Nutrient Digestion I (Carbohydrates and Proteins) Flashcards
What are the three monosaccharides?
Glucose
Galactose
Fructose
What three digestive enzymes are expressed on the surface of the small intestine?
Lactase
Sucrase
Maltase
What does Lactase break Lactose down into?
Glucose & Galactose
What does Sucrase break Sucrose down into?
Glucose & Fructose
What does Maltase break Maltose down into?
Glucose & Glucose
What happens to those people who can’t express Lactase?
The Lactose sits in the lumen of the tube causing water to be drawn in and causing osmotic diarrhoea
What is Amylopectin?
A highly branched glucose chain joined by alpha-1,4 glycosidic bonds
What is alpha-amylose?
Glucose linked in straight chains joined by α-1,4 Glycosidic bonds
What is Cellulose?
Unbranched, linear chains of Glucose joined by β-1,4 Glycosidic bonds
What is Glycogen?
Similar to α-amylose with Glucose being linked by α-1,4 Glycosidic bonds
How much Glycogen is stored in the liver at one time?
18 miles worth of running
What type of epithelium lines the small intestine?
Monolayer of columnar epithelial cells
What are the two membranes of the intestine and what is it lined with?
Top - Apical on the outside and it has microvilli on on the villi itself
Bottom & Side - Basolateral
What type of junctions exist between the basolateral membranes?
Tight junctions
What does paracellular indicate?
Around or between cells - Must be smaller than Glucose to do so e.g. Water
What does Glucose require for passing through a cell?
Two transport proteins
What is needed as well as Glucose for it pass through a cell?
Sodium is required with the use of a symporter (SGLT1)
How does the Glucose symporter work?
Works by secondary active transport from the gradient made by the Na/K pump
Why is no symporter needed to carry Fructose over the apical membrane?
The small intestine is enriched with GLUT-2 protein that transports it across
No water advantage because of no Na
What transports Glucose, Fructose and Galactose over the basolateral membrane?
GLUT-2 carrier found on the basolateral membrane
What can proteins undergo to create Glyco/Lipoproteins?
Post-translational modification
What hydrolyse peptide bonds to form Amino Acids?
Proteases and Peptidases
What do endopeptidases do?
Split proteins into two smaller fragments by working in the interior portion of the protein
What do exopeptidases do?
Act on exteriors of the protein to break off small fragments bit by bit
How do Amino Acids cross the apical membrane?
Use of a symporter similar like that of Glucose and Na Driven the same way by the Na/K pump
How do Amino Acids cross the basolateral membrane?
Separate transporter
How do most Amino Acids enter the body?
As di/tri peptides
How do these di/tripeptides enter the body?
Via the Proton motive force as they use a hydrogen ion
PepT1 is Hydrogen bound
What force drives the di/tripeptide entering the cell?
Na/K pump
As the Hydrogen leaves the cell what does it create?
Acid Microclimate as it gets stuck in the mucus as it leaves
What causes the hydrogen to leave the cell?
The Na/H exchanger
Is Penicillin a tripeptide? If so, what is it’s substrate?
Yes
PepT1
