Polysaccharides. Chemistry presentation on the topic "polysaccharides" Do taste sensations change?

LESSON TOPIC: POLYSACCHARIDES. STARCH AND CELLULOSE

Lesson objectives:

View in comparison

structure
properties
application
significance in the nature of starch and cellulose

STARCH and CELLULOSE

Chemical formula

(WITH 6 N 10 ABOUT 5 ) n

CELLULOSE. BEING IN NATURE

Cotton, flax, hemp fibers - almost pure cellulose

Wood contains 50% cellulose

Straw contains 30% cellulose

The structure of starch (C 6 N 10 ABOUT 5 ) n ( n= 200 - 1000)

starch macromolecules consist of residues of cyclic α-glucose molecules

STRUCTURE OF CELLULOSE (C 6 H 10 O 5 ) n

(n = 400,000 to 2 million )

Cellulose macromolecules consist of β-glucose residues

SHAPE OF STARCH MOLECULE

Amylose (10-20%) has linear structure

Amylopectin (80-90%) forms a branched structure

SHAPE OF CELLULOSE MOLECULE

Cellulose has a linear structure

Chemical properties of starch

Starch hydrolysis

Starch is easily hydrolyzed:

Stepwise enzymatic hydrolysis of starch.

Starch → dextrins → maltose → glucose

N 2 S ABOUT 4

(WITH 6 N 10 ABOUT 5 )n

+ nH 2 O

→ nC 6 H 12 O 6

N 2 ABOUT

Chemical properties of cellulose

Hydrolysis of cellulose

Cellulose (fiber), unlike starch, is difficult to hydrolyze

At hydrolysis plants, wood waste (chips, sawdust) is processed into glucose and then into alcohol

N 2 S ABOUT 4

(WITH 6 N 10 ABOUT 5 )n

+ nH 2 O

→ nC 6 H 12 O 6

(WITH 6 N 10 ABOUT 5 )n

→ WITH 6 N 12 ABOUT 6

→ WITH 2 N 5 HE

FORMATION OF CELLULOSE ESTERS

Trinitrocellulose –

explosive pyroxylin

cellulose

Cellulose triacetate

cellulose

Trinitrocellulose (pyroxylin) is used as an explosive and in the production of smokeless gunpowder.
Dinitrocellulose (colloxylin) is used to produce collodion (to create scars and scars)

Man-made fibers cellulose based

PHOTOSYNTHESIS

6СО 2 + 6H 2 O C 6 N 12 ABOUT 6 + 6O 2

light

Consolidation of knowledge

1. Choose the correct statements:

1. Disaccharides include starch and cellulose.

2. Starch and cellulose have the same molecular formula.

3. Cellulose has a branched molecular structure.

4. Starch swells in hot water.

5. Cellulose dissolves in organic solvents.

6. The hydrolysis reaction is characteristic only of starch.

7. The hydrolysis of cellulose produces glucose molecules.

8. Qualitative reaction for determining starch in natural objects is the reagent iodine

9. Cellulose is used to produce artificial silk.

Write it down homework

§ 13.8.

Home Study .

Enzymatic hydrolysis of starch .

Human saliva contains the digestive enzyme amylase. Under the action of amylase (ptialin), starch hydrolysis occurs.

Chew well (at least 10 minutes) a small piece of black bread.

Do taste sensations change?

How can this be explained?

Place it in a porcelain cup. Add a drop of iodine solution to it.

What are you observing? What can be concluded?

Tell us about the results of your experiments.

