exchange and transport (digestion) Flashcards
what is digestion?
when large insoluble molecules are hydrolysed into smaller molecules, which can be absorbed across cell membranes
what are carbohydrates broken down by?
amylase and membrane bound disaccharides
what does amylase catalyse the conversion of?
starch into maltose
how does starch get broken down?
hydrolysis of the glycosidic bonds in starch
where is amylase produced?
the salivary glands and pancreas
what are membrane bound disaccharides?
enzymes attached to cell membranes of epithelial cells lining the ileum- break down disaccharides into monosaccharides
what is maltose broken down into?
2 alpha glucose
what is sucrose broken down into?
glucose and fructose
what is lactose broken down into?
glucose and galactose
how is starch digested?
saliva enters the mouth from the salivary glands
hydrolyses starch in food to maltose
denatured in the stomach
enters the stomach- pancreatic juice hydrolyses starch to maltose
ileum produces maltase- hydrolyses starch to alpha glucose
what enzyme is a lipid broken down by?
lipase
what does lipase break a lipid down into?
monoglycerides and fatty acids
how are lipids broken down into monoglycerides and fatty acids?
hydrolysis of the ester bond
where are lipases made?
pancreas
where do lipases work?
small intestine
where are bile salts produced?
in the liver
what do bile salts do?
emulsify lipids- break down lipids into smaller droplets which increase the surface area for digestion
what is a micelle?
monolglycerides and fatty acids combined with bile salts
what is physical lipid digestion?
emulsification and micelle formation
what is chemical lipid digestion?
lipase hydrolyses lipids into fatty acids and glycerol
how are lipids digested?
micelles meet epithelial cells
fatty acids and monoglycerides are non polar
these diffuse across the membrane
and are modified to form triglycerides in the endoplasmic reticulum and golgi body
form chylomicrons
leave by exocytosis
what enzymes break down proteins?
proteases (endopeptidases, exopeptidases, dipeptidases)
what does an endopeptidase do?
hydrolyses peptide bonds between amino acids in the middle of polymer chain
what does an exopeptidase do?
hydrolyses peptide bonds between amino acids at the end of a polymer chain
what does a dipeptidase do?
hydrolyses peptide bonds between 2 amino acids
where does protein digestion start and end?
starts in the stomach
completed in the ileum
where are dipeptidases usually located?
cell surface membrane of epithelial cells in the small intestine
how are glucose and galactose absored into the bloodstream?
active transport with sodium ions via a co transporter protein
how is frutose absorbed into the bloodstream?
via faciliated diffusion through a transporter protein
how are monoglycerides and fatty acids absorbed into the bloodstream?
micelles release monoglycerides and fatty acids
these are lipid soluble so can diffuse directly across the epithelial cell membrane
how are amino acids absorbed into the bloodstream?
via co transport
sodium ions are actively transported out of the epithelial cells into the blood
creates a sodium ion concentration gradient
sodium ions can diffuse through sodium-dependent transporter proteins, carrying the amino acids with them
