CARBOHYDRATES

Properties CCarbohydrates – Carbon/Hydrogen/Oxygen FFormula – (CH 2 O) n RRatio: Carbon 1: Hydrogen 2: Oxygen 1 UUSES: energy source, structural components, combination with other compounds such as GLYCOPROTEINS IISOMERS are different structural arrangements of the same number and types of atoms Eg. C 6 H 12 O 6 – glucose, fructose and galactose OOPTICAL ISOMERS are identical in every way but are mirror images of each other Eg. α Glucose and β Glucose rings

Monosaccharides Simple sugars containing 3 to 7 carbon atoms Primary energy source for fuelling cell metabolism Reducing sugars and soluble in water Can bond together to form disaccharides and polysaccharides Egs. TRIOSE (3 carbon) glyceraldehyde *intermediate in carbohydrate metabolism PENTOSE (5 carbon) ribose *sugar unit of RNA HEXOSE (6 carbon) glucose fructose galactose *energy Most pentose & hexose sugars can exist in the form of rings and straight lines - rings provide the sub-units needed for building complex carbohydrates α- glucose & β- glucose differ in the position of the –OH and –H attached to the 1 st carbon atom (see above). This is an example of an OPTICAL ISOMER

Condensation of Glucose/Fructose  When simple carbohydrates are joined to make complex carbohydrates the process is called CONDENSATION  Macromolecules (such as sucrose) are often formed by removing ‘H’ from one atom and ‘OH’ from the other  The ‘H’ and ‘OH’ combine to form water  Monomers are joined to build macromolecules by the removal of water  The reverse reaction when a polysaccharide has water added and is broken down into mono and disaccharides is known as HYDROLYSIS Eg. Sucrose (carbohydrate) is formed when glucose and fructose are joined via a condensation reaction  Energy is required to form the bond (anabolic)  The bond is known as an a alpha (1-2) glycosidic bond

Disaccharides  C omposed of 2 monosaccharides joined together by a condensation reaction  Joined by a GLYCOSIDIC BOND  Soluble in water Eg. SUCROSE (glucose + fructose)  table sugar LACTOSE (glucose + galactose)  milk MALTOSE (glucose + glucose)  grains

Polysaccharides  Polymers with monosaccharide sub-units, joined via condensation reactions and glycosidic bonds  The polysaccharide can be made of several thousand monosaccharides (forming a macromoleclule)  Poly saccharides are not sugars and are generally insoluble  Glucose accumulation will affect cell osmotic properties as well as reacting with various chemicals - therefore stored as a polysaccharide  Glucose can be made available again quickly by an enzyme controlled reaction

Examples of Polysaccharides STARCH (PLANT CARBOHYDRATE) EEnergy storage molecule in plants LLong chains of α- glucose molecules CContains 25 – 30% AMYLOSE & 70 – 75% AMYLOPECTIN EEasily hydrolysed into soluble sugars when required CChains can be branched or helixed (amylopectin) or straight (amylose) GLYCOGEN (ANIMAL CARBOHYDRATE) EEnergy storage in liver and muscles of animals BBranched polysaccharide composed of α- glucose molecules with different links to starch MMore water soluble than starch EEasily hydrolysed by enzymes into glucose

CHITIN (ARTHROPOD EXOSKELETONS/FUNGI CELL WALLS) TTough modified polysaccharide made up of β-glucose molecules SSimilar to cellulose but each glucose has an amine (NH 2 ) group attached 22 nd most abundant carbohydrate CELLULOSE (STRUCTURAL MATERIAL IN PLANT CELL WALLS) LLinear polysaccharide made of β- Glucose joined by glycosidic links MMost abundant organic material PParallel chains become cross-linked with hydrogen bonds and form microfibrils MMicrofibrils are very strong (major structural component of plants) DDifficult to digest, humans cannot as they lack relevant enzymes AAnimals such as herbivores have modified digestive systems that harbour bacteria that can breakdown cellulose

Cellulose cont The nature of the glycosidic bond means that each glucose molecule is 180° rotated compared to those next to it (SEE ABOVE) This gives cellulose its linear shape and strength Allows many hydrogen bonds between parrallel cellulose chains

Hydrogen bonds between cellulose chains

Free to share, print, make copies and changes. Get yours at Biological Macromolecules Which of the following describe disaccharides? A) Glucose, galactose, and fructose are isomers with more than one asymmetric carbon. B) They are a long chain of monosaccharides linked by glycosidic bonds. C) Cellulose is the result of two monosaccharides that have undergone a condensation reaction. D) Lactose, maltose, and sucrose are the result of bonded monosaccharides after a dehydration reaction.

Free to share, print, make copies and changes. Get yours at Boundless - LO. "Boundless." CC BY-SA BY-SA 3.0http:// Biological Macromolecules Which of the following describe disaccharides? A) Glucose, galactose, and fructose are isomers with more than one asymmetric carbon. B) They are a long chain of monosaccharides linked by glycosidic bonds. C) Cellulose is the result of two monosaccharides that have undergone a condensation reaction. D) Lactose, maltose, and sucrose are the result of bonded monosaccharides after a dehydration reaction.

Free to share, print, make copies and changes. Get yours at Biological Macromolecules Why are carbohydrates an essential part of our diets? A) All of these answers. B) Carbohydrates provide more energy than lipids. C) Carbohydrates contain only soluble elements that are vital to the health of our bodies. D) Carbohydrates provide energy from our diets.

Free to share, print, make copies and changes. Get yours at Boundless - LO. "Boundless." CC BY-SA BY-SA 3.0http:// Biological Macromolecules Why are carbohydrates an essential part of our diets? A) All of these answers. B) Carbohydrates provide more energy than lipids. C) Carbohydrates contain only soluble elements that are vital to the health of our bodies. D) Carbohydrates provide energy from our diets.