digestion Flashcards
what is the definition of carbohydrate digestion?
the process by which large, insoluble starch is hydrolysed by enzymes to produce disaccharides and monosaccharides by breaking glycosidic bonds.
where is starch digested?
starch is large and insoluble and is digested in the mouth and small intestine to produce small, soluble molecules that can be absorbed into the blood.
what two locations is starch broken down into maltose?
-mouth by salivary amylase
-small intestine by pancreatic amylase
where is salivary amylase made and secreted? what does it do?
made in salivary glands and secreted into the mouth
catalyses hydrolysis reaction that breaks glycosidic bonds connecting glucose units in starch
it does this by forming enzyme-substrate complexes and lowering activation energy
how does amylase lower the activation energy to catalyse the hydrolysis of starch?
when starch binds to active site of amylase, the active site changes shape to fit the substrate and this puts a pressure on the glycosidic bond, making it easier to break.
where is pancreatic amylase made and secreted? what does it do?
made in the pancreas and secreted in the small intestine.
catalyses the hydrolysis of glycosidic bonds connecting glucose units in starch.
how is maltose broken down into glucose?
the enzyme maltase which is in the cell membrane of the small intestine epithelial cells
maltase catalyses the hydrolysis that breaks the glycosidic bond between glucose units in maltose
what is the product of hydrolysis of maltose?
small, soluble glucose units that can be absorbed into the blood
what do endopeptidases do?
catalyse the hydrolysis of peptide bonds in the middle of large polypeptide chains into smaller polypeptide chains.
what do exopeptidases do?
catalyse hydrolysis of peptide bonds at the end of polypeptide chains to make dipeptides and some single amino acids.
what do dipeptidases do?
catalyse hydrolysis of peptide bonds between two amino acids (dipeptides) to release singular amino acids.
what is the general name for enzymes that break down proteins?
proteases
where are pepsin and trypsin released?
pepsin- stomach, optimum pH of 2
trypsin- pancreas, optimum pH of 8 ACTS IN SMALL INT
where do the enzymes of protein digestion act?
endopeptidases- stomach and small intestine
exopeptidases- small intestine (duodenum)
dipeptidases- small intestine (duodenum)
where are exopeptidases and dipeptidases found?
in the cell membrane of small intestine epithelial cells
pepsin and trypsin are first released by cells in an inactive form, why?
to prevent auto digestion- stop enzymes breaking down proteins inside the cell
how are small intestine epithelial cells adapted for digestion?
-many mitochondria = high rates of resp= lots of ATP= more protein synthesis= more enzymes for digestion
-lots of ribosomes for protein synthesis
-lots of rough ER for transport of proteins
-lots of Golgi to modify proteins and transport them to cell surface
where does lipid digestion take place?
small intestine
how is the optimum pH provided for digestion of lipids?
bile is alkaline (sodium hydrogen carbonate) and it neutralises the stomach acid to provide the optimum pH for lipase to act
where is bile produced/ stored/ acts?
produced in the liver
stored in gall bladder
released into the duodenum
why do triglycerides have a small surface area to volume ratio?
they are non-polar and so form large lipid droplets
what does bile contain and what do these do?
bile salts are responsible for emulsification
describe the structure of bile salts?
hydrophobic tail and negatively charged hydrophilic head
describe bile salts role in emulsification?
mechanical digestion in the stomach breaks down large fat droplets into smaller ones
bile salts attach to droplets with hydrophobic tails within the droplets and hydrophilic heads on the outside, associating with water
the negative charge on the head of the bile salts repels droplets from each other so they don’t re-join
