Macromolecules - Biology Foundations - Textbook

Macromolecules Many of the carbon compounds in living cells are so large that they are known as macromolecules or “giant molecules.” Macromolecules carbohydrate are made from thousands or ev...

Macromolecules Many of the carbon compounds in living cells are so large that they are known as macromolecules or “giant molecules.” Macromolecules carbohydrate are made from thousands or even hundreds of thousands of smaller a compound made up of carbon, molecules. The smaller units, or monomers, join together to form hydrogen, and oxygen atoms; a polymers (pahl uh murz). The monomers in a polymer may be the type of nutrient that is the main source of energy for the body same, like links in a chain. Or, the monomers may be different, like different colored beads in a necklace. lipid a macromolecule made mostly Scientists sort the macromolecules found in living things into from carbon and hydrogen atoms; groups based on their chemical makeup. The four major groups of includes fats, oils, and waxes macromolecules found in living things are carbohydrates, lipids, word origins nucleic acids, and proteins. Carbohydrate is a combination of the prefix carbo-, which means Carbohydrates Compounds made up of carbon, hydrogen, and “carbon,” and the word hydrate, oxygen atoms are called carbohydrates. There are usually twice as which means “water.” many hydrogen atoms as carbon or oxygen atoms in these molecules. Living things use carbohydrates as their main source of energy. Carbohydrates give plants, some animals, and other organisms structure. Sugars are carbohydrates. The breakdown of sugars, such as glucose, supplies energy for cell activities. Many living things store extra sugar as a carbohydrate called starch. ▶ Simple Sugars Single sugar molecules are called both monosaccharides (mahn oh sak uh rydz) and simple sugars. Besides glucose, simple sugars include galactose, which is found in milk, and fructose, which is found in many fruits. Table sugar, sucrose, is made up of glucose and fructose. Since sucrose is made of two sugars it is called a disaccharide. Key Question What are the functions of carbohydrates? Carbohydrates provide energy and structural support for living things. Monomers Polymerization Polymerization Most macromolecules are formed by a process known as polymerization (pah lih mur ih zay shun). In this process, monomers join together to form polymers. Polymers can get very large. Polymer 38 Chapter 2 Lesson 3  Glucose Carbohydrates Sugars and starches are carbohydrates. Starches form when CH OH 2 sugars join together in long chains. C O H H H C C OH H HO OH Starch C C H OH ▶ Complex Carbohydrates The large macromolecules formed when simple sugars join together are called complex carbohydrates. Many animals store extra sugar in a complex carbohydrate called glycogen. When the amount of glucose in your blood runs low, glycogen is broken down into glucose, which then goes into the blood. The glycogen stored in your muscles gives energy to muscles so that you can move. Plants use a different complex carbohydrate, called starch, to store extra sugar. Plants also make another complex carbohydrate called cellulose. Cellulose gives plants their strength and rigidity. Cellulose is the major part of wood and paper, so you are looking at cellulose as you read these words! Lipids Fats, oils, and waxes are common lipids. Lipids are macromolecules that generally do not dissolve in water and are made mostly of carbon and hydrogen atoms. Some lipids store energy. Others form biological membranes, and some produce waterproof coverings on cells and tissues. Many lipids are formed when a glycerol molecule joins with compounds called fatty acids. If each carbon atom in a lipid’s fatty acids is joined to other carbon atoms by only single bonds, the lipid is called saturated. This means that the fatty acid has the most hydrogen atoms it can have. If there is at least one carbon-carbon double bond in a fatty acid, the fatty acid is called unsaturated. You have probably seen the terms saturated and unsaturated on food labels. Lipids that have unsaturated fatty acids are liquid at room temperature. Olive oil is one such lipid. Key Question What are the functions of lipids? Lipids are used to store energy and are parts of membranes and waterproof coverings. Lipids Lipids are made up of a glycerol molecule and fatty acids. The Chemistry of Life 39  Nucleotides Each nucleotide is made Nitrogenous up of a 5-carbon sugar, a phosphate base group, and a nitrogenous base. Phosphate Nucleic acids are made up of many group nucleotides joined together. 