The mole of an element is its atomic weight, while a mole of a compound is the sum of the atomic weights of its components, called the molecular weight. An often-used example is calculating a mole of glucose, with the chemical formula C6H12O6. Using the periodic table, the atomic weight of carbon C is Doing the same calculations for hydrogen H and oxygen O , the molecular weight equals When water is added to make one liter of solution, you have one mole 1M of glucose.
Many substances in the bloodstream and other tissue of the body are measured in thousandths of a mole, or millimoles mM. A colloid is a mixture that is somewhat like a heavy solution. The solute particles consist of tiny clumps of molecules large enough to make the liquid mixture opaque because the particles are large enough to scatter light. Familiar examples of colloids are milk and cream. In the thyroid glands, the thyroid hormone is stored as a thick protein mixture also called a colloid.
A suspension is a liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out. This separation of particles from a suspension is called sedimentation. An example of sedimentation occurs in the blood test that establishes sedimentation rate, or sed rate.
The test measures how quickly red blood cells in a test tube settle out of the watery portion of blood known as plasma over a set period of time. Rapid sedimentation of blood cells does not normally happen in the healthy body, but aspects of certain diseases can cause blood cells to clump together, and these heavy clumps of blood cells settle to the bottom of the test tube more quickly than do normal blood cells. Two types of chemical reactions involve the creation or the consumption of water: dehydration synthesis and hydrolysis.
These reactions are reversible, and play an important role in the chemistry of organic compounds which will be discussed shortly. Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged.
This fact is important in distinguishing salts from acids and bases, discussed next. A typical salt, NaCl, dissociates completely in water Figure 2. The positive and negative regions on the water molecule the hydrogen and oxygen ends respectively attract the negative chloride and positive sodium ions, pulling them away from each other.
Again, whereas nonpolar and polar covalently bonded compounds break apart into molecules in solution, salts dissociate into ions. These ions are electrolytes; they are capable of conducting an electrical current in solution.
This property is critical to the function of ions in transmitting nerve impulses and prompting muscle contraction. Many other salts are important in the body. For example, bile salts produced by the liver help break apart dietary fats, and calcium phosphate salts form the mineral portion of teeth and bones.
Acids and bases, like salts, dissociate in water into electrolytes. Acids and bases can very much change the properties of the solutions in which they are dissolved. Because an atom of hydrogen has just one proton and one electron, a positively charged hydrogen ion is simply a proton. This solitary proton is highly likely to participate in chemical reactions. This strong acid aids in digestion and kills ingested microbes. Weak acids do not ionize completely; that is, some of their hydrogen ions remain bonded within a compound in solution.
An example of a weak acid is vinegar, or acetic acid; it is called acetate after it gives up a proton.
The relative acidity or alkalinity of a solution can be indicated by its pH. That is, a solution with a pH of 4 is ten times more acidic than a solution with a pH of 5. The concept of pH will begin to make more sense when you study the pH scale, as shown in Figure 2.
The scale consists of a series of increments ranging from 0 to A solution with a pH of 7 is considered neutral—neither acidic nor basic. Many of the transformations of nitrogen are mediated by bacteria that use different forms of nitrogen to fuel some of their metabolic processes. These processes are called ammonification. Nitrogen leaves the septic tank primarily as ammonium in leachate. Some of the ammonium becomes adsorbed to soil particles and is effectively immobilized from further transport.
Other kinds of bacteria change ammonia to nitrite. And still other kinds of bacteria can change nitrite to nitrate. These processes are called nitrification. Nitrification is an aerobic process. That means nitrification can occur only in the presence of oxygen. The septic tank ammonium that escapes adsorption is subject to nitrification in aerobic leaching field soils. And yet still other bacterial species can take nitrate and change it back to nitrogen gas through a process called denitrification.
Animal cells do not have plastids, which are common in plant cells chloroplasts. Both cell types have vacuoles, however, in animal cells, vacuoles are very tiny or absent, while in plant cells vacuoles are generally quite large.
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Credit: Neural Academy. Quiz Choose the best answer. Cell organelle responsible for light absorption Nucleus. Part of the plant cell not present in an animal cell Nucleoid. Cell membrane. Cell wall.
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