Waxes Definition

Waxes Definition - Waxes consist of long-chain alcohols bonded to long-chain fatty acids and are used for protective coverings in living things.

Through the process of dehydration synthesis, long-chain alcohols sometimes combine with long-chain fatty acids to form waxes. Waxes differ from triglycerides in that waxes contain alcohols with more than three carbons. Waxes are either solid or oily at room temperature, depending on whether they are saturated or unsaturated, and they serve to cover and protect portions of plants and animals. For example, as you walk through a park, run your finger lightly over the surface of one of the green leaves growing on the trees there. The slightly waxy feel of the surface is caused by a substance called cutin.

Solid and oily waxes also form protective coverings for insects, skin, fur, and feathers. The mink oil that people use to waterproof their boots is made from a natural wax. If you have ever seen a duck preening its feathers as it floats along in the water, you have actually seen it spreading an oily wax over the feathers in order to waterproof them. Without lipids, a duck would sink because of the weight of the water soaked up by its feathers.

Triglycerides or Fats

Triglycerides, or Fats - Triglycerides consist of a glycerol (3-carbon alcohol) and three fatty acids. In saturated fats, all the carbon molecules in the carbon skeleton of the fatty acid are bonded with hydrogen atoms. In unsaturated fats, some carbon atoms in the carbon skeleton are double bonded to each other rather than to hydrogen. Triglycerides function in energy storage.

Ilustration

Fats are composed only of atoms of carbon, hydrogen, and oxygen (C, H, and O), which are arranged into two subunits: a glycerol unit (which is a three-carbon alcohol) and a fatty acid unit. Glycerol is composed of three carbons, to which three alcohol (OH) groups are attached. Fatty acids consist of an unbranched carbon skeleton to which hydrogen and a carboxyl group (COOH), an organic acid functional group, is attached.

Fats are formed by the dehydration synthesis of fatty acid chains to a glycerol molecule. As many as three fatty acid chains can bond to glycerol. When three fatty acids bind with glycerol, the fat is called a triglyceride, since tri- means three. Since the type of fatty acids attached to the glycerol can differ from one triglyceride to another, there are many types of this polymer. In Figure 3.7, stearic, oleic, and palmitic acids form the fatty acid tails.

Fats contain fewer oxygen atoms than other macromolecules and have more hydrogen bonds. For this reason these compounds hold more energy than other molecules. (The reason for this will be clear when we discuss oxidation and reduction in Chapter 6.) More oxygen is required to break down fat molecules during energy-releasing activities in cells. Since fat molecules weigh less than carbohydrate molecules, fats are ideal for the efficient storage of energy.

Having fewer oxygen atoms, fats lack the electropositive regions that would attract the hydrogen atoms (electronegative regions) in water molecules. In other words, fat molecules are nonpolar and hydrophobic they do not dissolve in water, only in other nonpolar substances like ether or methane. For instance, did you know that the wax you apply to a kitchen floor is a fat? That's why you cannot remove it by simply washing the floor with water water molecules are polar. You have to use wax remover (which is nonpolar) to remove wax, since fats are hydrophobic. In general, we can say that like dissolves like. That is, polar substances dissolve polar substances, and nonpolar dissolve nonpolar. That's why wax, a fat and therefore nonpolar, will dissolve only in a nonpolar substance.

As we mentioned in Chapter 1, living things are constantly changing their chemical makeup in order to remain the same, to maintain homeostasis. Fats are constantly being turned over, or converted. They are hydrolyzed to fatty acids and glycerol, and when completely broken down they yield as much as 9 Calories per gram, almost twice as much energy as a gram of carbohydrate, which yields 3.5 to 4 Calories per gram. (A Calorie is the amount of heat energy required to raise the temperature of 1000 grams of water 1 degree Celsius; see page 125.) This high-energy yield is due to the fact that fats contain a higher proportion of carbon-hydrogen bonds, or CH, than any other class of molecules in living things.

Triglycerides contain large amounts of chemical energy and are stored in seeds or in the fatty tissue of animals. Triglycerides are also used for thermal insulation and protection in animals such as the arctic seal.

