What is Life? Project PART 6: The molecules of life

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1 Name: Due Monday 9/17 (15 points) What is Life? Project PART 6: The molecules of life Read the following text and answer the questions: The Molecules of Life All living things are composed of chemical compounds. Cells consist mostly of water, but the rest of them consist mostly of carbon-based molecules. Carbon can form large, complex, diverse molecules that are necessary for life functions. Compounds that contain carbon are called organic compounds. Carbon is an important molecular ingredient in all living things because of its unique bonding ability. A carbon atom has 4 electrons in its outer shell that holds 8. This means that carbon can complete its outer shell by sharing electrons with 4 other atoms in four covalent bonds. Each carbon thus acts as an intersection from which an organic molecule can branch off in up to four different directions. And because the carbon can use one or more of its bonds to attach to other carbon atoms, it is possible to construct an endless diversity of carbon skeletons. Below are examples of different carbon molecules: C C C C All of these examples are examples of carbon bonding to hydrogen. 1. Can you complete the following molecule by bonding hydrogen atoms? (0.5 point) C 2. ow would your molecule change if you added one more carbon atom? Draw it. (0.5 point)

2 Below are examples of carbon molecules with double bonds: C = C C C - C C = C C - 3. Can you complete the following molecule by bonding hydrogen atoms? (0.5 point) C = C Below are examples of carbon molecules that are arranged in rings: Benzene Fructose Each type of organic molecule has a unique three-dimensional shape. Many vital processes within living organisms rely on the ability of molecules to recognize one another based on their shape. The unique properties of an organic molecule depend not only on its carbon skeleton, but also on the atoms attached to the skeleton. Certain atoms that usually participate in chemical reactions are called functional groups. These functional groups usually behave the same way on different molecules. Functional groups help give each molecule its unique properties. Below are some common functional groups on organic molecules: ydroxyl group: Carbonyl group: Amino group: Carboxyl group: O O C C O C C C C N C C O Found in sugars and alcohols Found in sugars Found in. Found in amino acids and fatty acids

3 5. What functional groups do you think you could find on amino acids (the monomers of proteins)? (0.5 point) Giant molecules from smaller building blocks On a molecular scale, many of life s molecules are gigantic; in fact, biologists call them macromolecules. DNA is a macromolecule, as are the carbohydrates in starchy foods and the proteins that compose your hair. Even though they are quite large, the structure of most macromolecules can be easily understood because they are the polymers, large molecules made by stringing together smaller molecules called monomers. Cells link monomers together through a dehydration reaction, a chemical reaction that removes a molecule of water. Organisms not only make macromolecules, but they also have to break them down. For example, many of the molecules in your food are macromolecules. You must digest these giant molecules in order to make their monomers available for your cells, which can rebuild the monomers into your own brand of macromolecules. Digestion occurs through the process known as hydrolysis. ydrolysis means to break down with water. The diagram below shows the synthesis and digestion of polymers: There are four main categories of molecules that we find in living things: carbohydrates, proteins, lipids, and nucleic acids. Carbohydrates Carbohydrates are a chemical compound consisting of carbon, hydrogen, and oxygen. Sugar, starch, and cellulose are all examples of carbohydrates. Usually the atoms of these molecules are present in a ratio that is expressed by the formula C n 2n O n. There are many types of carbohydrates. They have been placed into three groups: monosaccharides, disaccharides, and polysaccharides. 6. What does the prefix mono- mean? (0.5 point) 7. What does di- mean? (0.5 point)

4 8. What does poly- mean? (0.5 point) 9. What does saccharide mean? (0.5 point) Sugars have been used for ages to make food sweeter. The most common dietary sugars are glucose (or dextrose), fructose, and sucrose. Both glucose and fructose are monosaccharides. Sucrose is a disaccharide. Common table sugar is sucrose, usually obtained from sugarcane or sugar beets. Glucose is corn syrup. Glucose is also the sugar used by the cells of our bodies for energy. Because it is the sugar that circulates in the bloodstream, it is often called blood sugar. Fructose is found in honey and in some fruits, but much of it is made from glucose. Corn syrup can be treated with enzymes to convert much of the glucose to fructose. The result is high fructose corn syrup. Fructose is sweeter than sucrose or glucose. Foods sweetened to the same degree with high-fructose corn syrup have somewhat fewer calories than those sweetened with sucrose. Glucose is an example of a monosaccharide. Sucrose is an example of a disaccharide. When hydrolyzed, it will yield two monosaccharide units: glucose and fructose. Complex carbohydrates are polysaccharides. Starch and cellulose are examples of polysaccharides. Starch and cellulose are both polymers of glucose. Starch is the main energy storage system in plants. You can find roots and other plant organs. You observed starch when you looked at the potato cells under the microscope. The amyloplasts, starch storage sacks, turned purple with iodine.

