digestion of food Flashcards
what are the genreal dietary carbhohydrates consumed by humans?
1) starch
2) lactose
3) sucrose
4) cellulose(remains undigested)
explain digestion of carbohydrates in the mouth?
1) mechanical process: mastication of food with help of teeth and tongue(increases the surface are of enzyme action)
2) creation a ball or a mass of food called bolus with help of mucus
3) chemical process:
- the splitting of carbohydrate into maltose(disaccharides) + isoma/tose + dextrins with help of salivary amylase(ph-6.8)
- only 30% of carbohydrate is digested
- lysosome in the saliva acts as a anti-bacterial agent
- then the bolus is finally pushed down the pharynx, this is called swallowing or deglutition
explain digestion of carbohydrates in the stomach?
- absent
- cooking help in the action of salivary amylase by breaking the cellulosic cell wal
- salivary amylase action occur sometime in the stomach until HCl is released which destroys all the enzymes.
- food in the stomach is called chyme
explain digestion of carbohydrates in the small intestine?
1) carbohydrates in the chyme is hydrolysed by pancreatic enzymes
- ph - 7.8
- 70% of starch splits into maltose and dextrins
2) digestion mediated by succus entricus;
- maltose splits into glucose + glucose by maltase
- dextrins split into 3-5 glucose by dextrinase
- sucrose splits into glucose + fructose by sucrase
- lactose splits into glucose and galactose by lactase
- thay are all absorbed by blood capilaries
what are some disorders related to the digestion of carbohydrates?
1) lactose intolerance:
- Lactose intolerance is the inability to break down a type of natural sugar called lactose. Lactose is commonly found in dairy products, such as milk. You become lactose intolerant when your small intestine stops making enough of the enzyme lactase to digest and break down the lactose. this leads to the fermentation of the milk products in the intestine producing intestinal gas, this can cause flatulence, diarrhoea and intestinal cramps. this person can consume curd or yoghurt, in which lactose is fermented to lactic caid.
2) galactosemia:
- Galactosemia is a rare, hereditary disorder of carbohydrate metabolism that affects the body’s ability to convert galactose (a sugar contained in milk, including human mother’s milk) to glucose (a different type of sugar).
- Galactosemia is caused by mutations in genes and a deficiency of enzymes. That causes the sugar galactose to build up in the blood. It’s an inherited disorder, and parents can pass it down to their biological children.
explain digestion of protein in the mouth?
absent
explain digestion of protein in the stomach?
- food is stored in the stomach for 4-5 hours where it is churned along with gastric juices, from chyme.
pepsinogen on exposure to HCl(PH 1.8) gt converted to pepsin.
-with help of pepsin, protein is converted to proteoses and peptones(peptides)
-small amount of lipase is also produced
role of HCl in the stomach?
- provides optimum acidic PH for the activation of pepsin
- converts Fe3+ to Fe2+, making the absorption of iron possible
what is achlorhydria?
- absence of hydrochloric acid in the gastric secretions.
- lack of HCl production can lead to iron deficiency anaemia
what is gasterectomy?
- A gastrectomy is a medical procedure where all or part of the stomach is surgically removed.
- Iron deficiency anaemia develops because removal of the stomach often leads to a marked decrease in the production of gastric acid.
what is an autocatalytic activity?
- Autocatalytic Reaction is the reaction where a product itself acts as a catalyst for the reaction. It can act as a catalyst for the same reaction or the coupled reaction. It increases the rate of the reaction.
- example-:- pepsinogen to pepsin
what is the role of mucus and bicarbonate ions?
mucus and bicarbonate ions lubricate and protect the mucosal epithelium from the action of HCl.
what is the role of rennin?
- rennin is a proteolytic enzyme that helps in the digestion of milk protein in infants.
- HCl turn prorenin into rennin
- rennin turn casein into paracasein and Ca2+, which is later turned into peptones by pepsin
explain the role of trypsin(pancreatic enzyme)
enterokinase(small intestinal juice)(PH-7.8) turns trypsinogen into trypsin(autocatalytic reaction) into the small intestine.
