Monomers or base units are bonded together to create

  • No School
  • AA 1
  • 11

This preview shows page 3 - 6 out of 11 pages.

Monomers, or base units are bonded together to create larger molecules via dehydration. This involves the removal of a water molecule at the bonding site. The larger molecule can be broken down by the reverse process, hydrolysis. This occurs when water is added to break the covalent bonds created during dehydration. Carbohydrates The body uses carbohydrates as “fast fuel.” It is the first macromolecule used to obtain energy for the body because very little energy is required to break down carbohydrates. You will learn how it is used to create energy in the Photosynthesis and Respiration lab. Carbohydrates are sugar molecules. They are made up of the base elements C, H and O in a 1:2:1 ratio. The simplest carbohydrate is a monosaccharide (a simple sugar). An example of a simple sugar is glucose, which is created during photosynthesis. Monosaccharides are covalently bonded together to create more complex sugars. A disaccharide is two covalently bonded simple sugars or monosaccharides. A polysaccharide is the carbohydrate polymer and consists of several monosaccharides bonded together. A common polysaccharide, the one you will look at in lab, is starch. Starch is a storage polysaccharide found in plants. Another plant polysaccharide is cellulose , a major component of a plant’s cell wall. In lab you will test for the presence of glucose, a monosaccharide carbohydrate, and for starch, a polysaccharide carbohydrate, in a series of liquid substances.
Image of page 3

Subscribe to view the full document.

To test for the presence of glucose you will use the Benedict’s Test for Reducing Sugars (monosaccharides). Benedict’s reagent is clear blue (from the presence of cupric copper ions, Cu ++ ) but when combined and heated to boiling with a substance containing glucose in a chain form, the cupric ions are reduced to a cuprous form ( Cu + ) and then oxidized to form copper oxide (Cu 2 O) . Copper oxide is a brownish-orange substance that is insoluble in water. Therefore, a positive reaction in a Benedict’s Test is the change of the clear light blue solution to an opaque orange-brown solution in a boiling water bath. This color change indicates the presence of Glucose in a given solution. Can you identify the positive Benedict’s Test versus the negative test? To test for the presence of starch, the Starch Test is used. This is a simple test in which iodine is added to a given solution. If a polysaccharide such as starch is present then the iodine ion will lodge itself in the polysaccharide chain and give it a black-blue color. If iodine added to a solution turns black- blue than starch is present. If the solution remains the color of iodine, reddish-orange, there is no starch present, a negative test.
Image of page 4
Is this a positive or negative Starch Test?
Image of page 5

Subscribe to view the full document.

Image of page 6

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask 0 bonus questions You can ask 0 questions (0 expire soon) You can ask 0 questions (will expire )
Answers in as fast as 15 minutes