3.2 Carbohydrates

8/3/2019 3.2 Carbohydrates

1/70

IBDP 2011 Biology Core

Topic 3The Chemistry of Life

1

ACS(I) Menon 2011


2/70

2

Earths Crust % (by

mass)

Human Body % (by

mass)

Oxygen 47 Hydrogen 63

Silicon 28 Oxygen 25.5

Aluminium 7.9 Carbon 9.5

Iron 4.5 Nitrogen 1.4

Calcium 3.5 Calcium 0.31

Sodium 2.5 Phosphorus 0.22

Most Common Elements


3/70

Primordial Soup Theory


4/70

In 1920, chemist A.I. Oparin and geneticist J.B.S Haldane firstproposed that life began ~ 3.8 billion years ago in a warmpond/ocean.

In 1953, chemist Stanley Miller and physicist Harold Ureyconstructed an apparatus that supposedly re-created those earlyconditions.

They mixed gases thought to be present on primitive Earth:Methane, Ammonia, Water Vapour, Hydrogen

Electrically sparked the mixture to signify lightning.

Resulted in the production of amino acids, building blocks ofproteins.

4



5/70

5



6/70

Is it time to throw out the

Primordial Soup Theory?

Problems with the theory:

Early atmosphere contained gases different from those used by

Miller/Urey Amino acids have to become proteins. How?


7/70

New Research Rejects 80-Year Theory of 'Primordial Soup'

as the Origin of Life

ScienceDaily (Feb. 3, 2010) For 80 years it has been accepted that

early life began in a 'primordial soup' of organic molecules before evolving out

of the oceans millions of years later.

Today the 'soup' theory has been over turned in a pioneering paper in BioEssays

which claims it was the Earth's chemical energy, from hydrothermal vents

on the ocean floor, which kick-started early life.


8/708

Earths Crust % (by

mass)

Human Body % (by

mass)









9/70


Topic 3: The Chemistry Of Life

3.1 Chemical elements and water

3.2 Carbohydrates, lipids and proteins

3.3 DNA structure 3.4 DNA replication

3.5 Transcription and translation

3.6 Enzymes 3.7 Cell respiration

3.8 Photosynthesis

9


10/7010

Earths Crust % (by

mass)

Human Body % (by

mass)









11/70

3.2.1 Distinguish between

organic and inorganic compounds

11

Organic compounds

Compounds derived from living things

Carbon is uncommon in earths crust but most abundant elementby dry weight in living things

Compounds of carbon; often also contains hydrogen

Exceptions CO2, hydrogen carbonates (CO2 dissolved in water),mineral salts eg calcium carbonate are NOT organic


12/70

Carbon compounds

12

cysteine

Carbon forms 4 strong covalent bonds

Can bond with each other to form extended chains straight orbranched chains, or rings

Can bond with other atoms, such as O2, H2, N2 and S (sulphur)

Carbon compounds may be unsaturated ie. contain double or triplebonds


13/70

Monomer Polymer Supra Molecular

Structure

Carbon compounds: Macromolecules

Monosaccharides Polysaccharides Cellulose cell wall

Amino acids Polypeptides Protein ComplexNucleotides Nucleic acid Chromosome

Fatty acids Fats Cell membranes

Can form macromolecules (polymers) fromsmaller building blocks called monomers


14/70

Polysaccharides :polymers of monosaccharides

Polypeptides:polymers of amino acids



15/70


Nucleic acids :

polymers of nucleotides


16/70

Theory diversity of organic compounds madepossible the diversity of life

Carbon compounds


17/70


Topic 3: The Chemistry Of Life

3.1 Chemical elements and water

3.2 Carbohydrates, lipids and proteins

3.3 DNA structure 3.4 DNA replication

3.5 Transcription and translation

3.6 Enzymes 3.7 Cell respiration

3.8 Photosynthesis

17


18/70

1. Identify glucose and ribose from diagrams showingtheir structure.

2. List three examples each of monosaccharides,

disaccharides and polysaccharides.

3. State one function of glucose, lactose and glycogen inanimals, and of fructose, sucrose and cellulose inplants.

4. Outline the role of condensation and hydrolysis in therelationships between monosaccharides, disaccharidesand polysaccharides.

