Chemical Composition of Cells
BIOL 140 Lab—The Chemical Composition of Cells
Name ____________________________ I) Introduction All cells contain four major types of macromolecules: carbohydrates, lipids, nucleic acids, and proteins. In today’s lab, we will be studying three of the four-proteins, carbohydrates and lipids. Various chemical tests can be used to detect the presence of each of these molecules. Most of the tests involve a color change visible to the eye. If a color change is observed, the test is considered positive. If the color change is not observed, the test is negative, indicating that a particular molecule is not present. In all the chemical tests we will be performing, we will also be using a control. In most cases, the control will be a sample of distilled water (which should not contain any macromolecules). If your control gives you a positive result, you know your test is invalid. Another important aspect of the chemical composition of cells is the pH of their environment. Most cells operate in a narrow pH range. That is, pH values above or below a certain value may cause a cell distress or may even be fatal. To help maintain relatively constant pH levels, living systems use buffers. A buffer is a combination of a weak acid and a weak base that function together to minimize changes in the pH of a solution. In today’s lab, we will learn how to measure pH and demonstrate how buffers work. II) Procedure A) Carbohydrates The basic building blocks for carbohydrates are sugars, also called monosaccharides. These molecules are often linked together to form medium-length chains called oligosaccharides, or very long chains called polysaccharides. The chemical and physical properties of monosaccharides and polysaccharides are different and can be detected with specific chemical tests. Glucose is an example of a monosaccharide that can be linked together in long chains to make a polysaccharide called starch. Even though starch is made up of glucose, in chemical tests the two
Name ____________________________ I) Introduction All cells contain four major types of macromolecules: carbohydrates, lipids, nucleic acids, and proteins. In today’s lab, we will be studying three of the four-proteins, carbohydrates and lipids. Various chemical tests can be used to detect the presence of each of these molecules. Most of the tests involve a color change visible to the eye. If a color change is observed, the test is considered positive. If the color change is not observed, the test is negative, indicating that a particular molecule is not present. In all the chemical tests we will be performing, we will also be using a control. In most cases, the control will be a sample of distilled water (which should not contain any macromolecules). If your control gives you a positive result, you know your test is invalid. Another important aspect of the chemical composition of cells is the pH of their environment. Most cells operate in a narrow pH range. That is, pH values above or below a certain value may cause a cell distress or may even be fatal. To help maintain relatively constant pH levels, living systems use buffers. A buffer is a combination of a weak acid and a weak base that function together to minimize changes in the pH of a solution. In today’s lab, we will learn how to measure pH and demonstrate how buffers work. II) Procedure A) Carbohydrates The basic building blocks for carbohydrates are sugars, also called monosaccharides. These molecules are often linked together to form medium-length chains called oligosaccharides, or very long chains called polysaccharides. The chemical and physical properties of monosaccharides and polysaccharides are different and can be detected with specific chemical tests. Glucose is an example of a monosaccharide that can be linked together in long chains to make a polysaccharide called starch. Even though starch is made up of glucose, in chemical tests the two