Digestive System Flashcards
What is the role of the large intestine?
Absorb water
What are the 2 types of digestion?
Physical and chemical
What is the process by which fatty acids and glycerol enter the intestinal epithelial cell?
Diffusion
What is the action of salivary amylase?
Hydrolyses glycosisdic bond in starch to convert: starch —> maltose
How is the optimum neutral pH for amylase maintained in the mouth?
saliva contains mineral salts
Explain why alkaline salts are produced/where
to maintain a neutral pH for pancreatic amylase
-produces in pancreas and intestinal wall
What does sucrase hydrolyse/ products of this
sucrose–>
glucose+fructose
What does maltase hydrolyse/products of this
maltose –>
glucose+glucose
What does lactase hydrolyse/products of this
lactose–>
glucose+galactose
what is meant by ‘membrane bound disaccharidase’?
The disaccharidase is bound to Cell surface membrane of epithelial cells lining the ileum rather than being released into the intestine
What is the function of lipase/ what products does it form?
hydrolyse the ester bond in triglycerides to form monoglycerides and two fatty acids
What is the role of the liver in lipid digestion?
produces bile salts that emulsify fat
Explain why emulsification increases the rate of lipid digestion.
increases the surface area for lipase action
What is the group of enzymes that hydrolyse proteins?
peptidases
What is the function of endopeptidases?
hydrolyse peptide bonds in the centre of a protein molecule forming smaller peptides
What is the function of exopeptidases?
hydrolyse peptide bonds on the terminal amino acids of peptides to form dipeptides and single amino acids
What is the function of membrane bound dipeptidases?
hydrolyse dipeptides into amino acids
What is the structure of the ileum?
Folded, villi containing epithelial cells which contain capillaries and microvilli
how is the ileum is adapted for absorption?
-Villi - finger-like projections.
-Many blood capillaries, maintain diffusion gradient. Increase SA for diffusion.
-Thin walls so short diffusion pathway.
-Epithelial cells of villi have microvilli further increasing SA
How are triglycerides absorbed
- Micelle collides with the epithelial cell wall which releases monoglyceride, bile salt and fatty acids
- these diffuse into the cell
- go to SER where triglyceride is reformed
- goes to golgi apparatus where triglyceride combines with cholesterol and a lipoprotein to form a chylomicron
- moves out of cell by exocytosis into the lacteal
- transported to capillary
- hydrolysed by a membrane bound enzyme on the endothelium
- monoglyceride and fatty acids then absorbed into cells
where are membrane bound dipeptidases often located?
on the cell surface membrane of epithelial cells in small intestine
where is amylase produced
-salivary glands-release amylase into mouth
-pancreas-releases amylase into small intestine
what two types of enzyme can break down carbohydrates
amylase or membrane bound disacharidases
what is the ileum
-section of small intestine covered in villi, which are covered in epithelial cells
Where are bile salts produces?
the liver
How to bile salts aid in the hydrolysis of lipids by lipase?
-emulsify lipids, breaking them down inot small droplets increasing SA for lipases to work on
How are amino acids absorbed?
-sodium ions actively transported out of the ileum epithelial cells into the blood
-this creates a sodium ion conc. gradient
-sodium ions then diffuse from the lumen of the ileum into the epithelial cells through sodium dependant transport proteins, carrying a/a w/ them
How are micelles formed
-once the lipid has been broken down, the monoglycerides and fatty acids stick with the bile salts to form micelles
How do micelles aid in the absorption of monoglycerides and fatty acids
-micelles help to move monoglycerides and fatty acids towards the ileum
-micelles are constantly breaking and reforming
-this allows monoglycerides and fatty acids to be diffuse directly across the epithelial cell membrae
( as they are lipid-soluble)
What happens to the products of digestion
-the products of digestion are absorbed by the ileum epithelium into the blood stream
list three organeles/reasons why, that you would expect to be numerous /well developed in the epithelial cell of the ileum
-Endoplasmic reticulum to resynthesize tricglycerides from monoglycerides and fatty acids
-golgi apparatus to form chylomicrons from triglycerides, cholesterol, and lipoproteins
-mitochondria to provide ATP required for for co-transport of glucose and a/a molecules
How is glucose/ galactose absorbed
-absorbed into ileum epithelium by active transport with sodium ions via a co-transport protein
-galactose absorbed same way via a different transporter protein
how is fructose absorbed
-by facillitated diffusion through a different transporter protein