The fatty acid units in a triglyceride can be saturated or unsaturated. In a saturated fat, the carbon

skeleton of the fatty acid is saturated with hydrogens in other words, there are hydrogen atoms covalently bonded to all possible locations on the carbon atoms . Animal fats, such as butter, lard, and bacon fat, are saturated fats. Since saturated fats usually have fairly high melting temperatures, they are solid at room temperature.

In an unsaturated fat, on the other hand, some carbon atoms form double bonds with other carbon atoms , so that the molecule contains fewer hydrogen atoms than a saturated fat. The formation of these double bonds produces kinks in the fatty acid chains, preventing a tight fit between the fatty acid molecules (Figure 3.8c). The "looseness" of the molecule's structure affects its consistency. For example, plant fats (called oils) are usually unsaturated. This type of fat generally has a low melting point, which is why vegetable oils are usually liquid at room temperature.

When individuals, be they human or house pets, take in more energy in the form of food than they require, the excess energy is stored in fat, and excess fat can lead to obesity. Obesity is the most common chronic medical problem in the United States today. When individuals diet, they are living off their stored fat reserves. If they Use up these fat reserves faster than they replace them, they lose weight. As some of you may know, losing excess fat is not all that easy. In order to lose one pound of body weight, a human must decrease caloric consumption by 3500 Calories or exercise sufficiently to use up 3500 Calories. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 61-64)

Lipids Meaning

Lipids Meaning - Lipids are a diverse group of molecules that consist mainly of carbon, hydrogen, and oxygen and are nonpolar. Lipids function in energy storage and structural support.

Lipids Meaning

Lipids are a very diverse group of organic compounds. They consist of triglycerides, phospholipids, steroids, terpenes, and glycolipids. Because they are so diverse, you might wonder why they are all grouped together. They are grouped together because they are all nonpolar molecules (hydrophobic) and do not dissolve in water. Most lipids usually have an oily or waxy consistency, and they function primarily as a means of energy storage and as structural components for living cells. They also play a role in insulation, in padding (for protection), and as an insect attractant in flowers.

Approximately 15 to 25 percent of the human body is made of lipids, the majority of which are stored in fat cells. The two genders tend to distribute their fat cells unevenly. Women tend to store fat in the breasts, hips, and thighs, resulting in their characteristic shape. Men tend to store fat around their waist, hence their characteristic shape.

Polysaccharides: Definition, Structure & Examples

Polysaccharides: Definition, Structure & Examples - Polysaccharides are carbohydrates containing more than 10 monosaccharides; they function in energy storage and structural support in plants and animals. The way that monomer units are linked together determines the polysaccharide's properties.

Polysaccharides structure

When dehydration synthesis covalently bonds more than 10 monosaccharides together, the result is a macromolecule, sometimes called a polymer. Macromolecules containing monosaccharides are called polysaccharides, meaning many sugars. A polysaccharide may have a branched shape, or it may be arranged like a long linear chain. The chemical properties of polysaccharides are due to the different types of linkages that can occur between the monomer units.

Storage Polysaccharides

Both glycogen (animal starch stored in the liver and muscles of higher animals) and plant starch consist of several hundred glucose units. The two types of polysaccharides react differently because of the way their long chains are arranged. In glycogen, the glucose units are aligned in such a way that they form highly branched forms. In plant starch, the glucose units are aligned to form a twisted, coiled structure. The properties of polysaccharides are due to different types of linkage alignments that can occur between monomer units.

Polysaccharides serve as a means of storing carbohydrates. However, before their elements can be transported through living systems and used for energy, they must undergo hydrolysis and be broken down into monosaccharides or disaccharides. Many times large carbohydrates are formed of only one type of monosaccharide, but some are composed of two, three, or four different types.

Structural Polysaccharides.

Polysaccharides not only function in energy relationships in cells. They are also very important structural components of living things. For example, cellulose, which is made up of glucose monomers, is a fibrous, water-insoluble substance that functions as the main structural material in plant cell walls. In fact, cellulose may well be the most abundant organic chemical in the world. Humans benefit from this abundance, for we use this molecule for such things as lumber, rope fiber, and paper.

