Starch Digestion
Since enzymes are specific, it takes many to break down large molecules into its monomers. The reason different enzymes are produced at different parts of the digestive system, is because they often have a different optimum pH.
Mouth
-food is taken into the mouth and chewed by the teeth (mechanical) which breaks it into small pieces to increase its surface area.
-saliva containing salivary amylase is secreted from the salivary glands and is mixed with the food to begin starch digestion and to lubricate the food for swallowing.
-amylase hydrolyses the alternate glycocidic bonds of the starch molecule, making maltose (a disaccharide)
-the optimum pH here is neutral and mineral salts maintain this.
Stomach
-the food is swallowed and enters the stomach where the conditions are acidic (pH 2).
-this acidity denatures the amylase and prevents further hydrolysis of starch.
Small Intestine
-then, the food is passed into the small intestine where it mixes with the pancreatic juices secreted by the pancreas
-the pancreatic juice contains pancreatic amylase which continues the hydrolysis of remaining starch into maltose.
-a neutral pH is maintained my alkaline salts (sodium hydrocarbonate) produced by the pancreas and the intestinal wall.
-the epithelial lining produces maltase which hydrolyses maltose into alpha-glucose (a monosaccharide)
Mouth
-food is taken into the mouth and chewed by the teeth (mechanical) which breaks it into small pieces to increase its surface area.
-saliva containing salivary amylase is secreted from the salivary glands and is mixed with the food to begin starch digestion and to lubricate the food for swallowing.
-amylase hydrolyses the alternate glycocidic bonds of the starch molecule, making maltose (a disaccharide)
-the optimum pH here is neutral and mineral salts maintain this.
Stomach
-the food is swallowed and enters the stomach where the conditions are acidic (pH 2).
-this acidity denatures the amylase and prevents further hydrolysis of starch.
Small Intestine
-then, the food is passed into the small intestine where it mixes with the pancreatic juices secreted by the pancreas
-the pancreatic juice contains pancreatic amylase which continues the hydrolysis of remaining starch into maltose.
-a neutral pH is maintained my alkaline salts (sodium hydrocarbonate) produced by the pancreas and the intestinal wall.
-the epithelial lining produces maltase which hydrolyses maltose into alpha-glucose (a monosaccharide)
Disaccharide Digestion
In addition to maltose digestion, there are two other dissacharides that we need to know about the break down of; sucrose and lactose.
Sucrose
-in natural foods, sucrose is contained within cells which are physically broken down by teeth.
-the intestine's epithelial lining produces sucrase.
-sucrase hydrolyses the sucrose's glycocidic bond to produce alpha-glucose and fructose.
Lactose
-lactose is found in milk/dairy products.
-the intestine's epithelial lining produces lactase.
-lactase hydrolyses the lactose's glycocidic bond to produce alpha-glucose and glucose.
Sucrose
-in natural foods, sucrose is contained within cells which are physically broken down by teeth.
-the intestine's epithelial lining produces sucrase.
-sucrase hydrolyses the sucrose's glycocidic bond to produce alpha-glucose and fructose.
Lactose
-lactose is found in milk/dairy products.
-the intestine's epithelial lining produces lactase.
-lactase hydrolyses the lactose's glycocidic bond to produce alpha-glucose and glucose.
Lactose Intolerance
Cause
-babies produce lots of lactase since all they can only consume milk.
-as you get older, you consume less milk and so naturally your production of lactase decreases.
-however, for some people the decrease is so great that they produce very little or no lactase.
-this may not of been a problem in the past, but now we have modern storage and advanced distribution methods so we are using more dairy.
Effect
-therefore, some people do not produce enough lactase to meet the levels of lactose they consume.
-when the undigested lactose reaches the large intestine, microorganisms break it down, which releases gas, causing the person to feel bloated.
-it can also result in diarrhoea because soluble molecules will lower the water potential of the material in the colon, creating a water potential gradient which causes water to move by osmosis from, the epithelial cells into the lumen.
-people with the condition may have to limit their dairy intake or even completely eliminate it.
-to make up for avoided calcium, lactose intolerant people should eat calcium rich foods or add lactase enzyme to milk before drinking it.
-babies produce lots of lactase since all they can only consume milk.
-as you get older, you consume less milk and so naturally your production of lactase decreases.
-however, for some people the decrease is so great that they produce very little or no lactase.
-this may not of been a problem in the past, but now we have modern storage and advanced distribution methods so we are using more dairy.
Effect
-therefore, some people do not produce enough lactase to meet the levels of lactose they consume.
-when the undigested lactose reaches the large intestine, microorganisms break it down, which releases gas, causing the person to feel bloated.
-it can also result in diarrhoea because soluble molecules will lower the water potential of the material in the colon, creating a water potential gradient which causes water to move by osmosis from, the epithelial cells into the lumen.
-people with the condition may have to limit their dairy intake or even completely eliminate it.
-to make up for avoided calcium, lactose intolerant people should eat calcium rich foods or add lactase enzyme to milk before drinking it.