Back to AI Flashcard MakerBiology /Biology IB HL - 6.1 Digestion Part 3
Where are enzymes used for disaccharide hydrolysis usually located?
Enzymes for disaccharide hydrolysis are often immobilised on the epithelial lining of the small intestine, near channel proteins
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Key Terms
Term
Definition
Where are enzymes used for disaccharide hydrolysis usually located?
Enzymes for disaccharide hydrolysis are often immobilised on the epithelial lining of the small intestine, near channel proteins
Can humans digest cellulose? why?
NO
Humans do not possess an enzyme capable of digesting cellulose (cellulase) and hence it passes through the body undigested
Where does protein digestion begin?
Protein digestion begins in the stomach with the release of proteases that function optimally in an acidic pH (e.g. pepsin = pH 2)
What type of proteins enters the small intestine and what breaks them down?
Smaller polypeptide chains enter the small intestine where they are broken down by endopeptidases released by the pancreas
What is the optimum for endopeptidases?
These endopeptidases work optimally in neutral environments (pH ~ 7) as the pancreas neutralises the acids in the intestine
Where does lipid breakdown occur?
Lipid breakdown occurs in the intestines, beginning with emulsification of fat globules by bile released from the gall bladder
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| Term | Definition |
|---|---|
Where are enzymes used for disaccharide hydrolysis usually located? | Enzymes for disaccharide hydrolysis are often immobilised on the epithelial lining of the small intestine, near channel proteins |
Can humans digest cellulose? why? | NO
Humans do not possess an enzyme capable of digesting cellulose (cellulase) and hence it passes through the body undigested |
Where does protein digestion begin? | Protein digestion begins in the stomach with the release of proteases that function optimally in an acidic pH (e.g. pepsin = pH 2) |
What type of proteins enters the small intestine and what breaks them down? | Smaller polypeptide chains enter the small intestine where they are broken down by endopeptidases released by the pancreas |
What is the optimum for endopeptidases? | These endopeptidases work optimally in neutral environments (pH ~ 7) as the pancreas neutralises the acids in the intestine |
Where does lipid breakdown occur? | Lipid breakdown occurs in the intestines, beginning with emulsification of fat globules by bile released from the gall bladder |
What breaks down lipids after emulsification? | The smaller fat droplets are then digested by lipases released from the pancreas |
What does the pancreas secrete, apart from digestive enzymes? | The pancreas also releases nucleases which digest nucleic acids (DNA, RNA) into smaller nucleosides |
What is the role of human intestines? | The human intestines function to absorb the products of digestion and have specialised structures to fulfil this function |
What is the small intestine composed of? (4) | serosa; muscle layer; submucosa; mucosa |
What is the serosa? | a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue |
What is the muscle layer? | outer layer of longitudinal muscle (peristalsis) and inner layer of circular muscle (segmentation) |
What is the submucosa? | composed of connective tissue separating the muscle layer from the innermost mucosa |
What is the mucosa? | a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen |
How is the inner epithelial intestine arranged? | The inner epithelial lining of the intestine is highly folded into finger-like projections called villi (singular: villus) |
What is the role of the villi? | Many villi will protrude into the intestinal lumen, greatly increasing the available surface area for material absorption |
What features do villi have to facilitate the absorption of digestive products (monomers, ions and vitamins)? | Microvilli; Rich blood supply; Single-layer epithelium; Lacteals; Intestinal glands; Membrane proteins; Mr Slim |
How do microvilli facilitate absorption of digestive products? | Ruffling of epithelial membrane further increases surface area |
How does a rich blood supply facilitate absorption of digestive products? | Dense capillary network rapidly transports absorbed products |
How does a single layer epithelium facilitate absorption of digestive products? | Minimises diffusion distance between lumen and blood |
How do intestinal glands facilitate absorption of digestive products? | Exocrine pits (crypts of Lieberkuhn) release digestive juices |
How do lacteals facilitate absorption of digestive products? | Absorbs lipids from the intestine into the lymphatic system |
How do membrane proteins facilitate absorption of digestive products? | Facilitates transport of digested materials into epithelial cells |
What 4 features does the epithelial lining of villi to optimise capacity to absorb digested materials? | tight junctions microvilli mitochondria pinocytosis vesicles |
What are tight junctions? | Occluding associations between the plasma membrane of two adjacent cells, creating an impermeable barrier |