unit 3, the digestive system and absorbtion Flashcards
what is digestion?
large biological molecules that are hydrolysed into smaller molecules that can be absorbed across cell membranes
what enzymes hydrolyse carbohydrates?
-amylases
-membrande bound disacharides
where does the process start and finish in the carbohydrates digestion?
starts at the mouth
goes to duodenum
finishes in ileum
where is amylase produced and what does it hydrolyse?
-it is produced in the pancreas and the salivary glands
-it hydrolyses polysacharides into the diasacharide maltose by hydrolysing the gylcosidic bond
what are the membrane bound diasacharides and what do they hydrolyse into?
sucrase hydrolyses sucrose into glucose and fructose
lactase hydrolyses lactose into glucose and galactose
what are large polymers hydrolysed by?
-endopeptidases
-exopeptidases
-dipeptidases
what are endopeptidases?
they are in the middle of the peptide chain, hydrolysing the amino acids
what are exopeptidases?
they are at the end of the peptide chain, hydrolysing the bond at the end
what are dipeptidases?
hydrolyse between 2 amino acids
where does the process start and finish in the proteins digestion?
- begins in the stomach
-to the duodenum
-finishes in the ileum
what are lipids sigested by?
-lipase
-action of bile salts
where is lipase produced and what does it hydrolyse?
-produced in the pancreas
-hydrolyses ester bond in triglycerides, to form monogylcerides and fatty acids
-goes into duodenum
where is bile salts produced and what do they do?
-produced in liver
-they are before lipase, and they emulsify lipids to form tiny droplets called micelles
-they increase the surface are for the lipase to act on
-goes into duodenum
what is the physical reaction?
-lipids get coated in bile salts to create an emulsion
-many small droplets of lipids that are formed crete a large surface area to enable faster action of hydrolysis by lipase
what is the chemical reaction?
lipase hydrolyses lipids into gylcerol, fatty acids and some monoglycerides
what is a micelle and what do they do?
-water soluble vesicles formed from fatty acids, gylcerol, monogylcerides and bile salts
-they deliver fatty acids, gylcerol, monoglycerides to the epithelial cells of the ileum for absorbtion
-make lipids more soluble in water
where does absorbtion occur?
cells lining the ileum
what advanatgeous structures does the ileum have?
- covered in villi, to increase surface area
-thin walls, for a shorter diffusion pathway
-surrounded by capillaries to maintain concentration gradient.
where does amino acid and monosacharide absorbtion start and end up?
from lumen to the gut
when would facilitated diffusion be needed and when would a co transporter be needed for amino acid and monosacharide absorbtion?
facilitated diffusion- if there is higher concentration in the lumen than eptiehlial cell
co- transporter- higher cocentration in the epithelial cell than the lumen, this is usually the case
in lipid absorbtion, what do micelles deliver and where to?
-micelles deliver fatty acid and monogylcerides to epithelial cell which they diffuse across due to their non polar nature leaving behind the micelles
-lipids can simple diffuse in phospholipid bilayer (as phospholipid is a lipid)
what happens in the golgi apparatus and the endoplasmic reticulum?
triglycerides reform to be used in the body
how are chylomicrons formed?
fatty globules combine with proteins to form chylomicrons, inside the golgi apparatus
how are chlyomicrons transported away?
the lymph in the lacteal transports chylomicrons away from the intestine
