Digestion

• Amylase is an enzyme produced by the salivary glands and pancreas that breaks down starch into maltose
• The gall bladder is where bile is stored
• The duodenum is between the stomach and the small intestine
• The ilium is a small part of the small intestine used for absorption
• The stomach churns food and provides chemical digestion
• The digestive enzymes are endopeptidase, exopeptidase, lipase, amylase, maltase, dipeptidase
• The function of stomach acid is to emulsify lipids into smaller molecules/increase their surface area
• Exopeptidase will hydrolyse proteins by the terminals
• Endopeptidse will hydrolyse peptide chains in the centre
• Dipeptidase will hydrolyse dipeptides into amino acids
• Exopeptidase will produce dipeptides, amino acids
• Membrane bound maltase in the ilium hydrolyses maltose close to a columnar epithelial cell for absorption of alpha glucose
• The large intestine is used for absorption of minerals, water and vitamins
• The liver will produce bile and store glycogen
• Lipase will produce fatty acids and glycerol from lipids
• Micelles are the associations between bile salts, fatty acids and glycerol
• Once the micelle fuses with the cell membrane, fatty acids and glycerol travel to the smooth endoplasmic reticulum to be reassembled as triglycerides
• Once triglycerides are reassembled they travel to the golgi apparatus to be packaged in a chylomicron
• Chylomicrons are water soluble lipoproteins
• A monoglyceride is one fatty acid chain and a glycerol
• Dipeptidase is membrane bound and produces amino acids
• Adaptations for absorption include villi and microvilli increasing surface area, short diffusion paths, good blood supply and muscle contraction maintains concentration gradient
• In cotransport, sodium ions are pumped into the bloodstream and potassium is pumped into the cell in an antiport using ATP, this allows sodium ions in the lumen to diffuse down a concentration gradient into a columnar epithelial cell, as sodium ions diffuse in, glucose or amino acids are pulled into the cell, glucose or amino acids will diffuse into the blood stream through the cell
• Chylomicrons exit the cell via exocytosis and travel to a lacteal, the lymphatic system takes the triglycerides to the thoracic duct where they are released into the bloodstream
• Muscle contractions due to peristalsis will maintain a concentration gradient
• Micelles release fatty acids and glycerol close to the columnar epithelium cells membrane for easy absorption via simple lipid diffusion as they are non polar