2.4 Bioeconomy Resources STARCH AND CELLULOSE

Plants commonly have 2 forms of abundant polymers from glucose (polyssacharides):

starch and cellulose

Plants commonly have 2 forms of abundant polymers from glucose: Starch and Cellulose

Starch is known as a energy reserve polymer for plants

→ must have some reversible nature to “unzip” back into glucose.

Plants commonly have 2 forms of abundant polymers from glucose: Starch and Cellulose

Cellulose is known as a structural polymer for plants

→ Must meet demanding mechanical performance for plant survival.

Starch and Glucose:

What type of glycosidic linkage is found in starch?

Alpha (α) linkages.

How do α-linkages affect the structure of starch?

They allow the polymer backbone to bend and form a helical structure.

What type of glycosidic linkage is found in cellulose?

Beta (β-1,4) linkages

How do β-linkages affect the structure of cellulose?

They create straight, extended polymer chain

What is the main chemical structural difference between starch and cellulose?

Starch has α-linkages; cellulose has β-1,4 linkages between glucose units.

Why do starch and cellulose have different properties?

Their different linkages create different molecular shapes and structures.

What is the carbohydrate made of?

carbon + hydrate

hydrates (H2O) of carbon (C)

C_n(H2O)_n, where n is > or = than 3

How are the carbohydrates with 3-6 carbons called?

3C = Triose

4C = Tetroses

5C = Pentoses

6C = Hexoses

Carbohydrates

What are Aldoses?

Carbohydrates in which the 1-carbon is in the aldehyde.

Carbohydrates

What are Ketoses?

Carbohydrates in which the 2-Carbon is in the ketone

ex: fructose

Fischer projection to ring form

Most structured of carbohydrates come in 6C ring bonds.

What is the most abundant polymer on Earth?

CELLULOSE

Cellulose = glucose + linear chains + fibrils + semi-crystalline + structural support.

What type of polymer is cellulose?

A linear homopolymer.

What is the monomer of cellulose?

Glucose

What does it mean that cellulose is a homopolymer?

It contains only one type of monomer: glucose

How are cellulose chains organized?

Into highly organized fibrils.

Is cellulose crystalline, amorphous, or semi-crystalline?

Semi-crystalline: it has ordered and disordered regions.

Why is cellulose nearly insoluble in water?

ts chains pack tightly and form many hydrogen bonds

Name some uses of cellulose.

Paper, textiles, toothpaste, and computer-screen materials.

Repeat unit:

Linkages:

Homopolysaccharide:

Repeat unit: cellobiose → 2 glucose links = repeating units of cellobiose

Linkages: B-4, 4-glycosidic bond

Homopolysaccharide: no branching, no other monomers

Cellulose molecular weight—what does DP mean?

Degree of polymerization

Cellulose molecular weight—The longer the polymer, the … to dissolve?

The longer the polymer, the HARDER to dissolve?

Cellulose is found in nature as a microfibril

Sources of cellulose examples:

Hardwood

Softwood

Cotton

Bagasse

Coconut fibre

Corn cobs

STARCH is a combination of:

combination of 2 different glucose polymers.

What are the two forms of starch in granule? (important)

Linear amylose

Branched amylopectin

(highly crystalline branches)

What is the main difference between glucose and heteropolyssacharides?

The extra C

Enzymes can readily break down chains of starch into:

can readily break down chains of starch into glucose.

How is starch found in grains?

as granule

Endosperm = starch granules interdispersed in protein

Organization of starch in granule

• They are highly organized within themselves.

• Different plants have different levels of amylopectin (branched) /amylose (linear) ratios.

Amylopectin forms helixes that are crystalized.

Amylose holds regions together.

Hetero-polysaccharides

Hetero (different) made up of more than one type of monosaccharide unit.

Difference between Hetero-polysaccharides and cellulose

Cellulose is only made up of glucose units.

In wood Hetero-polysaccharides are referred to as:

Hemicelluloses

Example of a complicated carbohyrate

Pectins

What are pectins in primary cell walls of plants?

Hetero-polysaccharides

What is the most abundant pectin?

Homogalacturonan

What are some characteristics of pectin?

