Digestion Flashcards
What part of the digestive system is responsible for the secretion of bile?
The liver
What is the pancreas’ function in the digestive system?
secretion of enzymes into the duodenum
Secretes pancreatic juices
What is the function of the colon in the digestive system
Reabsorption of water
What is the function of the rectum in the digestive system?
Storages of undigested food prior to removal
What is the function of the stomach in the digestive system?
Mechanical and chemical digestion of proteins in low pH
Where is bile stored?
The gall bladder
How does bile enter the duodenum?
Via the bile duct
How do bile salts help in the digestion of lipids?
Emulsification of the lipids turns them into micelles which makes them more soluble so they are easier to transport and increases SA for chemical digestion with lipase
Why are hydrogen Carbonate ions secreted into the duodenum?
They neutralise the stomach acids
Where would the villus be found in the human gut?
On the epithelial cells in the ileum
Why is is more efficient for the endopeptidases to act before the exopeptidases?
Increasing SA for exopeptidases to work on therefore faster hydrolysis of polypeptides
What are the two types of digestion?
Mechanical
Chemical
Where does mechanical digestion take place?
Teeth and stomach
What does mechanical digestion do?
Breaks down large pieces of food into smaller pieces to increases the SA for chemical digestion which overall increases the rate of digestion
Where does chemical digestion take place?
mouth
stomach
small intestine
What does chemical digestion do?
Speeds up the hydrolysis reactions of bonds breaking
Breaks down large insoluble molecules into smaller soluble ones
Why is it necessary that food needs to be digested to be absorbed?
Makes the food smaller and soluble so it can be transported across membrane to be blurbed into the blood plasma
What do glands do in the digestive system?
Produce enzymes
What does the oesophagus do?
Caries food from the mouth to the stomach
What is the function of the ileum in the digestive system?
Food is further digested by enzymes
Absorbs the products of digestion into the bloodstream
What is the function of the salivary glands?
Secretes saliva that contains amylase do break down starch
How does the stomach break down food?
Churns it by using its muscles in the stomach wall
Where does intracellular digestion take place?
In the epithelial cells of the ileum
What are the 3 functions of mucus?
Neutralises acid
Provides lubrication
Protects gut wall from acid erosion
Where is amylase produced?
The salivary glands and the pancreatic juices
What is the optimum pH of amylase?
pH 8
What part of carbohydrate digestion takes place in the mouth and duodenum?
Hydrolysis of starch into maltose
What part of carbohydrate digestion takes place in the ileum?
Maltese hydrolysing maltose into alpha glucose
Describe carbohydrate digestion
Starch is broken down my amylase to produce maltose in the mouth and the duodenum
The amylase hydrolysis the glycosidic bonds
Then in the ileum
Maltase hydrolysis the glycosidic bonds in maltose to alpha glucose
What is an endopeptidase?
Hydrolyses the peptide bonds between amino acids in the central region of the protein forming smaller polypeptide chains
What part of protein digestion takes place in the stomach?
Endopeptidases hydrolysing proteins into smaller polypeptide chains
What are exopeptidases?
Hydrolyses peptide bonds on the terminal amino acids on the end of the polypeptide chain
They release single amino acids and dipeptides
What part of protein digestion takes place in the duodenum?
Exopeptidases hydrolysing polypeptide chains into amino acids and dipeptides
What are the 3 types of exopeptidases?
Carboxypeptidase
Aminopeptidase
Dipeptidase
Why are peptidases secreted in an inactive form?
To protect the gut from harm as they would breakdown the gut
What are dipeptidases?
Hydrolyses the bond between two amino acids in a dipeptide
Membrane-bound part of the epithelial cells of the ileum
What part of protein digestion takes place in the ileum?
Dipeptidases hydrolysing dipeptides into amino acids
What type of digestion is breaking lipid droplets down to micelles?
Mechanical digestion
What are the role of bile salts?
Emulsification of lipids into micelles
What is the role of sodium hydrogen carbonate in lipid digestion?
Neutralises the stomach acid for the optimum pH of lipase - pH 8
What is the role of micelles in the absorption of fats into the epithelial cells?
To increase SA for lipase to act on fatty acids for faster hydrolysis and digestion of lipids
makes fatty acids more soluble in water
maintain high conc of fatty acids to the cell
fatty acids absorbed by diffusion
brings fatty acids to the cell lining of the ileum
What is the function of micelles in digestion?
Makes lipids more soluble and easier to transport through membranes to the intestinal epithelial cells
What are the two sites of secretion for amylase?
Salivary glands and pancreas
Where are the two sites of action for amylase?
Mouth and duodenum
Where are the two sites of secretion for endopeptidases?
Gastric glands and pancreas
What are the two sites of action of endopeptidases?
Stomach and duodenum
What are the two sites of secretion for exopeptidases?
Pancreas and epithelial cells
What are the two sites of action of exopeptidases?
Duodenum and ileum
What is the site of secretion for lipase?
Pancreas
What is the site of action for lipase?
Duodenum
What is the site of secretion of disaccharidases?
Epithelial cells
Where is the site of action for disaccharidases?
Ileum
What are all the parts of the human digestive system?
Mouth
Tongue
Salivary gland
Oesophagus
Stomach
Liver
Gall bladder
Bile duct
Pancreas
Duodenum
Ileum
Appendix
Colon
Rectum
Anus
What parts of the digestive system are part of the alimentary canal?
Mouth
Oesophagus
Stomach
Duodenum
Ileum
Appendix
Colon
Rectum
Anus
How is starch broken down in the mouth by chemical digestion?
