Cells And Cell Theory :: essays research papers

Cells and Cell Theory What advantages does small size give to a cell? Many cellular processes occur by diffusion, which is efficient over short distances, but less efficient over long distances. Since all materials going in and out of a cell must pass through the plasma membrane, the greater the surface area of this membrane, the faster a given quantity of molecules can pass through. Smaller cells have a much greater surface-to-volume ratio than larger cells and therefore can "feed" all areas of the cell in less time. What is "surface-to-volume ratio," and how does it affect cell size? The surface-to-volume ratio is a mathematical relationship between the volume of an object and the amount of surface area it has. This ratio often plays an important role in biological structures. Think of a cell as a sphere: The surface area of a sphere can be calculated by 4Ã ° r2 where r is the radius of the sphere. Volume of a sphere can be calculated by 4/3 Ã ° r3. An increase in r will increase the surface area by a power of two, but increase the volume by a power of three. This means that the volume will increase much faster than the surface area. This puts an upper limit on the size of a cell, because if the cell volume gets too big, there won't be enough membrane to transport the amount of food in and wastes out to support that large cell size. What is the difference between prokaryotic and eukaryotic cells? Prokaryotic cells are more simple: they are usually much smaller and don't have a nucleus or any other membrane-bound organelles. Bacteria are prokaryotes. Eukaryotic cells are much more complex, are usually larger, and have a nucleus and several other membrane-bound organelles that allow them to compartmentalize their functions. All multicellular plants and animals are eukaryotes. A helpful trick to remember is that "you" are a "eu"karyote. Are there any single-celled eukaryotes? Yes--yeast, for example. Yeast are single-celled organisms, but they do contain a membrane-bound nucleus, mitochondria, and other organelles. What are the advantages and disadvantages of prokaryotic compared to eukaryotic cells? Although prokaryotes may seem more primitive than eukaryotes, they are among the most successful species on our plant and comprise a very large percentage of the total mass of all living things on earth. Simple, small, and single-celled organisms can reproduce quickly and evolve quickly. Prokaryotes can generate millions of progeny in a short period of time.