isomers
Both structures represent molecules having the formula C4H10.However, the arrangements of the atoms are different. These compounds are related as isomers (two compounds of the same formula, but different arrangement of atoms)
chiral
When a central carbon atom is bonded to 4 different groups, the mirror image is not identical to the original.
Biological Function of Carbohydrates
� Immediate energy source for cell metabolism(glucose) � Nutritional sources of energy (glucose, fructose, maltose, lactose) � Short term storage of energy (starch, glycogen) � Structural component in plant cell walls (cellulose) � Markers on cell walls to identify cell type (e.g. blood type)
Carbohydrates
� Carbohydrates are composed of C H and O.� The simple carbohydrates have the empirical formula CH2O � "hydrate" of carbon � All carbohydrates contain the "carbonyl group" ( C=O ) � either aldehyde or ketone � All carbohydrates contain several �OH groups (hydroxy groups).
General Types of Carbohydrates
� Monosaccharides � the simple sugars � examples: glucose, fructose � Disaccharides � two monosaccharides bonded together � examples: sucrose, lactose � Polysaccharides- many glucose units linked together � examples: starch, cellulose
aldoses
�Aldoses are monosacchrides with an aldehyde group and many hydroxyl (-OH) groups.
ketose
Ketoses are monosacchrides with a ketone group and many hydroxyl (-OH) groupsc=o
D and L Notation
�D,L tells which of the two chiral isomers we are referring to.�If the �OH group on the next to the bottom carbon atom points to the right , the isomer is a D-isomer; if it points left, the isomer is L.The D form is usually the isomer found in nature.
Monosaccharides
� Monosaccharides are the simplest carbohydrates� cannot be broken down into simpler carbohydrates � They all contain several OH groups (hydroxy) and 1carbonyl group (C=O) � They are chiral molecules (they are not identical to their mirror images) � They differ in the arrangement of the groups around the chiral carbons.
Fischer Projections
� A method is needed to unambiguously designate the spatial arrangement of atoms when drawing a structure. � A convention was developed by Emil Fischer (1852-1919) to show the exact arrangement of the atoms around a chiral carbon.
�Monosaccharides are classified:
�According to # of carbons, �Glucose is a hexose �(a five carbon sugar is called a pentose)�According to the nature of the carbonyl �Glucose is an aldose �(sugars that have a ketone are called ketoses) �The complete classification of glucose is aldohexose
Glucose
�Glucose is a monosaccharide (can't be broken into simpler sugars) �Glucose is an aldose (contains an aldehyde group) �Glucose is a aldohexose (an aldehyde group with a total of 6 carbon atoms) �Glucose = "blood sugar
Galactose
�Galactose is a monosaccharide (can't be broken into simpler sugars) �Galactose is a aldose (contains an aldehyde group) �Galactose is a aldohexose (contains an aldehyde and a total of 6 carbon atoms) �Galactose is a component of milk sugar ( lactose, a disaccharide)
RIBOSE
�Ribose is a monosaccharide (can't be broken down into simple sugars) �Ribose is an aldose (contains an aldehyde group) �Ribose is a aldopentose (contains an aldehyde and a total of 5 carbon atoms)
FRUCTOSE
�Fructose is a monosaccharide (can't be broken into simpler sugars) �Fructose is a ketose (contains a ketone group) �Fructose is a ketohexose (contains a ketone and a total of 6 carbon atoms) �Fructose is the sweetest of sugars
Reactions of Monosaccharides (Reducing Sugars)
Certain sugars have the ability to convert Cu+2 solutions (Benedict�s solution) to Cu2O, which is a red solid. Since the Cu+2 is reduced to Cu+1, these sugars are called reducing sugars
Cyclic Structures of Monosaccharides
�Monosaccharides with 5-6 carbon atoms form cyclic structures �The hydroxyl group on C-5 reacts with the aldehyde group or ketone group
Haworth Structure for D-Isomers
The cyclic structure of a D-isomer has the final CH2OH group located above the ring.
Disaccharides Disaccharides can be broken down by acidic water (hydrolyzed) to give monosaccharides
Maltose (malt sugar) glucose + glucose Lactose (milk sugar) glucose + galactose Sucrose (table sugar) glucose + fructose
Carbohydrates as Cell Markers
� Modified carbohydrates are attached to cell membranes (cell walls) � They serve as �markers� to identify the cell type � In this way, they tell the immune system that the cell belongs to the organism and is not a foreign organism (bacteria or parasite) � A common example of this is in the determination of blood types
Polysaccharides
� Starch-storage form of glucose in plants � Amylose (20%): 200-4000 a glucose monomers attached a-1,4 in a continuous chain (polymer) � chains tend to coil so as to pack more tightly � Amylopectin (80%): Similar to amylose, but contains occasional branches on the main chain. � chains tend to coil like amylose
Polysaccharides (cont)
� Glycogen("animal starch"- storage form of glucose in animals � mainly in liver and muscle � similar to amylopectin, but more highly branched� Cellulose: major structural material in plants � gives strength to cell walls � long chain of mainly unbranched glucose units � however, glucose units are linked via 1,4 b linkages. � chains tend to be aligned and held together by H bonds.
Summary-Functions of Carbohydrates
� Carbohydrates are a used to provide energy for cellular functions (ex-glucose) � Carbohydrates are used to provide (relatively short term) storage of energy (starch) � Carbohydrates are an important component in cell walls of plants (cellulose) � Carbohydrate derivatives are used as cell markers (antigens for blood type)
Key Features of Organic Chemistry
�Carbon forms 4 bonds when forming molecules (exception: carbon monoxide) �Compounds containing only carbon and hydrogen are called hydrocarbons. �Atoms bonded together by single bonds are can rotate about the bond. �Atoms bonded together by double bonds cannot rotate about the bond. �Compounds having the same molecular formula but different arrangement of atoms are called isomers
enantiomers
two mirror images