Carbohydrates Carbohydrates are composed of C, H, O8/27/2014 4 Bond formation: Condensation Condensation: The name for the bonding process by which two monosaccharides form a disaccharide

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Carbohydrates

AICE BIOLOGY

JONES & FOSBERY CHAPTER 2

Carbohydrates

Carbohydrates are composed of C, H, O

carbo - hydr - ate

CH2O

(CH2O)x C6H12O6

Function:

fast energy u energy storage

raw materials u structural materials

Monomer: sugars

ex: sugars, starches, cellulose

sugar sugar sugar sugar sugar sugar sugarsugar

C6H12O6(CH2O)x

Sugars Most names for sugars end in -ose

Classified by number of carbons◦ 6C = hexose (glucose)

◦ 5C = pentose (ribose)

◦ 3C = triose (glyceraldehyde)

OH

OH

H

H

HO

CH2OH

H

H

H

OH

O

Glucose

H

OH

HO

O H

HHO

H

Ribose

CH2OH

Glyceraldehyde

H

H

H

H

OH

OH

O

C

C

C6 5 3

Monosaccharides Single Sugars

Dissolve easily in water

Sweet taste

3 forms: Sugars all end in “ose” Triose (3C) C3H6O3

(Gylceraldehyde) Pentose (5 C) C5H10O5

(Ribose, Deoxyribose = components of nucleic acids) Hexose (6 C) C6H12O6

(Glucose, Fructose, Galactose)

H H HHH

H

OH OH

OHO

OH H

OHO

CH2OH

RiboseGlyceraldehyde

3-carbonsugar

5-carbon sugars

Deoxyribose

HH

H

H

H

H

OH

OH

O

C

C

C4

5

1

3 2

4

5

1

3 2

1

3

2

CH2OH

Fig. 3.23b(TE Art)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

CH2 OH

OH

HO

O

OH

OH H

H

HHO

H H

HH

OH

H

OH

OH

OH

O

H

H

HO

CH2OH

HH

H

OH

O

GalactoseFructoseGlucose

6-carbon sugars

4

4

4

5

5

5

666

1

1

1

3 233

2

2

CH2OH CH2OH

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A. Molecular Formula (empirical formula) ie. C6H12O6

B. Structural FormulaDiagram showing the arrangement of atoms. Glucose, fructose & galactose all have the same empirical

formula, but have different structural formulae.

Structural FormsChain Form: Carbon backbone with oxygen & hydrogen forming side bonds.

Ring Form: In aqueous solution, the molecule closes upon itself to form a more stable ring form.

Fig. 3.24(TE Art)


H

H

HH

H

C H

C OHH

C HHO

C OHH

C OHH

C

H

OHH HO

OH

HO

O

CH2OH

OH

H

OH

H

C

CH

H C

C

H

OH

C

O

C

C

HOH

H

C C

C

H

HH

OH

H

OH

C

OH

H

OH

CH2OH

1

2

3

4

5

6 4

6

5

32 1

6 5

41

2

3

23

4

56

1

23

4

56

1

OH

OH

O

O

Numbered carbons

C

CC

C

C

C

1'

2'3'

4'

5'

6'

O

energy stored in C-C bonds

harvested in cellular respiration

These will become

important!

Isomers

Molecules with the same empirical formula but different structural formulae (arrangement of atoms determines functional differences)

Fig. 3.25(TE Art)


Sucrose

OH

HO

O

HO

OH

OH

O

O

Lactose

OH

OHHO

H

H H

HH

H

H

H

H

H

HH

H

OH

OH

OH

O

H

H

OH HOH

O

GalactoseGlucose

Glucose

Glucose

Glucose

Fructose

Maltose

CH2OH

HO

OHH

H H H HH HH H

H

OH

O

O

OH

OHOH

OCH2OH

CH2OH CH2OH

CH2OH

CH2OHCH2OH

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There are 2 types of isomersStructural Isomers: different arrangement of bonds. eg glucose & fructose (See O=C Bonds)

Your taste buds can tell the difference fructose much sweeter

Form different polymers (repeating subunits)

Stereoisomers: Same bond structure but different orientations of molecule groups.eg. Glucose & galactose: Hydroxyl groups are mirror images of

one another

∂ glucose (OH above the plane)

ß glucose (OH below the plane)

Fig. 3.26(TE Art)


C O

H C OH

OH

H C OH

H

HO C H

C O

H C OH

H

Fructose

H C OH

H C OH

H C OH

H

HO C H

H C OH

H

Glucose Galactose

Structuralisomer

Stereo-isomer

H C

C O

HO C H

H C OH

H C OH

H

HO C H

H C OH

H

Roles of MonosaccharidesSource of energy in respiration.C-H bonds release lots of energy when broken used to convert ADP to

ATP.

Glucose is the most important, metabolically.

