Review Question 1

• How many molecules of water are needed to completely hydrolyze a polymer that is 10 monomers long?

9

Review Question 2

• After you eat a slice of apple, which reactions must occur for the amino acid monomers in the protein of the apple to be converted into proteins in your body?

Amino acids are incorporated into proteins in your body by dehydration reactions

CARBOHYDRATES

3

4

Carbohydrates

• Serve as fuel and building material

• Include both sugars and their polymers (starch, cellulose, etc.)

5

Sugars

• Monosaccharides– Are the simplest sugars– Contain a single chain of carbon atoms

with hydroxyl groups– They also contain carbonyl (aldehyde

or keytone) groups– Can be combined into polymers

6

• Examples of monosaccharidesTriose sugars

(C3H6O3)Pentose sugars

(C5H10O5)Hexose sugars

(C6H12O6)

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

HO C H

H C OH

H C OH

H C OH

H C OH

HO C H

HO C H

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

C OC O

H C OH

H C OH

H C OH

HO C H

H C OH

C O

H

H

H

H H H

H

H H H H

H

H H

C C C COOOO

Aldo

ses

Glyceraldehyde

RiboseGlucose Galactose

Dihydroxyacetone

Ribulose

Keto

ses

FructoseFigure 5.3

7

• Monosaccharides– May be linear– Can form rings

H

H C OH

HO C H

H C OH

H C OH

H C

O

C

H

1

2

3

4

5

6

H

OH

4C

6CH2OH 6CH2OH

5C

HOH

C

H OH

H

2 C

1C

H

O

H

OH

4C

5C

3 C

H

HOH

OH

H

2C

1 C

OH

H

CH2OH

H

H

OHHO

H

OH

OH

H5

3 2

4

(a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5.

OH3

O H OO

6

1

Figure 5.4

α glucose vs. β glucose

8

9

• Oligosaccharides – contain two or three monosaccarides attached by covalent bonds called glycosidic linkages

– Disaccharides• Consist of two monosaccharides• Are joined by a single glycosidic linkage

10

Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide.

Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose.Notice that fructose,though a hexose like glucose, forms a five-sided ring.

(a)

(b)

H

HO

H

HOH H

OH

O H

OH

CH2OH

H

HO

H

HOH H

OH

O H

OH

CH2OH

H

O

H

HOH H

OH

O H

OH

CH2OH

H

H2O

H2O

H

H

O

H

HOH

OH

OH

CH2OH

CH2OH HO

OHH

CH2OH

HOH H

H

HO

OHH

CH2OH

HOH H

O

O H

OHH

CH2OH

HOH H

O

HOH

CH2OH

H HO

O

CH2OH

H

H

OH

O

O

1 2

1 41– 4

glycosidiclinkage

1–2glycosidic

linkage

Glucose

Glucose Glucose

Fructose

Maltose

Sucrose

OH

H

H

Figure 5.5

11

Polysaccharides

• Polysaccharides– Are polymers of sugars with several hundred to

several thousand monosaccharide subunits held together by glycosidic linkages

– Serve many roles in organisms

12

Storage Polysaccharides

• Starch– Is a polymer

consisting entirely of glucose monomers

– Is the major storage form of glucose in plants

Chloroplast Starch

Amylose Amylopectin

1 m

(a) Starch: a plant polysaccharideFigure 5.6

Two types of Starch

• Amylose– Straight chain polymer of α (alpha) glucose– Has 1-4 glycosidic linkages

• Amylopectin– Branched chains of α glucose and β glucose– Has 1-4 glycosidic linkages in the main chains and

1-6 glycosidic linkages at the branch points

13

14

Glucose Storage in Animals

• Glycogen– Consists of glucose monomers– Similar to Amylopectin (has 1-4 and 1-6

glycosidic linkages), but there are more branches in glycogen

– Stored in muscle and liver

15

16

MitochondriaGiycogen granules

0.5 m

(b) Glycogen: an animal polysaccharide

Glycogen

Figure 5.6

17

Structural Polysaccharides• Cellulose– Is a polymer of glucose– Has different glycosidic linkages than starch– The main structural polysaccharide in plants and plant cell

walls

18

– Cellulose is a straight chain polymer of β glucose with 1-4 glycosidic linkages

(c) Cellulose: 1– 4 linkage of glucose monomers

H O

O

CH2OH

HOH H

H

OH

OHH

H

HO

4

C

C

C

C

C

C

H

H

H

HO

OH

H

OH

OH

OH

H

O

CH2OH

HH

H

OH

OHH

H

HO4 OH

CH2OHO

OH

OH

HO41

O

CH2OH

O

OH

OH

O

CH2OH

O

OH

OH

CH2OH

O

OH

OH

O O

CH2OHO

OH

OH

HO 4O

1

OH

O

OH OHO

CH2OHO

OH

O OH

O

OH

OH

(a) and glucose ring structures

(b) Starch: 1– 4 linkage of glucose monomers

1

glucose glucose

CH2OH CH2OH

1 4 41 1

Figure 5.7 A–C

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Plant cells

0.5 m

Cell walls

Cellulose microfibrils in a plant cell wall

Microfibril

CH2OH

CH2OH

OH

OHO

OOHO

CH2OHO

OOH

OCH2OH OH

OH OHO

O

CH2OH

OO

OH

CH2OH

OO

OHO

O

CH2OHOH

CH2OHOHOOH OH OH OH

O

OH OH

CH2OH

CH2OH

OHO

OH CH2OH

OO

OH CH2OH

OH

Glucose monomer

O

O

O

O

O

O

Parallel cellulose molecules areheld together by hydrogenbonds between hydroxyl

groups attached to carbonatoms 3 and 6.

About 80 cellulosemolecules associate

to form a microfibril, themain architectural unitof the plant cell wall.

A cellulose moleculeis an unbranched glucose polymer.

OH

OH

O

OOH

Cellulosemolecules

Figure 5.8

– Unlike amylose and amylopectin (starches), cellulose molecules are neither coiled nor branched

20

• Cellulose is difficult to digest– However, it does contribute to “roughage” in the

diet fibre– Cows have microbes in their stomachs to facilitate

this process

Figure 5.9

21

• Chitin, another important structural polysaccharide– Is found in the exoskeleton of arthropods– Can be used as surgical thread

(a) The structure of the chitin monomer.

OCH2OH

OHHH OH

H

NH

CCH3

O

H

H

(b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emergingin adult form.

(c) Chitin is used to make a strong and flexible surgical

thread that decomposes after the wound or incision heals.

OH

Figure 5.10 A–C