Digestion And Absorption Flashcards
(18 cards)
What is digestion ?
Process of hydrolytic enzymes hydrolysing large insoluble food molecules into smaller soluble molecules which can be absorbed and assimilated through lining of intestine
What do salivary glands produce ?
Salivary amylase
What does the stomach produce ?
Endo and exopeptidases
What does the pancreas produce ?
Pancreatic amylase
Lipases
Exopeptidases
What does the ileum produce ?
Membrane bound dipeptidases and dissacharidases
How is starch digested ?
- Food mechanically digested in mouth by teeth to increase surface area of substance
- Salivary amylase produce by salivary glands is secreted and starts to hydrolyse glycosidic bonds in starch producing maltose
- Salivary amylase denatures in the stomach due to pH acidity
- Pancreatic amylase breakdown any remaining starch into maltose
- Membrane bound maltase in small intestine hydrolyses maltose into glucose
- Glucose absorbed in ileum
Give examples of membrane bound dissacharidases:
Maltase
Lactase
Sucrase
How is glucose absorbed ?
- Sodium ions actively transport out of epithelial cell into blood via sodium potassium pump which requires ATP.
- This creates a concentration gradient of sodium ions between lumen of ileum and epithelial cells
- Sodium ions and glucose enter epithelial cell from lumen of small intestine using co transporter proteins via facilitated diffusion down a concentration gradient
- Glucose then moves into blood from epithelial cells by facilitated diffusion using carrier proteins
What’re endopeptidases ?
- Released from stomach and pancreas
- Hydrolyse internal peptide bonds of polypeptide
- Produces smaller/shorter polypeptide chains
- Increase surface area for next enzyme
- Making digestion faster and efficient
What’re exopeptidases?
Released from pancreas
Work in small intestine
Hydrolyses peptide bonds at terminal ends of polypeptide chains
Produced amino acids or dipeptides
What are dipeptidases ?
- Embedded within cell surface membrane of epithelial cells
- They hydrolyse single peptide bonds in dipeptide
- forming amino acids
How are amino acids absorbed ?
- Sodium ions AT from epithelial cells into blood by sodium potassium pump which requires ATP
- This creates a concentration gradient for sodium ions
- Sodium ions and amino acids enter epithelial cell from lumen of small intestine via facilitated diffusion using co transport proteins
- Amino acids then move from epithelia cell into blood via facilitated diffusion
Where does lipid digestion occur ?
In the lumen of the ileum
What is lipid turned into ?
Fat droplets in the stomach
Where is bile produced, stored and released ?
Liver
Stored in gall bladder
Released to small intestine
What does bile contain ?
Bike salted which emulsify fat droplets and form micelles which increase surface area for lipasase
What do lipases hydrolyse ?
Lipids into glycerol, fatty acids and monoglycerides
How is lipid digested and absorbed ?
- Lipid droplets mix wi bile salts to form smaller droplets (emulsification)
- Smaller droplets increase SAnfor faster hydrolysis by lipases
- Triglycerides hydrolysed into glycerol, fatty acids and monoglycerides
- Bile salts, fatty acids form micelles
- Micelles make fatty acids soluble and brings them to surface of epithelial cell membrane
- Fatty acids, glycerol and monoglycerides enter epithelial cell via simple diffusion
- Smooth endoplasmic reticulum reforms triglyceride
- Golgi apparatus triglycerides are modified to form lipoproteins (chylomicrons) and packaged into vesicles
- Chylomicrons are transported into lymph vessel by exocytosis
- They then enter the blood
