Semipermeable means only certain substances can pass through. I imagine you are talking about cell membranes which are semipermeable. This means vital things like oxygen and nutrients are able to pass through the membrane, while not allowing everything to enter the cell
In acid soils you can select the crops that can growth in this conditions (pH 6.0 - 6.5 is slightly acidic, and you can find cultures that can be cropped under this conditions). If soil is acid to highly acidic , in some areas of Northern Spain the use to increase the pH by liming the soil in a gradual / gentle way. You can find different product for liming fron rocks, wastes (from marble industries; animal bones; etc
All macromolecules have carbon atom and the hydrogen atom.
<h3>What are macromolecules?</h3>
The term macromolecules refers to the molecules that are composed of smaller units. These smaller units are called monomers. The macromolecules that we are concerned with here are the macromolecules that could be found in the human body.
The biological macromolecules are often very large as we can see. This is because the number of units that are joined to form the macromolecules are usually very much. There are thousands of monomer molecules that are joined together to give proteins, lipids, carbohydrates and the nucleic acid macromolecules.
All the macromolecules have the carbon atom and the hydrogen atom. These are found across all the macromolecules. The carbohydrates are reducing sugars thus they contain the carbonyl bond. The carbonyl group is absent in lipids, nucleic acids, proteins, and amino hence they do not undergo carbonyl reduction reactions.
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