Digestion and Absorption 3.3.3 Flashcards
define digestion
the hydrolysis of large insoluble molecules into smaller molecules that can be absorbed across the cell membrane
what enzymes are involved in carbohydrate absorption and where?
amylase - mouth
maltase, sucrase, lactase in small intestine membrane
what does amylase break carbohydrates into
starch = polysacharrides
what does maltase break down and into what?
maltose = 2x glucose
what does sucrase break down and into what
sucrose = glucose and fructose
what does lactase break down and into what
lactose = galactose and glucose
where are lipids digested?
lipids
what needs to happen to lipids before they are digested
they must be emulsified by bile salts produced by the liver
what does emulsification by bile salts do
breaks down large fat molecules into smaller soluble molecules called micelles that are soluble
what are lipids emulsified into by bile salts
micelles
why are micelles useful
they are soluble and increase surface area
what enzyme digests lipids
lipase hydrolyses the ester bond between the monoglycerides and fatty acids
what does endopeptidase do
break between specific amino acids in the middle of the polypeptide chain
what does exopeptidase do
break between specific amino acids at the end of the polypeptide chain
what does dipeptidase do
break down dipeptides into amino acids
how are certain molecules absorbed into the ileum of the small intestine despite a negative concentration gradient
co-transport
how are sodium ions involved in active transport
-Na+ are actively transported out of the cell into the lumen creating a diffusion gradient
-nutrients are then taken up into the cell along with Na+ ions
why do monoglycerides and fatty acids not require co-transport
they are non-polar
they can therefore diffuse easily across the membrane of the epithelial cell