Building blocks of larger molecules. glucose starch, glycogen, cellulose

ribose RNA (ribonucleic acid) & ATP

deoxyribose DNA (deoxyribonucleic acid)

Disaccharides•Two monosaccharides joined by a covalent bond

Fig. 3.27(TE Art)


Glucose

HO

OH

OH

O

MaltoseGlucose

OHH

HHHHH

H

H

HHOH

OH

O

HO

OH

OH

O

O

OHH

H

HH HHH HH

H

OHOH

O

Glucose

HO

OHH

HH HH

OH

OH

OH

O

SucroseFructoseOH

HOH

H

HO

CH2OH

CH2OH

OH

HO

O

HO

OHH

HH

H H

H

HH

OH

O

O

H2O

HO

HO

CH2OH CH2OH CH2OH

CH2OH

CH2OH CH2OH CH2OH CH2OH

H2O

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Bond formation: CondensationCondensation: The name for the bonding process by which two monosaccharides form a disaccharide. AKA dehydration synthesis.

2 hydroxyl (-OH) groups line up with one anotherOne combines with a hydrogen from the other to form a

water molecule: HENCE, CONDENSATIONForms an oxygen bridge “glycosidic bond”Any two hydroxyl groups can line up & bondLarge variety of possible disaccharides

Breaking Bonds: HydrolysisHydrolysis: When polysaccharides break apart to form smaller molecules.

Hydro = water

Lysis = breaking apart

Breaking a molecule apart by adding water

Both Condensation & hydrolysis are controlled by enzymes.

Fig. 3.27a(TE Art)


Glucose

HO

OHH

HH H

H

OHOH

O

SucroseFructoseOH

HOH

H

HO

CH2OH

OH

HO

O

HO

OHH

H HH H

H

HH

OH

O

O

H2OHO

CH2OH CH2OHCH2OH

CH2OHCH2OH

Transport DisaccharidesoIn humans, glucose can circulate in the blood

oIn plants & many other organisms, glucose must be converted for transport to keep glucose from being “used up” while in transport

oThe bond breaking enzymes are only located in tissue where glucose is meant to be used.

oGlucose + fructose = sucrose

oGlucose + galactose = lactose

oGlucose + glucose = maltose

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Fig. 3.25a(TE Art)


GlucoseGlucose

Maltose

CH2OH

HO

OHH

H H H HH H

H H

H

OH

O

O

OH

OHOH

O

CH2OH Fig. 3.25b(TE Art)


Sucrose

OH

HO

O

CH2OH

HO

OH

OH

O

O

H H

H

H

H

H

H

H

Glucose Fructose

CH2OH

CH2OH

Fig. 3.25c(TE Art)


Lactose

OH

OH

H

H

H

HH

OH

OH

OH

O

H

H

O

H

H

H

OH

O

Galactose

Glucose

CH2OH

CH2OH PolysaccharidesFormed by joining long chains of monosaccharides through condensation.

Each successive monosaccharide is joined by a glycosidic bond.

Polysaccharides are not sugars.

Most important: Starch, cellulose & glycogen

Storage PolysaccharidesTransport disaccharides may be linked together as polysaccharides for storage within cells.

Plant polysaccharides = starches.

Animal polysaccharides = glycogen

Starches: AmyloseAmylose = simplest starch, hundreds / thousands of linked, unbranched alpha glucose molecules.

#1 carbon links to #4 of next molecule = long chains of maltose.

Long chains coil up in water making it insoluable in water

Potato starch ~ 20% amylose

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Fig. 3.28a(TE Art)


CH2OH

Starch: chain of a-glucose subunits

HO

OH

OH HHH

H

H

O O O O O

OH

OH HH

H H

H OH

OH HH

H H

H OH

OH HH

H H

H OH

OH HH

H H

H

OHO O O

1 4

a form of glucose

4 1

CH2OHCH2OHCH2OHCH2OH

Starch: AmylopectinoMost plant starch is amylopectin.

oAlso made of many 1,4 linked glucose, but also have 1,6 branching linkages (2.6 JF)

oOnly 20-30 glucose subunits.

oMixtures of amylose & amylopectin build up as starch grains in chloroplasts & stroage vaculoes.

Glycogeno“Animal version of starch.”

oInsoluable polysaccharide of branched amylose chains

oAverage chain much longer and greater # of branches than plant starch.

oAnimal form of energy storage.

Structural Carbohydrates: CelluloseoUnbranched chains of beta glucose

oSeveral chains are crosslinked by H-bonding to form fibrils

oSeveral fibrils crosslink to form fibres

oForms cell walls of plants

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Fig. 3.28b(TE Art)


Cellulose: chain of b-glucose subunits

Plantcell wall

b form of glucose

HO

OH

OH HH

H

H

H

H

OO

HH

H

OH

OH

H

OH

OO4 1

41

H OH

H

O HOH

H H

O

O

OH

H

OH

HOHH

HO

CH2OHCH2OH

CH2OH

CH2OH

CH2OHH

OHH

H HH

OH

O

Fig. 3.29

Documents

Carbohydrates Carbohydrates are composed of C, H, O8/27/2014 4 Bond formation: Condensation Condensation: The name for the bonding process by which two monosaccharides form a disaccharide