Sunday, November 11, 2007

Heyy, period 8 and 9!
Today we learned all about Carbohydrates. The name "carbohydrate" means a "hydrate of carbon.” Carbohydrates always have a 1:2:1 ratio of carbon, hydrogen, and oxygen.
The general formula of carbohydrate Cx(H2O)y - x and y may or may not be equal and range in value from 3 to 12 or more. For example glucose is: C6(H2O)6 or is more commonly written, C6H12O6.The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups. The chemistry of carbohydrates is complicated by the fact that there is a functional group (alcohol) on almost every carbon. In addition, the carbohydrate may exist in either a straight chain or a ring structure.
A major part of the carbon cycle occurs as carbon dioxide is converted to carbohydrates through photosynthesis. Carbohydrates are utilized by animals and humans in metabolism to produce energy and other compounds.

Carbohydrate Functions:
Carbohydrates are initially synthesized in plants from a complex series of reactions involving photosynthesis.
-Store energy in the form of starch (photosynthesis in plants) or glycogen (in animals and humans).
-Provide energy through metabolism pathways and cycles.
-Supply carbon for synthesis of other compounds.
-Form structural components in cells and tissues.


is a complex series of reactions carried out by algae, phytoplankton, and the leaves in plants, which utilize the energy from the sun. The simplified version of this chemical reaction is to utilize carbon dioxide molecules from the air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product. The simple sugars are then converted into other molecules such as starch, fats, proteins, enzymes, and DNA/RNA i.e. all of the other molecules in living plants. All of the "matter/stuff" of a plant ultimately is produced as a result of this photosynthesis reaction.

Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert for example glucose sugar into the products of carbon dioxide and water and ENERGY. This reaction is also carried out by bacteria in the decomposition/decay of waste materials on land and in the water.
Combustion occurs when any organic material is reacted in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be any fossil fuel such as natural gas oil, or coal. Other organic materials that combust are wood, paper, plastics, and cloth.

The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat.

The monomers of carbohydrates are called monosaccharides and are also called simple sugars. They are usually ring-like and are composed of five or six carbons. They are either a polyhydroxy aldehyde or a polyhydroxy ketone, which means they have more than one hydroxide group (-OH) and one carbonyl group (C=O). Some popular monosaccharides are glucose, fructose, and galactose.However, some very important carbohydrates are composed of thousands of monomers and are called polysaccharides. Here are the main important polysaccharides:- starch: Plants store their energy as starch using photosynthesis. We eat plants, breaking down the starch into its monomers and putting it to good use.- cellulose: The cell walls around plants are composed of cellulose. Cellulose is a very important structural component of plants and it's what makes them snap when you rip them apart. Err, I mean - they provide support for the plant.- glycogen: Animals store energy as glycogen. It's stored in the liver.

A carbonyl group is a functional group composed of a carbon atom double bonded to an oxygen atom : C=O.

An aldehyde is an organic compound containing a terminal carbonyl group. This functional group which consists of a carbon atom which is bonded to a hydrogen atom and double bonded to an oxygen atom (chemical formula O=CH-), is called the aldehyde group.

A ketone (pronounced as key tone) is either the functionalgroup characterized by a carbonyl group (O=C) linked to two other crbon atoms or a chemical compound that contains this functional group. A ketone can be generally represented by the formula:

The major component in the rigid cell walls in plants is cellulose. Cellulose is a linear polysaccharide polymer with many glucose monosaccharide units. The acetal linkage is beta which makes it different from starch. This peculiar difference in acetal linkages results in a major difference in digestibility in humans. Humans are unable to digest cellulose because the appropriate enzymes to breakdown the beta acetal linkages are lacking. Indigestible cellulose is the fiber which aids in the smooth working of the intestinal tract.
Animals such as cows, horses, sheep, goats, and termites have symbiotic bacteria in the intestinal tract. These symbiotic bacteria possess the necessary enzymes to digest cellulose in the GI tract. They have the required enzymes for the breakdown or hydrolysis of the cellulose; the animals do not, not even termites, have the correct enzymes. No vertebrate can digest cellulose directly.

Compare Cellulose and Starch Structures:
Cellulose: Beta glucose is the monomer unit in cellulose. As a result of the bond angles in the beta acetal linkage, cellulose is mostly a linear chain.
Starch: Alpha glucose is the monomer unit in starch. As a result of the bond angles in the alpha acetal linkage, starch-amylose actually forms a spiral much like a coiled spring.

Tommorows sherpa is.. Kim

Later Class!

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