Regulation of gene expression and cell specialization Show
How different genes are expressed in different cell types. The big picture of eukaryotic gene regulation. Regulation of gene expression and cell specializationBiology is brought to you with support from the Amgen Foundation AP® is a registered trademark of the College Board, which has not reviewed this resource. Chapter 3: Introduction to Cell Structure and Function By the end of this section, you will be able to:
Cells fall into one of two broad categories: prokaryotic and eukaryotic. The predominantly single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes (pro– = before; –karyon– = nucleus). Animal cells, plant cells, fungi, and protists are eukaryotes (eu– = true). Components of Prokaryotic CellsAll cells share four common components: 1) a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, particles that synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways. A prokaryotic cell is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid.  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 3.6). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion, while most pili are used to exchange genetic material during a type of reproduction called conjugation. Eukaryotic CellsIn 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. The principle “form follows function” is found in many contexts. 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. It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched. A eukaryotic cell is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles, which have specialized functions. The word eukaryotic means “true kernel” or “true nucleus,” alluding to the presence of the membrane-bound nucleus in these cells. The word “organelle” means “little organ,” and, as already mentioned, organelles have specialized cellular functions, just as the organs of your body have specialized functions. Cell SizeAt 0.1–5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10–100 µm (Figure 3.7). The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly move out. However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport. Indeed, the large size of these cells would not be possible without these adaptations. In general, cell size is limited because volume increases much more quickly than does cell surface area. As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area across which materials must be transported declines. Section SummaryProkaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles. Many also have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1–5.0 µm. Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells. eukaryotic cell: a cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs organelle: a membrane-bound compartment or sac within a cell prokaryotic cell: a unicellular organism that lacks a nucleus or any other membrane-bound organelle What is the difference between gene regulation in prokaryotes and eukaryotes?Prokaryotic gene expression is primarily controlled at the level of transcription. Eukaryotic gene expression is controlled at the levels of epigenetics, transcription, post-transcription, translation, and post-translation.
Which of the following statements correctly compares prokaryotes and eukaryotes?Hence, the correct answer is 'Prokaryotic cells do not have a membrane-bounded nucleus, but eukaryotic cells do not have such a nucleus'.
How is gene regulation in prokaryotes and eukaryotes similar?In both prokaryotes and eukaryotes, the gene expression is regulated at the transcriptional level. Both mechanisms are controlled by transcription factors, activators, and repressors. Both prokaryotic and eukaryotic genes can be regulated to produce multiple gene products.
What is the main difference between eukaryotic and prokaryotic gene regulation quizlet?What is the main difference between eukaryotic and prokaryotic gene regulation? Groups of eukaryotic genes are likely to be regulated together, whereas each prokaryotic gene is usually regulated separately.
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