Answer:
The preceding section reviewed the major metabolic reactions by which the cell obtains and stores energy in the form of ATP. This metabolic energy is then used to accomplish various tasks, including the synthesis of macromolecules and other cell constituents. Thus, energy derived from the breakdown of organic molecules (catabolism) is used to drive the synthesis of other required components of the cell. Most catabolic pathways involve the oxidation of organic molecules coupled to the generation of both energy (ATP) and reducing power (NADH). In contrast, biosynthetic (anabolic) pathways generally involve the use of both ATP and reducing power (usually in the form of NADPH) for the production of new organic compounds. One major biosynthetic pathway, the synthesis of carbohydrates from CO2 and H2O during the dark reactions of photosynthesis, was discussed in the preceding section. Additional pathways leading to the biosynthesis of major cellular constituents (carbohydrates, lipids, proteins, and nucleic acids) are reviewed in the sections that follow.
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Carbohydrates
In addition to being obtained directly from food or generated by photosynthesis, glucose can be synthesized from other organic molecules. In animal cells, glucose synthesis (gluconeogenesis) usually starts with lactate (produced by anaerobic glycolysis), amino acids (derived from the breakdown of proteins), or glycerol (produced by the breakdown of lipids). Plants (but not animals) are also able to synthesize glucose from fatty acids—a process that is particularly important during the germination of seeds, when energy stored as fats must be converted to carbohydrates to support growth of the plant. In both animal and plant cells, simple sugars are polymerized and stored as polysaccharides.
Gluconeogenesis involves the conversion of pyruvate to glucose—essentially the reverse of glycolysis. However, as discussed earlier, the glycolytic conversion of glucose to pyruvate is an energy-yielding pathway, generating two molecules each of ATP and NADH. Although some reactions of glycolysis are readily reversible, others will proceed only in the direction of glucose breakdown, because they are associated with a large decrease in free energy. These energetically favorable reactions of glycolysis are bypassed during gluconeogenesis by other reactions (catalyzed by different enzymes) that are coupled to the expenditure of ATP and NADH in order to drive them in the direction of glucose synthesis. Overall, the generation of glucose from two molecules of pyruvate requires four molecules of ATP, two of GTP, and two of NADH. This process is considerably more costly than the simple reversal of glycolysis (which would require two molecules of ATP and two of NADH), illustrating the additional energy required to drive the pathway in the direction of biosynthesis.
Answer:
Because it was a dead language.
Explanation:
Nobody uses latin anymore.
Answer:
Mutation, Gene flow/Migration/Immigration of gene and Recombination
Explanation:
For any species there are majorly three sources of genetic variations –
a) Mutation – This leads to change in the genetic code with in the DNA of an organism. Sometimes mutation does not produce any effect on the organism. Mutation can produce both positive and negative impact. Its effect is observed in long run as its rate is slow.
b) Recombination – When an organism undergoes sex, his/her genes recombine with the genes of mating partner. The rate of recombination is faster than the rate of mutation
c) Gene flow /Migration/Immigration of gene – In this gene travel from one set of population to the other. The frequency of gene in the mixed population lies between the original population gene frequency and the migrated or donor population gene frequency
Addition of a nucleotide onto a DNA is an endergonic reaction. In such reactions, the energy is provided by ATP.
ATP is the immediate source of energy for any endergonic reaction occuring in the body. Reactions such as addition of nucleotides are endergonic and anabolic reaction that is, these reactions consume energy which is provided by ATP.