–trypsin activates the following enzymes in pancreatic juice:
chymotrypsinogen –> chymotrypsin
prop carboxy poly peptidase–>carboxy poly peptidase
–proteases and peptones–> polypeptides and dipeptides
–coagulation of blood protein
role of carboxypolypeptidase(pancreatic enzyme)?
–polypeptides–>oligopeptides and dipeptides
-Carboxypolypeptidases cleave the polypeptide chain from the side of the carboxylic group
role of chymotrypsin(pancreatic enzyme)?
-Chymotrypsinogen, like pepsin, can cause curdling of milk but does it in an alkaline medium
–proteases and peptones–> polypeptides and dieptides
role of aminopeptidase(pancreatic enzyme)?
aminopeptidase An enzyme secreted in the pancreatic juice which removes amino acids sequentially from the free amino-terminal of a peptide or protein (i.e. the end that has a free amino group exposed), until the final product is a dipeptide.
aminopeptidase vs carboxy polypeptide?
Aminopeptidase hydrolyses the peptide bond of the amino acid at the amino-terminal of a protein or peptide, releasing a free amino acid. Carboxypeptidase hydrolyses the peptide bond of the amino acid at the carboxyl-terminal of a protein or peptide, again releasing a free amino acid.
Exopeptidase vs endopeptidase?
Exopeptidase: An enzyme that catalyzes the cleavage of the terminal (last) or next-to-last peptide bond from a polypeptide or protein, releasing a single amino acid or dipeptide.
eg: pepsin, trypsin, chymotrypsin
-an endopeptidase catalyzes the cleavage of then internal peptide bonds within a polypeptide or protein.
An exopeptidase catalyzes the cleavage of the terminal or penultimate peptide bond, releasing a single amino acid or dipeptide from the peptide chain.
eg:aminopeptidase,carboxy polypeptide
role of succus entricus(small intestine)
Dipeptidases are enzymes secreted by enterocytes into the small intestine. Dipeptidases hydrolyze bound pairs of amino acids, called dipeptides. Dipeptidases are secreted onto the brush border of the villi in the small intestine, where they cleave dipeptides into their two component amino acids prior to absorption.
–dipeptides into amino acids
what is elastase?
Elastase is an enzyme made by special tissue in the pancreas, an organ in your upper abdomen. Elastase helps break down fats, proteins, and carbohydrates after you eat. It’s a key part of your digestive process. In a healthy pancreas, elastase will be passed in the stool.
role of erepsin in the digestion of protein?
Erepsin is a mixture of enzymes of pancreatic juice and intestinal juices contained in a protein fraction that is found in the intestinal juices that digest peptones, proteins, and proteases into amino acids. It is produced in the ileum and the pancreas.
-digest peptides into dipeptides and amino acids
explain the role of lingual lipase?
–The enzyme, released into the mouth along with the saliva, catalyzes the first reaction in the digestion of dietary lipid, with diglycerides being the primary reaction product.[1] However, due to the unique characteristics of lingual lipase, including a pH optimum of 4.5–5.4 and its ability to catalyze reactions without bile salts, the lipolytic activity continues through to the stomach.[2]
–
explain the role of gastric lipase?
- -Human gastric lipase is produced by chief cells and is colocated with pepsin.
- -In the stomach, gastric lipase starts to break down triacylglycerols into diglycerides and fatty acids. Within two to four hours after eating a meal, roughly 30 per cent of the triacylglycerols are converted to diglycerides and fatty acids.
explain the role of steapsin in digestion?
–Pancreatic lipase, also known as pancreatic triacylglycerol lipase or steapsin, is an enzyme secreted from the pancreas.
–fat –>catalyzes the hydrolysis of triglycerides to monoglycerides
role of bile salt?
- big droplet of fat into small droplets or micelles(diglyceride + monglyceride+ glycerol+ fatty acids)
- activation of lipase
role of pancreatic juice in the digestion of nucleic acid?
nucleic acid turned into nucleotides by nucleases(PH 7.8)
-DNA turned into deoxyribnucleotides by DNases
RNA turned into ribonucleotides
by RNases
role of intestinal juice in the digestion of nucleic acid?
- nucleotides turned into nucleosides by nucleotiases
- nucleosides turned into sugar and nitrogen bases (absorbed by blood capillaries) by nuleosidases
