It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched.Ī eukaryotic cell is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles, which have specialized functions. For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water. The principle “form follows function” is found in many contexts. In nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells. Fimbriae are protein appendages used by bacteria to attach to other cells. Pili are used to exchange genetic material during a type of reproduction called conjugation. Some prokaryotes have flagella, pili, or fimbriae. The capsule enables the cell to attach to surfaces in its environment. The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule (Figure 1). Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid (Figure 1). We will shortly come to see that this is significantly different in eukaryotes. This figure shows the generalized structure of a prokaryotic cell.Ī prokaryotic cell is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle.
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