3.3 Digestion Flashcards
Which membrane are digestive enzymes bound to?
Small intestine
Why is it advantageous that enzymes are membrane bound?
- so that enzymes won’t be egested with the contents of the small intestine
- so that the products of digestion are right next to the proteins which will transport them into the epithelial cell to be absorbed
distinguish between digestion and absorbtion
- hydrolisis of large insoluble molecules to make smaller soluble molecules
- transferring the small soluble molecules from the lumen of the small intestine to the blood
Describe the processes involved in the absorbtion of the products of protein digestion (6)
- amino acids move into the epithelial cell from the lumen of the small intestine with sodium
- via symport protein
- sodium removed from epithelial cell by active transport
- into the blood
- maintaining sodium concentration gradient (betw/ lumen and epithelial cell)
- amino acid moves into blood
- by facilitated diffusion
What adaptations do epithelial cells have for absorbtion of glucose (6)
- lots of mitochondria
release energy in form of ATP: needed for active transport -
lots of membrane bound disaccharidases
breaks down disaccharides into glucose - microvilli
large surface area for diffusion - symport proteins
for co-transport of glucose and sodium - channel / carrier froteins for facilitated diffusion
- carrier proteins for active transport
What are the 3 functions of bile
- bile emulsifies the fat
increases SA that lipase can act on
rate of digestion by lipase increases - bile neutralises stomach acid providing the right pH for lipase and other enzymes to function in
- helps to form micelles which make fatty acids soluble in water and transport them to the lining of the ileum
what is a micelle
an aggregate of lipid molecules within an aqueous solutions
Glucose is absorbed from the lumen of the small intestine into epithelial cells. Explain how the transport of sodium ions is involved in the absorption of glucose by epithelial cells. (5 marks)
- Na+ ions leave epithelial cell and enter blood;
- (Transport out is by) active transport / pump / via carrier protein using ATP;
- So, Na+ conc. in cell is lower than in lumen (of gut);
- Sodium/Na+ ions enter by FACILITATED diffusion;
- Glucose absorbed with Na+ ions against their concentration
Describe role of micelles in absorbtion of lipids
- monoglycerides and fatty acids associate w/ bile salts to form micelles
- micelles transport f.a. and monoglyc to lining of ileum
- micelles release monog. and f.a. when in contact w/ epithelial cell
- mono and f.a. diffuse into across phos.layer. into epithelial cell
- -> enter SER and converted back into 3glyc
- vesicle buds off SER and fuses w/ golgi apparatus
- 3glyc associates w/ proteins to form lipoproteins
- lipoproteins combine w/ cholesterol to form chylomicrons
- chylomicrons leave epithelial by exocytosis
- chylomicrons enter lymphatic capillaries
- lymphatic vessels (joins with blood at subclavian vein) transport chylo to blood
role of micelles
- makes fatty acids soluble in water
- transport fatty acids to lining of ileum
why are tests using monoclonal antibodies specific
- specific primary structure
- specific tertiary structure
- so only binds to specifc antigen
why does respiratory inhibition prevent absorbtion of amino acids
- No/less ATP produced
- Sodium (ions) not moved (into/out of cell);
- No concentration gradient for sodium (to move into cell with amino acid);
why do chylomicrons need to leave by exocytosis
- because too large to leave cell by other methods
Why is digestion of triglycerides faster when there is a higher bile salt concentration? (3)
- more bile salts means more emulsification -> smaller drops.
- higher SA for lipase to act on -> faster hydrolysis of 3G
- more ES complexes formed per unit time
How does an animal with high surface area cope with heat loss? (3)
- Higher SA:vol ratio
- Higher rate of respiration/ more heat lost per gram of tissue
- Respire more to generate more heat higher metabolic rate.
