Topic 3 - Digestion and Absorption Flashcards
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into the lymph vessels?
- micelles contain bile salts and fatty acids + monoglycerides
- make fatty acids +monoglycerides more soluble in water
- fatty acids + monoglycerides absorbed by diffusion
- triglycerides reformed in cells
- vesicles move to cell membrane
What is the function of ATP hydrolase?
- Hydrolyses ATP to ADP+ Pi
- releasing energy
- if in ileum and near carrier protein the energy used to AT Na+ out of epithelial cells
How does the movement of Na+ out of the cell allow the absorption of glucose into the cell lining the ileum
- movement of Na+ out creates a conc gradient
- so Na+ move from the ileum
- binding to co-transporter proteins in the cell surface membrane of the epithelial cells
- so glucose also binds to the co-transporter protein
- and diffuses into the cell by facilitated diffusion.
Scientists taking samples from gut to measure lipids (passed through stomach but not ileum) at different times after meal. Why does the concentration of fatty acids and triglycerides differ?
- As time inc after meal, inc conc of fatty acids and dec conc of triglycerides
- triglycerides dec bc more time for ester bonds between fatty acids and glycerol to be digested and hydrolysed by lipase.
- explain the inc in conc of fatty acids over time
Measuring lipase activity in gut samples : why would scientists immediately heat the sample at 70ºC?
- denature lipase enzyme
- so that it can no longer hydrolyse triglycerides and change the conc of each.
Describe the role of micelles in the absorption of fats into the cells lining the ileum.
- micelles include bile salts and fatty acids
- they make the fatty acids more soluble in water
- they bring fatty acids to the cell lining the ileum and released them
- maintaining a high conc of fatty acids compared to the cell lining the ileum
- so fatty acids absorbed by diffusion
Describe the role of enzymes in the digestion of proteins in a mammal
- peptide bonds are hydrolysed
- endopeptidases act in the middle of the protein
- exopeptidase act at the ends of the protein
- dipeptidase acts on any dipeptides
Graph with error bars evaluate whether increased protein percentage in food means more percent of protein ingested is absorbed?
- do SD error bars overlap - if yes then not statistically significant
- if not significant could something else eg. protease be limiting absorption
- did they only investigatea small range of protein in diet?
Why can animals re-eating their droppings help absorb a named nutrient?
- more of named nutrient that is undigested then gets broken down
- so more subunit (eg. AA) absorbed
- bc food passes again through stomach
By which process do fatty acids and glycerol enter the intestinal epithelial cell?
- diffusion
Explain the advantage of lipid droplet and micelle formation.
- both inc the SA for the lipids to be hydrolysed by lipase
- micelles carry fatty acids + glycerol through membrane
How is the Golgi apparatus involved in the absorption of lipids?
- modifies triglycerides
- combines triglycerides with proteins
- packages them in vesicles so they can be released from the cell
Explain how cells lining the ileum of mammals absorb glucose by co-transport with sodium ions?
- Na+ are AT out of the epithelial cells in the ileum into the blood from a high conc to a low conc.
- Dec conc of Na+ in epithelial cells which forms a diffusion conc gradient
- so Na+ from gut binds to co-transporter proteins and then also cause glucose to bind to the co-transporter protein
- meaning glucose enters the epithelial cell by facilitated diffusion with the Na+ ions.
What molecules are too large to pass through partically permeable visking tubing?
- protein molecukes
- starch molecules