18

3.2 Carbohydrates: Learning Objectives


19/70

3.2.2. List three examples each ofmonosaccharides, disaccharides andpolysaccharides.


20/70

Carbohydrates

General formula: Cx(H2O)y

H:O generally 2:1

20

Monosaccharide (singe sugars)

(eg. glucose, galactose, fructose)

Disaccharide (double sugars)

(eg. maltose, lactose and sucrose)

Polysaccharide (Complex sugars)

(eg. starch, glycogen, cellulose)


21/70

Monosaccharides

Cannot be broken down into smaller units

General formula: Cx(H2O)y where x=y

Have a maximum of 6-carbon atoms, ie. x=y=6

eg. Glucose, fructose C6H1206 Sweet & water soluble molecules

21

3-carbon : triose sugar

4-carbon : tetrose sugar

5-carbon : pentose sugar

6-carbon : hexose sugar


22/70

Triose: eg. Glyceraldehyde Pentose: eg. Ribose Hexose: eg. Glucose

When C in carbonyl group (C=O) is at the very end of the chainit becomes an aldehyde group (H- C=O) and the monosaccharide is

called an aldose.eg. Aldotriose, aldopentose, aldohexose

I

C


23/70

Hexose: eg. Fructose (Ketohexose)

When C in carbonyl group (C=O) is at the second position of the

chain and it becomes a ketone group (C=O) and themonosaccharide is called a ketose. I

C

CI


24/70

In general, alcohols can attack the C=O group in

sugars to form hemiacetals

Since sugars have OH groups, they can formhemiacetals by an intramolecular reaction, formingclosed rings

Hexoses and pentoses are able to form closed rings

24

Cyclic Structures: Anomers


25/70

25

Under physiological conditions, glucose exists in a cyclic hemiacetal form where the C-5hydroxyl reacts with the C-1 aldehyde group

The 2 isomers that are formed are called anomers since they only differ in the location of theOH on the acetal carbon, C-1. ie. and forms of D-glucose are anomers of D-glucose


26/70

Animation: Cyclization of Glucose into Anomers


27/70

27

3.2.1 Identify glucose from diagramsshowing its structure


28/70

Note: Ring consists of 5 carbon atomsand an oxygen atom


29/70

29

Structure of Glucose Molecular formula: C6H12O6

An aldohexose

Common names: Dextrose, blood sugar

Structure of the molecule cannot be determined frommolecular formula (due to existence of isomers, anomers)

Each carbon arranges it four bonds into a tetrahedon, sothe molecule is not flat


30/70

3.2.3 State one function of glucose & lactose in animals,and of fructose & sucrose in plants.


31/70

31

Some Functions of Glucose

Especially important in energy production andformation of macromolecules in cells

During photosynthesis, light energy is trapped and

stored as chemical energy in the form of glucose

All cells use glucose as substrate in respiration,producing chemical energy ATP

Building block for many larger molecules eg.Monomer for glycogen, starch, cellulose


32/70

Glucose & Diabetes


33/70

Glucose & Diabetes

Video: Type 1 and Type 2 Diabetes


34/70

34

Reducing Sugars

+ Cu2O (red-orange)

The aldehyde groups of aldoses and ketone group of fructoseare oxidized by Benedicts reagent, an alkaline copper(II)

solution

The clear blue color of the reagent fades as it is replaced by ared-orange precipitate when Cu2+ is reduced to Cu+

Test can measure glucose in urine

All monosaccharides and disaccharides except sucrose arereducing sugars

C

C

O H

CH2OH

OHH

C

C

O O

CH2OH

OHH+2 Cu2+


35/70

35

Other Monosaccharides

Fructose (ketohexose)

Galactose (aldohexose)

Ribose and Deoxyribose (aldopentoses)

- components of nucleic acids RNA, DNA

respectively

Trioses (early products of photosynthesis)


36/70

36

Fructose

Fructose is also called Levulose

Fruit sugar

Found in large amounts in Honey

Corn syrup

Fruits

The sweetest of all sugars

Ketohexose

An intermediate of glucosemetabolism duringrespiration

D-fructose

CH2OH

C

C

O

OHC OHHC

H

OHCH

2OH

H

1

2

3

4

5

6

OCH

2OH

CH2OH

HOHH

OH

O

CH2OH

CH2OH

HOHH

OH


37/70

Relative sweetness of sugars and sweeteners


38/70

38

Galactose

Galactose is the principal sugar found inmammalian milk

Aldohexose

-D-galactosamine is a component of the blood

group antigens

-D-galactose

CHOC

C

OH

OHCOH HC

H

OH

CH2

OH

H

H

1

2

3

4

5

6

OCH

2OH

H

H

OH

H

OH

OH

HOH

HOH

H

NH2

NH2

-D-galactosamine


39/70

39

Aldopentose

Exists mainly in the cyclic form

Component of ribonucleic acid (RNA).