Chitin is another polysaccharide, one that is called a modified carbohydrate because it contains nitrogen atoms in its monomer units. Chitin, which is secreted by the outer tissue layer of the animal group that includes lobsters and insects, is the main structural component of the animals' outer skeletons (or exoskeleton). Until recently chitin was thought to have little food value for humans, since humans do not have enzymes to break down this polysaccharide to simpler units. However, biologists now know that some bacteria contain enzymes that can break down chitin into sugars so that the material could be used as a dietary energy source. As a result, some molecular biologists are trying to determine the nature of the gene that controls the production of the enzyme so that we can produce it in large amounts. With this enzyme we can transform the chitin previously believed to be of no use to humans and break it down into sugar.

(Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 59-60)

Disaccharides: Definition, Structure & Examples

Disaccharides: Definition, Structure & Examples - Disaccharides are formed when two monosaccharide units covalently bond together through dehydration synthesis. A common example is sucrose, or table sugar.

When the process of dehydration synthesis covalently bonds two monosaccharides together, the result is a disaccharide. (Remember that saccharide means sugar. The prefix di- means two.) We are all aware of many disaccharides. Common table sugar, sucrose, is a disaccharide, composed of a molecule of glucose bonded to a molecule of fructose. Lactose, or milk sugar, is a disaccharide composed of glucose combined with the monosaccharide galactose. Oligosaccharides consist of two to ten monosaccharide units bonded together, and some types can cause very unique problems, such as the excessive gas and stomach distress you get when you eat beans. Beans contain large amounts of oligosaccharides.

Some adults lose the ability to digest the milk sugar lactose, because their bodies produce insufficient amounts of the enzyme lactase. Lactase is responsible for the hydrolysis of lactose to glucose and galactose. Individuals with this condition suffer from gas, diarrhea, and cramps after the ingestion of lactose. The condition is more prominent in blacks than in members of other races, compounding the difficulty of relief efforts in African countries suffering from famine due to years of drought. A major food supplement shipped to famine-stricken areas is dried milk, because it is light and easier to transport than other protein sources. However, because of enzyme deficiencies, the recipients of this aid do not always benefit as much as their benefactors intend. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 59)

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

Monosaccharides: Definition, Structure & Examples

Monosaccharides: Definition, Structure & Examples - The simplest carbohydrate unit is called a monosaccharide. In some cases, monosaccharides (as well as other molecules) have identical empirical formulas, but their structural formulas differ, giving each variety unique chemical properties. Such molecules are called isomers.

The simplest units of carbohydrates (which are the building blocks of all complex carbohydrates) are monomers known as simple sugars, or monosaccharides. (The term mono-means one, and the term -saccharide means sugar unit.) Typically, simple sugars consist of three to seven carbon atoms. Of special importance to biologists are two types of monosaccharides: the five-carbon (or pentose) molecules, such as those that are part of DNA and RNA; and the six-carbon (hexose) molecules, such as glucose and fructose. The common ending -ose indicates a sugar.

Mnosaccharides Structure

Glucose and fructose are examples of what are called isomers olecules that have identical empirical formulas but have different properties. We touched briefly on this topic in Chapter 2. The empirical formula for both glucose and fructose is C6H12O6, indicating that each consists of 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen.

In an instance like this, in order to see the differences between the two kinds of molecules, a structural formula is more useful than a general formula. (A structural formula shows the position of the atoms within a molecule.) This type of formula illustrates the significant nature of each isomer by showing variations in molecular arrangement. The differences in the bonds between the carbons change the properties of the chemicals. For example, because of the molecular structure of fructose, it stimulates our taste buds more than glucose, so it tastes sweeter than glucose.

One comment about the notation you will see in a structural formula of carbon molecules. Some monosaccharides, especially those having five or six carbon atoms, form a ring when placed in water, as in the watery interior of living cells. In a structural formula, as a matter of convention, the locations of the carbon atoms are numbered for reference, and the numbers serve as an indication of the placement of the carbons at the intersection of the links in the ring. (Source: Avila, Vernon L. Biology : Investigating Life On Earth Jones and Bartlett/Bookmark Series in Biology Page 55)