Digestion And Absorption Flashcards
Digestion of starch
Food enters the month and is broken up by the teeth by mechanical digestion and then mixed with saliva
Saliva contains salivary amylase which hydrolysis glycolytic bonds in starch producing maltose
In the stomach, the salivary amylase is denatured due to acidic pH
In the small intestine pancreatic amylase continues to hydrolyse starch into maltose
Maltose is then hydrolysed into glucose by Maltase enzymes embedded in the epithelial cell membrane.
Glucose is small enough to be absorbed
Co transport of glucose
Sodium ions actively transported all the epithelial salt into the blood via the sodium potassium pump
This creates a concentration gradient of sodium between the lumen of the illium and the epithelial cell
Co transporter proteins have two binding sites complementary sodium and glucose only when both molecules bind with the molecules be moved across the membrane
Sodium and glucose enter by facilitated diffusion using complementary co transporter proteins
Sodium ions diffuse into the cell down its concentration gradient
Glucose move into the cell against its concentration gradient
Glucose moves into the blood by facilitated diffusion
Protein digestion
Proteins and polypeptide are hydrolysed by enzymes called proteases in the stomach
Endopeptidases hydrolyse the peptide bonds within the polypeptide chain
This produces smaller polypeptide chains and increase the surface area for next enzyme making digestion more faster and efficient
Exopeptiadeses hydrolyse the peptide bonds at the terminal ends of the protein removing one amino acid at a time producing dipeptides
Diptidases are enzymes embedded in the cell surface membrane of the epithelial cells. They hydrolysed diet peptides into amino acids which can now be absorbed by facilitated diffusion active transport and co transport
Co-transport of amino acids
Sodium ions activity transported out the epithelial cell into the blood via the sodium potassium pump
This creates a concentration gradient of sodium ions between the lumen of the illium and the epithelial cells
Sodium and amino acids enter by facilitated diffusion
Sodium ions move into the cell down its concentration gradient
Amino acids move into the cell against their concentration gradient
Amino acids move into the blood by facilitated diffusion
Lipid digestion
Bile is produced in the liver and stored in the gallbladder and it is released into the small intestine with the food
Lipid droplets are mixed with bile salts to form smaller droplets so they are emulsified
This increases surface area for faster hydrolysis by lipase
Triglycerides are hydrolyse into glycerol fatty acids are monoglycerides
Bile salts, glycerol and fatty acids form micelles
Micelles make fatty acid soluble in water and bring fatty acids to the surface of the epithelial cell membrane
Fatty acids enter the epithelial cells by simple diffusion
At the smooth endoplasmic reticulum fatty acids glycerol are recombined to form triglycerides
At the Golgi apparatus triglycerides are modified into proteins called chylomicrons
Chylomicrons are water soluble and salt can be carried in the blood. They are transported into a lymph vessel by exocytosis
