Chapter 5 Carbohydrates How is Energy Stored in Carbohydrates Key Concepts Sugars and other carbohydrates are highly variable in structure are monomers that polymerize to form polymers called polysaccharides and are joined by different types of Carbohydrates perform a wide variety of functions in cells serving as raw material for synthesizing other molecules providing structural support indicating cell identity and storing chemical energy Glycosidic Linkages The glycosidic linkages can form between any two hydroxyl groups thus the location and geometry of these bonds vary widely Biologically Relevant Polysaccharides 1 Plants store sugar as Mixture of branched amylopectin and unbranched amylose glucose polymer 2 Animals store sugar as Highly branched glucose polymer 3 is a structural polymer found in plant cell walls Polymer of glucose monomers 4 is a structural polymer found in fungi cell walls some algae and many animal exoskeletons Comprised of N acetylglucosamine NAc monomers 5 Bacterial cell walls get structural support from Backbones of alternating monosaccharides Carbohydrate Function Carbohydrates as Structural Molecules Cellulose Chitin Peptidoglycan Form Tough Fibers Cellulose in plant cell wall Chitin in insect exoskeleton Peptidoglycan in bacterial cell wall Glycoproteins Cell Identity Although polysaccharides are unable to information they do information on the outer surface of cells in the form of glycoproteins proteins joined to carbohydrates by covalent bonds Glycoproteins are key molecules in cell cell recognition and cell cell signaling Each cell in your body has glycoproteins on its surface that identify it as part of your body Cell Identity don t store information but display it Glycoproteins Determine Blood Type Carbohydrates and Energy Storage Carbohydrates store and provide in cells Today most sugars are produced via a key process that transforms the energy of sunlight into the chemical energy of C H bonds in carbohydrates Carbohydrates have more than CO2 because the electrons in C H bonds and C C bonds are shared more equally and held less tightly than they are in C O bonds Energy Stored in Glucose Is Transferred to ATP When a cell needs energy carbohydrates participate in exergonic reactions that synthesize CH2O O2 ADP Pi CO2 H2O ATP The free energy in ATP is used to drive endergonic reactions and Carbohydrates contain a large number of which have high free energy Fatty acids have even more C H bonds and consequently more free energy than carbohydrates Get in your groups Molecule Proteins DNA RNA Carbohydrates Monomeric Unit Composition of Type of monomeric bonding unit Function
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