The digestive system Flashcards
What does the digestive system consist of?
the gut/alimentary canal
associated glands
What is the gut?
a long muscular tube that stretches from the mouth to anus
Are the contents of the gut inside the body?
NO
What is digestion?
(KEY DEFINITION)
the process in which large biological molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed across cell membranes and assimilated
What are endopeptidases?
hydrolyse internal peptide bonds to form smaller polypeptide chains
What are exopeptidases?
hydrolyse terminal peptide bonds to form single amino acids or dipeptides
What is dipeptidases?
hydrolyse dipeptides into amino acids
Describe the basic breakdown of carbohydrate/starch in the gut
starch is hydrolysed by amylase, leaving maltose
maltose is then hydrolysed by maltase, leaving glucose
What is broken during the digestion of carbohydrates?
glycosidic bonds
What enzymes are embedded in the cell membrane?
maltase
dipeptidase
What are the organs involved in the digestive system?
-oesophagus
-stomach
-small intestine/duodenum
-small intestine/ileum
-large intestine
-rectum
What are the glands involved in the digestive system?
-salivary gland
-pancreas
What are the four stages to digestion?
-ingestion
-digestion
-absorption
-egestion
What is ingestion?
food is taken into the mouth
What is digestion?
(stage description)
enzymes break large insoluble molecules into small insoluble ones
What is absorption?
the products of digestion are absorbed through the lining of the intestine
What is egestion?
the removal of faeces containing:
-undigested food
-bacteria
-cells from the intestine lining
-enzymes
Explain the advantages of endopeptidases hydrolysing proteins before exopeptidases?
the endopeptidases will break down the polypeptide chain into smaller chains, leaving more terminal peptide bonds exposed for the exopeptidases to hydrolyse
Why is the lining of the stomach covered in thick mucus?
to protect the stomach lining from being digested by the protein enzymes
List the similarities and differences between carbohydrate and protein digestion
similarities:
-both have enzymes which are embedded in the cell membrane
differences:
-both have different enzymes (dipeptidase/amylase)
-protein digestion is in the stomach + small intestine
-carbohydrate digestion is in the small intestine only
Describe the digestion of lipids
lipids are emulsified by bile into emulsified lipids/small fat droplets, which are hydrolysed into fatty acids and glycerol
Explain lipid absorption
lipids are hydrolysed into glycerol, fatty acids, and monoglycerides; then monoglycerides and fatty acids associate with bile salts to form micelles
What are micelles?
droplets that are about 200 times smaller than the small fat droplets in the emulsified lipids
What do micelles do and how?
they transport the poorly soluble monoglycerides and fatty acids to the surface of the epithelial cells where they can be absorbed- the micelles constantly break up and reform which allows them to release the monoglycerides and fatty acids so they can be absorbed (whole micelles are not absorbed)