PROPERTIES

STARCH

1.Being in nature

2. Chemical formula

CELLULOSE

3. The molecule consists of residues...

PROPERTIES

STARCH

4. Structural link formula

5.Number of structural links

CELLULOSE

6.Molecular weight

7. Molecule shape

STARCH

8. Physical properties

CELLULOSE

STARCH

9. Chemical properties

CELLULOSE

Hydrolysis reaction

Hydrolysis reaction:

Determination of starch in food

STARCH

8.Receipt

A) in nature

B) in industry

Application

1
Since his appearance on Earth, man has consumed plant foods containing starch, used wood and other plant objects, consisting mainly of another natural polysaccharide - cellulose, for his needs.
The structure of starch molecules: a – amylose; b – amylopectin

Carbohydrates are natural polymers consisting of a large number of monosaccharide units that are part of one macromolecule. Therefore, such substances are called polysaccharides. The most important among them are starch and cellulose.
General formula of polysaccharides
Physical properties:
STARCH occurs in the form of white grains. Starch grains are insoluble in cold water; If you destroy the outer membrane by rubbing, the starch in cold water swells and forms a gel. In hot water, the membrane of the grains bursts and the starch also forms a colloidal solution (gel).
From food greatest number starch is found in bread, pasta and other flour products, cereals, potatoes.

Biological role
For the human body, starch serves as the main supplier of carbohydrates - one of the most important components of food. Under the action of enzymes, starch is hydrolyzed to glucose, which is oxidized in cells to carbon dioxide and water, releasing the energy necessary for the functioning of a living organism.
For various plants, it is a reserve nutrient material and is found mainly in fruits, seeds and tubers. The grains of cereal plants are the richest in starch: rice (up to 86%), wheat (up to 75%), corn (up to 72%), potato tubers (up to 24%).
In tubers, starch grains float in cell sap, so potatoes are the main raw material for starch production. In cereals, starch particles are tightly glued together by a protein substance called gluten.
CELLULOSE.
Pure CELLULOSE is a solid white substance. It is insoluble in water and organic solvents.
The second most abundant polysaccharide in nature is cellulose or fiber. The elementary unit of this natural polymer is also glucose residues.
The relative molecular weight of cellulose macromolecules ranges from 250,000 to 1,000,000 or more. These long chains are stretched out and arranged in bundles. These bundles are woven like ropes and form fibers that are visible to the eye.
arrangement of cellulose macromolecules in natural fibers (wool)
Wood contains from 40 to 50% cellulose, straw - 30%. Plant cellulose serves as a nutrient for herbivores, whose bodies contain enzymes that break down fiber.
Chemical properties
1. Starch and cellulose undergo hydrolysis to form glucose in the presence of mineral acids, such as sulfuric acid:
Acid hydrolysis of cellulose is called saccharification. This process is carried out on a large scale at hydrolysis plants, which process wood waste (chips, sawdust) into glucose-containing solutions and then into alcohol.
2. Interaction with nitric acid
+ 3nHNO3 → +3 H2O

Trinitrocellulose
3) Combustion.
Cellulose burns easily to produce carbon dioxide and water. (С6Н6О5)n + 6nО2 → nСО2 + nН2О + Q
Qualitative reaction to starch
Starch gives a blue color when reacting with iodine.
Obtaining starch
Industrially, starch is obtained mainly from potatoes, rice or corn. Significant quantities of starch are processed into molasses and glucose, used in the food industry.
Application of starch
From the hydrolysis products they obtain food grade alcohol, lactic acid and other valuable products. Starch is used as an adhesive and used for finishing fabrics. In medicine, some ointments and powders are prepared based on starch.
application of cellulose
The following are made from cellulose: artificial fibers, polymer films, plastics, smokeless powder, varnishes, paper. Glucose is obtained by saccharification of cellulose; used for the production of ethyl alcohol. Ethanol obtained in this way is called hydrolysis.
Comparison of starch and cellulose
Starch
Cellulose
Structure
Physical properties
Chemical properties
Being in nature
Biological role
Application

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Carbohydrates

Monosaccharides

Oligosaccharides

Polysaccharides

fructose,

Sucrose

cellulose

Polysaccharides

Cellulose

The purpose of the lesson

1.To consolidate knowledge about the classification of carbohydrates.

2. Study the properties of polysaccharides using the example of starch and cellulose.

3. Be able to find similarities and differences in the structure and properties of polysaccharides, draw up equations for the hydrolysis reaction.

