Moulton, Ed. All rights reserved including the right of reproduction in whole or in part in any form. To order this book direct from the publisher, visit the Penguin USA website or call You can also purchase this book at Amazon. Bionote During asexual reproduction, an exact copy of the parent DNA is copied and supplied to all offspring so that both parent and offspring are identical.
See also:. Trending Here are the facts and trivia that people are buzzing about. Is Vatican City a Country? The Languages of Africa. This characteristic, called specificity, is due to the fact that a substrate with a particular shape and electrical charge can bind only to an active site corresponding to that substrate. Binding of a substrate produces an enzyme—substrate complex. It is likely that enzymes speed up chemical reactions in part because the enzyme—substrate complex undergoes a set of temporary and reversible changes that cause the substrates to be oriented toward each other in an optimal position to facilitate their interaction.
This promotes increased reaction speed. The enzyme then releases the product s , and resumes its original shape. The enzyme is then free to engage in the process again, and will do so as long as substrate remains. Advertisements for protein bars, powders, and shakes all say that protein is important in building, repairing, and maintaining muscle tissue, but the truth is that proteins contribute to all body tissues, from the skin to the brain cells. Also, certain proteins act as hormones and chemical messengers that help regulate body functions.
For example, growth hormone is important for skeletal growth, among other roles. As was noted earlier, the basic and acidic components enable proteins to function as buffers in maintaining acid—base balance, but they also help regulate fluid—electrolyte balance. Like lipids, proteins can bind with carbohydrates.
They can thereby produce glycoproteins or proteoglycans, both of which have many functions in the body. The body can use proteins for energy when carbohydrate and fat intake is inadequate, and stores of glycogen and adipose tissue become depleted.
However, since there is no storage site for protein except functional tissues, using protein for energy causes tissue breakdown and results in body wasting. The fourth type of organic compound important to human structure and function are the nucleotides Figure 2.
A nucleotide is one of a class of organic compounds composed of three subunits:. The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid DNA is nucleotide that stores genetic information. DNA contains deoxyribose so-called because it has one less atom of oxygen than ribose plus one phosphate group and one nitrogen-containing base.
Ribonucleic acid RNA is a ribose-containing nucleotide that helps manifest the genetic code as protein. The nitrogen-containing bases adenine and guanine are classified as purines. A purine is a nitrogen-containing molecule with a double ring structure, which accommodates several nitrogen atoms. A pyramidine is a nitrogen-containing base with a single ring structure. In DNA, two such backbones attach at their protruding bases via hydrogen bonds. These twist to form a shape known as a double helix Figure 2.
The sequence of nitrogen-containing bases within a strand of DNA form the genes that act as a molecular code instructing cells in the assembly of amino acids into proteins. Humans have almost 22, genes in their DNA, locked up in the 46 chromosomes inside the nucleus of each cell except red blood cells which lose their nuclei during development. In contrast, RNA consists of a single strand of sugar-phosphate backbone studded with bases.
The nucleotide adenosine triphosphate ATP , is composed of a ribose sugar, an adenine base, and three phosphate groups Figure 2. ATP is classified as a high energy compound because the two covalent bonds linking its three phosphates store a significant amount of potential energy. This hydrolysis reaction can be written:. Removal of a second phosphate leaves adenosine monophosphate AMP and two phosphate groups. Again, these reactions also liberate the energy that had been stored in the phosphate-phosphate bonds.
They are reversible, too, as when ADP undergoes phosphorylation. Phosphorylation is the addition of a phosphate group to an organic compound, in this case, resulting in ATP.
In such cases, the same level of energy that had been released during hydrolysis must be reinvested to power dehydration synthesis. Cells can also transfer a phosphate group from ATP to another organic compound. Once glucose is phosphorylated in this way, it can be stored as glycogen or metabolized for immediate energy.
Organic compounds essential to human functioning include carbohydrates, lipids, proteins, and nucleotides. These compounds are said to be organic because they contain both carbon and hydrogen. Carbon atoms in organic compounds readily share electrons with hydrogen and other atoms, usually oxygen, and sometimes nitrogen.
Carbon atoms also may bond with one or more functional groups such as carboxyls, hydroxyls, aminos, or phosphates. Monomers are single units of organic compounds.
They bond by dehydration synthesis to form polymers, which can in turn be broken by hydrolysis. Carbohydrate compounds provide essential body fuel. Their structural forms include monosaccharides such as glucose, disaccharides such as lactose, and polysaccharides, including starches polymers of glucose , glycogen the storage form of glucose , and fiber. All body cells can use glucose for fuel.
