chemical biology

• Carbohydrates are generally defined as polyhydroxy aldehydes or ketones or substances that yield these compounds when hydrolyzed.
• monosaccharide is the basic carbohydrate unit of cellular metabolism.
• Monosaccharide – a carbohydrate that cannot be hydrolyzed to simpler carbohydrate units.
• Disaccharides – yields two monosaccharides – either alike or different when hydrolyzed.
• disaccharides are often used by plants or animals to transport monosaccharides from one cell to another.
• monosaccharides and disaccharides generally have the ending –ose. For example, glucose, sucrose, and lactose.
• monosaccharides and disaccharides are water-soluble carbohydrates, which have a characteristically sweet taste and are called sugars.
• Oligosaccharides– has two to six monosaccharide units linked together.
• Polysaccharides – is a macromolecular substance that can be hydrolyzed to yield many monosaccharide units
• polysaccharides are important structural supports, particularly in plants, and also serve as a storage depot for monosaccharides, which cells use for energy.
• Other Ways to Classify Carbohydrates:

  • As a triose, tetrose, pentose, hexose, or heptose
  • As an aldose or ketose
  • As a D or L isomer
  • As a (+) or (-) isomer
  • As a furanose or a pyranose
  • As having an alpha or beta configuration
• true or false: Carbohydrates are very effective energy yielding nutrients

  true
• Carbohydrates are very effective energy yielding nutrients
• Carbohydrates can serve as very effective building materials
• Carbohydrates are important water soluble molecules
• The hexose monosaccharides are the most important carbohydrate sources of cellular energy
• Three hexose: glucose, galactose, and fructose are of major significance in nutrition.
• glucose, galactose, and fructose have the same formula, C6H12O and thus deliver the same amount of cellular energy.
• Glucose (dextrose)– is the most important of the monosaccharides
• glucose (dextrose) – It is an aldohexose and is found in the free state in plant and animal tissue
• Galactose – Is also an aldohexose and occurs, along with glucose, in lactose and in many oligo- and polysaccharides such as pectin and gums.
• Fructose – Also known as levulose, is a ketohexose that occurs in fruit juices, honey, and along with glucose, as a constitituent of sucrose.
• Any two monosaccharides that differ only in the configuration around a single carbon atom are called epimers.
• guess the structure

  A) L-glyceraldehyde

  B) D-glyceraldehyde

  
• When two cyclic isomers differ only in their stereo arrangement about the carbon involved in mutarotation, they are called anomers.
• Mutarotation is the process by which anomers are interconverted.
• Cyclic structures of monosaccharides are intramolecular hemiacetals
• When a monosaccharide hemiacetal reacts with an alcohol, the product is an acetal. In carbohydrate terminology, this acetal structure is called glycoside
• guess the structures

  A) D-galactose

  B) α-D-galactopyranose

  C) β-D-galactopyranose

  
• Disaccharides are carbohydrates composed of two monosaccharide residues united by a glycosidic linkage
• sucrose + water  - sucrase →   glucose + fructose
• lactose + water  - lactase →   galactose + glucose
• maltose + water  - maltase →   glucose + glucose
• The aldehyde groups in monosaccharides can be oxidized to monocarboxylic acids by mild oxidizing agents such as bromine water.
• Monosaccharides can be reduced to their corresponding polyhydroxy alcohols by reducing agents such as H2/Pt or sodium amalgam, Na(Hg).
• Under prescribed conditions, some sugars reduce silver ions to free silver, and copper (II) ions to copper (I) ions.
• Under prescribed conditions, some sugars reduce silver ions to free silver, and copper (II) ions to copper (I) ions. Such sugars are called reducing sugars.
• Starch is found in plants, mainly in the seeds, roots, or tubers.
• Corn, wheat potatoes, rice and cassava are the chief sources of dietary starch.
• The two main components of starch are amylose and amylopectin.