Physiology of digestion Flashcards
Digestion of starch
-this begins in the mouth, where it is mixed with saliva that contains amylase
What is starch
-is a polysaccharide formed by repeating units of glucose
-starch is broken down by hydrolysis into smaller oligosaccharides called dextrins
-amylase can further be broken down into a disaccharide called maltose
What is starch
-is a polysaccharide formed by repeating units of glucose
-starch is broken down by hydrolysis into smaller oligosaccharides called dextrins
-amylase can further be broken down into a disaccharide called maltose
starch + amylase =
dextrins
dextrins + amylase =
maltose
enzymes are affected by what
-pH and temperature
benedict’s test
-used to indicate the presence of reducing sugar (maltose in this lab)
-benedict’s solution contains copper
-Maltose reduces the cupric ions of benedict’s solution blue to yellow forming precipitate of cuprous oxide
what is the pH in the duodenum
-pH is near basic because the pancreatic juices neutralize it
Tubes for the digestion of starch lab
- 1 ml of distilled water (control)
- 1 ml salivary amylase (most digestion)
- 1ml salivary amylase + 10 drops HCL
-1 ml boiled salivary amylase
*the last two tubes were an attempt to denature amylase, so you may see digestion if it did not work
Iodine test used for digestion of starch lab
-turn blue-black in the presence of starch
-if no starch present it will be an amber color or the color of the iodine solution
benedict test color meaning
Blue = color of the solution (least maltose)
green = +
yellow = ++
orange = +++
Red = ++++ (most maltose present)
Iodine test results
Tube 1: Starch + dH2O (positive)
Tube 2: Starch + salivary amylase (negative)
Tube 3: Starch + salivary amylase + HCl (positive)
Tube 4: starch + boiled salivary amylase (lighter positive)
Where does physical digestion of carbohydrates take place
-in the mouth (chewing)
Where does chemical digestion of carbohydrates take place
-mouth (salivary amylase)
What was the substrate in this exercise (digestion of carbohydrates)
starch
what was the enzyme in this exercise (digestion of carbohydrates)
amylase
What were the products in this exercise (digestion of carbohydrates)
maltose
What are the building blocks of a carbohydrate
-monosaccharide
in which tube did the most carbohydrate digestion occur
in tube #2
What was the effect of HCl on the activity of amylase
-denatures the amylase
what was the effect of boiling on the activity of the amylase
-denatures the amylase
why is benedict solution test used for maltose
-copper salts react with maltose to show digestion
What conclusion can you make if in the boiled salivary amylase tube you had a positive test for maltose
-that boiling did not denature (maybe even renatured), or the set up was messed up
Name three polysaccharides
- starch
- glycogen
- cellulose
Name three disaccahrides
- lactose
- maltose
- sucrose
name three monosaccharides
- glucose
- fructose
- galactose
how would dextrin be classified as a carbohydrate
-is a short chain oligosaccharide, building block of sugar
Lipases
-are not active at the low pH of the stomach
-most aids in breaking down neutral fats from tri, di, mono glycerides into fatty acids and glycerol
Bile
-produced in the liver and stored in the gall bladder
-emulsifies fat (physical not chemical) and facilities the action of lipases by making fat particles smaller and exposing greater surface area for lipase to work on
Litmus test for digestion of triglycerides
-litmus is blue in alkaline solutions and red in acidic
-the more digestion takes place the more fatty acids are liberated and solution becomes more acidic (red)
-blue solution means more lipids (less fatty acids) –> less digestion
Tubes for the digestion of triglycerides lab
Tube 1: 5 mL dH2O + few grains of bile salt (control)
Tube 2: 5mL of pancreatic lipase + few grains of bile salt (most digestion)
Tube 3: 5 mL of pancreatic lipase
how many dietary calories in starch
4 kcal/g
how many dietary calories in egg (albumin) protein
4 kcal/g
Why is fat harder to digest
-because it is water soluble
Where does physical digestion of lipids begin
-mouth
Where does chemical digestion of lipids begin
begins in the tongue (lingual lipase)
-most chemical digestion of fat occurs in the small intestines through gastric and pancreatic lipase
What was the substrate in this experiment (digestion of triglycerides)
cream (triglycerides)
What was the enzyme in this experiment (digestion of triglycerides)
lipase
What were the products in this exercise (digestion of triglycerides)
fatty acids and glycerol
What is the role of bile salts in the digestion of fats
bile emulsifies triglycerides into smaller fat droplets
In which tube did the most lipid digestion occur
Tube #2 (cream, lipase, and bile)
Why is litmus solution used in this exercise?
show pH change
What are the three primary sources of lipase in the digestive system
- pancreas
- stomach
- tongue
what do zygomatic cells secrete
-cells of the stomach mucosa which secrete pepsin
what is pepsin
-proteolytic enzyme, that works best at a low pH
what is the pH of the stomach
less than 2.0 due to secretin of HCl by the parietal cell
biuret test for digestion of proteins
-used to demonstrate the presence of peptide bonds
-reagent contains cupric ions that react with peptide bonds to produce a pink to violet color
-intensity of color depends on the number of peptide bonds broken
-as digestion occurs and more peptide bonds are broken the color changes to a pale pink
Tubes for the digestion of protein lab
- 5 mL pepsin solution (most pink)
- 5mL pepsin solution + 10 drops HCl (acidic solution = greater change, least pink/clear)
- 5mL pepsin solution + 10 drops NaOH (basic solution) (cloudy, blueish-brown)
Where does physical digestion of proteins begin
mouth (chew)
Where does chemical digestion of proteins begin
stomach
- less than 15% of digestion occurs in the stomach
-the major site of protein digestion is in the small intestines (over 85%) where trypsin and chymotrypsin from pancreas and intestinal juices hydrolyze proteins and smaller polypeptides into amino acids
what was the substrate in this experiment (digestion of proteins)
egg albumin
What was the enzyme in this experiment (digestion of proteins)
pepsin
What were the products in this experiment (digestion of proteins)
amino acids
In which tube did the most digestion of protein occur
-Tube 2
What does the biuret test demonstrate the presence of
peptide bonds (intact proteins)
If this test were done with trypsin and not pepsin, which tube would have the most digestion
-tube 3, depending on the alkaline pH in the small intestine 7.4-7.8 whichever tube is closet to that pH might work
What are two ways proteins can become irreversibly changed
-heat
-pH alteration
What is normal arterial blood body pH
7.35-7.45
effects of antacid on protein digestion
-the antacid will neutralize the stomach contents making the enzyme pepsin less effective