4. Be able to carry out a qualitative reaction to starch.

Polysaccharides

These are natural high-molecular substances, the macromolecules of which consist of residues of monosaccharide molecules.
Polysaccharides are classified as biopolymers.
Examples of polysaccharides: starch, cellulose, glycogen, chitin.

Comparison of starch and cellulose

Starch

Cellulose

Structure

Physical properties

Chemical properties

Being in nature

Biological role

Application

Spreading in nature

STARCH

CELLULOSE

RICE 80%

POTATO 20%

FLAX 80%

WOOD 50%

COTTON 98%

WHEAT 70%

Structural formula of starch

α-Glucose residues

STARCH

(C 6 H 10 O 5 ) n

Relative molecular weight ranges from several hundred to several thousand carbon units.

Structural formula of cellulose

β-Glucose residues

CELLULOSE

(C 6 H 10 O 5 ) n

Relative molecular weight is several million carbon units.

Physical properties

starch

cellulose

hard, fibrous white substance
does not dissolve in water
does not have a sweet taste

white amorphous powder
does not dissolve in cold water
swells in hot water
does not have a sweet taste

Chemical properties of starch

1. Hydrolysis
1. Hydrolysis

Starch → dextrins → maltose → glucose

2.Qualitative reaction

2.Qualitative reaction

(C 6 H 10 O 5) n + I 2 → blue color

Chemical properties of cellulose

1. Hydrolysis

(C 6 H 10 O 5) n + nH 2 O → nC 6 H 12 O 6

2. Formation of esters

Let's check ourselves

1. The starch macromolecule consists of molecular residues...

α - glucose

β - glucose

fructose

Let's check ourselves

2. Qualitative reaction to starch - interaction with...

copper(II) hydroxide

ammonia solution of silver oxide

Let's check ourselves

3. The hydrolysis of cellulose produces...

Let's check ourselves

4. Cellulose trinitrate is used as...

medicine

explosive

fire extinguishing agent

Let's check ourselves

5. To make acetate fiber,…

cellulose salts

cellulose oxides

cellulose esters

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Slide 1

Slide 2

Carbohydrates are widespread in nature and play big role in biological processes of living organisms and humans. These include, for example, grape sugar, or glucose, beet (cane) sugar, or sucrose, starch and fiber. The name "carbohydrates" comes from the fact that chemical composition Most compounds of this class are expressed by the general formula Cn(H4O)m. Further research into carbohydrates showed that this name is filamentous. Firstly, carbohydrates have been found whose composition does not correspond to this formula. Secondly, there are known compounds (formaldehyde CH2O, acetic acid C2H4O2), the composition of which, although it corresponds to the general formula Cn(H2O)m, differs in properties from carbohydrates.

Slide 3

Carbohydrates can be divided depending on their structure. The classification of carbohydrates is reflected in the diagram. Carbohydrates Monosaccharides Disaccharides Polysaccharides Glucose Ribose Fructose Sucrose Cellulose Starch

Slide 4

What are polysaccharides? Polysaccharides are high molecular weight compounds containing hundreds of monosaccharide residues. What is common to the structure of polysaccharides is that monosaccharide residues are linked by the hemiacetal hydroxyl of one molecule and the alcohol hydroxyl of another, etc. Each monosaccharide residue is linked to adjacent residues by glycosidic bonds. Polyglycosides can contain branched and unbranched chains. The monosaccharide residues that make up the molecule can be the same or different. The most important of the higher polysaccharides are starch, glycogen (animal starch), fiber (or cellulose). All three of these polysaccharides are made up of glucose molecules linked together in different ways. The composition of all three compounds can be expressed as general (C6H10O5)n

Slide 5

Starch Starch is a polysaccharide. The molecular mass of this substance has not been precisely established, but it is known that it is very large (about 100,000) and may vary for different samples. Therefore, the formula of starch, like other polysaccharides, is depicted as (C6H10O5)p. For each polysaccharide n has different meanings.