Ribose

1

2

5

4

3

1

23

4

5

-D ribose


40/70

40

Aldopentose

Exists mainly in the cyclic form

Component of deoxyribonucleic acid (DNA).

Deoxyribose

1

2

5

4

3

1

23

4

5

H

H

-D deoxyribose

f d


41/70

Structure of DNA and RNA

DNA :

Polymer of deoxyribonucleotides


42/70

Disaccharides

Maltose: glucose + glucose

42

Sucrose: glucose + fructose

Lactose: glucose + galactose

Consists of 2 molecules of monosaccharides joined together

General formula Cx(H2O)y


43/70

3.2.4 Outline the role of condensation and hydrolysis in

the relationships between monosaccharides and

disaccharides.


44/70

Formation of Disaccharides

44

2monosaccharides disaccharide

Condensation

Hydrolysis

O HH O O HH O+

OH O O H

H2OH2O

Glycosidic bond

Definition: A condensation reaction is a chemical reaction in which two simple moleculesare joined together to form a larger molecule with the removal of one molecule of water.


45/70

45

1

234

5

6

1

23

4

56

Maltose is formed by joining

-D-glucose to

-D-glucose to give an 1,4-glycoside

Also known as malt sugar

Formed as an intermediate of starch hydrolysis

Source: Germinating grains

Formation of Maltose

D- D-

Lactose


46/70

Lactose

46

Lactose is formed by joining -D-galactose to -D-glucose to give a-1,4-glycoside

Also known as milk sugar Principle source of energy in the diet of young mammals

Must be hydrolyzed to glucose and galactose for use as an energysource

Lactose intolerance results from lack oflactase to hydrolyze theglycosidic link of lactose


47/70

Lactose Intolerance

Inability to digest lactose Caused by a deficiency of the enzyme lactase, produced by the cellslining the small intestine.

Primary lactase deficiency develops over time and begins after

about age 2 when the body begins to produce less lactase. Mostchildren who have lactase deficiency do not experience symptoms oflactose intolerance until late adolescence or adulthood.

A possible genetic link to primary lactase deficiency. Some people

inherit a gene from their parents that makes it likely they will developprimary lactase deficiency.

Some racial/ethnic populations are more affected than others


48/70

Global Distribution of Lactose Intolerance


49/70

49

S


50/70

Sucrose

Sucrose is formed by linking -D-glucose with -D-

fructose to give a 1,2 glycosidic linkage

Sucrose if NOT a reducing sugar because the aldehydeand ketone groups in its component monosaccharideshave been lost in the formation of the glycosidic bond

50

D- D-

1

2

3 4

5

6

1

23

4

5

6

Sucrose


51/70

Sucrose

Plants can synthesize sucrose. Animals cannot.

Sucrose is Water soluble Easily transported in plant circulatory system

Sucrose called: Table sugar Cane sugar

Beet sugar

51


52/70

1. Identify glucose and ribose from diagrams showingtheir structure.

2. List three examples each of monosaccharides,

disaccharides and polysaccharides.

3. State one function of glucose & lactose in animals, andof fructose & sucrose in plants.

4. Outline the role of condensation and hydrolysis in therelationships between monosaccharides &disaccharides.

52

3.2 Carbohydrates: What we have learnt

today


53/70

Test yourself!

53

3. What is the major difference between lactose intolerance

and galactosemia?

