Digestion And Absorbsion Flashcards
Why can’t large biological molecules be absorbed from the gut into the blood
They are too big to pass through the cell membranes
What reaction takes place in digestion to break up large molecules into smaller ones?
Hydrolysis
What does amylase do
Catalyses the conversion of starch into smaller sugar Maltese
What bonds are broken when breaking down starch?
Glucosidic bonds through hydrolysis
Where is amylase produced
Saliva glands and the pancreas which releases amylase into the small intestine
What membrane-bound disaccharidases do in break down of starch
Enzymes that are attached to cell membranes in epithelial cells lining the ileum
- Breakdown disaccharides into monosaccharides
Examples of disaccharides
Maltese sucrose and lactase
What are lipids broken down by?
Lipase with the help of bile salts
Describe how lipase breakdown lipids
- Lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids involving hydrolysis of ester bonds
Where are lipase made?
Made in the pancreas and working in the small intestine
Where are bile salts made and what do they do?
Made in the pancreas and emulsify lipids meaning they cause the lipids to form small droplets
How do bile salts help lipase?
They increase the surface
What do endopeptidases do?
- breakdown of proteins
- Active hydrolyse
peptide bonds within a protein - trypsin and chymotrypsin are two examples and they are synthesised in the pancreas and secreted in the small intestine
What is Pepsin, where is it released and what conditions does it work in?
- endopeptidase
- Released into the stomach by cells in the stomach lining
- Only works in acidic conditions provided by hydrochloric acid in the stomach
What do exopeptidase do?
Act to hydrolyse peptide bonds at the end of the protein molecules
- Remove single amino acids from proteins
What are dipeptidases
- exopeptidases that works specifically on dipeptides
- To separate the two amino acids that make up a dipeptide by hydrolysing the peptide bond between them
- dipeptidases are often located in the cell surface membrane of epithelial cells in the small intestine
How are monosaccharides absorbed in the ileum epithelium into the bloodstream?
- glucose is absorbed by active transport with sodium ions via a co- transporter protein
- ## galactose is absorbed in the same way using the same co-transporter protein
How is fructose absorbed across the ileum epithelium?
Via facilitated diffusion through a different transporter protein
How are monoglycerides and fatty acids absorbed across the ileum epithelium?
- micelles help to move monoglycerides and fatty acids towards the epithelium
- micelles release monoglyceride and fatty acids allowing them to be absorbed
- Monoglycerides and fatty acids are lipid soluble so can diffuse directly across the epithelial cell membrane
What do micelles do that? Allow them to release monoglycerides and fatty acids in the Ilium epithelium?
They constantly break up and reform so they can release monoglycerides and fatty acids,
- whole micelles I’m not taken up across the epithelium
How are amino absorbed across the ileum epithelium into the bloodstream?
- Amino acids are absorbed via co-transport in a similar way to glucose and galactose
- Sodium ions are actively transported out of the Ilium epithelial cells into the blood
- Creates a sodium concentration gradient
- Sodium ions, then diffuse from the lumen of the helium into the epithelial cells through sodium dependent transporter proteins carrying the amino acids with them
