Digestion and absorption Flashcards
Define digestion
The breakdown of large insoluble molecules into smaller molecules by hydrolysis
Explain what happens during the digestion of starch
Amylase catalyses the conversion of starch into maltase. Involves hydrolysis of glycosidic bonds.
Where is amylase produced?
Salivary glands
Pancreas
How are disaccharides broken down?
By membrane bound disaccharides (enzymes) that are attached to cell membranes of epithelium cells. They break down disaccharides into monosaccharides.
Name the enzymes that break down each disaccharide
Maltase breaks down maltose = glucose + glucose
Sucrase breaks down sucrose = glucose + fructose
Lactase breaks down lactose = glucose + galactose
How are lipids broken down into fatty acids and monoglycerides?
Lipase enzymes catalyses the break down of lipids. Involves the hydrolysis of ester bonds.
Where is lipase produced?
Pancreas
What are bile salts and what do they do?
Bile salts are produced by the liver and emulsify lipids (cause lipids to form small droplets). Increases the surface area of a lipid that is available for lipases to work on.
What happens after the lipid have been broken down?
Fatty acids and monoglycerides stick will bile salts to form micelles
How are proteins digested?
Proteins are broken down by a combination of different proteases
What does endopeptidase do?
Hydrolyse peptide bonds within a protein
(e.g. trypsin, chymotrypsin, pepsin)
What does exopeptidase do?
Hydrolyse peptide bonds at the end of the protein molecules. (removes single amino acids)
What does dipeptidase do?
(a type of exopeptidase that works specifically on dipeptides)
Acts to separate 2 amino acids that make up a dipeptide by hydrolysing the peptide bond between them
How are monosaccharides absorbed across cell membrane?
Glucose and galactose is absorbed by active transport with sodium ions.
Fructose is absorbed via facilitated diffusion through a different transporter protein.
How are monoglycerides and fatty acids absorbed across cell membrane?
Micelles move monoglycerides towards epithelium as the constantly break up and reform which releases monoglycerides and fatty acids allowing them the be absorbed. They are lipid soluble so can diffuse directly across cell membrane.
