Digestion Flashcards
what do the salivary glands produce?
salivary amylase and saliva
what do the salivary glands do?
lubricate food to make it easier to swallow
what does the liver produce?
bile and urea
what does the liver store?
glycogen, iron, vitamins, ADEK
what does the liver remove?
toxins
what does the gall bladder store?
bile
what is the ileum?
a long, muscular tube
what does the ileum absorb?
soluble food into the bloodstream
how does the oesophagus move?
peristalsis
what does the oesophagus carry?
food from the mouth to the stomach
what is the stomach?
a muscular sac with an inner layer that produces enzymes
what does the stomach do?
stores and digests food
what does the HCL acid in the stomach do?
neutralises bacteria
what does the pancreas secrete?
digestive enzymes and neutraliser (sodium hydrogen carbonate)
what does the large intestines store?
faeces in the rectum
what do the villi of the iluem do?
increase SA for faster absorption of soluble food
where are microvilli found?
on the epithelial cells of the lining of the ileum
how is the lining of the ileum adapted for quick absorption?
one cell thick and rich blood supply
where is bile produced?
liver
where is bile stored?
gall bladder
where is bile released into?
small intestine
what does bile do?
emulsifies fats and neutralises stomach acid
what is the purpose of digestion?
hydrolyse large, insoluble molecules into small soluble molecules so they can be absorbed and assimilated
what is physical digestion?
structures like teeth break down large food into smaller pieces to increase SA
what is chemical digestion?
enzymes hydrolyse large, insoluble molecules into small, soluble molecules
what enzyme hydrolyses starch?
salivary and pancreatic amylase
what enzyme hydrolyses maltose?
maltase
what enzyme hydrolyses sucrose?
sucrase
what enzyme hydrolyses lactose?
lactase
what enzyme hydrolyses lipids?
lipase
what enzyme hydrolyses proteins?
endo-peptidase, exo-peptidase, and dipeptidases
what is the product of the hydrolysis of starch?
maltose
what is the product of the hydrolysis of maltose?
2x alpha glucose
what is the product of the hydrolysis of sucrose?
alpha glucose and fructose
what is the product of the hydrolysis of lactose?
alpha glucose and galactose
what is the product of the hydrolysis of lipids?
3 fatty acids and 1 glycerol
what is the product of the hydrolysis of protein?
endo-peptidase = peptides exo-peptidase = peptides dipeptidases = amino acids
How many enzymes does it take to completely hydrolyse a starch molecule?
more than one
How must enzymes be added when hydrolysing starch?
in the right order
Hydrolysis of starch step 1
saliva enters the mouth from the salivary glands and mixes with food
Hydrolysis of starch step 2
salivary amylase hydrolyses starch to maltose
what does saliva also contain?
mineral salts to maintain pH at neutral (optimum for salivary amylase)
Hydrolysis of starch step 3
food enters stomach. Acidic conditions denature the amylase, preventing further hydrolysis of starch
Hydrolysis of starch step 4
food in small intestine mixes with pancreatic juice which contains pancreatic amylase. This hydrolyses the remaining starch to maltose.
What do alkaline salts do?
keep pH neutral so the amylase can function
where are alkaline salts produced?
pancreas and intestinal wall
Hydrolysis of starch step 5
the epithelial lining of the ileum produces maltase which hydrolyses the maltose into alpha glucose
what is maltase?
a membrane-bound disaccharide
what is maltase a part of?
the cell surface membrane of the epithelial cells lining the ileum
what bond do lipases hydrolyse?
the ester bond in triglycerides
what is formed when lipase hydrolyses a triglyceride?
fatty acids and monoglycerides
what is a monoglyceride?
a glycerol molecule with a single fatty acid molecule attached
what do bile salts produced in the liver do?
emulsify lipids into tiny droplets called micelles
what do endo-peptidases hydrolyse?
the peptide bonds between amino acids in the central region of a protein. This forms peptides.
what do exo-peptidases hydrolyse?
the peptide bonds on the terminal amino acids of the peptides formed from endo-peptidase hydrolysis.
what do dipeptidases hydrolyse?
the bond between the 2 amino acids of a dipeptide.
are dipeptidases membrane-bound?
yes - they are part of the cell surface membrane of the epithelial cells lining the ileum
ingestion
putting food into the alimentary canal/digestive system
digestion
breakdown of large insoluble molecules into small soluble ones
absorption
the uptake of soluble food molecules into body cells
assimilation
incorporation and use of soluble food molecules into body cells
egestion
removal of undigested food from the body
what is the ileum adapted for?
absorbing the products of digestion
how long are villi?
1mm
where do villi sit?
the interface between the lumen (cavity) of the intestines, and the blood and tissues inside the body
what do the villi do?
increase SA for diffusion
what do the thin walls of the villi do?
reduce the distance diffusion takes place over
what do the muscles of the villi do?
allow them to move. This helps maintain a diffusion gradient as the movement mixes the content of the ileum, so new material rich in digestion products is readily available
what does a good blood vessel supply to the villi do?
maintain a diffusion gradient
what do microvilli do?
increase SA for absorption
absorption of triglycerides step 1
fatty acids and monoglycerides emulsified by bile then hydrolysed by lipase
bile salts surround the digestion products to form micelles
absorption of triglycerides step 2
micelles come into contact with the epithelial cells lining the villi of the ileum and breakdown
this releases the monoglycerides and fatty acids.
these are non-polar so diffuse easily into the epithelial cells across the CSM
absorption of triglycerides step 3
inside the epithelial cells monoglycerides and fatty acids are transported to the SER where they recombine to form trigylcerides
absorption of triglycerides step 4
in the golgi apparatus triglycerides associate with cholesterol and lipoproteins to form chylomicrons (special particles adapted for the transport of lipids)
absorption of triglycerides step 5
chylomicrons move out the epithelial cells by exocytosis. They enter lymphatic capillaries celled lacteals in the centre of each villus
absorption of triglycerides step 6
chylomicrons pass via lymphatic vessels into the blood system. The triglycerides inside are hydrolysed by an enzyme in the endothelial cells of blood capillaries where they diffuse into cells.
