3. Enzymes - Digestion Flashcards
Carbohydrate digestion
Carbohydrases- Break down carbohydrates, ultimately to monosaccharides.
Amylase breaks down starch to maltose. Amylase is produced by the salivary glands and the pancreas
Membrane bound disaccharidases
enzymes that are attached to the cell membranes of epithelial cells lining the ileum (the final part of the small intestine).
They help to break down disaccharides into monosaccharides.
Sucrose Digestion
Which enzyme breaks down sucrose?
Sucrase
What type of reaction is it?
Hydrolysis
What are the products?
Glucose and Fructose
LIPID DIGESTION
Lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids. This involves the hydrolysis of the ester bonds in lipids. Lipases are mainly in the pancreas- they are then secreted into the small intestine where they act.
Bile salts are produced by the liver and emulsify lipids – this means they cause the lipids to form small droplets.
This increases the surface area of lipid that is available for faster hydrolysis action by lipase
Once the lipid has been broken down by lipase, the monoglycerides and fatty acids remain with the bile salts to form tiny structures called micelles.
Micelles help the products of lipid digestion to be absorbed. Micelles are necessary because they transport the poorly soluble monoglycerides and fatty acids to the surface of the epithelial cell where they can be absorbed by diffusion across the bilayer as they are lipid soluble.
PROTEIN DIGESTION
Proteins are digested by a combination of different peptidases. These are enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between the amino acids.
Endopeptidases act to hydrolyse peptide bonds within a protein
Exopeptidases act to hydrolyse peptide bonds at the ends of protein molecules. They remove single amino acids from proteins
Dipeptidases are exopeptidases that work specifically on dipeptides.They are often located on the cell surface membrane of epithelial cells of the small intestine
what is the advantage of having both endopeptidases and exopeptidases?
Having endopeptidases allows more separate smaller chains to be broken down from larger ones. This means more ends/increases surface area available for exopeptidases to work on.
Co transport glucose
Sodium ions are transported out actively using the Na+/K+ pump
Once inside the cell glucose passes into the blood plasma by facilitated diffusion.
Absorption of lipids.
Assimilation
The small soluble products of digestion are absorbed from the small intestine. They travel to different parts of the body in the blood stream and are often used to build up larger molecules. These molecules can be incorporated into body tissues (i.e. used for growth) or used in processes within the body. This is called ASSIMILATION.
