Why should we clip our nails?
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Explanation:
We now shift our attention to photosynthesis, the second main process for synthesizing ATP. In plants, photosynthesis occurs in chloroplasts, large organelles found mainly in leaf cells. The principal end products are two carbohydrates that are polymers of hexose (six-carbon) sugars: the disaccharide sucrose (see Figure 2-10) and leaf starch, a large, insoluble glucose polymer (Figure 16-33). Leaf starch is synthesized and stored in the chloroplast. Sucrose is synthesized in the cytosol from three-carbon precursors generated in the chloroplast and is transported from the leaf to other parts of the plant. Nonphotosynthetic (nongreen) plant tissues like roots and seeds metabolize sucrose for energy by the pathways described in the previous sections. Photosynthesis in plants, as well as in eukaryotic single-celled algae and in several photosynthetic prokaryotes (the cyanobacteria and prochlorophytes), also generates oxygen. The overall reaction of oxygen-generating photosynthesis,
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is the reverse of the overall reaction by which carbohydrates are oxidized to CO2 and H2O.
Figure 16-33. Structure of starch.
Figure 16-33
Structure of starch. This large glucose polymer and the disaccharide sucrose (see Figure 2-10) are the principal end products of photosynthesis. Both are built of six-carbon sugars.
Our emphasis is on photosynthesis in plant chloroplasts, but we also discuss a simpler photosynthetic process that occurs in green and purple bacteria. Although photosynthesis in these bacteria does not generate oxygen, detailed analysis of their photosynthetic systems has provided insights about the first stages in oxygen-generating photosynthesis — how light energy is converted to a separation of negative and positive charges across the thylakoid membrane, with the simultaneous generation of a strong oxidant and a strong reductant. In this section, we provide an overview of the stages in photosynthesis and introduce the main components, including the chlorophylls, the principal lightabsorbing pigments.
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Photosynthesis Occurs on Thylakoid Membranes
Chloroplasts are bounded by two membranes, which do not contain chlorophyll and do not participate directly in photosynthesis (Figure 16-34). Of these two membranes, the outer one, like the outer mitochondrial membrane, is permeable to metabolites of small molecular weight; it contains proteins that form very large aqueous channels. The inner membrane, conversely, is the permeability barrier of the chloroplast; it contains transporters that regulate the movement of metabolites into and out of the organelle.
Figure 16-34. The structure of a leaf and chloroplast.
Figure 16-34
The structure of a leaf and chloroplast. The chloroplast is bounded by a double membrane: the outer membrane contains proteins that render it permeable to small molecules (MW < 6000); the inner membrane forms the permeability barrier (more...)
Unlike mitochondria, chloroplasts contain a third membrane — the thylakoid membrane — that is the site of photosynthesis. In each chloroplast, the thylakoid membrane is believed to constitute a single, interconnected sheet that forms numerous small flattened vesicles, the thylakoids, which commonly are arranged in stacks termed grana (see Figure 16-34). The spaces within all the thylakoids constitute a single continuous compartment, the thylakoid lumen. The thylakoid membrane contains a number of integral membrane proteins to which are bound several important prosthetic groups and light-absorbing pigments, most notably chlorophyll. Carbohydrate synthesis occurs in the stroma, the soluble phase between the thylakoid membrane and the inner membrane. In photosynthetic bacteria extensive invaginations of the plasma membrane form a set of internal membranes, also termed thylakoid membranes, or simply thylakoids, where photosynthesis occurs.
Answer:
keeping your nails long can cause bacteria infection .this is because dirt can accumulate in your nails .we all know that bacteria and germs are attracted to dirt when you don't rein your nails ,bacteria and germs will start growing on your toenails and this can cause bacterial infection