Chemicals come from salivary glands that secrete saliva that contains amylase and breaks down starch
What is in saliva?
Amylase
Mucus
Mineral ions
What is the role of mineral ions in saliva?
Maintains pH
What are the two layers of muscle in the oesophagus?
Circular and longitudinal muscle
What happens when the circular muscles in the oesophagus contract?
Contracts to squeeze the gut
What happens when the longitudinal muscles contracts in the oesophagus?
Contracts to shorten the gut
What is the optimum pH in the stomach?
pH 2
Why is there an extra layer of muscle in the stomach?
For mechanical digestion - the muscles contract to churn contents to form acidic chyme
What are the 3 types of muscle in the stomach?
Longitudinal
Circular
Oblique
What is the role of HCl stomach acid?
Maintains pH to activate enzymes and to kill bacteria
What is bile made of?
Bile salts
Sodium hydrogen carbonate
What is in pancreatic juices?
Amylase
Lipase
Exopeptidases
Endopeptidases
Hydrogen carbonate ions
What does the Brunner’s gland do in the gut wall?
Releases mucus
What substances in the duodenum neutralises the acids from the stomach?
Sodium hydrogen carbonate
Mucus
Hydrogen carbonate ions
What is the process of carbs and proteins being digestion in the ileum?
Hydrolysis of enzymes in the membrane of microvilli
Crosses the membrane with enzymes breaking them down - constant hydrolysis
Digestion occurs as absorption occurs
Diffuses into blood capillary
What is assimilation?
How the products of digestion are used by the body cells
How are mooglycerides and fatty acids used by cells?
The formation of cell membranes
How do villi and microvilli increase absorption efficiency in the ileum?
Larger SA for carrier proteins for facilt. Diff. Increases SA for diffusion
How does a thin gut wall increase absorption efficiency in the ileum?
Shorter diffusion pathway for absorption
How do muscle layers increase absorption efficiency in the ileum?
Ensures molecules are kept in contact with villi - increases rates of absorption
What are all the parts of a villus?
Epithelial cell
Goblet cells
Lacteal
Nerve
Capillary
Lymphatic vessel
Smooth muscle
What products does the lacteal absorb?
Products of lipid digestion
What products does the capillary network absorb?
Products of carbs and proteins digestion
Describe the process of absorption of lipids
Fatty acids and monoglycerides leave the micelles and enter the epithelial cells of mucosa by simple diff
Fatty acids and monoglycerides reform as triglycerides
Chemical modification in the Golgi body - combines with proteins to form chylomicrons
Chylomicrons released from the epithelial cells by exocytosis and enters the lacteal
Chylomicrons in the lymph are transported to the thoracic duct and enter the blood stream
Why do lipids become chylomicrons?
Makes them soluble in water to be absorbed in the blood plasma and be transported by mass flow
Summarise absorption of glucose/amino acids by sodium co-transport?
- Sodium ions actively pumped out and potassium ions actively transported in
- Sodium conc grad forms so sodium ions actively transported out
- Co-transport of glucose and sodium ions
- Glucose leaves the epithelial cell into the blood by facial.diff
Describe the sodium and potassium pump in co-transport.
Sodium ions are pumped out as potassium ions are actively transported in
Describe the concentration grad of sodium forming in co-transport.
The sodium conc falls due to actively pumped out
Sets up a conc grad of sodium ions between the lumen of the ileum and in the ileum wall
Describe the co-transport of sodium ad glucose.
Sodium ions actively transported from ileum epithelial cell to blood
maintains and forms a grad for sodium to diffuse from the ileum lumen to the epithelial cell
Glucose enters cell by faciliated diff with sodium ions
What protein is the sodium and potassium ion pump?
Anti-port
What is indirect active transport in co-transport of glucose?
Uses ATP from the active transport of sodium ions in the pumping out ofte ileum
Describe assimilation of glucose in the liver.
glucose transported from the ileum to liver
Excess glucose is coveted to glycogen and stores in the liver
Some glucose is transported to other tissues
Why doesn’t the liver stored amino acids?
Nitrogen in high conc is toxic to cells
What is deamination of amino acids in the liver.
Removes the amino group and the H atom from the central carbon
How is the amino group removed in deamination?
Forms ammonia which is toxic to cells
Converted into urea which can now bc excreted as urine
Where is maltase produced?
In the epithelium of the small intestine
What are all the adaptations of intestinal epithelial cells?
microvilli
villi
one cell thick villus wall
blood capillaries
lacteal
co-transport proteins
How do the microvilli and villi increase absorption of nutrients?
increase SA for absorption
microvilli = more nutrients come in contact with the cell
villi = increase SA of the cells
How do blood capillaries increase absorption of nutrients in the intestinal epithelial cells?
transport glucose and amino acids away from small intestine = maintain conc grad
How does the lacteal increase absorption of nutrients in the intestinal epithelial cells?
runs through the centre of the villus and transports fatty acids and glycerol away from the small intestine
What is a micelle?
water soluble vesicles formed of fatty acids, glycerides, monoglycerides and bile salts
Describe the complete digestion of starch by a mammel
amylase breaks down starch into maltose in the mouth
by hydrolysing glycosidic bonds
Maltase is a membrane-bound disaccharides and breaks down maltose into glucose
what is a membrane-bound disaccharides?
enzymes in the cell membrane of the epithelial cells of the ileum
they catalyse the hydrolysis of disaccharides into monosaccharides
