CARBOHYDRATES

• Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones, or other substances that can be hydrolyzed to them.
• Carbohydrates are organic compounds made up of carbon, hydrogen and oxygen.
• For example, l- and d-glucose have the same water solubility.
• In sugars that contain many chiral centers, only the one that is most distant from the carbonyl carbon is designated as d (right) or l (left).
• Stereoisomers are compounds with the same molecular formula and functional groups but with different conformations.
• d and l isomers of a sugar are enantiomers.
• Isomers of carbohydrates are a type of stereoisomers.
• Carbohydrates are called carbohydrates because hydrogen and oxygen (that are attached to carbon) are present in the same proportion as found in water, H:O=2:1.
• Carbohydrates are found in grains, fruits, vegetables, legumes and sugar.
• If we eat more carbohydrates than are needed for energy, the extra is stored in the liver or in the tissues as fat.
• Aldehyde and Ketone are types of carbohydrates.
• Green plants use light energy from the sun, water from the soil and carbon dioxide from the air to manufacture carbohydrates.
• Glucose cannot be stored on a large scale, so it is converted into starch with the removal of water and stored in plants.
• In cereal grains and potatoes, carbohydrate is stored as starch.
• In fruits such as bananas, mango and sugar beets, carbohydrate is stored as sugar.
• Carbohydrates are classified based on the number of sugar units in the total chain.
• Monosaccharides are single sugar units.
• Disaccharides are two sugar units.
• Oligosaccharides are 3-10 sugar units.
• Polysaccharides are > 10 sugar units.
• Simple carbohydrates are quick energy sources and they do not usually supply any other nutrients or fiber.
• Simple carbohydrates are referred to as simple sugars and are often sweet to the taste.
• Glucose, also known as dextrose, is the carbohydrate form used by the body, referred to as “blood sugar” and is the basic sub-unit of other larger carbohydrate molecules.
• Fructose, also called levulose, is the sweetest of the sugars and occurs naturally in fruits & honey.
• Galactose combines with glucose to form lactose, “milk sugar” and this sugar is converted to glucose in the human body.
• Sucrose, the name given to sugar that we use daily, is prepared from sugar cane and sugar beet and is also present in some fruits and vegetables.
• Lactose, the sugar present in milk, is Glucose+galactose.
• Sucrose is the sweetest of all the sugars and is easily fermented to lactic acid by lactic acid bacteria.
• Amylose is less soluble in water, while amylopectin is more soluble in water.
• Structural isomers are compounds with the same molecular formula but with different structures (different functional groups).
• Glycogen is a highly branched chains of glucose units, found in liver and muscle, and is the animal storage form of carbohydrate.
• Amylose constitutes about 20-30% of the starch, while amylopectin constitutes about 70-80% of the starch.
• Glucose and glucose form maltose in the body during digestion of starch.
• Complex carbohydrates come from starchy foods such as whole grains, flour, seeds, nuts, vegetables and fruits.
• Amylose gives a dark blue/black color when iodine solution is added, while amylopectin gives a reddish brown color when iodine solution is added.
• Fibers are types of non-starch polysaccharides include: cellulose, hemicelluloses, pectins, gums & mucilages, b-glucans, chitin & chitosan, lignans.
• Complex carbohydrates supply longer lasting energy, as well as other nutrients and fiber that the body needs.
• Maltose is formed when whole grains are sprouted and in the commercial preparation of malt from starch.
• The Glycemic Index is a measure of the extent to which a food raises blood glucose concentration & elicits an insulin response compared to pure glucose.
• Amylose can be hydrolyzed with α amylase and β amylase enzymes completely, while amylopectin cannot be hydrolyzed with α amylase and β amylase enzymes completely.