Lab 4: Digestion Flashcards
Where does the majority of protein digestion take place?
Duodenum
When starch is in contact with iodine what colour does it go?
Black
What percent of the weight of the pancreas supports exocrine function?
80%
α- amylase digests what?
α1-4 bonds in starch and glycogen
Name the 4 pancreatic protein digesting enzymes?
Trypsin
Chymotrysin
Carboxypeptidase
Elastase
The pancreatic protein digesting enzymes are secreted as?
Zymogens
Why are the pancreatic protein digestion enzymes secreted as zymogens?
To prevent digestion of human tissues
These enzymes would digest the proteins in the cells in which they are synthesised
Describe the activation of trypsinogen?
Activated by enterokinase, an enzyme located on the brush border of the gut mucosa
Describe the activation of the zymogens from the pancreas?
- Activated on the brush border of the gut
- Trypsinogen needs to be activated first by enterokinase, an enzyme located on the gut mucosa.
- Trypinsogen is activated to trypsin.
- Trypsin acts to activate the other zymogens (chymotrypsin, carboxypeptidase, elastase)
Why is it the only protein digesting enzymes that are secreted in their zymogen form and not pancreatic lipase and amylase?
Because amylase and lipase are not dangerous to human tissue
Therefore can be secreted in their active form
Why is it important for bicarbonate to be secreted by the duct cells in the pancreas?
Important to neutralise the gastric acid and have the pH in the small intestine slightly alkaline as the pancreatic enzymes are active at this pH.
What is the products of amylase digestion?
Disaccharides and oligosaccharides
The enzymes on the brush border of the mucosa digests which carbohydrates?
- Disaccharides and oligosaccharides (the products of amylase digestion)
- Lactose
- Sucrose
What are “reducing sugars”?
Those that contain aldehyde groups e.g. glucose, galactose, lactose etc
All monosacchrides are reducing sugars
Give an example of isoenzymes?
Isoenzyme is when two or more enzymes has an identical function but different structure
Salivary amylase and pancreatic amylase
Why are salivary and pancreatic amylase known as isoenzymes?
They are very similar.
Has the same action but are coded by different genes, which are expressed in the salivary glands and pancreas respectively
What does the Benedict’s test indicate?
The presence of reducing sugars
i.e. all monosaccharides and maltose
What does the Barfoed’s test indicate?
Specific for monosaccharides
Useful to indicate the presence of glucose
What is the difference between oligosaccharides and polysaccharides?
Oligosaccharides: Composed of only a few number of monosaccharide units (up to 10 sugar units)
Polysaccharides: Composed of more than 10 monosaccharide units.
What are the 2 components of starch?
Amylose and amylopectin
What is the glycosidic bonds for amylose and amylopectin
Amylose is composed of α 1 - 4 glycosidic bonds.
Amylopectin is composed of α 1 - 4 and α 1 - 6 glycosidic bonds.
Describe the break down of starch?
- Starch has two components: amylose and amylopectin.
- Amylase breaks down α 1 - 4 glycosidic bonds.
- Amylose gets broken down into maltose
- Amylopectin gets broken down into dextrins (branched chains because of the presence of α 1 - 6 glycosidic bonds)
- Both maltose and dextrins are broken down into glucose (by the brush border enzyme, maltase)
Why does the break down of amylopectin and amylose different?
- Both are broken down by amylase
- Amylopectin break down produces dextrin because the α 1 - 6 glycosidic bonds are present, which cannot be broken down by amylase therefore form these branched structures known as dextrin.
- Amylase contains only α 1 - 4 glycosidic bonds, therefore are broken down into maltose
Which bonds does amylase digest?
α 1 - 4 glycosidic bonds.
