LECTURE                               SUGARS AND CARBOHYDRATES

In this lecture you will learn:

ENERGY
- monosaccharides are single sugars. .. like glucose, fructose, and galactose

-- sugars can be a straight chain or a ring.
-- most common form is a hexagonal ring composed of five carbons and an oxygen.
-- Two monosaccharide can link together through an oxygen to form a disaccharide. The most common disaccharide is sucrose, ordinary table sugar.
- consists of a glucose linked to a fructose pentagon.

- Other common disaccharides are
maltose (malt sugar),
lactose (milk sugar)
Sugars differ in sweetness.
Sucrose is about six times sweeter than lactose, about three times sweeter than maltose, slightly sweeter than glucose, but only about half as sweet as fructose.
-  structural elements of plants and fungi
The linking of monosaccharide rings can be continued into a polymer, called a polysaccharide, which is not a sugar.
- important polysaccharides are starch, glycogen, and cellulose.
-- They are all formed from repeating glucose units.
Carbohydrates which means carbon, hydrate is water altho the hydrogen and oxygen are not in the form of water molecules but of H and OH groups.



 
STORAGE

-- Starch is the major method of food storage in plant seeds and tubers such as corn, wheat, potatoes, and rice.
-- In digestion, enzymes catalyze the breakdown of starch into glucose so it can be used by cells. *** glucose is used as a food substitute for intravenous feeding.
-- Starch can be coiled linear chains and branched chains.

-- Glycogen is similar to starch but is composed of very highly branched molecules.
 
 

- it is made in animals to serve as energy storage concentrated in the MUSCLE AND LIVER
-- The branched structure allows it to be broken down rapidly to supply quick energy for muscular activity. In the liver glycogen serves as storage for glucose and helps maintain a constant level of glucose in the blood. The LIVER supplies the body with its glucose supply.
 



 
 
STRUCTURAL 
Cellulose, like starch, is a polysaccharide formed from glucose links.
- However, in cellulose the glucose is in the beta rather than the alpha form. Cellulose forms the main structural material of plants.

-- Wood is about half cellulose, cotton fibers are almost all cellulose.
 

-- The enzymes that break down starch into glucose have no effect on cellulose so cellulose has no food value. Some bacteria and fungi have an enzyme, called cellulase, that breaks down cellulose. One reason we see fungi growing on trees.

 

- animals like cow (ruminants) have the right bacteria in the digestive tracts that allows them to use cellulose for food. The eat the grass, chew it and it goes into the first stomach, later they regurgitate the grass and chew their cud breaking the walls of the grass down, then the bacteria start fermenting and breaking down the bonds.

REVIEW QUESTIONS:

What are sugars?  What are carbohydrates?
What is the difference between sugars, starches, cellulose, and glycogen.
Which sugar molecules are used for energy storage,  and which kinds are used by plant vs animal?  Where is that energy stored?
What are the carbohydrate molecules of structure? In what kinds of living things?
Be able to identify the difference between the various build blocks and polymers by sight.
Which sugar is the only sugar used by all cells?
Where is sugar stored in the human body and what is the name of the molecule?
What is a polymer? A polysaccharide?  How are polymers of the building blocks formed?
How is starch different than cellulose?
What kind of living things break down cellulose?  Give an example?
What is the difference between cellulose and starch?