Tissues are composed of cells that are held together by a variety of cell to cell junctions created by transmembrane and extracellular proteins and ions. These junctions include: adherence junctions, tight junctions and gap junctions. Adherence junctions are composed of transmembrane proteins cadherin. These proteins require calcium to facilitate their interactions. Certain cadherins are tissue specific ...
Two paragraphs with web references as to the role of cadherins in cell to cell adhesion and their function in the organism as a whole.
4 Biology Problems
1. The integrity of the plasma membrane is essential for cellular survival. Could the immune system utilize this fact to destroy foreign cells that have invaded the body? How might cells of the immune system disrupt membranes of foreign cells? (Two hints: virtually all cells can secrete proteins, and some proteins form pores in membranes.)
2. Most cells are very small. What physical and metabolic constraints limit cell size? What problems would an enormous cell encounter? What adaptations might help a very large cell to survive?
4. Some species of bacteria that live at the surface of sediment on the bottom of lakes are facultative anaerobes; that is, they are capable of either aerobic or anaerobic respiration. How will their metabolism change during the summer when the deep water becomes anoxic (deoxygenated)? If the bacteria continue to grow at the same rate, will glycolysis increase, decrease, or remain the same after the lake becomes anoxic? Explain why.
5. Often, prokaryotic cells exist as simple unicellular organisms, but in some species, prokaryotic cells can grow together in colonies or filaments. In addition, some species, such as Cynaobacteria or Myxobacteria, demonstrate intercellular communicate , or might even produce specialized cells and structures. However, only eukaryotic cells form the bodies of multicellular organisms with complex internal specialization. Develop one or two hypotheses explaining why only eukaryotic cells are found in multicellular organisms.View Full Posting Details