CARBOHYDRATES: (hydro means water)
o Are compounds made of carbon, hydrogen and oxygen in a ratio of approximately 2 hydrogen to 1 oxygen atom. The number of carbon atoms may vary.
o The cells of the human body obtain MOST of their ENERGY from CARBOHYDRATES. Carbohydrates provide short- or long term energy storage for living organisms.
There are THREE TYPES of Carbohydrates, grouped according to complexity: MONOSACCHARIDES, DISACCHARIDES, and POLYSACCHARIDES
MONOSACCHARIDES: (mono means one; sakkharon means sugar)
o Are (Simple Sugar) such as glucose, galactose a sugar found in milk, and fructose, a sugar found in fruits. (C6 H12 O6). Its structure usually is made up of 3 to 7 carbon atoms and the right amount of hydrogen and oxygen atoms.
(see diagram in text pg 11. figure 1.8 and draw them into your notes)
o Glucose, Fructose, and Galactose have the same molecular formula, (C6 H12 O6).
C6 H12 O6. but their Differing Structures determine the different properties. Compounds like these sugars, with a single chemical formula but different forms, are called ISOMERS.
DISACCHARIDES: (di means two)
o Consist of two single sugars (Monosaccharides) linked together. Common disaccharides include SUCROSE, or table sugar; LACTOSE, or milk sugar; and MALTOSE; a sugar contained in cereal grains. The figure below demonstrates how two glucose molecules link to form one molecule of the disaccharide maltose.
(text figure 1.9 draw into notes)
* note the role of water when the glucose units are linked to form maltose and when maltose is broken apart to form individual glucose molecules.
o Another disaccharide of particular importance is sucrose. It is a disaccharide that can be made from the combinations of the two monosaccharides, glucose and fructose. Sucrose can be found in many food sources from ice-cream to brownies, to BBQ sauce.
POLYSACCHARIDES: (poly which means many)
o Are carbohydrates that are made-up of long chains of sugars. Polysaccharides are made-up of three or more monosaccharides.
o Starches perform an important function of energy storage in plants. Starches can be found in such food sources as bread, pasta, and potatoes. Plants convert excess sugars into Starches for long-term storage. (Amylose diagram of generalized starch chain. It loops)
o Glycogen performs the same function as starches but it in animals. Glycogen consists of hundreds of Glucose Molecules strung together in a highly branched chain. Animals store Glucose in the form of polysaccharide glycogen in the liver and muscles to be used as quick energy. (above diagram of generalized glycogen (b))
Q. Note the difference between the structures of starches to that of the glycogen structure. What’s the difference? WHY?
A. The larger amount of branching in glycogen means that glycogen molecules pack more glucose units into a cell that do starch molecules.
o Cellulose which is produced by plants contains an even greater amount of glucose molecules than that of glycogen macromolecule. Plants use cellulose to build their cell walls. Cellulose gives the strength and rigidity to plant cells and is considered a structural molecule because it protects and provides support for the entire plant. Cellulose is a made up of glucose units therefore makes it have a high storage capacity of energy.
Only a few bacterial species produce the digestive chemicals needed to break cellulose down into glucose units and release its energy. These bacteria can be found in the stomach and intestines of certain animals and creatures. However, humans do not host these bacteria; therefore the food energy in cellulose is not directly available to us.
HOMEWORK:
1. List the similarities and differences between monosaccharides, and polysaccharides.
2. Name a mono, di, and polysaccharides and describe the biological importance of each.
3. Why is a condensation reaction considered to be the opposite reaction of a hydrolysis reaction?