BMS Digestive System Physiology Lab

Micelle

A small particle formed by aggregates of molecules with both polar and nonpolar segments; This allows the nonpolar substance to be washed away by the polar substance.- help in breakdown of lipids/bile salts

o Describe the role of bile and lipases in the digestion of triglycerides.

Bile play a role in emulsification because it mechanically separates the lipids. Pancreatic lipase enzymatically degrades lipids into fatty acids.

Describe the activation of these proteases

HCl causes a low ph in the stomach lumen which activates proteases

o Identify the direct impact of HCl on the digestion of a protein (beyond protease activation).

HCl in the stomach denatures amylase so that it can't digest starch. That's why amylase is secreted in both the oral cavity and the pancreas. - HCl denatures proteins to make them easier to digest

Identify the digestion product of lipids that is absorbed by the small intestine

Micelles: transport lipids to the epithelial lining of the small intestine chylomicrons: formed within epithelial cells; lipid molecules are wrapped in a protein and secreted

Identify the structure secreting bile and lipases.

Pancreas

describe the digestion of carbohydrates by amylase

Salivary Amylase: breaks starch (polysaccharides) by breaking bonds between glucose molecules to create shorter glucose chains Pancreatic Amylase: breaks partially digested starch into oligosaccharides, maltose, and glucose

Describe the digestion of carbohydrates from the mouth through the small intestine

Salivary amylase begins the digestion in the oral cavity and breaks bonds between glucose molecules. In the duodenum pancreatic amylase continues to break down the starch molecules into smaller oligosaccharides, disaccharides, and monosaccharides. Brush border enzymes break these molecules down further into singular glucose molecules.

salivary amylase

Site of production: salivary glands site of action: oral cavity Substrate: starch product: short strands of starch

· Explain the impact of a reduction in temperature on chemical digestion.

The decrease in temperature slows enzymatic function. Trypsin experiment: tube 4 didn't have as strong as a result because the enzymes were not functioning as well due to the ice bath.

identify the class of carbohydrate absorbed by the small intestine

The small intestine absorbs monosaccharides such as glucose, fructose, and galactose

Action of trypsin experiment

Trypsin and artificial substrate BAPNA (synthetic substrate with a dye bound to an amino acid), trypsin cleaves the dye molecule from the amino acid in BAPNA to cause the solution to change to bright yellow. - Yellow color change means that trypsin hydrolyzes the peptide bonds in proteins to produce short chain polypeptides. - BAPNA was digested in tubes 3 and 4 but not as well in tube 4 because the temperature was lower

Describe the action of a protease on a protein

activated by low pH, chemically digests proteins into shorter strands of amino acids

Identify the digestion product of proteins that is absorbed by the small intestine

amino acids

Enterokinase

converts trypsinogen to trypsin

identify the structures secreting amylase

exocrine salivary glands and exocrine pancreas

describe the impact of gastric acidity on amylase function

gastric acidity/HCl, will denature amylase and therefore inhibit its function.

function of trypsin

hydrolyzes peptide bonds of other zymogens to activate them (long chains to short chains)

Emulsification (lipid digestion)

lipids are mechanically separated into smaller and smaller droplets by bile.

identify the enzymes that digest disaccharides and their location in the small intestine

maltase, lactase, and sucrase: located in the brush border of the small intestine

Maltase, lactase, sucrase

site of production and action: small intestine substrate: oligosaccharides, disaccharides, maltose, lactose, sucrose Product: monosaccharides

pepsinogen --> pepsin

site of production and action: stomach substrate: denatured proteins product: polypeptides and peptide fragments

Enzymatic degradation of lipids

the action of pancreatic lipase on triglycerides. Fatty acids (the result of enzymatic lipid degradation by pancreatic lipase) are organic acids that will lower the pH of a solution and change its color.

· Describe the digestion of triglycerides from the mouth through the small intestine:

- lingual lipase breaks down lipids in the oral cavity - in the stomach lipids are broken down by lingual and gastric lipase large lipid droplets are separated mechanically (emulsification) which occurs by the action of bile salts - once emulsified, pancreatic lipase is able to chemically digest triglyceride molecules

Three classes of carbohydrates

1. Monosaccharides 2. Disaccharides 3. Polysaccharides

Action of amylase experiment

Amylase is released from the exocrine salivary glands into the oral cavity as salivary amylase and from the exocrine portion of the pancreas as pancreatic amylase into the duodenum. Salivary amylase begins the process of starch (polysaccharide) digestion by breaking the bonds between glucose molecules resulting in shorter glucose chains. In the duodenum pancreatic amylase continues to break down the starch molecules into smaller oligosaccharides, disaccharides, and monosaccharides. Observe the action of amylase and the effects of HCl acid on enzyme activity. - add idonine-pottassium iodide - if starch is present the solution will turn dark blue/black/purple - Enzymatic degradation didn't occur in tubes 1 and 4 (purple color change) - tube 1 was the control because it contained no amylase - what happened to HCl: HCl neutralizes/denatures amylase that's why the pancreas and oral cavity also secrete amylase because the stomach inhibits its function

Action of lipase experiment

Digestion of lipids requires emulsification and enzymatic degradation of the triglyceride to fatty acids and glycerol. Litmus cream (substrate) is high in triglycerides to detect the presence of free fatty acids. The litmus cream will change from blue or lavender to pink when fatty acids are present (enzymatic degradation has occurred) - Tube 5 had bile salts so the lipids were emulsified - Tube 6 had the least amount of digestion because cold inhibited the function of lipase

Peptidases (peptides)

produced and act on small intestine (brush border enzyme) substrate: peptides product: amino acids

describe the digestion of proteins from the mouth through the small intestine

protein digestion begins in the stomach lumen and is broken down by proteases into shorter chains of amino acids - high pH of small intestine inhibits pepsin - trypsin is activated by enteropeptidase and creates small chains of amino acids called peptides, these are further broken down into dipeptides and free amino acids - amino acids are absorbed across the epithelial lining and into the blood - if there are excess they can be used for fuel for respiration or turned into glucose

gastric lipase

site of production and action: stomach substrate: triglycerides product: diglyceride and fatty acid

bile

site of production: liver site of action: small intestine substrate: large droplets of triglycerides product: micelles (small fat droplets)

trypsinogen/trypsin

site of production: pancreas site of action: small intestine substrate: denatured proteins product: polypeptides/peptides

Pancreatic amylase

site of production: pancreas site of action: small intestine substrate: partially digested starch product: oligosaccharides, disaccharides, individual glucose molecules

pancreatic lipase

site of production: pancrease site of action: small intestine substrate: small triglycerides and diglycerides product: monoglyceride and 2 fatty acids

lingual lipase

site of production: tongue and oral cavity Site of action: stomach Substrate: triglycerides Products: diglycerides and one fatty acid

Identify the structures secreting inactive proteases (pepsinogen and trypsinogen).

stomach

· Identify the two classes of lipids.

triglycerides and cholesterol

Trypsingoen

zymogen, precursor to trypsin