Digestion Questions Flashcards
What can you conclude from figure 5 about the importance of bile-activated lipase in breast milk? (3)
- results for formula with lipase not significantly different from breast milk
- showing addition of bile activated lipase is the likely cause of increased growth
- lipase increases rate of digestion of lipids/ absorption of fatty acids
Cells lining the ileum of mammals absorb the monosaccharide glucose by co transport with sodium ions. Explain why. (3)
- sodium ions actively transported from ileum cell to blood
- maintains diffusion gradient for sodium ions to enter from gut
- glucose enters via facilitated diffusion with sodium ions
Endopeptidases and exopeptidases are involved in the hydrolysis of proteins.
Name the other type of enzyme required for the complete hydrolysis of proteins to amino acids. (1)
Dipeptidase
Suggest and explain why the combined actions of endopeptidase and exopeptidases are more effucient than exopeptidases on their own. (2)
- endopeptidases hydrolyse internal peptide bonds
- exopeptidases remove amino acids at ends
- more ends increase surface area for exopeptidases
Figure 1 shows the co-transport mechanism for the absorption of amino acids into the blood by a cell lining the ileum.
The addition of a respiratory inhibitor stops the absorption of amino acids.
Explain why. (3)
- no ATP produced
- sodium ions aren’t moved out of epithelial cells into blood
- no diffusion gradient for sodium ions to move into cell with amino acids
Describe how digested lipids are absorbed and then transported into the ileum and lymphatic system. (5)
- micelles are made of monoglycerides, bile salts, fatty acids
- micelles carry fatty acids and monoglycerides to the epithelial cells in ileum
- fatty acids and monoglycerides are absorbed into the cells by simple diffusion
- triglycerides or chylomicrons are formed
- vesicles are removed by exocytosis
Describe the importance of micelles in absorbing lipids into epithelial cells of the ileum. (3)
- micelles are made of bile salts, fatty acids and monoglycerides
- micelles make fatty acids more soluble in water
- micelles carry fatty acids to the epithelial cells of the ileum
- the fatty acids are released from the micelle and are absorbed into the cell by simple diffusion
Explain the advantages of lipid droplet and micelles formation. (3)
- formation of lipid droplets increase surface area for lipase action
- so faster hydrolysis of lipids
- micelles carry fatty acids and monoglycerides through membrane to intestinal epithelial cells
How is Golgi apparatus involved in the absorption of lipids. (3)
- modifies/ processes triglycerides
- combines triglycerides with protein
- packaged for exocytosis
Following digestion and absorption of food, the undigested remains are processed to form faeces in the parts of the intestine below the ileum.
The faeces of people with constipation are dry and hard. Constipation can be treated by drinking lactulose. Lactulose is soluble, but it isn’t digested or absorbed in the human intestine.
Use your knowledge of water potential to suggest why lactose can be used to help people suffering from constipation. (2)
- lactulose lowers water potential of faeces
- so water enters via osmosis and softens faeces
What is digestion? (2)
- hydrolysis
- of large insoluble substances to smaller soluble substances
Endocellulases act in the middle of cellulose molecule and exocellulases act at the ends of cellulose molecule.
Suggest why they act at different places on cellulose molecules. (2)
- active sites are different shapes
- so different e-s complexes formed
- so complementary to different parts of cellulose
Describe the role of enzymes in the digestion of proteins in a mammal. (4)
- endopeptidases in stomach hydrolyse peptide bonds between amino acids in central region of protein
- exopeptidases hydrolyse peptide bonds at the end of protein to produce dipeptides
- dipeptidase enzymes further hydrolyse dipeptides to single amino acids
What can you conclude about the absorption of the products of protein digestion as the percentage of protein increased in the rabbits food? (3)
- no significant difference in protein absorption
- significant differences overlap
- so mean % absorbed not affected by % in diet
The food eaten by a rabbit is digested mainly by microorganisms in its caecum. The caecum is a section of intestine attached between the ileum and the large intestine. The resulting semi-digested material leaves the anus of a rabbit as soft, caecal droppings. The rabbit then eats these caecal droppings.
Suggest how eating its own caecal droppings helps a rabbits digestion and absorption of dietary protein. (3)
- more undigested protein can be digested
- so more amino acids absorbed
- bc protein passes again through ileum
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into the lymph vessels. (5)
- micelles contain bile salts, fatty acids and monoglycerides
- make fatty acids and monoglycerides more soluble
- they are absorbed by diffusion
- triglycerides reformed in cells
- vesicles move to cell membrane
Describe how the structure of glycogen is related to its function. (4)
- helix so compact
- branched so more ends for faster hydrolysis
- polymer of glucose so easily hydrolysed
- glucose polymer so provides respiratory substrate for energy release
- insoluble so has no osmotic effect
Describe the mechanism for the absorption of amino acids in the ileum. (4)
- facilitated diffusion of amino acid into cell down conc gradient
- co-transport
- sodium ions actively transported from cell to blood
- creating sodium ion diffusion gradient
- facilitated diffusion of amino acid into blood