It is converted via an oxidation-reduction reaction to ATP. Lipids are hydrophobic compounds that provide body fuel and are important components of many biological compounds. Triglycerides are the most abundant lipid in the body, and are composed of a glycerol backbone attached to three fatty acid chains.
The result is a molecule with polar and nonpolar regions. Steroids are lipids formed of four hydrocarbon rings. The most important is cholesterol. Prostaglandins are signaling molecules derived from unsaturated fatty acids. Proteins are critical components of all body tissues. They are made up of monomers called amino acids, which contain nitrogen, joined by peptide bonds.
Protein shape is critical to its function. Most body proteins are globular. An example is enzymes, which catalyze chemical reactions. Nucleotides are compounds with three building blocks: one or more phosphate groups, a pentose sugar, and a nitrogen-containing base. Removal or addition of phosphates releases or invests energy. If the disaccharide maltose is formed from two glucose monosaccharides, which are hexose sugars, how many atoms of carbon, hydrogen, and oxygen does maltose contain and why?
Maltose contains 12 atoms of carbon, but only 22 atoms of hydrogen and 11 atoms of oxygen, because a molecule of water is removed during its formation via dehydration synthesis. Once dietary fats are digested and absorbed, why can they not be released directly into the bloodstream?
All lipids are hydrophobic and unable to dissolve in the watery environment of blood. They are packaged into lipoproteins, whose outer protein envelope enables them to transport fats in the bloodstream. External Website.
Chapter Review Organic compounds essential to human functioning include carbohydrates, lipids, proteins, and nucleotides. Interactive Link Questions Watch this video to observe the formation of a disaccharide. The water hydrolyses, or breaks, the glycosidic bond, forming two monosaccharides. Review Questions. Critical Thinking Questions If the disaccharide maltose is formed from two glucose monosaccharides, which are hexose sugars, how many atoms of carbon, hydrogen, and oxygen does maltose contain and why?
Previous: 2. Next: 3. Share This Book Share on Twitter. Hydroxyl groups are polar. Carboxyl groups are found within fatty acids, amino acids, and many other acids.
Amino groups are found within amino acids, the building blocks of proteins. Your account has been created successfully, and a confirmation email is on the way. Each has a pattern of coding regions colored rectangles that direct the split-pool synthesis of a small molecule colored balls on the end of the oligomer. A new technique called DNA display makes it possible to use short DNA sequences to direct the synthesis of large collections libraries of small organic molecules.
The method provides a new option for creating and screening libraries of small molecules to discover agents with desired properties for a range of research and drug discovery applications. It's like a genetic code for organic chemistry, say its developers, graduate student David R. Halpin, assistant professor of biochemistry Pehr A. In DNA display, small molecules are assembled on the ends of DNA oligomers in a split-pool reaction network--a system of reactions designed to create a large number of diverse compounds in a small number of steps.
First, one constructs a library of DNA oligomers, each containing a series of coding sequences. Each coding sequence directs the DNA oligomer to one of several possible sites in a split-pool reaction network by hybridizing with a complementary DNA sequence at the site. A chemical subunit is then added to the end of the DNA oligomer at each site, and a small organic compound is built up on the oligomer as it visits a series of sites in the network.
The result is a large library of small molecules attached to the ends of the oligomers that encoded their synthesis. Such attachment makes iterative screening possible. Harbury and coworkers demonstrated the technique by using it to carry out two cycles of in vitro selection screening for binding or activity on a library of 1 million nonnatural peptides, yielding a high-affinity protein ligand.
Liu , an associate professor of chemistry and chemical biology at Harvard University, and coworkers. In DTS, organic reagents bound to complementary DNA strands are brought into close proximity when the strands hybridize with each other, inducing the reagents to react in a sequence-programmed manner. Each of the two techniques will most likely prove useful for different types of syntheses, but both can be used to identify functional agents. This is done by using the techniques in iterative procedures--in which large libraries of organic compounds are synthesized, active compounds from those libraries are identified by in vitro selection, and the encoding DNA that remains associated with selected compounds is then amplified for reintroduction into the cycle.
A key goal is to also use the techniques to carry out "molecular evolution," in which encoding DNA for selected compounds is also modified in an effort to create novel agents with even better activity. DTS and DNA display "are the types of techniques that will be needed to manage the big numbers [of compounds] we hoped for in the early days of combinatorial chemistry," comments Gerald F. Joyce , professor of chemistry and molecular biology at Scripps Research Institute.
They are "complementary approaches that will enable the evolution of small organic molecules," he says. Contact the reporter.
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