Your SlideShare is downloading. ×
Protein digestion
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Saving this for later?

Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime - even offline.

Text the download link to your phone

Standard text messaging rates apply

Protein digestion

14,728
views

Published on

Published in: Technology, Business

0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
14,728
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
392
Comments
0
Likes
3
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide
  • The enzymes for protein digestion are collectively called proteinases (protein-ACES) or proteases (pro-tea-ACES). Proteins are broken apart by the protein-digesting enzymes in a process called hydrolysis.Proteases- enzymes that hydrolyze protein
  • Protein Digestion Lab In this lab, we will use the same chemicals and enzymes our body uses to observe how we digest protein.  Proteins start breaking down in our stomach, which has an acidic pH of around 2-3 due to the hydrochloric acid.  The enzyme in the stomach that cuts up the bonds between the amino acids in the protein we eat is called pepsin, and it only works in acidic conditions.   Once the food moves into the small intestine, the pancreas releases sodium bicarbonate (NaHCO3), which makes the pH change into a slightly basic (alkaline) pH of 8.  The pancreas also makes the enzyme called trypsin, which works well in these conditions and does a similar job to what pepsin did in the stomach.  After being broken down by both enzymes, the protein you ate is pretty much amino acid
  • Actually, the digestion of dietary protein begins in cooking, which DENATURES proteins.DENATURED proteins are then broken down more easily by digestive enzymes.
  • The protein digesting enzyme pepsin has a pH optimum that is adapted to the normal very low pH of the stomach (a pH of less than 2). The pH of the stomach is due to the secretion of hydrochloric acid by parietal cells in gastric glands that line the stomach.
  • .Entry of dietary protein into the stomachstimulates the gastric mucosa to secrete the hormone gastrin, which in turn stimulates the secretion of hydrochloric acid by the parietal cells and pepsinogen by the chief cells of the gastric glands .The acidic gastric juice (pH 1.0t o 2.5) is both an antiseptic,killing most bacteria and other foreign cells, and a denaturing agent, unfolding globular proteins and rendering their internal peptide bonds m ore accessible to enzymatic hydrolysis. Pepsinogen ,an inactive precursor or zymogen is converted to active pepsin by an autocatalytic cleavage(a cleavage mediated b y thepepsinogen it self) that occurs only at low pH. In the stomach, pepsin hydrolyzes ingested proteins at peptide bonds on the amino terminai side of the aromatic amino acid residues Phe, Ttp, and T}rr cleaving long polypeptide chains into a mixture of smaller peptides.
  • Enteropeptidase ( an enzyme in the small intestine activates trpsinogen to trypsin/ it converts pancreatic trypsinogen to trypsin.)
  • As the acidic stomach contents pass into the small intestine,the low pH triggers secretion of the hormone secretin into the blood. Secretin stimulates the pancreas to secrete bicarbonate into the small intestine to neutralize the gastnc HCl, abruptly increasing the pH to about 7.(All pancreatic secretions pass into the small intestine through the pancreatic duct.) The digestion of proteins now continues in the small intestine. Arrival of amino acids in the upper part of the intestine (duodenum) causes release into the blood of the hormone cholecystokinin, which stimulates secretion of several pancreatic enzyme with activity optima pH 7 to 8.
  • Enteropeptidase converts pancreatic trypsinogen to trypsin.Trypsinogen,chymotrypsinogen, and procarboxypeptidases A and B—the zymogens of trypsin, chymotrypsin, and carboxypeptidases A and B--are synthesized and secreted by the exocrine cells of the pancreas. Trypsinogen is converted to its active form, trypsin, by enteropeptidase, a proteolytic enzymes secreted by intestinal cells. Free trypsin then catalyzes the conversion of additional trypsinogen to trypsin .Trypsin also activates chymotrypsinogen, the procarboxypeptidases and proelastase. Trypsin and chymotrypsin further hydrolyze the peptides that were produced by pepsin in the stomach. This stage of protein digestion is accomplished very efflciently,because pepsin, trypsin, and chymotrypsin have different amino acid speciflcities .
  • Degradation of the short peptides in the small intestine is then completed by other intestinal peptidases. These include carboxypeptidases A and B (both of which are zinc-containing enzymes), which remove successive carboxyl-terminal residues from peptides,
  • aminopeptidase that hydrolyzes successive amino-terminal residues from short peptides.
  • The resulting mixture of free amino acids is transported into the epithelial cells lining the small intestine, through which the amino acids enter the blood capillaries in the villi and travel to the liver and then go into the blood of the general circulationIn humans, most globular proteins from animal sources are almost completely hydrolyzed to amino acids in the gastrointestinal tract, but some fibrous proteins,such as keratin, are only partly digested. In addition, theprotein content of some plant foods is protected against breakdown by indigestible cellulose husks. 
  • Test Tube A: because it will not cleave on all peptide chains.
  • These factors include the concentration of the enzyme, that is, how much of it is present;the amount of protein food needing action; the acidity of the food and of the stomach; the temperature of the food; time; and the presence of any digestion inhibitors, such as antacids.Cooking and chewing The low pH (~2) of the gastric juice aids protein digestion in a couple of ways. : First, the low pH denatures the tertiary structures of ingested protein, making them easier to digest enzymatically. Secondly, the low pH is required for the activation of pepsin.
  • Gastric Protease (Pepsin)Pancreatic Protease (Trypsin)Alkaline environmentEnterokinasecomposed of Trypsinogen and ChymotrypsinCarboxypeptidase Aacts on the C terminal; exopeptidaseExopeptidases – outside the peptide chainEndopeptidases – within the peptide chain
  • Transcript