5-carbon sugar Nucleic Acids Nucleic (noo klee ik) acids are macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. Nucleic acids are polymers. They are made up of monomers called nucleic acid nucleotides (noo klee oh tydz). Nucleotides have three parts: a a macromolecule containing 5-carbon sugar, a phosphate group (2PO4), and a nitrogenous base. hydrogen, oxygen, nitrogen, Some nucleotides, including adenosine triphosphate (ATP), help in carbon, and phosphorus storing and transferring energy. protein a macromolecule that contains Single nucleotides can be linked by covalent bonds into long chains carbon, hydrogen, oxygen, and known as nucleic acids. Nucleic acids store and transmit genetic nitrogen; needed by the body for information. There are two kinds of nucleic acids: ribonucleic acid growth and repair (RNA) and deoxyribonucleic acid (DNA). RNA contains the sugar amino acid ribose, and DNA contains the sugar deoxyribose. a compound with an amino group on one end and a carboxyl group on the other end Key Question What are the functions of nucleic acids? Nucleic acids store and transmit genetic information. word origins The root word nucle- refers to a Proteins Proteins are macromolecules that contain nitrogen as well nucleus, or center, of something. as carbon, hydrogen, and oxygen. Proteins are polymers of molecules In nucleic acid the root word called amino acids. Amino acids are compounds with an amino refers to the nucleus of a cell, group (–NH2) on one end and a carboxyl group (–COOH) on the not of an atom. other end. Covalent bonds called peptide bonds link amino acids to form one or more polypeptides. A protein is a molecule made from one or more polypeptides. Some proteins control cell processes and the rate of reactions. Others form important parts in cells, while still others move substances into or out of cells or help to fight disease. General Structure of Amino Acids Amino Acids All amino acids H H O have an amino group and a carboxyl group. The R in the N C C structure shows where the side chain of the amino acid H OH R goes. Different side chains have different properties. Amino Carboxyl group group 40 Chapter 2 Lesson 3 ▶ Structure and Function More than 20 different amino acids are found in nature. All amino acids are the same in the regions where they may be joined together by covalent bonds. This uniformity allows any amino acid to be joined to any other amino acid. Each amino acid has a different side chain called an R-group. The side chains have different properties. Some chains are acidic and some are basic. Some are polar, some are nonpolar, Heme and some even contain large ring structures. Because the side group chains are so different, proteins are diverse macromolecules. ▶ Levels of Structure Amino acids are joined in long chains according to instructions coded in DNA. Scientists describe proteins as having four levels of structure. A protein’s primary structure is the order of its amino acids. Its secondary structure is the folding of the polypeptide chain. The third level of structure is the three-dimensional arrangement of a chain. Proteins that have more than one chain have a fourth level of structure. The fourth level describes how the different chains are placed next to each other. Hemoglobin, a protein in red blood cells that helps move oxygen in blood, has four levels of structure. The shape of a protein is kept by many forces, including ionic, covalent, and hydrogen bonds. The heme groups in the protein bind oxygen and also give hemoglobin its red color. Amino acids Key Question What are the functions of proteins? Some proteins control cell processes and the rate of reactions. Others form important parts in cells, while still others move substances into or out of cells or help to fight disease. Protein Structure Hemoglobin is a protein made up of four polypeptide chains. Near the center of each polypeptide is an iron-containing heme group. An oxygen molecule is bound by each heme group. Apply Vocabulary Critical Thinking Use the highlighted words from the lesson to 4. Relate Cause and Effect Why can carbon complete each sentence correctly. form so many different structures? 1. Fats, oils, and waxes do not dissolve in water and 5. Explain How do living things use lipids? are kinds of macromolecules called _______. 6. Sequence What are the four levels of 2. _______ store genetic information. organization in a protein? 3. Compounds made up of carbon, hydrogen, and 7. Write to Learn Make a chart that shows the oxygen that are the main source of energy for monomers that make up three of the four the body are called _______. kinds of macromolecules. Lesson 2.3 Lesson Assessment The Chemistry of Life 41