Enzymes and digestion in humans Flashcards
What is the role of the oesophagus?
Carries food from the mouth to the stomach
What is the structure and role of the stomach?
A muscular sac with an inner layer that produces enzymes
- Stores and digests food
- Has glands which release enzymes that digest proteins
What is the structure and role of the illeum?
- Long muscular tube where food is further digested by enzymes that produced by walls and glands which release their secretions into it
-Inner walls of the illeum are folded into villi which gives them a large surface area - ## The SA of these is further increased by millions of tiny projections called microvilli on the epithelial cells of each villus
What is the structure and role of the large intestine?
- This absorbs water, which has mainly been released from the secretions of other digestive glands
What is the role of the rectum?
Final section of the intestines, faeces are stored here before being periodically removed during egestion
What is the role of the salivary glands?
- Near the mouth, passing their secretions through a duct into the mouth
-Secretions contain amalayse which hydrolyses starch into maltose
Describe the function of proteases
Hydrolyses proteins into amino acids
Describe the process of physical digestion
-When food is large it is broken into smaller pieces by structures such as teeth in order for it to be injested
- Provides a large surface area for chemical digestion (enzymes)
- Food is also churned by muscular walls of the stomach physcially breaking it up
Give 2 other common dissacharides found in food that are hydrolysed by a membrane bound dissacharidase in digestion
- Sucrose is found in fruits, and sucrase will hydrolyse the single glysosidic bond in the sucrose producing glucose and fructose monosachharides
- Lactose is found in milk and is hydrolysed into the monoscaharides glucose and galactose
Describe the functions of carbohydrases
- Hydrolyses cabohydrates into monosaccharides
Describe the process of chemical digestion
Involves enzymes which hydolyse bonds in food molecules
-Food is hydrolysed from large insoluble molecules into smaller soluble molecules by enzymes
- Hydrolysis is when water is added to chemical bonds holding molecules together
- More than one enzyme might be required to fully hydrolyse a large molecule
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What is the role of the pancreas?
- Large gland below the stomach releasing pancreatic juice
- This juice contains amalayse to hydrolyse starch, protease to hydrolyse proteins and lipase to hydrolyse lipids
Describe the function of lipases
- Hydrolyses lipids into fatty acids and glycerol
Describe all the bodily processes of carbohydrate digestion
- Saliva enters the mouth from salivary glands and is mixed with food during chewing
- This saliva contains amylase and will hydrolyse any starch in the food to maltose, and it also contains mineral salts which will maintain an optimum PH of neutral for amylase to work
- Food is then swallowed entering the stomach with acidic conditions meaning amylase is denatured preventing any further hydrolysis of starch
- Food is then passed to SI, mixing with pancreatic juice secreted by the pancreas
- Pancreatic amylase in the juice will then digest any remaining starch to maltose, alkaline salts will then also be released by pancreas and intestinal walls to maintain a PH of neutral so amylase can function
- Muscles in intestinal walls push food along the illeum and its lining produces maltase ( not released into the lumen)
- This membrane bound disaccharidase hydrolyses the maltose into a glucose
How are lipids digested in the digestive system?
- Lipids are hydrolysed by lipases which are enzymes produced by the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides
- A monoglyceride is a glycerol molecule attached to a single fatty acid
- Lipids are first split up into tiny micelles by bile salts which are produced by the liver, this process is called emulsification and increases the SA at which lipase can work on
How are proteins digested?
By multiple types of peptidases which hydrolyse proteins
- Endopeptidases hydrolyse peptide bonds between amino acids in the central region of a protein forming individual peptides
- Exopeptidases hydrolyse peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases meaning they release dipeptides and single amino acids
- Membrane bound dipeptidases hydrolyse the bond between two amino acids of a dipeptide, they are found on the cell surface membrane of epithelial cells lining the illeum
