3. digestion fact test Flashcards
what is the role of the mouth in the digestive system
carries out
physical breakdown (chewing by teeth which increases surface area)
chemical digestion (salivary amylase)
what is the role of the oesophagus in the digestive system
transports food (bolus) from mouth to stomach, facilitated by a wave of muscle contraction
what is the role of the stomach in the digestive system
carries out physical breakdown (contraction of muscular walls to churn the food), temporarily stores food, carries out chemical digestion (glands release proteases) and contains hydrochloric acid
what is the role of the liver in the digestive system
produces bile which contains bile salts. these facilitate lipid digestion due to emulsification
what is the role of the pancreas in the digestive system
secretes pancreatic juice into small intestine
juice contains proteases, lipases and pancreatic amylase
the juices are alkaline to help create optimum pH in ileum
what is the role of the large intestine (colon) in the digestive system
absorbs excess water and ions, contains a plethora of bacteria which produce certain vitamins
what is the role of the rectum in the digestive system
stores compacted, indigestible material (faeces) before it is removed from the body via the anus
what happens in the small intestine (ileum) in the digestive system
where chemical digestion and absorption of soluble food molecules takes place
how is the small intestine adapted to its functions
- villi and microvilli provide a very large surface area for diffusion of food molecules
- epithelium is one cell thick for reduced diffusion distance
- muscle in villi allows movement and increased contact with food molecules
- rich blood supply to maintain diffusion gradient
- lacteals to allow lipid transport
- epithelial cells have many mitochondria to produce ATP and co-transport proteins for active transport
what is physical digestion
breaking down large food molecules into smaller pieces, increases surface area for chemical digestion
what is chemical digestion
hydrolysis of large insoluble molecules into smaller soluble ones, completed by enzymes
what do endopeptidases do
hydrolyse peptide bonds between amino acids in central region of a protein molecule forming a series of peptide molecules
what do exopeptidases do
hydrolyse peptide bonds on the terminal amino acids of peptide molecules
what do dipeptidases do
hydrolyse bond between 2 amino acids of a dipeptide
what enzymes are involved in lipid digestion
lipase
where is lipase made and where does it work
made in pancreas
works in small intestine
what is the substrate which binds to the lipase
triglyceride
what is the product formed after lipase action
fatty acids and monoglycerides
what enzymes are involved in protein digestion
endopeptidases
exopeptidases
dipeptidases
where are endopeptidases made and where do they work
made in stomach and pancreas
work in stomach and small intestine
what substrate binds to endopeptidases
polypeptides
what product is formed from endopeptidase action
short chain polypeptides
where is exopeptidase made and where does it work
made in pancreas
works in small intestine
what is the substrate that binds to exopeptidases
polypeptides
what product is formed from exopeptidase action
shorter chain polypeptides
where is dipeptidase made and where does it work
epithelium of small intestine (membrane-bound)
what is the substrate which binds to dipeptidases
dipeptides
what is the product of dipeptidase action
amino acids
what enzymes are involved in carbohydrate digestion
salivary amylase
pancreatic amylase
maltase
sucrase
lactase
where is salivary amylase made and where does it work
made in salivary glands
works in mouth
what substrate binds to salivary amylase
starch
what is the product of salivary amylase action
maltose
where is pancreatic amylase made and where does it work
made in pancreas
works in small intestine
what is the substrate that binds to pancreatic amylase
starch
what is the product of pancreatic amylase action
maltose
where is maltase made and where does it work
epithelium of small intestine (membrane-bound)
what is the substrate which binds to maltase
maltose
what product is formed from maltase action
glucose
where is sucrase made and where does it work
epithelium of small intestine
what is the substrate that binds to sucrase
sucrose
what are the products formed from sucrase action
glucose and fructose
where is lactase made and where does it work
epithelium of small intestine
what substrate binds to lactase
lactose
what are the products formed from lactase action
glucose and galactose
what is the process of the absorption of lipids
- large lipid droplet is emulsified by bile, creating smaller fat droplets. this creates a larger surface area for lipase to hydrolyse triglycerides into fatty acids and monoglycerides
- they form micelles with bile salts
- micelles come into contact with epithelial cells lining villi of ileum. micelles release monoglycerides and fatty acids. fat soluble components diffuse into epithelial cell leaving behind fat insoluble bile salts
- once inside epithelial cell, monoglycerides and fatty acids are transported to smooth endoplasmic reticulum where they are recombined to form triglycerides
- triglycerides are transported in vesicles to golgi apparatus where they associate with cholesterol and proteins to form chylomicrons
- chylomicrons move out of epithelial cells via exocytosis. they enter lymphatic capillaries called lacteals that are found in the center of the villi and eventually enter the bloodstream
