Digestion Flashcards
Generally describe the process of digestion
Large biological molecules are hydrolysed by enzymes into smaller molecules that can be absorbed across cell membranes, during digestion
Describe the digestion of carbohydrates by amylase
- Saliva from salivary glands enters the mouth during chewing, it contains salivary amylase which starts hydrolysing starch to maltose 2. Food enters the stomach and the acid denatures amylase (prevents further hydrolysis) 3. Food passed into small intestine where it mixes with pancreatic juice that contains pancreatic amylase which continues hydrolysis 4. Muscles in intestine wall push food along ileum, lining produces maltase (disaccharidase) hydrolysis maltose into a-glucose
Describe the process of lipid digestion
Lipids are firstly split into micelles (tiny droplets) by bile salts produced by the liver, this process is called emulsification and increases the SA so action of lipases is sped up. Lipases are enzymes produced in the pancreas and hydrolyse ester bond in triglyceride to form fatty acids and MONO glycerides (glycerol + 1 fatty acid)
Describe protein digestion
- Endopeptidases hydrolyse peptide bonds between amino acids in central region of protein molecule, forming series of peptide molecules 2. Exopeptidases hydrolyse peptide bonds on terminal AAs of peptide molecules, they release dipeptides and single AAs 3. Dipeptidases hydrolyse peptide bond between 2 AAs of a dipeptide
What does it mean when dipeptidases are membrane bound
As they are part of the cell surface membrane of the epithelial cells lining the ileum
How are villi adapted for absorption
They increase the sa for diffusion, thin walled so diffusion distance is short, have microvilli which increases sa
How are amino acids and monosaccharides absorbed
Absorbed by diffusion and co transport into the ileum
Explain the advantages of lipid droplet and Micelle formation
Micelle/ droplet formation increases their surface area for lipases to act which means a faster rate of hydrolysis of lipids. Micelles also carry fatty acids and monoglycerides through the membrane/ intestinal epithelial cells
How is the Golgi apparatus involved with the absorption of triglycerides
It modifies/ processes triglycerides by combining them with proteins (e.g. cholesterol and lipoproteins) and packages them for release in vesicles for exocytosis
Describe the full process of the absorption of triglycerides
- Micelles come into contact with epithelial cells lining villi of ileum, here they break down, releasing monoglycerides and fatty acids. As they are non polar, they diffuse across the CSM into epithelial cells. 2.In epithelial cells, monoglycerides + fatty acids are transported to the ER where they are recombined to form triglycerides 3. In Golgi apparatus, triglycerides associate with cholesterol and lipoproteins to form chylomicrons 4. Chylomicrons move out of epithelial cells via exocytosis and enter lymphatic capillaries/ lacteals in centre of villli
What is the process of which amino acids and monoglycerides are absorbed and describe it
Co transport:
Na+ ions are actively transported OUT of epithelial cells via sodium potassium pump into the blood 2. This maintains a higher conc of Na+ ions in the lumen of intestine than in epithelial cells 3. Na+ diffuse into the epithelial cells via facilitated diffusion down this conc gradient through a protein carrier but as they diffuse in, they carry either an AA or glucose molecule with them, AGAINST their conc gradient
What is the fluid surrounding epithelial cells and lacteals
Tissue fluid
How could the rough endoplasmic reticulum be involved in lipid absorption
It has ribosomes which synthesis proteins, involved in vesicles formation and The RER also transports the proteins
Why must chylomicrons leave via exocytosis
As they are too large to leave by other methods
