Question

1. Draw a picture of a cell located in the intestines for yourself and label the surfaces and draw the location of the different receptors found on the plasma membranes. Then explain in your own words to turn in all of the different carrier proteins involved in the reabsorbtion of sodium and glucose from the intestinal mucosa to the blood.
2. What is the functional significance of tight junctions? Reflect on the fact that this is the same system involved in the kidneys for the reuptake of sodium and glucose in the kidney tubules. Why is that important to consider?
3. Draw a picture of a parietal cell located in the stomach for yourself. What protein carriers are important in the production and secretion of HCl in the stomach. How is this process influenced by carbon dioxide transport on the erythrocyte plasma membrane?
4. What is the importance of solute concentration on the reuptake of water in animal and plant cells?
5. How do vacuoles work? What is the importance of V-class H+ ATP-ase pumps in the uptake of water?
6. Channel proteins are typically involved in the import of ions across the plasma membrane. What are the major characteristics of potassium leak channels?
7. What is the importance of the water of hydration in the importance of movement of ions, like potassium, through channel proteins?
8. How is the Na+/K+ ATP-ase critical in the re-establishment of the resting membrane potential across the plasma membrane of animal cells.
9. How do voltage-gated ion channels work in the venus fly trap.
10. In anatomy and physiology, we discussed how nerve signals travel to the cochlear nerve allowing us to hear. Using your knowledge of anatomy and the information provided on the power point slides provided to you explain the role of stress-activated channels in this process.
11. Cholera toxin, a pathogenic intestinal bacterium, causes an indirect reduction in the activity of the Na+/K+-ATPase in intestinal epithelial cells. This results in reduced uptake of small sugars and amino acids from the intestine, as well as severe diarrhea. How are these two problems (eg. reduced nutrient uptake and diarrhea) coupled to impaired Na+/K+- ATPase function?
12. Like animal cells, the plasma membrane of plant cells has a membrane potential and plant cells also use cation-based symport for nutrient uptake. However, plant cells do not have Na+/K+-ATPase in their plasma membranes. Explain, then, how they establish and maintain a membrane potential and how they co-import nutrients in the absence of the Na+/K+ pump. Also explain how plant cell volume is regulated in light of this major difference.

Answer 1

Question 1. Sol:

1. Many cells, such as those lining the small intestine and the kidney tubules, need to concentration glucose against a very large concentration gradient.
2. The Transporter (symporter), an integral membrane protein, present on the epithelial cells coordinately binds and transports glucose molecules and Na+ ions into the cells, as active transport driven by Na+/K+ pump on basolateral membrane drives this uptake of glucose from the intestine lumen (apical domain).
3. Glucose is then transported from the cell into the underlying connective tissue and blood supply by facilitated diffusion, via a transporter in the basolateral membrane.
4. The Na+/glucose transporter is used to actively transport glucose out of the intestine and back into the blood.

Question 2. Sol:

Tight Junction act like "gates," preventing the movement of fluids, ions, and molecules between cells. In addition, tight Junction act like "fences," blocking the lateral movement of lipids and proteins within the membrane. Lipid movement is blocked in the outer monolayee only, but the movement of integral membrane proteins is blocked entirely. As a result, different kinds of integral membrane proteins can be maintained in the portions of a plasma membrane on opposite sides of a tight Junction belt.

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