AP Biology

The Chemical Building Blocks 3.2 Carbohydrates

AP Biology

Carbohydrates

AP Biology 2006-2007

OH

OH

H

H

HO

CH2OH

HH

H

OH

O

Carbohydratesenergy

molecules

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Carbohydrates Carbohydrates are composed of C, H, O

carbo - hydr - ate

CH2O

(CH2O)x C6H12O6

Function: energy energy storage raw materials structural materials

Monomer: sugars

ex: sugars, starches, cellulose

sugar sugar sugar sugar sugar sugar sugarsgar

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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

HH

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

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Functional groups determine function

carbonyl

ketone

aldehyde

carbonyl

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Sugar structure5C & 6C sugars form rings in solution

Carbons are numberedCarbons are numbered

Where do you find solutions?

In cells!

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Numbered carbons

C

CC

C

CC

1'

2'3'

4'

5'

6'

O

energy stored in C-C bondsenergy stored in C-C bonds

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Simple & complex sugars Monosaccharides

simple 1 monomer sugars glucose

Disaccharides 2 monomers sucrose

Polysaccharides large polymers starch

OH

OH

H

H

HO

CH2OH

H

H

H

OH

O

Glucose

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Building sugars Dehydration synthesis

glycosidic linkage

|glucose

|glucose

monosaccharides disaccharide

|maltose

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Building sugars Synthesis

|fructose

|glucose

monosaccharides

|sucrose

(table sugar)

disaccharide

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Polysaccharides Polymers of sugars

costs little energy to build easily reversible = release energy

Function: energy storage

starch (plants) glycogen (animals)

structure = building materials cellulose (plants) chitin (arthropods & fungi)

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Linear vs. branched polysaccharides

starch(plant)

glycogen(animal)

energystorage

What doesbranching do?

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Polysaccharide diversity Molecular structure determines function

isomers of glucose structure determines function…

in starch in cellulose

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Digesting starch vs. cellulose

starcheasy todigest

starcheasy todigest

enzyme

enzyme

cellulosehard todigest

cellulosehard todigest

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Cellulose Most abundant organic

compound on Earth herbivores can digest cellulose most carnivores cannot digest cellulose

that’s why they eat meat to get their energy & nutrients

cellulose = roughage

BIG DEAL!Who can live

on this stuff?!

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Cowcan digest cellulose well; no need to eat other sugars

Gorillacan’t digest cellulose well; must add another sugar source, like fruit to diet

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Helpful bacteria How can cows digest cellulose?

bacteria live in their gut & help digest cellulose-rich (grass) meals