最低限价是为了遏制某个行业的发展

最低限价低于市场均衡价格

最低限价高于市场均衡价格

最低限价会导致商品供不应求

pooled

spent

To provide energy and reducing power for the rest of the cell, the ATP and NADPH are instead used within the chloroplast stroma to produce a simple three-carbon sugar that can be exported to the cytosol by specific carrier proteins in the chloroplast inner membrane. This production of sugar from CO 2 and water, which occurs during stage 2 of photosynthesis, is called carbon fixation.

In the central reaction of photosynthetic carbon fixation, CO 2 from the atmosphere is attached to a five-carbon sugar derivative, ribulose 1,5-bisphosphate, to yield two molecules of the three-carbon compound 3-phosphoglycerate. This carbon-fixing reaction is catalyzed in the chloroplast stroma by a large enzyme called ribulose bisphosphate carboxylase or Rubisco.

Rubisco works much more slowly than most other enzymes: it processes about three molecules of substrate per second― compared with 1,000 molecules per second for a typical enzyme. The enzyme generally represents more than 50% of the total chloroplast protein, and it is widely claimed to be the most abundant protein on Earth. The energy and reducing power needed to regenerate ribulose 1,5-bisphosphate come from the ATP and NADPH produced by the photosynthetic light reactions.

The elaborate series of reactions in which CO 2 combines with ribulose 1,5-bisphosphate to produce a simple three-carbon sugar—a portion of which is used to regenerate the ribulose 1,5-bisphosphate that’s consumed—forms a cycle, called the carbon-fixation cycle, or the Calvin cycle. For every three molecules of CO 2 that enter the cycle, one molecule of glyceraldehyde 3-phosphate is ultimately produced, at the expense of nine molecules of ATP and six molecules of NADPH, which are consumed in the process. Glyceraldehyde 3-phosphate, the three-carbon sugar that is the final product of the cycle, provides the starting material for the synthesis of the many other sugars and other organic molecules that the plant needs.

弯曲

约束；限制

以销子联接的

固定措施

联接；接合

实际上的

适当的

正确

错误

High [ADP], an indicator of low [ATP], is a strong inhibitor of nitrogenase.

NH 4 + represses the expression of the ~20 nitrogen fixation ( nif ) genes, effectively shutting down the pathway.

Covalent alteration of nitrogenase is also used in some diazotrophs to control nitrogen fixation in response to the availability of NH 4 + in the surroundings.

Transfer of an ADP-ribosyl group from NADH to a specific Arg residue in the nitrogenase reductase shuts down N 2 fixation in Rhodospirillum, for example. This is the same covalent modification that we saw in the case of G protein inhibition by the toxins of cholera and pertussis.