    • 1. Protein Digestion
      Presented by: GROUP 1 – DAA
      Coojacinto
      De Asis
      Go
      Saunar
    • 2. Proteins are…
       biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function.
      A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues
    • 3. Protein digestion
      The process of digestion is defined as the ‘process by which macromolecules in food are broken down into their component small-molecule subunits’.
      The macromolecules are the proteins or polypeptides themselves, and the subunits are the amino acids. The bonds holding the subunits together are peptide bonds
    • 4. Protein Digestion
      is the degradation of proteins by cellular enzymes enzymes in a process called hydrolysis.
      Protein digestion takes place in two different phases:
      In the stomach
      In the small intestine
      Both of these phases of digestion are based on several types of enzymes that are called proteinases and proteases.
    • 5. Proteases- endo- & exo- peptidases; enzymes that degrade proteins by hydrolysis of peptide bonds
      Proteinases- endo-peptidases; proteases that show specificity for intact proteins
    • 6. Peptide bond hydrolase
      Peptidase
      (=Protease)
      Endo-acting peptide bond hydrolase
      Endopeptidase
      (=Proteinase)
      Exo-acting peptide bond hydrolase
      Exopeptidase
    • 7. Mouth and Salivary Glands
      Chewing and crushing of protein rich foods and mix them with saliva to be swallowed
    • 8.
    • 9.
    • 10. In the Stomach : start of protein Digestion
      Gastrin
      -stimulates Parietal cells to secrete HCL; Chief cells of the gastric glands to secrete pepsinogen
      Hydrochloric acid
      -Denatures protein structure
      -Activates pepsinogen(zymogen) to pepsin
      Pepsin
      -hydrolyzes proteins to smaller polypeptides and some free amino acids.
    • 11. In the intestine
      . The remainder of protein digestion occurs in the small intestine as the result of the action of enzymes
      such as trypsin (secreted by the pancreas) and peptidases (located in the cells that line the small intestine).
    • 12. In the Small Intestine : enzymes
      Secretin
      - stimulates the pancreas to secrete bicarbonate into the small intestine to neutralize the gastric HCl
      Cholecystokinin
      -stimulates secretion of several pancreatic enzyme with activity optima pH 7 to 8.
    • 13. In the Small Intestine
      Cont....
      Trypsin
      - activates chymotrypsinogenchymotrypsin
      procarboxypeptidasescarboxypeptidases
      proelastaseelastase
      -further hydrolyze the peptides that were produced by pepsin in the stomach specifically the peptide bonds next to lysine and arginine
      Chymotrypsin
      -cleaves peptide bonds next to phe, tyr, trp,met, asp, and his
    • 14. Cont....
      Carboxypeptidase A & B
      -cleave amino acids from the acid (carboxyl) ends of polypeptides
      Elastase and collagenase
      -cleave polypeptides into smaller polypeptides and tripeptides
    • 15. Cont....
      Intestinal tripeptidases
      -Cleave tripeptides to dipeptides and amino acids
      Intestinal dipeptidases
      -cleave dipeptides to amino acids
      Intestinal aminopeptidases
      -cleave amino acids from the amino ends of small polypeptides(oligopeptides)
    • 16. Amino acids absorbed
      Free amino acid  small intestine(villi)Liverblood circulation
    • 17. Materials:
      Commercial pepsin
      Trypsin
      Concentrated HCl
      NaOH
      CuSO4 solution
      0.5% Na2CO3
      Hard Boiled Egg (Protein) albumin
    • 18. Biuret Test
      a chemical test used to detect the presence of peptide bonds
      Reagent: Potassium hydroxide (KOH) and hydrated copper(II) sulfate, sodium tartarate
      Result:
      • (+) test = purple (presence of proteins)
      • 19. (−) test = blue
      • 20. blue to pink when combined with short-chain polypeptides (it will not cleave on all peptide chains)
    • Procedure
      Action of the Gastric Protease (Pepsin) on Proteins
      Action of Pancreatic Protease (Trypsin) on Proteins
