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Chapter 8: Membranes And Transport Processes |
1. Relevance of Topic
Virtually all cellular processes are regulated somehow by a membrane. For example, most processes involving the Golgi apparatus and the endoplasmic reticulum are membrane-driven. Fertilization in animals is another process that involves changes in a membrane.
Every year, thousands of people suffer diseases that cause their kidneys to fail either completely or to some degree. Most of these people use dialysis to do the work of their kidneys by detoxifying their blood. Dialysis tubing is an example of a selectively permeable membrane.
2. Continuity
Membranes surround the cell and conduct the business of the cell internally by way of organelles. This chapter can easily be related to the cell chapter material.
Respiration, covered in Chapter 9, is carried out in the mitochondria, which are double-membrane organelles.
Photosynthesis, covered in Chapter 10, is carried out in the chloroplasts, which are triple-membrane organelles.
3. Demonstration Activities
Text section 8.1
1. Molecules move by diffusion; use dialysis tubing and colored liquids to show diffusion through a semi-permeable membrane.
Text section 8.2
1. Once again, the use of dialysis tubing can illustrate passage through a semi-permeable membrane.
Text section 8.3
1. Figure 8.3 shows the range of hypotonicity.
2. Show a picture of a patient with an intravenous injection apparatus.
Text section 8.4
1. Demonstrate this by shaking a mixture of oil and water, and watching each component return to its respective phase.
2. Add a detergent to the oil and water mixture, and shake it again. Point out that like substances dissolve like substances.
3. Figure 8.5, showing the hydrophobic ends of a cloud of soap molecules encompassing the greasy material and leaving the hydrophilic ends exposed to water, can be shown with this demonstration.
Text section 8.5
1. Show Figure 8.7 and discuss the partition coefficient.
2. Show Figure 8.9 to illustrate the structure of a phospholipid.
Text section 8.6
1. Show Figure 8.10, the Langmuir trough, and discuss how lipid molecules spread into a monolayer when compressed between the surfaces of a liquid and a wire.
2. Show Figure 8.11, a nice illustration of a lipid bilayer with heads and tails.
3. Show Figures 8.12 and 8.14, the myelin sheath, and discuss how Schwann cells wrap themselves around a nerve and leave a spiral of closely packed membranes.
Text section 8.7
1. Show Figure 8.13, a nice illustration of the freeze-fracture method that splits membranes down the middle of the lipid bilayer.
2. Figures 8.15 and 8.16 demonstrate that the lipid bilayer is very fluid in nature and that proteins are buried in it to various depths.
Text section 8.8
1. Show Figure 8.18, and discuss saturated and unsaturated fatty acid chains and the fact that membranes made mostly of unsaturated chains are more fluid in nature.
Text section 8.9
1. Figure 8.19 demonstrates that it would be energetically unfavorable for a protein to "flip-flop" through a membrane.
Text section 8.10
1. Show slides of healthy biconcave RBCs.
2. Figure 8.21 shows the structure of the protein network inside a RBC.
Text section 8.11
1. If possible, show a computer model of protein-facilitated diffusion.
Text section 8.12
1. Figure 8.23 illustrates the sodium-potassium ATPase actively transporting ions in opposite directions across a membrane.
Text section 8.13
1. Figure 8.24 shows channel proteins allowing some ions to diffuse passively through membranes.
Text section 8.14
1. Figures 8.25 and 8.26 illustrate the processes of symport and antiport.
Text section 8.15
1. Figure 8.29 is a nice summary of every membrane process.
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