CarbohydratesCarbohydrates

Aims:Aims:

Must be able to state the main forms of Must be able to state the main forms of Polysaccharides.Polysaccharides.

Should be able to describe the formation of Should be able to describe the formation of Polysaccharides.Polysaccharides.

Could be able to explain why starch and Could be able to explain why starch and cellulose are suited for their function.cellulose are suited for their function.

CarbohydratesCarbohydrates

60 – 90% of plant dry mass.60 – 90% of plant dry mass.

General formula CGeneral formula Cnn(H(H22O)O)mm

Main groups are SIMPLE SUGARS and Main groups are SIMPLE SUGARS and POLYSACCHARIDES.POLYSACCHARIDES.

Used as storage molecules, building blocks and for Used as storage molecules, building blocks and for energy.energy.

Sugars, Starch, Cellulose, Glycogen and Lignin are Sugars, Starch, Cellulose, Glycogen and Lignin are well known examples.well known examples.

MonosaccharidesMonosaccharides All contain Carbon, Hydrogen, and Oxygen in a ring structure.All contain Carbon, Hydrogen, and Oxygen in a ring structure.

Can have different numbers of carbon atoms and different arrangements.Can have different numbers of carbon atoms and different arrangements.

TRIOSE sugars have 3 CarbonsTRIOSE sugars have 3 Carbons

PENTOSE sugars have 5 CarbonsPENTOSE sugars have 5 Carbons

HEXOSE sugars, e.g. Glucose have 6 Carbons.HEXOSE sugars, e.g. Glucose have 6 Carbons.

Monosaccharides are sweet, soluble and have a low molecular mass.Monosaccharides are sweet, soluble and have a low molecular mass.

Best known hexose sugars are GLUCOSE and FRUCTOSE.Best known hexose sugars are GLUCOSE and FRUCTOSE.

All hexose sugars have chemical formula CAll hexose sugars have chemical formula C66HH1212OO6 6 but different structural formula – but different structural formula – They are isomers.They are isomers.

Triose SugarsTriose Sugars

Ketone – Ketone – Aldehyde – Aldehyde –

These can both donate electrons to other These can both donate electrons to other molecules = Reducing Agentsmolecules = Reducing Agents

Importance of Glyceraldehyde:Importance of Glyceraldehyde: Common intermediary compound in photosynthesis Common intermediary compound in photosynthesis

and respiration – provides a linkand respiration – provides a link Can be converted to glycerol for lipid synthesisCan be converted to glycerol for lipid synthesis Involved in intermediary metabolism – e.g. LiverInvolved in intermediary metabolism – e.g. Liver

Pentose SugarsPentose Sugars

E.g. Ribose – Formation of RNAE.g. Ribose – Formation of RNA

ATP energy carriersATP energy carriers

NAD – Electron carrierNAD – Electron carrier Deoxyribose – Formation of DNADeoxyribose – Formation of DNA

Ribulose – Involved in carbon dioxide Ribulose – Involved in carbon dioxide fixation – photosynthesisfixation – photosynthesis

Hexose SugarsHexose Sugars

Divided into;Divided into;

Aldoses – Aldehyde group present. Aldoses – Aldehyde group present. E.g. Glucose and GalactoseE.g. Glucose and Galactose

Ketones – Ketone group present.Ketones – Ketone group present. E.g. FructoseE.g. Fructose

All Hexoses are WHITE, CRYSTALLINE, All Hexoses are WHITE, CRYSTALLINE, SWEET compounds, REDUCING SUGARSSWEET compounds, REDUCING SUGARS

DisaccharidesDisaccharides

Monosaccharides can join together to Monosaccharides can join together to form DISACCHARIDES.form DISACCHARIDES.

These are all white, sweet and crystalline These are all white, sweet and crystalline sugars.sugars.

