Jennifer Forrester

Biology 101-Section 700

February 10, 2009.  Lab Report#1

ORGANIC MOLECULES

Introduction

Organic molecules are essential to life and are found in living organisms.  The four basic types of molecules are carbohydrates, lipids, proteins and nucleic acids which can be found in the foods that we consume.  (SYMBIOSIS p19)  Each of these molecules and compounds has a different purpose.  (McDarby)  In fact everything that humans consume are a mixture of these molecules and also inorganic molecules.  In consuming these organic molecules, we are able to survive, mature and reproduce.

Organic molecules are more often made up of carbon, hydrogen and oxygen atoms.  However, sometimes other atoms can be found within these compounds such as nitrogen, phosphorus and sulfur.  These carbon atoms bond to other atoms through covalent bonds and can be either single, double or triple bonds.  This depends on whether there are one, two or three pairs of electrons shared within the atoms.  (SYMBIOSIS p19)

        The molecules of these four compounds are made up of monomers, which are small building blocks.  For example, carbohydrates are often constructed of monomer units of sugar (typically glucose), but the monomer units for proteins are amino acids.  However when two monomers are linked together, this new molecule is now called a dimer and when more than two are linked it is referred to as polymer. (SYMBIOSIS p20)

Purpose

In this lab, we will perform simple tests to determine the absence or presence of the four different organic compounds.  These tests will, of course, be qualitative rather than quantitative.  Meaning we will not be determining the quantity of these compounds within the samples, but simply whether or not they are present.

        Carbohydrates are what give the cells within our body it’s energy.  As mentioned before, the building blocks of carbohydrates are sugars.  These sugars can are classified according to the amount of sugar molecules they have.  Monosaccharides, such as glucose or fructose most commonly found in soft drinks, have only one sugar molecule;  Disaccharides, such as sucrose or lactose which is found in milk, contain two molecules;  Polysaccharides, such as starch or cellulose contain many more sugar molecules that are linked together.  (Holland)  It is possible to detect these sugars within a substance using a reagent called Benedict’s solution, which is a blue solution that turns multiple colors when it is heated with a reducing sugar.  The research hypothesis is that should you add Benedict’s solution to a substance and it turns either the color green, yellow, orange or red, then the test will prove that these sugars are present.  However, to test for starch, which is a complex carbohydrate, we will have to use Lugol’s solution, which is an amber or brown-red substance.  The research hypothesis is that if you add the Lugol’s solution to a substance and it turns dark blue-black color, then it will prove that there are complex carbohydrates present within the substance.  (SYMBIOSIS p21)

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        Lipids are typically the fat or oils found in the foods that we eat.  These types of lipids are also known as triglycerides.  They serve as energy storage molecules but can have other functions as well.  (Holland)  For instance, phospholipids make up the main component of cholesterol, which provides the foundation for many of our hormones.  Lipids are hydrophobic and are almost never soluble in water.  (Holland)  In order to detect the presence of lipids within a substance a reagent called Sudan IV will be necessary.  Sudan IV is a very strong red dye.  The research hypothesis is that should ...

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