.
What is the function of enzymes?
Chemical digestion uses enzymes to break complex molecules into simpler molecules.
What is the function of enzymes in the stomach?
Chemical digestion in the stomach occurs through enzymes in the gastric juice
What enzyme works in the stomach and what is its function?
Pepsin breaks the bonds between certain amino acids so that the long chains of amino acids that make up protein molecules are broken into shorter chains called polypeptides
What environment does pepsin work in?
Pepsin works in very acidic solutions.
The hydrochloric acid in gastric juice allows pepsin to act, killing many bacteria that enter the stomach with food.
What is the role of pancreatic juice?
Pancreatic juice enters the duodenum through the common bile duct, helping to neutralise the acid that has come with the material from the stomach
What enzymes does pancreatic juice contain?
- Pancreatic Amylase (breaks down starch into the disaccharide maltose)
- Pancreatic Protease (breaks down proteins into small chains of amino acids)
- Pancreatic lipases (break down fats into fatty acids and glycerol)
- Ribonuclease and Deoxyribonuclease (digest RNA and DNA).
What is the function of enzymes in the small intestine?
The lining of the small intestine secretes intestinal juice that contain many enzymes that complete the digestion of carbs, proteins and lipids.
What enzymes are found in the small intestine?
- Peptidase: breaks down peptides into amino acids.
- Sucrase, lactase, and maltase: breaks down sucrose, lactose, and maltose into the monosaccharides glucose, fructose, and galactose.
- Lipases: breaks down lipids into fatty acid and glycerol.
What is the function of enzymes in the mouth?
Food is chewed with saliva. It contains mucus to lubricate food and salivary amylase (a digestive enzyme) which begins the chemical digestion of starch into the disaccharide maltose.
What is the pH of the stomach?
The pH in the stomach is approx. 2-3, due to the hydrochloric acid.
The cells lining the stomach are protected from the acid by a lay of mucus.
What are the optimal pH conditions for enzyme activity?
The acidic environment allows the enzyme pepsinogen to be converted to pepsin, an active form of the enzyme. Pepsin breaks proteins down into shorter peptides and the nucleic acids DNA and RNA.
