Digestive System Physiology

True/False. Digestion occurred in tube B.

**Tube B = Yellow Tube**

Digestive System Overview

-Digestive system is responsible for the MECHANICAL and CHEMICAL digestion of food into small nutrient molecules. -Absorbed across the wall of the GI tract. -Make their way into blood stream.

What enzymes are involved in carbohydrate digestion? (list them all)

-Salivary Amylase -Pancreatic Amylase -Disaccharidases

What is chemical digestion?

-Series of chemical reactions, catalyzed by ENZYMES that break down large ingested food molecules (POLYMERS). -Starch, Fats, Proteins.

Discuss the the SPECIFICITY of enzymes.

-Since enzymes are specific for their substrate, a variety of different enzymes are necessary to complete the digestive process.

In what organ is pancreatic lipase active?

-Small Intestine

What is the primary source of CARBOHYDRATES?

-The primary source of carbohydrates is STARCH. -Starch = large GLUCOSE polymer found in bread, pasta, and potatoes.

What is Trypsin?

A protease secreted by the pancreas and added to the small intestines.

List the monomer unit of protein digestion.

Amino Acid

What is needed to reach fats? Organ involved? Name of this process ? Purpose of this process?

BILE SALTS from the liver are first mixed with these globules to disperse them into smaller droplet (EMULSIFICATION). Emulsification increases the surface area so that lipase can more efficiently digest the fats.

Name the indicator used to test for the presence of sugar.

Benedict

Lactose and Sucrose along with maltose are broken down into ? What happens to these molecules next?

Broken down into three monosaccharides: -glucose, galactose, fructose. -These molecules are then absorbed into the bloodstream across the GI tract.

Name the indicator used to test for the presence of fatty acids.

Litmus

Litmus Milk Test

Litmus (Milk) Indicates pH Terms "positive" and "negative" are not applicable Can infer digestion Method 1. Label test 1-4 2. Load test tubes 3.Cover each test tube with parafilm and shake. 4. Uncover the test tubes and place them in 37C water bath for 1 hour. Shake each test tube occasionally to keep contents mixed. Contents of Test Tubes Test tube 1: 0 pancreatin, 3 mL Litmus, 0 bile salts. Test tube 2: pancreatin, 3mL litmus, 0 bile salts. Test Tube 3: pancreatin, 3mL litmus, bile salts. Test Tube 4: 0 pancreatin, 3mL litmus, bile salts. Assessing Digestion As lipids are digested they release free fatty acids chains. Fatty acids are acidic which lowers pH. LITMUS POWDER added to the cream as the pH indicator. BLUE = alkaline and neutral pH solutions. RED = in acidic pH solutions.

Examples of Mechanical Digestion?

Mastication Peristalsis Emulsification

List the monomer unit of carbohydrate digestion.

Monosaccharides -Galactose -Glucose -Fructose

Protein is the molecule found in? Where does protein digestion begin? Enzyme involved?

Nutrient molecule found in meat, eggs and legumes. Digestion of these very large amino acid polymers is begun in the stomach by PEPSIN.

List the first enzyme needed for protein digestion to occur.

Pepsin

Given that Enzymes are proteins what are they subject to?

Subject to environmental conditions -Denaturation by pH -Denaturation by Heat

Additional sources of carbohydrates? Where are they broken down?

Two disaccharides -LACTOSE (milk sugar) and SUCROSE (table sugar) are also dietary sources of carbs. -These molecules along with maltose, are broken down in the small intestine.

Benedict Testing

-Testing for simple sugars Presence of sugars** Positive and negative only refer to the presence or absence of sugars, NOT digestion Can infer digestion occurred Method 1. Label test tubes 1-6 2.Load test tubes as indicated. 3. For test tube 4, first add the amylase and place it in the boiling hot water bath for 4 minutes. 4.Place each test tube in the appropriate water for 1 hour. Shake each test occasionally to keep the contents mixed. **incubated at 37C**

Describe the fats? What do they not mix with? What is the name for this interaction? What do they form in the digestive system?

Fats are hydrophobic and do not mix with water. They form large globules in the watery environment of the digestive system.

Are fats easily reached by enzymes when they are in watery environments? What enzyme is involved ?

In this form, the fat molecules are not easily reached by lipase, the primary fat digesting enzyme. Lipase is a pancreatic enzyme added to the small intestine.

What cells secrete Pepsinogen? What happens when it is exposed to an acidic environment in the stomach? Where is the process completed? With the help of what enzymes? Secreted by?

Chief cells secrete pepsinogen (inactive proenzyme). It is converted into pepsin (the active protein digesting enzyme) when exposed to an acidic environment. Completed in the small intestine with the help of a variety of PROTEASES & PEPTIDASES (protein digesting enzymes). Secreted by pancreas and brush border lining of the small intestine, as well as by enzymes found in epithelial cells.

Biueret's Solution

Concentration of peptide bonds Protein intact vs protein not intact Can infer digestion Method. 1. Label test tubes 1 & 2 2. Load Test Tubes as indicated/ 3. Use pH paper to record the pH of each test tube. 4. Place each test tube in 37C water bath for 1 hour. Test Tube 1: Albumin 1-scoop, Pepsinogen: 6mL, no gastric juices. Test Tube 2: 1-scoop Albumin, no pepsinogen, 6ML of gastric juices + HCL Assessing Digestion -1 Remove the test tube from the water bath. 2. 10 drops of Biurets reagent to each tube. -Used to test changes in the amount of the peptide bonds. -When proteins have not been broken down, and are still large molecules, the reagent is only able to react with the small peptide bonds on the outer walls of the proteins (blue-purple color solution). -When proteins are broken down, more of their peptide bonds are exposed to the chemical reagent and will cause a purple reddish color.

Examples of Chemical Digestion

Enzymatic action Gastric juice and HCl

True/False. Digestion occurred in tube A (LEFT TUBE)

False

Lugol'sTest

IKI/Lugol's Presence of starch Positive and negative only refer to the presence or absence of starch, NOT digestion Can infer if digestion occurred

Enzymes are involved in what kind of digestions? What are enzymes? What to they do?

Involved in Chemical digestions. Enzymes are large protein molecules that increase the rate of chemical reactions. Help to hydrolyze food. Breaks bonds. Creates monomers.

Name the indicator used to test for the presence of starch

Lugols

Chemical Digestion breaks Polymers into what?

MONOMERS -Glucose -Fatty acids, -Amino Acids

Where does starch DIGESTION begin? What enzyme is involved ? Function of Enzyme?

Starch digestion begins in the MOUTH through the action of salivary AMYLASE. -Salivary Amylase produced by the salivary glands and added to the mouth in saliva. -Amylase breaks down starch into MALTOSE = a glucose disaccharide.

Where is the process of amylase break down finished? What additional enzyme is involved & from what organ?

The process is completed in the small intestine with additional amylase from the pancrease.