Nanotechnology: Definition & Products

Nanotechnology: Definition & Products - Can we see the birth of molecules? What really happens to atoms during chemical reactions? Can we move atoms? Can we actually visualize biological processes at the molecular level? The answer to all of these questions is yes. Today, because of the advent of new instrumentation like the family of scanning-tunneling microscopes, scientists can now pick up and move atoms, and, with the use of molecular cameras, they can take photographs as fast as one quadrillionth of a second (a femtosecond). Scientists can image the step -by-step changes that occur in atoms and molecules as chemical reactions progress.

Nanotechnology product

As was discussed in the Human Endeavors box in Chapter 2, scanning-tunneling microscopes ''feel" the surface of the molecular or atomic specimens to form the image. A tiny platinum probe is given a small electrical charge and the specimen is scanned, atomic diameter by atomic diameter, across its surface. As the probe moves, electrons respond to the voltage differential between the probe and the surface of the specimen by tunneling across the gap, which produces a very small current. The variations in the currentwhich are due to the miniscule differences in the distance between the probe and the objectare detected. The computer produces the image from these distances.

In 1989, Donald Eigler and Erhard Schweitzer of IBM in San Jose, California, lowered the temperature of a plate of nickel to about absolute zero (-456° F), which minimized atomic vibrations. Then, by spraying atoms of xenon gas over the plate and by increasing the electrical charge on the probe of the scanning-tunneling microscope, they were able to drag the xenon atoms across the nickel to spell out "IBM" in letters only five atoms tall, the entire logo only about 660 billionths of an inch long (Figure A). This example of the manipulation of materials, be they inorganic or organic, atom by atom, is what is meant by nanoengineering. The new nanotechnology combines the technological capabilities of the scanning-tunneling microscope with laser cameras that can detect changes that occur in quadrillionths of a second, and you can image what happens in atoms and molecules as they react. The synchroton ray camera can do just that. When you pulse an atom with a specific frequency of energy, the atom will absorb that energy and the electrons are moved to a higher energy state. When the electrons return to their original ground state, energy of a specific frequency is emitted. Using this principle, scientists can pulse molecule A and molecule B and detect how their frequencies change to form molecule C. But how can you do that and how can you record the snapshots or "frames" of this continuous event, since it only occurs in quadrillionths of a second? Figure B illustrates how this camera works.

So today we can see the advent of a new technology even more exciting or as exciting as genetic engineering. Not only can we now manipulate genetic variation, but we can actually manipulate atoms and molecules. With this technology our advances in science, including biology, will truly expand. Just think, today not only can we image atoms, but we can manipulate them as well and detect the actual events in the birth of new molecules as atoms and molecules react.

Source: Zewail, Ahmed H., "The Birth of Molecules," Scientific American, 263:6, Dec. 1990, pp. 7682. - See more at: http://www.biologysmart.com/2015/07/the-functions-of-carbohydrates-in-body.html#sthash.RXSQcqFS.dpuf

Chemical Reactions in Biological Terms

Chemical Reactions in Biological Terms - During hydrolysis macromolecules are cleaved into their smaller subunits by adding water. Dehydration synthesis is the linking of smaller subunits by removing water to form larger molecules.

Chemical

Let us see how some of these types of reactions affect my meal. Earlier I said that my meal actually consisted of large molecules (often called macromolecules or polymers) of proteins, carbohydrates, and lipids. To change those macromolecules into the types of proteins, carbohydrates, and lipids that my body can use, a set of paired reactions occurs in my cells: hydrolysis and dehydration synthesis (Figure 3.2). Both of these reactions are mediated by enzymes.

The first type of reaction is a degradation reaction called hydrolysis, a term that means water

 splitting. In hydrolysis, water molecules are enzymatically added to macromolecules, splitting them into their component subunits. Such small molecules are called monomers.

The second type of reaction is a synthesis reaction called dehydration synthesis. This step recycles the monomers by removing the water used in hydrolysis. The monomers are then joined to form polymers, such as the proteins, carbohydrates, and lipids that my body needs. Hence the name of the process, which means synthesis (or putting together) by dehydration (the removal of water).

So I benefit from my breakfast because of a pair of reactions that are the reverse of each other. One reaction adds water to a macromolecule to degrade it into monomers, and the other process removes water from monomers to form macromolecules. At present I am hydrolyzing, or breaking down, my meal into its component parts, its monomers. Once these simple molecules get into my cells, they will be utilized as sources of energy or as the raw materials used to synthesize the macromolecules that make up me.

