12.9 Digestion and absorption Flashcards
What enzyme is found in the salivary glands?
Salivary amylase
What enzyme is found in the stomach?
Endopeptidase and exopeptidase
What enzyme is found in the pancreas?
Pancreatic amylase, lipases and exopeptidase
What emzyme is found in the ileum?
Membrane bound dipeptidases and dissacharidases
Describe the route of the digestive system
Ingestion
Digestion
Absorption
Ejection
Describe the role of the salivary glands
Secretes salivary amylase which hydrolyses starch to maltose
Describe the role of the stomach
Food is mixed with gastric juices to kill microorganisms and contains endo and exo peptidases to hydrolyse peptides into dipeptides
Describe the role of the pancreas
Secretes pancreatic amylase, endo and eco peptidases and lipases
Describe the role of the small intestine (ileum)
Maltase enzymes are embedded within the epithelium cell membrane to hydrolyse maltose to glucose for rapid absorption
It also contains sucrase, lactase and dipeptidase
How is the ileum adapted for absorption?
Large surface area for absorption of products of digestion
Describe the breakdown of starch
Food enters the mouth and is mixed with saliva and broken down by teeth
Salivary amylase starts to hydrolyse the glycosidic bonds in starch to maltose
The salivary amylase is denatured in the stomach due to high pH
Pancreatic amylase continues ton hydrolyse starch to maltose
Maltose is hydrolysed to glucose by maltase in the membrane of the epithelium cells
Glucose is then absorbed
Summarise amylase
Hydrolyses starch to maltose
Synthesised and secreted from salivary glands and pancreas
Summarise maltase
Hydrolyses maltose to glucose
Found within the epithelium cell membrane of ileum
Describe the co transport of glucose
Sodium ions leave the cell and enter the blood by active transport
Concentration of sodium low in the cell so sodium and glucose enter by facilitated diffusion using co transporter proteins
Sodium diffuses into the cell down the concentration gradient
Glucose moves into the cell against the concentration gradient
Glucose then moves out of the cell, into the blood via facilitated diffusion
Describe protein digestion
Proteins hydrolysed b y proteases in the stomach
Endopeptidases hydrolyse peptide bonds within the polypeptide chain
Producing smaller polypeptide chains
Exopeptidases hydrolyse peptide bonds at the terminal ends of the chain
What is the role of exopeptidases?
Hydrolyses peptide bonds at the terminal ends of the polypeptide chain, removing one amino acid at a time
Specific to one end of the polypeptide chain - either C or N terminal
What is the role of endopeptidases?
Hydrolyses peptide bonds within the polypeptide chain
Increases surface area for faster and more efficient digestion
Where is bile produced and stored?
Produced in the liver
Stored in the gall bladder
What does bile contain?
Bile salts
What do bile salts do?
Emulsify fat droplets and form micelles
What is the role of lipase?
Hydrolyse lipids into glycerol, fatty acids and monoglycerides
Describe lipid digestion and absorption
Lipids droplets are mixed with bile salts to form smaller droplets
This increases surface area for faster hydrolysis
Triglycerides are hydrolysed into glycerol, fatty acids and monoglycerides
The glycerol and fatty acids form micelles
The micelles make fatty acids soluble in water and bring fatty acids to the surface of the epithelial membrane
Fatty acids enter epithelial membrane by simple diffusion
At the smooth ER, faatty acids ands glycerol recombined to form triglycerides
At the Golgi, triglycerides modified, proteins are added to form lipoproteins called chylomicrons which are transported into lymph vessels by exocytosis
