Exchange and transport - DIGESTION AND ABSORPTION Flashcards
Where is amylase produced?
Pancreas/salivary gland
Where are the sites of action for amylase?
Duodenum/mouth
What are the 3 enzymes that break down carbohydrates?
Salivary amylase, pancreatic amylase, maltase
Where is maltase secreted?
Lining of the ileum
Where is lipase produced?
pancreas
What is the difference between exopeptidase and endopeptidase?
Exopeptidase hydrolyses the end of the polypeptide chains whereas endopeptidase hydrolyses within the polypeptide chains
What is digestion?
A process where large, insoluble biological molecules in food are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membrane into the blood stream.
What effect does the pH of the stomach have on amylase?
- Denatures amylase
- Starch is no longer hydrolysed
What are membrane bound disaccharidases?
- Enzymes that are attached to the epithelial cells that line the ileum
- Break disaccharides into monosaccharides in the small intestine
Hydrochloric acid is produced in the stomach. What is its role?
It provides the optimum pH for the enzymes in the stomach and kills harmful pathogens.
Describe the role of the enzymes of the digestive system in the complete breakdown of proteins (PPQ)
- Endopeptidases; Break bonds in the central region of protein molecules
- Exopeptidases; Break bonds at the end of protein molecules
- Dipeptidases; Break bonds in dipeptides to form amino acids
- Hydrolysis of peptide bonds
Describe the processes involved in the absorption of the products of protein digestion (PPQ)
- Amino acids move in with sodium, via protein
- Co transport of sodium down conc. gradient and amino acids against conc. gradient
- Sodium removed by active transport into blood
- Maintaining low conc. of sodium
- Amino acids move into blood by facilitated diffusion
Describe the role of bile in digestion and absorption of triglycerides (PPQ)
- Emulsifies lipid drops into smaller droplets
- Increases surface area of droplets
- Increases rate of digestion by lipases
- Bile forms micelles; To transport monoglycerides and fatty acids - because bile is amphipathic
Describe the processes involved in the absorption of the products of triglyceride digestion (PPQ)
- Micelle collides with cell membrane
- Monoglycerides and fatty acids enter cell by simple diffusion
- Reformed into triglycerides in the smooth endoplasmic reticulum
- Combined with proteins to form chylomicrons
- Exocytosis of chylomicrons
- Chylomicrons enter the lacteals/then enter blood
What are some adaptations of the ileum?
- Villi (and microvilli) increase surface area; for increased diffusion
- Epithelial cells are very thin; reducing diffusion distance
- Concentration gradient is maintained
- Many capillaries
