digestion + absorption Flashcards
what does the salivary glands produce
amylase
what is the ilium
small intestine
where is amylase produced
salivary glands or pancreas
where does the pancreas secrete amylase
small intestine
what is the role of amylase
hydrolyses starch (carb) / polysaccharide into maltose which is a disaccharide
where are membrane-bound disaccharides found
they are present in the membrane of the small intestine
what is the role of membrane-bound disaccharidases
to hydrolyse disaccharides eg maltose into monosaccharides eg glucose
examples of membrane-bound
maltase, sucrase, lipase
role of lipase
hydrolyse lipids to monoglycerides and fatty acids
where is lipase present
in the small intestine
adaptations of lipase
bile salts - made by liver - emulsify lipids, giving them a large SA, so they’re easily hydrolysed by lipases
produces can remain associated with bile salts to form micelles
micelles travel
to ileum and are broken down when in contact with epithelium, products can then diffuse straight into epithelium
proteases role
hydrolyse proteins (polypeptides) into amino acids
three types of protease
endopeptidase, exopeptidase, and membrane-bound dipeptidases
endopeptidases
eg trypsin, chymotrypsin and pepsin
hydrolyse peptide bonds in the middle region of the polypeptide chain
exopeptidases
hydrolyse peptide bonds on terminal amino acids
membrane-bound dipeptidases
hydrolyse dipeptides (2 amino acids condensed together) into 2 amino acids
how are amino acids and monosaccharides absorbed into the blood
co-transport
there is a high concentration of glucose inside the epithelial cell than in the lumen
there is a lower concentration of Na+ inside the epithelial cell than in the lumen
the co-transport/carrier protein has two binding sites, one for glucose and one for Na+
when both glucose and Na+ bind to the carrier protein, the protein changes its tertiary structure to transport them into the cell
what happens to food during digestion and why
the large biological molecules are too big to cross cell membranes - cannot be absorbed from the gut into blood
during digestion - large molecules broken down into smaller molecules which can be easily absorbed
polymers -> monomers by hydrolysis
what are carbohydrates broken down into to
carbohydrates are broken down into disaccharides then monosaccharides
what are fats broken down into
fatty acids and monoglycerides
what are proteins broken down into
amino acids
what does amylase do
convert starch (polysaccharide) into a smaller sugar maltose (disaccharide)
hydrolysis of glycosidic bonds in starch
where is amylase produced
in the salivary glands and in the pancreas
what do lipase do
lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids
hydrolysis of ester bonds
where is lipase made
pancreas
what are membrane-bound disaccharides
enzymes that are attached to the cell membranes of epithelial cells lining the ileum
help break down disaccharides (maltose, sucrose and lactose) into monosaccharides (glucose, fructose and galactose)
maltase, sucrase, lactase
what do bile salts do and where are they made
produced by the liver, emulsify lipids - cause the lipids to form small droplets
why are bile salts important
several small lipid droplets have a bigger surface area than a single large droplet, so increases the surface area that’s available for lipases to work on
once the lipid has been broken down - monoglycerides and fatty acids stick with the bile salts to form micelles
what is endopeptidases
act the hydrolyse peptide bonds within a protein
trypsin and chymotrypsin are two examples
- synthesised in pancreas and secrete to small intestine
pepsin - released into the stomach by cells in the stomach lining - only works in acidic conditions
what are exopeptidases
act to hydrolyse peptide bonds at the ends of the protein molecules - remove single amino acids from proteins
dipeptidases are example - work specifically on dipeptides to separate the amino acids that make up a dipeptide by hydrolysing the peptide bond between them
- located in the cell-surface membrane on epithelial cells
how are monosaccharides absorbed
glucose is absorbed by active transport with sodium ions via a co-transporter protein
galactose is absorbed in the same way using the same co-transporter protein
fructose is absorbed via facilitated diffusion through a different transporter protein
how are monoglycerides and fatty acids absorbed
micelles help to move monoglycerides and fatty acids towards the epithelium
micelles constantly break up and reform - they can ‘release’ monoglycerides and fatty acids allowing them to be absorbed
whole micelles cannot be taken up across the epithelium
monoglycerides and fatty acids are lipid-soluble so can diffuse directly across
how are amino acids absorbed
via co-transport, in a similar way to glucose and galactose
sodium ions are actively transported out of the ileum epithelial cells into the blood
creates a sodium ion concentration gradient
sodium ions can then diffuse from the lumen of the ileum into the epithelial cells through sodium-dependent transporter proteins, carrying the amino acids with them
