TOPIC 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 carbohydrate digestion? where are they produced?
- amylase in mouth
- maltase , sucrase , lactase in membrane of small intestines
what are the substrates and products of carbohydrate digestive enzymes?
amylase - starch into smaller polysaccharides
maltase - maltose into 2x glucose
sucrase - sucrose into glucose and fructose
lactase - lactose into glucose and galactose
where are lipids digested?
small intestine
what needs to happen before lipids can be digested?
lipids must be emulsifies by bile salts into smaller soluble molecules called micelles= increasing SA
where is bile produced?
in the liver
how are lipids digested?
lipase hydrolyses the ester bonds between the monoglycerides and the fatty acids.
which enzymes are involved in protein digestion? what are their roles?
endopeptidase = break between specific amino acids in the middle of a polypeptide
exopeptidase = break between specific amino acids at the end of a polypeptide.
dipeptidase = break dipeptides into amino acids.
how are certain molecules absorbed into the ileum despite a negative concentration gradient?
through co-transport
which molecules require co transport?
amino acids and monosaccharides
explain how sodium ions are involved in co transport?
Na+ is actively transported out of the cell into lumen, creating a diffusion gradient.
Nutrients are then taken up into the cells along with Na+ ions.
why do fatty acids and monoglycerides not require co transport?
these molecules are non polar which means they can easily diffuse across the membrane of epithelial cells.