5 Cellulose is the structural material of plants. Plant cell walls are made of polysaccarhrides called cellulose. The cellulose molecules are assembled into fibrils that make up the main fabric of cell walls. Wood is composed of cellulose and other polymers. Starch and cellulose differ in the connecting links between the glucose units. umans can digest starch, but not cellulose. Starch is hydrolyzed to glucose when it is digested. The body then metabolizes the glucose, using it as a source of energy. Glucose is broken down through a complex set of more than 50 chemical reactions to produce carbon dioxide and water with the release of energy. C 6 12 O O 2 6 CO O + Energy These reactions are essentially the reverse of photosynthesis. In this way, animal organisms are able to make use of the energy from the sun that was captured by plants in the process of photosynthesis. We can eat cellulose, but we cannot digest it. We get no nutrient value from it. It is just fiber. Certain bacteria have such enzymes, however, and they are present in grazing animals, such as cows, and in termites. These animals can also convert cellulose to glucose. 10. Cut out the sugars on the attached colored paper. In the space below, tape and label the following saccharides. For each bond you make, be sure to show the water formed as well. Glucose, a monosaccharide Fructose, a monosaccharide Sucrose, a disaccharide consisting of glucose and fructose Starch, a polysaccharide consisting of three or more glucose (2 points)

6 Proteins Proteins are an important molecular component of all living things. Your body contains tens of thousands of different proteins. Each protein has a unique three-dimensional shape that corresponds to a specific function. Proteins make up many of the structures in your body; every time you look at your hair, your toenails, your skin, and your muscles, they re all protein. Proteins are found within the plasma membrane and other membranes of the cell. These proteins are called membrane proteins. Proteins also make up the cytoskeleton of the cell. Not only do proteins help maintain cell structure, but they also help change the rate of chemical reactions in cells and organisms. Special proteins, called enzymes, can change the rate of the reaction without being used in the process. Proteins are made up of Amino Acids. The 20 amino acids make up all the proteins in your body. Some amino acids the body can make by itself, others must be eaten as part of your diet. The amino acids that must be eaten are called Essential Amino Acids. Vegetarians must be especially careful that their diet includes these essential amino acids, as they are most commonly found in eggs and meats. 11. Cut out the amino acids on the attached colored paper. In the space below, tape and label the following molecules. For each bond, make sure you show the water formed as well. Alanine, an amino acid Valine-tryptophan, a dipeptide Use all the rest to create a large polypeptide (1. 5 points) 12. What do you think peptide means? (0.5 point)

7 Lipids Lipids are another important class of organic molecules. Lipids are partially made of fats, and partially made from alcohol. The fats are called fatty acids and the alcohol is glycerol. The fatty end of these molecules will not dissolve in water, but the glycerol end will. For this reason when you drop lipids in water, they form little balls, with the glycerol ends touching the water, and the fatty ends in the middle. The plasma membrane, as well as other membranes in the cell, is composed mostly of lipids and proteins. The lipids belong to a special category called phospholipids. They are related to dietary fats but have only two fatty acid tails instead of three. A phospholipid has a phosphate group in place of the third fatty acid. 13. To build a lipid, you need to combine three fatty acids and one glycerol molecule. Cut out the appropriate molecules from the Pieces paper. Label each part of the lipid as Fatty Acid or Glycerol. For each bond you make, be sure to show the water formed as well. There should be three waters formed for each lipid you make. (1 point)

8 Nucleic Acids DNA is a nucleic acid. DNA is the chemical in your body that carries the genes used to determine your hair color, eye color, skin color, gender and many other things. When something is cloned, scientists must start with a good copy of that animal s DNA. The building blocks of nucleic acids are nucleotides. Nucleotides stack in a special way. They stack in pairs, like a big zipper. Then, if the long chain is unzipped, each side can be used to make a whole new side, resulting in two chains exactly like the first one. The sequence of nucleotides in a long chain is actually an instruction manual for making proteins. You will learn more about DNA and other nucleic acids, like RNA, later in the semester. 14. Cut out the nucleotides. In the space below, create a double strand of DNA. Be sure to match them up appropriately by shape! (1 point)

9 15. Now choose one organelle/structure of the cell to investigate in more detail. You will find this organelle s chemical composition (Is it a fat, protein, sugar, or nucleic acid?) You will draw an enlarged picture of the organelle and show the macromolecules, and atoms that compose these macromolecules on your cell poster. Please do your drawing IN PENCIL. (5 points) Resources: Boyes, Lee. Poly Bio Chem Activity. Unpublished Lesson Campbell, N. A., Reece, J. B., and Simon, E. J. Essential Biology with Physiology. 2 nd Ed. Pearson/Benjamin Cummings, ill, J. W., and Kolb, D. K. (2001). Chemistry for Changing Times. 9 th Ed. Upper Saddle River, New Jersey: Prentice all. Moniz de Sá, Mário. Langara College. Biology 2315 Lecture Notes. Chapter 1: An Introduction to Biochemistry. January, September 16,