2. What is the difference between Type 1 and Type 2diabetes?

1. Why does cyclization of D-glucose give 2 isomerscalled anomers, - and - D- glucose?

l h d


54/70

Polysaccharides

Polymer of monosaccharides

Built by many monosaccharide units condensedtogether, all linked by glycosidic bonds

Condensing process = polymerisation

Can be divided into 2 groups

A. Storage polysaccharides1. Starch

2. GlycogenB. Structural polysaccharides

1. Cellulose

2. Chitin54

Starch


55/70

55

Starch

Energy storage in plants

A mixture of amylose & amylopectin

Amylose is a linear polymer of hundreds of glucoseunits, with all the residues linked together by (1-4)bonds

Amylopectin is a highly branched chain polymer ofseveral thousand glucose units, with (1-6) linkagescreating branches along the chain of (1-4) linkages


56/70

56

Before starch can enter (or leave) cells it must be


57/70

57

Before starch can enter (or leave) cells, it must bedigested

The hydrolysis of starch is done by amylases.

With the aid of an amylase, water molecules enter at the(1-4) linkages, breaking the chain & eventually producinga mixture of glucose & maltose

A debranching enzyme is needed to break the (1-6)bonds of amylopectin

Glycogen


58/70

Glycogen

Energy storage polysaccharides in animals

Also made by fungi

58

l l b l f l


59/70

Animals store excess glucose by polymerizing it to form glycogen

The structure of glycogen is similar to that of amylopectin, although

the branches in glycogen tend to be shorter & more frequent

Glycogen is broken back down into glucose when energy is needed (aprocess called glycogenolysis)

Glucose units are released by the enzyme glycogen phosphorylase toproduce glucose-1-phosphate, which is then used to generate energy

59

St h & l d t b t


60/70

Starch & glycogen good storage substances.Why?

Hydroxyl (OH) groups project into the interior of helix

1. Insoluble in water- Does not affect water potential of cells- Large amounts can be stored without gain of water

2. Can be compacted- Branched structure allows for extensive coiling & entangling- > carbohydrate stored per unit volume

3. Easily hydrolysed- No cross-linkages between chains- Easily broken down into monosaccharides

60


61/70

STARCH

Cellulose


62/70

Cellulose

Structural polysaccharides in plants

Like starch, cellulose is a polysaccharide made fromglucose monomers

However, cellulose differs profoundly from starch in

its properties

The glucose units are linked by (1-4) glycosidiclinkages, which cannot be digested by mammalian

enzymes

62

Because the glycosidic bonds are (1-4) the rings of


63/70

Because the glycosidic bonds are (1 4), the rings ofglucose are arranged in a flip-flop manner

This produces a long, straight, rigid molecule

There are no branches in cellulose as there are in

starch

The absence of side chain allows these linear

molecules to lie close together Because of the many OH groups, as well as the

oxygen atom in the ring, there are many

opportunities for hydrogen bonds to form between

adjacent chains

The result is a series of stiff, elongated fibrils the

perfect material for building the cell walls of plants

63


64/70

64

Parallelarrangement of

unbranchedcellulose molecules

Functions of Cellulose


65/70

Adds strength to cell walls- macrofibrils arranged inlayers- 90o orientation- glue-like matrix (pectin)

Prevents cells from bursting

Helps determine shape ofcells Enable development of

turgidity

Has gaps between chains &layers- channels for water- can be filled with lignin for

extra tensile strength (eg.xylem vessels)Spaces in cellulose 65

Since both starch and cellulose are made of glucose


66/70

66

Since both starch and cellulose are made of glucose

units joined together, why then only starch can bedigested in our bodies but not cellulose?

STARCH

CELLULOSE


67/70

67

1. What is the difference between acondensation and a hydrolysisreaction? Give an example of each.

2. What are the key features of biological

macromolecules?

3. What is the significance of hydrogen

bonds in fibres of cellulose?

Test Yourself!

3.2 Carbohydrates:Learning objectives


68/70

1. Distinguish between organic and inorganiccompounds2. Identify glucose and ribose from diagrams showing

their structure

3. List three examples each of monosaccharides,disaccharides and polysaccharides4. State one function of glucose, lactose and glycogen in

animals, and of fructose, sucrose and cellulose inplants

5. Outline the role of condensation and hydrolysis in therelationships between monosaccharides, disaccharidesand polysaccharides

68

3.2 Carbohydrates:Learning objectives


69/70

Biology Clegg

Biology Concepts and Connections Campbell

Advanced Biology Principles andApplications Clegg with Mackean

Biological Science Green Stout Taylor

69

Further Reading


70/70

THE END!

3.2 Carbohydrates

Documents

Transcript of 3.2 Carbohydrates