adaptation for nutrition Flashcards
how is food digested in the buccal cavity/mouth
mechanical nutrition-food chewed, increase sa for enzymes. Saliva is mixed in -chemical digestion. saliva contains amylase HCO3- and CO32- ions give a slightly alkaline PH-optimum for amylase. mucus lubricates food passing down oesophagus.
what is the role of the stomach in digestion
mechanical digestion by contractions of stomach wall-secretes gastric juice.
what does gastric juice contain
hydrochloric acid- PH2 optimum for enzymes and kills bacteria.
-pepsinogen-inactive form of pepsin-an endopeptidase activates by H+ ions hydrolysing proteins to polypeptides.
what is the role of mucus in the stomach
forms a lining which protects the stomach wall from enzymes and lubricates food.
what are specialised cells in gastric gland
goblet cells-produce mucus.
-oxyntic cells-produce hydrochloric acid.
-chief/peptic cells-produce pesinogen.
what organ produces bile
liver
how does bile enter he duodenum,
bile is secreted from gall bladder into duodenum via the bile duct.
what is the function of bile salts
emulsify lipids by lowering their surface tension and break up globules into smaller ones to increase sa for lipase digestion .
bile is alkaline what is the function of this
neutralises acid in food from stomach producing a suitable PH for enzyme action .
in the pancreas what secretes pancreatic juice
islet cells
what does pancreatic juice contain
sodium hydrogen carbonate ions-raises pH to neutralise stomach acid.
-amylase-starch to maltose.
-lipase
-trypsinogen-is an endopeptidase activated by enterokinase and hydrolyses proteins to polypeptides.
-enterokinase-trypsinogen-trypsin.
what are endopeptidaases-
hydrolyses proteins to peptides.
what are exopeptidases
hydrolyses peptide bonds at the end of protein to amino acids.
in the small intestine how is food lubricated.
mucus from goblet cells. it is neutralised by alkaline secretions from brunner glands at the base of the crypts of Lieberkühn in the lining of small intestine.
epithelial cells in the crypts of Lieberkühn secrete enzymes, what are these
dipeptidases-dipeptides to amino acids.
-maltase
-sucrose
-lactase
-exopeptidases-peptides to amino acids.
how are amino acids absorbed
absorbed by epithelial cells by active transport.
-then go into capillaries by facilitated diffusion.
-they are water soluble so dissolve in plasma
-transported via the hepatic portal vein into liver.
how is glucose absorbed
passes into epithelial cells with sodium ions by co transport.
-sodium moves into capillaries by active transport
-glucose moves into capillaries by facilitated diffusion.
- dissolve in plasma.
-some glucose is transported by active transport as facilitated diffusion is slow . Is transported via hepatic portal vein to liver.
how are lipids absorbed
fatty acids and glycerol diffuse into epithelial cells and reassembled into triglycerides
-proteins are combined to form chylomicrons.
-these moves into lacteals by exocytosis
-carried via lymphatic system to blood and enter the blood via the thoracic duct at the subclavian vein.
how is vitamin b and c absorbed
water soluble so absorbed into blood.
how are vitamins A,D and E absorbed
fat soluble so absorbed into lacteals.
what happens in the large intestine-colon
undigested food mucus and bacteria pass into colon,
-absorbs water.-vitamin K and folic acid secreted by mutualistic bacteria living here.
-these are absorbed.
what is ingestion
taking food through mouth
what is digestion
breakdown of large insoluble molecules into soluble molecules small enough to be absorbed.
what is assimilation
incorporation of products of digestion into the structures of an organism .
