3.3.3 Digestion and absorption Flashcards
Define digestion
The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes
Which enzymes are involved in carb digestion, where are they found
Amylase in mouth and pancreas
Maltase, sucrase, lactase in small intestine
What are the substrates and products of carb digestive enzymes
Amylase -> starch into smaller polysaccharides
Maltase -> maltose into 2x glucose
Sucrase -> sucrose into glucose and fructose
Lactase -> lactose in to glucose and galactose
Where are lipids digested
Small intestine
What needs to happen before lipids can be digested
They must be emulsified by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing SA
How are lipids digested
Lipase hydrolyses the ester bond between monoglycerides and fatty acids
Which enzymes are involved in protein digestion, what are their roles
Endopeptidases - hydrolyse peptide bonds in the middle of a polypeptide
Exopeptidases - hydrolyses peptide bonds at the end of a polypeptide
How are certain molecules absorbed into the ileum despite a negative conc gradient
Through co-transport
Which molecules require co-transport
Amino acids and monosaccharides
Explain how sodium ions are involved in co-transport
Sodium ions are actively transported out of the cell into the lumen, by the sodium potassium pump, creating a diffusion gradient. Sodium ions diffuse from ileum to epithelial cells down conc gradient, glucose is cotransported in with sodium ions. Higher conc of glucose in cell so it diffuses out into the blood by facilitated diffusion through a channel protein
Why do fatty acids and monoglycerides not require co transport
The molecules are nonpolar, meaning they can easily diffuse across the membrane of the epithelial cells