    • 21. Action of the Gastric Protease (Pepsin) on Proteins
    • 22. Action of Pancreatic Protease (Trypsin) on Proteins
    • 23. B. THE ACTION OF PANCREATIC PROTEASE (TRYPSIN) ON PROTEINS
      Label 3 tubes, each half full of warm H2O
      To the first tube add a small amount of grated white of hard boiled egg.
      To the first tube add a 0.5g of trypsin and 2ml of 0.5% NaCO3.
      To the second tube add 0.5g trypsin.
      To the third tube add 2ml of Na2CO3 solution.
      Keep the tube in a warm H2O bath kept at body temperature for an hour.
      Filter the contents of each tube and the Biuret test on each of the filtrates.
      Observe and record the results.
    • 24. Ideal Results:
    • 25. POST LAB QUESTIONS
    • 26. POST LAB QUESTIONS
      What are the enzymes used in Protein Digestion?
      Gastric Protease (Pepsin)
      Pancreatic Protease (Trypsin)
      Small intestine enzymes (peptidases)
    • 27. POST LAB QUESTIONS
      What are the similarities and differences of these enzymes?
      These enzyme hydrolyze proteins and their main difference is the location where they are found.
    • 28. POST LAB QUESTIONS
      What are the factors that would bring about Protein digestion?
      • the acidity of the food and of the stomach
      • 29. Temperature
      • 30. the presence of any digestion inhibitors, such as antacids
    • POST LAB QUESTIONS
      Trace the pathway of Protein Digestion
      Stomach
      Gastrin stimulates:
      Parietal cells secrete HCl
      Chief cells secrete pepsinogen then HCL convert it to pepsin but acts only on certain amino acids
      Small Intestine
      released in the lumen
      Cholecystokinin stimulates pancreatic enzymes such as:
      TrypsinTrypsinogen (active form)
      specific for Lys and Arg (carboxyl side)
      ChymotrypsinChymotrypsinogen (active form)
      specific for Tyr, Trp, Phe, Leu and Met (carboxyl side)
    • 31. Protein Digestion Pathway
      ( digestion doesn’t happen yet)
      Mouth and Salivary Glands
      Stomach( Gastric Phase)
      Small Intestine and Pancreas
      (Pancreatic Phase)
      Blood
    • 32. POST LAB QUESTIONS
      What tests are used to detect the completeness of protein digestion?
      MILLON’S TEST
      NITROPRUSSIDE TEST
      HOPKIN’S COLE TEST
      XANTHOPROTEIC TEST
      SAKAGUCHI TEST
      PAULY TEST
    • 33. 5.
      MILLON’S TEST
      • Test for tyrosine (tyr)
      • 34. Used to detect the presence of soluble proteins
      • 35. Given by phenols or phenolic substances such as Salicylic acid
      Principle
      Mercuric sulphate forms a colored compound with hydroxyl group of Tyr.
      Result: (+) red ppt
    • 36. 5.
      HOPKIN’S COLE TEST
      • specific for tryptophan --- indole group.
      Principle
      The indole ring reacts with glyoxylic acid in the presence of a strong acid: H2SO4
      Reagent: glyoxylic acid
      Result: violet cyclic product
    • 37. 5.
      PAULY’S TEST
      • For tyr, trp, and his
      Principle
      Diazotisedsulphanilic acid couples with amino phenol and immidazole to form a colored azocomp’d in cold condition.
      Result: (+) Deep red color dye
    • 38. 5.
      SAKAGUCHI TEST
      • Test for Arg -- guanido group
      Principle
      Alkaline solution
      SakaguchiReagent:α-naphthol and sodium hypochlorite
      Result: (+) reddish wine color
    • 39. 5.
      XANTHOPROTEIC TEST
      • For aromatic groups: tyr, trp, phe(unactivated)
      Principle
      Nitration of a Benzene ring with Nitric Acid
      Reagent: Nitric acid (HNO3) and NaOH
      Result: (+) yellow (tyr); orange (trp) --alkali
    • 40. 5.
      SODIUM NITROPRUSSIDE TEST
      • Bollin’s test
      • 41. specific for cys – free thiol group (S—H)
      Principle
      Cystine whichcontains disulphide linkage (S—S) may be reduced to cysteine
      reducing agent/s: sodium cyanide, sodium brohydride or sodium bisulphate
      Result: (+) red complex
    • 42. What are the factors affecting protein digestion?
      pH: acidity and alkalinity of environment
      Regulating activity of inhibitors