Digestion Flashcards
Where does carbohydrate digestion take place?
- mouth (salivary amylase).
- oesophagus and stomach (VERY LITTLE).
- duodenum (pancreatic amylase and brush border enzymes; maltase, sucrase and lactase).
Where does digestion of proteins take place?
- stomach (HCL and pepsin).
- pancreas (trypsin and chymotrypsin, carboxypeptidase).
- brush border enzymes (aminopeptidase and dipetidase).
Where does digestion of lipids take place?
- mouth (lingual lipase).
- stomach (gastric lipase).
- small intestine (bile and pancreatic lipase).
Where does the digestion of nucleic acids take place?
- pancreatic juice secretes two nucleases (ribonuclease and deoxyribonuclease).
- brush border enzymes.
- all absorbed by active transport.
What carbohyrdrates move into the epithelial cell?
Glucose and galactose (secondary active transport- sodium symporter).
Fructose (facilitated diffusion).
How do carbohydrates move out of the epithelial cells and into the bloodstream?
Facilitated diffusion.
How are amino acids absorbed into the epithelial cells?
Active transport with Na+ or H+ ions (symporters).
How do amino acids move out of the epithelial cells?
Diffusion.
Absorption in the small intestine.
-90% total.
-mostly duodenum and jejenum.
-ultimately depends upon cell membrane transport processes.
-gut lumen -> mucosa -> blood caps -> HPV -> liver.
OR
-gut lumen -> mucosa -> lacteals -> lymphatic vessels -> thoracic duct -> Left subclavian vein -> liver.
Absorption of vitamins.
Diffusion.
B12 combines with intrinsic factor before it is transported into cells
Sources of electrolytes?
GI secretions and ingested foods and lipids.
Absorption of electrolytes.
Diffusion or secondary active transport.
Absorption of water.
-9L of fluid enters GI each day,
Small intestine reabsorbs 8L.
Large intestine reabsorbs 90% of the last litre.
-osmosis into vascular capillaries inside villi.
