Module 3 - Absorption and digestion Flashcards
5 marks
Explain how the epithelial cells are adapted for the absorption of glucose
- Microvilli to increase surface area
- Many mitochondria to produce ATP for active transport
- Carrier proteins for active trasnport
- Channel and carrier protiens for facilitated diffusion
- Co- transport of sodium ions and glucose
- Membrane- bound enzymes digest disaccharides / produce glucose
5 marks
Describe the processes involved in the absorption of the products of starch digestion
- Glucose moves in with sodium ions into epithelial cell via co -transport
- Via channel/ carrier protein
- Sodium ions removed from epithelial cell by active transport/ sodium-potassium pump
- Into blood
- Maintaining low concentration of sodium ions in epithelial cell
- Glucose moves into blood
- Via facilitated diffusion
4 marks
Toxins cause lining of ileum to lose microvilli
Explain why damage to the cells lining the ileum reduces the absorption of the products of digestion and why this reduces absorption of water.
- Surface area reduced
- and so less digestion products enter cell (sodium ions and glucose)
- and so water potential does not decrease
- and so less water enters cell by osmosis
4 marks
Describe digestion of proteins
- Hydrolyisis of peptide bonds
- Endopeptidases break bonds in the middle of the AA chain
- Exopeptiades remove terminal amino acids
- Dipeptidases breaks bonds between dipeptides into single AA
2 marks
Desribe functions of bile salts
- Emulsify lipids/fats;
- Increases surface area (of lipid/fat) for (increased) lipase activity;
- Form micelles;
Mechanism for absorption of amino acids into the ileum
- Glucose moves in with sodium into epithelial cell
- Via carrier/channel protein
- Sodium removed from epthelial cell by active transport using sodium- potassium pump
- Maintaining low concentration of sodium in epithelial cell
- Glucose moves into blood
- By facilitated diffusion
5 marks
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels
- Micelles contain bile salts, fatty acids and monoglycerides
2.Micelles release fatty acids to the lining of the iluem - Fatty acids absorbed by diffusion
- Triglycerides reformed in cells
- Vesicles move to cell membrane
2 marks
The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.
Explain how.
- Maintains a sodium concentration gradient
- Na+ moving in by facilitated diffusion, brings glucose with it/ Na+ moving in by co-transport, brings glucose with it
4 marks
Describe and explain features you would expect to find in a cell specialised for absorption.
- microvilli so large surface area for absorption
- Large number of co-transport/carrier proteins for active transport and FD
- Large number of mitochondria so make more ATP by respiration fot AT
- Membrane-bound digestive enzymes so maintains concentration gradient for fast absorption
Some proteases are secreted as extracellular enzymes by bacteria.
Suggest one advantage to a bacterium of secreting an extracellular protease in its
natural environment.
Explain your answer.
- To digest protein
- So they can absorb amino acids for protein synthesis/ growth
2 marks
Mammals have some cells that produce extracellular proteases. They also have
cells with membrane-bound dipeptidases.
Describe the action of these membrane-bound dipeptidases and explain their
importance.
- Hydrolyse peptide bonds to release amino acids
- Amino acids can cross cell membrane as dipeptides cannot cross cell membrane (too large)
3 marks
Describe the role of micelles in the absorption of fats into the cells lining the ileum
- Micelles include bile salts, monoglycerides and fatty acids
- Make the fatty acids more soluble in water
- Release fatty acids to the cells lining the ileum
- Maintain higher concentration of fatty acids to the cells lining the ileum
- Fatty acids absorbed by diffusion
