1 macromolecules – are large molecules composed of a large number of repeated subunits – are...

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Macromolecules

– Are large molecules composed of a large number of repeated subunits

– Are complex in their structures

Figure 5.1

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MacromoleculesMacromolecule Subunit

Complex Carbohydrates(e.g. starch)

Simple sugar (e.g. glucose)

Lipid (triglycerides) Glycerol and fatty acids

Protein Amino Acids

Nucleic Acids (DNA or RNA) Nucleotides

3

• A polymer– Is a long molecule consisting of many similar

smaller building blocks called monomers– Specific monomers make up each

macromolecule– E.g. amino acids are the monomers for proteins

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The Synthesis and Breakdown of Macromolecules

• Monomers form larger molecules by condensation reactions called dehydration synthesis

(a) Dehydration reaction in the synthesis of a polymer

HO H1 2 3 HO

HO H1 2 3 4

H

H2O

Short polymer Unlinked monomer

Longer polymer

Dehydration removes a watermolecule, forming a new bond

Figure 5.2A

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Condensation Reactions

• Requires energy because new bonds are being formed

• Are also called a anabolic reactions because smaller molecules join together to form larger molecules

small LARGE

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The Synthesis and Breakdown of Macromolecules

• Polymers can disassemble by– Hydrolysis (addition of water molecules to lyse or

“break apart” the macromolecule)

(b) Hydrolysis of a polymer

HO 1 2 3 H

HO H1 2 3 4

H2O

HHO

Hydrolysis adds a watermolecule, breaking a bond

Figure 5.2B

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Hydrolysis

• Releases energy because bonds are being broken

• Are also called a Catabolic reactions because larger molecules are being broken down into smaller subunits

LARGE small

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• An immense variety of polymers can be built from a small set of monomers

Question 1

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

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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

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Carbohydrates

• Serve as fuel and building material

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

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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

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• 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

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• 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

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• 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

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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

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Polysaccharides

• Polysaccharides– Are polymers of sugars with several hundred to

several thousand monosaccharide subunits held together by glycosidic linkages

– Serve many roles in organisms

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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

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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

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MitochondriaGiycogen granules

0.5 m

(b) Glycogen: an animal polysaccharide

Glycogen

Figure 5.6

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

walls

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– 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

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• 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

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• 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

LIPIDS

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Lipids

• Lipids are hydrophobic molecules• Mostly C-H (non-polar)• are the one class of large biological molecules

that do not consist of polymers• Uses: structure of cell membranes, energy

source

Lipids

• Fats• Phospholipids• Steroids

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Fats– Are constructed from two types of smaller

molecules:• single glycerol and • three fatty acids

Fatty Acid

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Glycerol

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ESTER LINKAGE

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• Saturated fatty acids– Have the maximum number of hydrogen

atoms possible– Have no double bonds– Are solid at room temperature (e.g. animal

fats)

(a) Saturated fat and fatty acid

Stearic acid

Figure 5.12

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• Unsaturated fatty acids– Have one or more double bonds, causing a bend in its

structure– Are liquids at room temperature (e.g. vegetable fats)

(b) Unsaturated fat and fatty acidcis double bondcauses bending

Oleic acid

Figure 5.12

Unsaturated Fats• Monounsaturated fats (MUFA)– Have one double bond in their fatty acids

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•Polyunsaturated fats (PUFA)

Have more than one double bond in their fatty acid chains

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Phospholipids– Have only two fatty acids– Have a phosphate group instead of a third

fatty acid

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• Phospholipid structure–Consists of a hydrophilic “head” and

hydrophobic “tails”CH2

O

PO O

O

CH2CHCH2

OO

C O C O

Phosphate

Glycerol

(a) Structural formula (b) Space-filling model

Fatty acids

(c) Phospholipid symbol

Hyd

rop

hob

i c t

ails

Hydrophilichead

Hydrophobictails

–

Hyd

rop

hi li c

head

CH2 Choline+

Figure 5.13

N(CH3)3

Micelles

• When phospholipids are added to water, they form micelles

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Phospholipid Bilayer

– Results in a phospholipid bilayer arrangement found in cell membranes

Hydrophilichead

WATER

WATER

Hydrophobictail

Figure 5.14

Water and other polar and ionic materials cannot pass through the membrane except by the help of proteins in the membrane

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Steroids

• Steroids– Are lipids that have a carbon skeleton consisting

of four fused rings– Contain many different functional groups

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• One steroid, cholesterol– Is found in cell membranes– Is a precursor for some hormones

HO

CH3

CH3

H3C CH3

CH3

Figure 5.15

NUCLEIC ACIDS

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Nucleic Acids

• Nucleic acids store and transmit hereditary information

• There are two types of nucleic acids– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)

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• DNA– Stores information for the synthesis of specific proteins– Found in the nucleus of cells

• RNA– Reads information in DNA– Transports information to protein building structures within cell

Function of DNA and RNA

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The Structure of Nucleic Acids

• Nucleic acids (also called Polynucleotides)– Are polymers made up of

individual nucleotide monomers

(a) Polynucleotide, or nucleic acid

3’C

5’ end

5’C

3’C

5’C

3’ endOH

Figure 5.26

O

O

O

O

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• Each Nucleotide contains– Sugar + phosphate + nitrogen base

Nitrogenousbase

Nucleoside

O

O

O

O P CH2

5’C

3’CPhosphate

group Pentosesugar

(b) NucleotideFigure 5.26

O

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Nucleotide Monomers(c) Nucleoside components

Figure 5.26

CH

CH

Uracil (in RNA)U

Ribose (in RNA)

Nitrogenous bases Pyrimidines

CN

NC

OH

NH2

CH

CHO

CN

H

CH

HNC

O

CCH3

N

HNC

C

HO

O

CytosineC

Thymine (in DNA)T

NHC

N C

CN

C

CH

N

NH2 O

N

HC

NHH

CC

N

NH

CNH2

AdenineA

GuanineG

OHOCH2

H

H H

OH

H

OHOCH2

H

H H

OH

H

Pentose sugars

Deoxyribose (in DNA) Ribose (in RNA)

OHOH

CH

CH

Uracil (in RNA)U

4’

5”

3’

OH H2’

1’

5”

4’

3’ 2’

1’

Pyrimidines (single ring)

Purines (double ring)

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Nucleotide Polymers

• nucleotides linked by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next

• Phosphodiester bond

3’C

5’ end

5’C

3’C

5’C

3’ endOH

Figure 5.26

O

O

O

O

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Gene

• The sequence of bases along a nucleotide polymer– Is unique for each gene

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The DNA Double Helix• Have two polynucleotides that

spiral around each other• held together by hydrogen

bonds between nitrogenous bases– A (adenine) will always bond with

T (thymine – DNA only), or U (uracil – RNA only) 2 hydrogen bonds

– C (cytosine) will always bond with G (guanine) 3 hydrogen bonds

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• The DNA double helix– Consists of two antiparallel nucleotide strands

3’ end

Sugar-phosphatebackbone

Base pair (joined byhydrogen bonding)

Old strands

Nucleotideabout to be added to a new strand

A

3’ end

3’ end

5’ end

Newstrands

3’ end

5’ end

5’ end

Figure 5.27