Diagram:Diagram:

DisaccharidesDisaccharides

Name Monosaccarides Present Bond Reducing Agent (Y/N)

Maltose α Glucose + α Glucose 1/4 Y

Lactose β Galactose + α Glucose 1/4 Y

Sucrose α Glucose + β Fructose 1/2 N

DisaccharidesDisaccharides

Functions:Functions:

MaltoseMaltose – First product of starch digestion by amylase – First product of starch digestion by amylase

LactoseLactose – Milk sugar – Primary source of energy in – Milk sugar – Primary source of energy in new born mammalsnew born mammals

SucroseSucrose – Found in vacuole – important in turgor – Found in vacuole – important in turgor maintenance.maintenance.Soluble so an ideal transport form. Soluble so an ideal transport form. Primary energy source in the developed world as a Primary energy source in the developed world as a sweetener.sweetener.

PolysaccharidesPolysaccharides

αα and and ββ glucose molecules produce different glucose molecules produce different polymers.polymers.

Starch and Glycogen (storage) are polymers of Starch and Glycogen (storage) are polymers of the the αα form. form.

Cellulose (structural) is a polymer of the Cellulose (structural) is a polymer of the ββ form.form.

Polysaccharides - StarchPolysaccharides - Starch

Starch – Mixture of ‘soluble’ starch or Amylose and Amylopectin.Starch – Mixture of ‘soluble’ starch or Amylose and Amylopectin.

Amylose – Amylose – αα helix helix soluble by forming a colloid by hydrogen bonding to soluble by forming a colloid by hydrogen bonding to

waterwater Traps iodine molecules in helixTraps iodine molecules in helix

Amylopectin – Chain molecule of glucose with branches (1-6 Amylopectin – Chain molecule of glucose with branches (1-6 bond) every 10bond) every 10thth glucose. glucose.

Amylose helix entangled with Amylopectin branches – Starch is Amylose helix entangled with Amylopectin branches – Starch is INSOLUBLEINSOLUBLE

Polysaccharides - StarchPolysaccharides - Starch

Role:Role:

Energy store in plants – All plant cells and Energy store in plants – All plant cells and specialised organs.specialised organs.

Starch is an ideal storage compound because Starch is an ideal storage compound because it is INSOLUBLE.it is INSOLUBLE.

Starch is the primary energy source in L.D.C.Starch is the primary energy source in L.D.C.

PolysaccharidesPolysaccharides GlycogenGlycogen:: Structure similar to Amylopectin but side branches occur MORE Structure similar to Amylopectin but side branches occur MORE

frequently.frequently.

INSOLUBLE – Energy source in Liver and Muscles.INSOLUBLE – Energy source in Liver and Muscles.

CelluloseCellulose:: 1-4 1-4 ββ glucose polymer glucose polymer Long straight fibrils (unbranched) Long straight fibrils (unbranched) Forms regular crystalline lattice due to H-bondsForms regular crystalline lattice due to H-bonds Function – formation of cell walls, support plantFunction – formation of cell walls, support plant

Important source of roughage due to resistance to Important source of roughage due to resistance to digestive enzymes.digestive enzymes.

Complex CarbohydratesComplex Carbohydrates

Monosaccharide molecules can be joined to proteins and Monosaccharide molecules can be joined to proteins and lipids to form glycolipids and glycoproteins.lipids to form glycolipids and glycoproteins.

Glycoproteins – Cell adhesionGlycoproteins – Cell adhesion Immunological markersImmunological markers

Glycolipids – part of Myelin sheathGlycolipids – part of Myelin sheath

Chitin – exoskeleton of insectsChitin – exoskeleton of insects

Hemicelluloses – Polymer of pentosesHemicelluloses – Polymer of pentoses Structure of plantsStructure of plants

ResearchResearch

Research one naturally occurring Research one naturally occurring Monosaccharide or Disaccharide:Monosaccharide or Disaccharide:

Chemical formulaChemical formula Structural formulaStructural formula Where it is foundWhere it is found Use(s)Use(s) synthesissynthesis