Eukaryotes characteristics

As we can see, the features that one can reasonably attribute to the common ancestor are not bacterial ones, but the very features that later, in a more complex form, will be found in eukaryotes. The separation between transcription and translation, the use of stable messengers, and a genome organised in linear chromosomes are all typical eukaryotic characteristics, and yet they are also intrinsically primitive features. 

Biochemistry resulted from the early elucidation of the pathway of enzymatic conversion of glucose to ethanol by yeasts and its relation to carbohydrate metaboHsm in animals. The word enzyme means "in yeast," and the earfler word ferment has an obvious connection. Partly because of the importance of wine and related products and partly because yeasts are relatively easily studied, yeasts and fermentation were important in early scientific development and stiU figure widely in studies of biochemical mechanisms, genetic control, cell characteristics, etc. Fermentation yeast was the first eukaryote to have its genome elucidated. 

Plant cells also contain all of these characteristic eukaryotic organelles, essentially in the form described for animal cells. 

Without consulting chapter figures, sketch the characteristic prokaryotic and eukaryotic cell types and label their pertinent organelle and membrane systems. 

As has been reviewed extensively elsewhere (Wyn Jones Pollard, 1983), the evidence from many eukaryotic cells and eubacteria suggests common ionic and osmotic characteristics in the cytoplasm of cells, espe-cialy a high selectivity and similar ionic strength giving... 

From individual to individual within a single species, the pattern of staining (banding) of the entire chromosome complement is highly reproducible nonetheless, it differs significantly from other species, even those closely related. Thus, the packaging of the nucleoproteins in chromosomes of higher eukaryotes must in some way be dependent upon species-specific characteristics of the DNA molecules. 

Figure 2. Sodium and chloride uptake across an idealised freshwater-adapted gill epithelium (chloride cell), which has the typical characteristics of ion-transporting epithelia in eukaryotes. In the example, the abundance of fixed negative charges (muco-proteins) in the unstirred layer may generate a Donnan potential (mucus positive with respect to the water) which is a major part of the net transepithelial potential (serosal positive with respect to water). Mucus also contains carbonic anhydrase (CA) which facilitates dissipation of the [H+] and [HCO(] to CO2, thus maintaining the concentration gradients for these counter ions which partly contribute to Na+ import (secondary transport), whilst the main driving force is derived from the electrogenic sodium pump (see the text for details). Large arrow indicates water flow...

Lipid A constitutes the covalently bound lipid component and the least variable component of LPS (25). It anchors LPS to the bacterial cell by hydrophobic and electrostatic forces and mediates or contributes to many of the functions and activities that LPS exerts in prokaryotic and eukaryotic organisms. In the following sections, the primary structure of lipid A of different Gram-negative bacteria is described, together with some of its characteristic biological properties. Furthermore, this article describes some of the principal methods that have been used for the structural analysis of lipid A and discusses their merits and limitations. 

Zinc, in addition to its use as a Lewis acid in enzyme catalysis, plays a structural role in stabilizing protein molecules. It is also involved in a characteristic motif, termed zinc finger, in a number of eukaryotic DNA-binding proteins (that regulate the transcription of DNA into RNA), first described by Aaron Klug. 

Endonuclease activation and chromatin fr mentation are characteristic features of eukaryotic cell death by apoptosis. Which of the following chromosome structures would most likely be degraded first in an apoptotic cell ... 

Archaea Unicellular microorganisms that are structurally similar to prokaryotes but include some metabolic characteristics of eukaryotes. The archaea are genetically distinct from the other two domains. Most extremoptules are members of the archaea. 

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