Biology: A Guide to the Natural World - Biological Molecules PDF

BIOLOGY A GUIDE TO THE NATURAL WORLD FOURTH EDITION DAVID KROGH...

BIOLOGY A GUIDE TO THE NATURAL WORLD FOURTH EDITION DAVID KROGH Life’s Components: Biological Molecules Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. 2.2 Carbon is Central to the Living World Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Carbon is Central to the Living World Carbon is a central element to life because most biological molecules are built on a carbon framework. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Why is Carbon Central to Life? The complexity of living things is facilitated by carbon’s linkage capacity. Carbon has great bonding capacity due to its structure. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Why is Carbon Central to Life? Carbon’s outer shell has only four of the eight electrons necessary for maximum stability in most elements. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Why is Carbon Central to Life? Carbon atoms are thus able to form stable, covalent bonds with a wide variety of atoms, including other carbon atoms. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. 3.2 Functional Groups Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Functional Groups Groups of atoms known as functional groups can confer special properties on carbon-based molecules. Carbon is a central element to life because most biological molecules are built on a carbon framework. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Functional Groups For example, the addition of an –OH group to a hydrocarbon molecule always results in the formation of an alcohol. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Functional Groups Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Table 3.1 Functional Groups Functional groups often impart an electrical charge or polarity onto molecules, thus affecting their bonding capacity. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. 3.3 The Molecules of Life: Carbohydrates Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Carbohydrates Carbohydrates are formed from the building blocks or monomers of simple sugars, such as glucose. These monomers can be linked to form larger carbohydrate polymers, which are known as polysaccharides or complex carbohydrates. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Carbohydrates PLAY Animation 3.2: Monomers and Polymers Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Complex Carbohydrates Four polysaccharides are critical in the living world: – starch – glycogen – cellulose – chitin Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Four Complex Carbohydrates (a) Potato (b) Liver (c) Algae (d) Tick Starch Glycogen Cellulose Chitin Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.6 Four Complex Carbohydrates 1. Starch is the nutrient storage form of carbohydrates in plants. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Four Complex Carbohydrates 2. Glycogen is the nutrient storage form of carbohydrates in animals. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Four Complex Carbohydrates 3. Cellulose is a rigid, structural carbohydrate found in the cells walls of many organisms. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Four Complex Carbohydrates 4. Chitin is a tough carbohydrate that forms the external skeleton of arthropods. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Four Complex Carbohydrates PLAY Animation 3.3: Carbohydrates Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.  3.4 Lipids Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Lipids The defining characteristic of all lipids is that they do not readily dissolve in water. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Lipids Lipids do not possess the monomers-to- polymers structure seen in other biological molecules; no one structural element is common to all lipids. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Lipids Among the most important lipids are the triglycerides, composed of a glyceride and three fatty acids. Most of the fats that human beings consume are triglycerides. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. The Triglyceride Tristearin glycerol fatty acids Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.9 Steroids Another important variety of lipids is the steroids, all of which have a core of four carbon rings. Examples include cholesterol and such hormones as testosterone and estrogen. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Steroids (a) Four-ring steroid structure (b) Side chains make each steroid unique testosterone estrogen cholesterol Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.12 Phospholipids A third class of lipids is the phospholipids, each of which is composed of two fatty acids, glycerol, and a phosphate group. The material forming the outer membrane of cells is largely composed of phospholipids. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Phospholipids (a) Phospholipid structure — variable phosphate group group polar head nonpolar tails (b) Phospholipid orientation “like attracts like” phospholipids nonpolar hydrophobic tails (fatty acids) exposed to oil oil (nonpolar) polar hydrophilic water (polar) heads exposed to water Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.14 Waxes A fourth class of lipids is the waxes, each of which is composed of a single fatty acid linked to a long-chain alcohol. Waxes have an important “sealing” function in the living world. Almost all plant surfaces exposed to air, for example, have a protective covering made largely of wax. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Waxes Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.15  3.5 Proteins Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Proteins Proteins are an extremely diverse group of biological molecules composed of the monomers called amino acids. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Proteins Sequences of amino acids are strung together to produce polypeptide chains, which then fold up into working proteins. Important groups of proteins include enzymes, which hasten chemical reactions, and structural proteins, which make up such structures as hair. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Types of Protein Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Table 3.3 Levels of Protein Structure The primary structure of a protein is its amino acid sequence; this sequence determines a protein’s secondary structure—the form a protein assumes after having folded up. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Beginnings of a Protein The linkage of several amino acids... ala gln ile ala gln ile A typical protein would consist of hundreds of... produces a polypeptide chain like this: amino acids Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.18 Levels of Protein Structure The larger-scale three-dimensional shape that a protein assumes is its tertiary structure, and the way two or more polypeptide chains come together to form a protein results in that protein’s quaternary structure. The activities of proteins are determined by their final folded shapes. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Levels of Protein Structure Four Levels of Structure In Proteins (a) Primary structure The primary structure of any protein is simply its sequence of amino acids. This sequence amino acid sequence determines everything else about the protein’s final shape. (b) Secondary structure Structural motifs, such as the corkscrew-like alpha helix, beta pleated sheets, alpha helix and the less organized “random coils” are parts random coil beta pleated sheet of many polypeptide chains, forming their secondary structure. (c) Tertiary structure These motifs may persist through a set of larger-scale turns that make up the tertiary structure of the folded polypeptide molecule chain (d) Quaternary structure Several polypeptide chains two or more may be linked together in a polypeptide chains given protein, in this case hemoglobin, with their configuration forming its quaternary structure. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.20 Lipoproteins Lipoproteins are biological molecules that are combinations of lipids and proteins. High-density and low-density lipoproteins (HDLs and LDLs, respectively), which transport cholesterol in human beings, are important determinants of human heart disease. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Glycoproteins Glycoproteins are combinations of carbohydrates and proteins. The signal-receiving receptors found on cell surfaces often are glycoproteins. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Proteins PLAY Animation 3.5: Proteins Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. 3.6 Nucleic Acids Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nucleic Acids Nucleic acids are polymers composed of nucleotides. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nucleotides The nucleic acid DNA (deoxyribonucleic acid) is composed of nucleotides that contain a sugar (deoxyribose), a phosphate group, and one of four nitrogen-containing bases. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nucleotides (a) Nucleotides are the building blocks of DNA. Nucleotide nitrogenous DNA consists of two base strands of nucleotides sugar linked by hydrogen (deoxyribose) bonds phosphate group (b) A computer-generated model of DNA The outer “rails” of the double helix are composed of sugar and The rungs phosphate consist of components of bases the molecule hydrogen- bonded together DNA double helix Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 3.21 Nucleic Acids DNA is a repository of genetic information. The sequence of its bases encodes the information for the production of the huge array of proteins produced by living things. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nucleic Acids A second nucleic acid is RNA (ribonucleic acid), which transports the information encoded in DNA to the sites of protein synthesis— structures called ribosomes—and which helps make up the structure of ribosomes. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nucleic Acids PLAY Animation 3.6: Nucleic Acids Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Biological Molecules Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Table 3.4