High in molecular weight

high solubility

other polysaccharides

CHITIN

• Natural sources: crustaceans, arthropods, fungi

• Serves as a structural matrix polymer in these organisms as cellulose does in plants

• Essentially a homopolymer of D-2-amino-2-deoxyglucose → linkage is exclusively beta

• Semicrystaline morphology

• hard to dissolve

• Separation is required

• 33% of the shell of a crustacean

• Pure chitin is expensive

CHITIN and CHITOSAN

Chitosan is produced from chitin

→ Chitin is partially hydrolized to produce chitosan

→ Chitosan is a broad term meaning any partially hydrolyzed chitin; almost always semisynthetic (less common in nature)

CHITIN and CHITOSAN

What is unique about chitin relative to other polyssacharides and lignocellulosic materials?

It contains nitrogen in its monomers; nitrogen containing modified glucose that provides structural support.

Seaweed — polysaccharide

Where are alginates found?

In brown seaweed.

Seaweed — polysaccharide

What are alginates made of, and what is their structure?

A block copolymer of mannuronic acid (M) and guluronic acid (G).

Seaweed — polysaccharide

What are key properties and applications of alginates?

Water-soluble, anionic polysaccharides used in biomedicine, compostable plastics, and the food industry.

What sulfated polysaccharide comes from red seaweed, and what is it used for?

sulfur like in keratin!!

Carrageenan; used for thickening, gelling, and stabilization.

What sulfated polysaccharide comes from brown seaweed?

Fucoidan; a bioactive polysaccharide used in medicinal and nutraceutical applications.

What sulfated polysaccharide comes from green seaweed, and what are its applications?

Ulvan; used for antioxidant, anticoagulant, and tissue-engineering applications.

LIGNIN

What is lignin?

A complex natural aromatic polymer found in plant cell walls.

LIGNIN
What are the main functions of lignin?

Protects cell walls, binds cells together, and provides mechanical strength.

LIGNIN

Why is lignin hydrophobic?

Its hydrophobic nature helps regulate liquid transport and prevent cell wall swelling.

LIGNIN

What are the building blocks of lignin?

Aromatic compounds containing phenylpropane units.

LIGNIN

What type of polymer is lignin structurally?

A heterogeneous, amorphous phenolic polymer.

• Heterogeneous = different components.

• Amorphous = disorganized.

• Phenolic = aromatic rings.

LIGNIN

What types of chemical linkages are found in lignin?

Ether linkages (C–O–C) and carbon–carbon linkages (C–C).

LIGNIN

When is lignin extracted industrially?

During papermaking and partially during cellulosic bioethanol production.

What is unique about lignin's aromatic structure compared with other natural polymers?

It contains aromatic phenylpropane units connected through irregular C–O–C and C–C bonds, forming a complex network.

Complex, irregular network containing aromatic rings and different linkages.

Cellulose = repeating sugar units. vs Lignin = irregular aromatic network.

Lignin content of different trees:

More lignin in softwoods

More hemicellulose in hardwood

More lignin in juvenile wood

Natural Rubber

What is the monomer of natural rubber/chemical functionality?

Isoprene

Natural Rubber

What polymer is formed when isoprene molecules join together?

Polyisoprene.

Natural Rubber
Why is stereochemistry important in natural rubber?

It influences chain arrangement, flexibility, and elasticity.

Natural Rubber

In what form is natural rubber obtained from plants?

As a colloidal latex emulsion containing rubber particles dispersed in water.

Natural Rubber

What other components in latex can influence rubber properties?

Proteins and other non-rubber substances.

Natural Rubber

What is vulcanization?

it was developed to create rubber as a solid material at room temperature. It improves rubber’s strength, elasticity, and stability.

Natural rubber is hard and stiff at low temperatures and too soft at room temperature.

Natural Rubber

What is the main chemical structure of natural rubber?

Highly regular cis-1,4-polyisoprene.

Which material dominates commercial rubber production

Hevea b. 500-3000 kg/year ha

Seeds have been taken from the Amazon to UK, then planted in India.

SUMMARY

What are natural polymers?

Large molecules of repeating units connected by covalent bonds.

SUMMARY
How does chemical functionality influence natural polymers?

Functional groups create interactions that influence secondary and tertiary structures.

SUMMARY

Can chemically similar natural polymers have different properties?

Yes. Small structural differences can produce very small different properties.

SUMMARY

How does starch differ from cellulose despite both being made of glucose?

Different glycosidic linkages create different structures and properties.

SUMMARY

Why do natural polymers have unique structures?

Their structures provide specific functions and material performance.

SUMMARY

What does nature’s performance engineering mean?

Evolution has favored polymer structures suited to specific biological functions.