So through these two paired reactions, monomers are synthesized into macromolecules that are of biological importance. What are the properties of these biological compounds, and what are their functions? Let us discuss them.

There are four groups of biological compounds that are important in living things: carbohydrates, lipids, proteins, and nucleic acids. Each group is divided into smaller subgroups that play an important role in the chemical activities of living things. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 53-54)

Displacement Reactions

Displacement Reactions  - In displacement reactions, there is an exchange of atoms (or groups of atoms) between molecules. There are two types of displacement reactions, single and double displacement. In a single displacement reaction, such as A + BC « AC + B, one element shifts position. In living systems, for example, hemoglobin (an iron-containing molecule) can combine with CO2 from the cells to form carbamino hemoglobin. When this carbamino hemoglobin is transported by the blood to the lungs, the carbon dioxide is displaced by O2. This single displacement reaction can be represented as follows:

In a double displacement, as in AB + CD « AC + BD, two elements shift position. A double displacement reaction occurs when silver nitrate reacts with hydrochloric acid to form silver chloride and nitric acid.

All four types of reactions take place during the various life processes in living things, such as the utilization of my breakfast. Often the reactions occur in pairs something is taken apart (degraded) in order to be put together (synthesized) in another arrangement. Such an arrangement is called a paired reaction. It is rather like cutting apart several types of board in order to build a bookcase. You have the same wood when you have finished that you had when you started, but the structure and arrangement are different. Paired reactions are an essential characteristic of chemical reactions in living things. In other words, if you put things together, you can usually break them apart. In fact, most chemical reactions are reversible. Chemists use a pair of arrows to indicate a reversible reaction:

Collision Theory

Collision Theory - The collision theory states that chemical reactions occur when molecules collide. The energy required to start a reaction is called the minimum energy of activation. There are four general types of chemical reactions: rearrangement, synthesis, degradation, and displacement.

Collision Theory

Today is a very exciting time in chemistry, since scientists can actually move atoms and also image the progress of chemical reactions. But, what are chemical reactions?

Simply stated, chemical reactions involve breaking and reforming chemical bonds. In order to do this, energy is required, and the amount of energy available in the system determines whether or not a reaction will occur. For example, if you assume that all atoms, ions, and molecules are constantly moving, then a chemical reaction can occur when they collide with one another. This is what happens when two atoms of hydrogen unite with a molecule of oxygen to form water (H2O). Chemists call this explanation the collision theory.

For example, when you played with your old chemistry set you learned that if you simply mixed two chemicals together, it usually took a long time for a chemical reaction to occur. However, if you heated the mixture (which is one way to put energy into a system), the reaction proceeded much more quickly. Basically, according to the collision theory, the addition of heat increased the speed at which the atoms and molecules were moving, and thus increased the likelihood that they would collide and react. (There are other ways to add energy to a material by shaking or increasing pressure, for instance but heat is the one that is most common, especially in biological processes.)

Adding just a little heat will not necessarily get results. Before a reaction can occur, a certain minimum amount of energy must be added, which chemists call the minimum energy of activation. What is more, the level of the minimum energy of activation depends on the substances involved. For instance, if you light a match and toss it into a small pan of gasoline, you provide enough energy (in the form of heat) to combine the gasoline and oxygen to form carbon dioxide, water, and a tremendous amount of liberated energy (in other words, the explosion will be something to see). However, if you fill the pan with another liquid, such as plain water, the lighted match will have no effect. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 52)

Chemical Reactions and the Molecules of Life

Chemical Reactions and the Molecules of Life - I just finished eating breakfast, which today consisted of a glass of low-fat milk and French toast covered with peanut butter and syrup. (I happen to like peanut butter on my pancakes and French toast you should try it.) How do we as living things break this meal down into its constituent parts and reconstitute or assimilate the chemical components into ourselves?

Chemical Reaction (source: http://www2.estrellamountain.edu/faculty/farabee/BIOBK/atweights.gif)

Although my breakfast consisted of the things I just mentioned, to the biological system that is my body, my meal consisted of carbohydrates, lipids, and proteins, the large molecular constructions that are found in all foods. It also contained water, minerals, and nucleic acids. The cells of my body and of other living things do not distinguish between a meal of insects or of steak. Protein is protein, and it will be broken down into the amino acids that make up that protein. The amino acids will eventually enter my cells and be reunited into new amino acid sequences that form the protein in my cells. 

How does nature degrade, or break down, large molecules into their component subunits? And how does nature take these component subunits and reunite them to form other complex molecules?

To begin with, all these activities are chemical reactions; so in order to answer our questions, we must first understand how chemical reactions take place.