Digestion ( 1 ) Flashcards
What are the two types of digestion?
- Physical Digestion
* Chemical Digestion
Why is physical digestion needed?
- Food may be very large, it can be broken down into smaller pieces through structures such as the teeth, or getting churned by muscles in the stomach wall
- This makes it possible to ingest the food.
- Provides a larger surface area for chemical digestion
What is the purpose of chemical digestion?
Hydrolyses large, insoluble molecules into smaller soluble ones.
What is chemical digestion carried out by?
Enzymes
By which process do all enzymes carry out chemical digestion?
Hydrolysis
What is hydrolysis?
Hydrolysis is the splitting up of molecules by adding water to the chemical bonds so that hold them together
Why is more than one molecule required to hydrolyse a large molecule?
Enzymes are specific, a large molecule may consist of many different molecules
What are the main three enzymes involved in chemical digestion?
- Carbohydrase - hydrolyses carbohydrates, to monosaccharides
- Lipases - Hydrolyse lipids into glycerol and fatty acids
- Proteases - Hydrolyse proteins to amino acids
What occurs during chemical digestion?
- One enzyme hydrolyses a large molecule into sections
* These sections are then hydrolysed into smaller molecules by one or more additional enzymes
What are carbohydrates broken down into, and by what?
- Carbohydrase breaks them down
* Broken down into disaccharides and then monosaccharides
What are fats broken down into, and by what?
- Lipases break them down
* Broken down into fatty acids and monoglycerides
What are proteins broken down into, and by what?
- Protease breaks them down
* Broken down into fatty acids and monoglycerides
Where is the enzyme amylase produced?
- Mouth
* Pancreas
What does amylase do?
• Hydrolyses the alternate glycosidic bonds of the starch molecule to produce the disaccharide maltose.
What does maltose get hydrolysed into, and by what?
- Maltose is hydrolysed into the monosaccharide alpha glucose by a second enzyme
- Maltase breaks down maltose
What is maltase produced by?
lining of the ileum
What does saliva contain?
Salivary Amylase
What is the process of carbohydrate digestion in the mouth?
- Saliva enters the mouth from the salivary glands, and is mixed with food during chewing
- Saliva containing salivary amylase starts hydrolysing any starch in the food to maltose
- Contains mineral salts that help maintain the pH at neutral levels, as it is the optimal pH for salivary amylase to function
What is the optimal pH for salivary amylase?
Neutral
How is the pH maintained in the mouth?
Saliva contains mineral salts that help maintain the pH at neutral levels
What is the process of carbohydrate digestion in the stomach?
- Food is swallowed and enters the stomach
- Conditions are acidic in the stomach
- Acid denatures the amylase and prevents further hydrolysation of the starch
- After some time time the food food is passed into the small intestine
What is the process of carbohydrate digestion in the small intestine?
- In the small intestine, food mixes with the secretion from pancreas ( known as pancreatic juice )
- Pancreatic juice contains pancreatic amylase, this continues the hydrolysis of any remaining starch to maltose
- Alkaline salts are produced by both the pancreas and the intestinal wall to maintain pH at neutral so that the amylase can function
- Muscles in the intestine wall push the food along the ileum
- Epithelial lining produces maltase, maltase is not released into the lumen of the ileum but is part of the cell surface membrane of the epithelial cells that line the ileum
- Referred to as a membrane bound disaccharide
- Maltase hydrolyses the maltose from starch breakdown into alpha glucose
What do the muscles in the intestine wall do?
Push food along the ileum
Where is maltase produced in the intestine?
- Epithelial lining produces maltase
* Maltase is not released into the lumen, but a part oif the cell surface membrane of epithelial cells
How is the pH maintained in the ileum?
• Alkaline salts produced by both the pancreas and intestinal wall maintain pH at neutral so amylase can function
What are the alkaline salts produced by?
Pancreas and intestinal wall
What does the pancreatic juice contain?
Pancreatic amylase which continues hydrolysis of starch to maltose