Slide 6

Physical properties Starch is a tasteless powder, insoluble in cold water. It swells in hot water, forming a paste. Starch is widely distributed in nature. It is a reserve nutrient material for various plants and is contained in them in the form of starch grains. The richest grains in starch are cereals: rice (up to 86%), wheat (up to 75%), corn (up to 72%), and potato tubers (up to 24%). In potato tubers, starch grains float in cell sap, and in cereals they are tightly glued together with a protein substance called gluten. Starch is one of the plants that extract starch by breaking down the cells and washing it off with water. On a large scale, it is obtained mainly from potato tubers (in the form of potato flour), but also from corn.

Slide 7

Slide 8

Chemical properties 1) Under the action of enzymes or when heated with acids (hydrogen ions serve as a catalyst), starch, like all complex carbohydrates, undergoes hydrolysis. In this case, soluble starch is formed, then less complex substances - dextrins. The final product of hydrolysis is glucose. The overall reaction equation can be expressed as follows:

Slide 9

There is a gradual breakdown of macromolecules. Hydrolysis of starch - its important chemical property. starch dextrins maltose glucose

Slide 10

2) Starch does not give the “silver mirror” reaction, but the products of its hydrolysis do. Starch macromolecules consist of many molecules of cyclic P-glucose. The process of starch formation can be expressed as follows (polycondensation reaction):

Slide 11

Slide 12

3) A characteristic reaction is the interaction of starch with iodine solutions. If an iodine solution is added to a cooled starch paste, a blue color appears. When the paste is heated, it disappears, and when cooled, it appears again. This property is used in determining starch in food products. So, for example, if a drop of iodine is applied to a cut potato or a slice of white bread, a blue color appears

Slide 13

Application Starch is the main carbohydrate in human food; it is found in large quantities in bread, cereals, potatoes, and vegetables. Significant quantities of starch are processed into dextrins, molasses, and glucose, which are used in the confectionery industry. Starch is used as an adhesive, used for finishing fabrics and starching linen. In medicine, ointments, powders, etc. are prepared based on starch.

Slide 14

Cellulose Cellulose is an even more common carbohydrate than starch. It consists mainly of the walls of plant cells. Wood contains up to 60%, cotton wool and filter paper - up to 90% cellulose.

Slide 15

Physical properties Pure cellulose is a white solid, insoluble in water and in common organic solvents, highly soluble in concentrated ammonia solution of copper (II) hydroxide (Schweitzer reagent). From this acid solution, cellulose is precipitated in the form of fibers (hydrated cellulose). Fiber has quite high mechanical strength.

Slide 16

Composition and structure The composition of cellulose, as well as starch, is expressed by the formula (C6H10O5)p. The n value in some types of cellulose reaches 10-12 thousand, and the molecular weight reaches several million. Its molecules have a linear (unbranched) structure, as a result of which cellulose easily forms fibers. Starch molecules have both linear and branched structures. This is the main difference between starch and cellulose. There are also differences in the structure of these substances: starch macromolecules consist of residues of P-glucose molecules, and cellulose macromolecules consist of residues of P-glucose. The process of formation of a fragment of a cellulose macromolecule can be represented by the diagram:

Presentation on the topic “Polysaccharides. Starch and cellulose"

LESSON TOPIC: POLYSACCHARIDES. STARCH AND CELLULOSE
2
Lesson objectives: Compare the structure, properties, application, meaning in the nature of starch and cellulose

Classification of carbohydrates
Trioses
Tetroses
Pentoses Ribose C5H10O5 Deoxyribose C5H10O4
Hexoses C6H12O6 Glucose Fructose
С12Н22О11
Sucrose – table sugar
Maltose – malt sugar
Lactose - milk sugar
Glycogen
Cellulose
Starch
(C6H10O5)n
Carbohydrates
Monosaccharides
Polysaccharides
Disaccharides

Structure of starch (C6H10O5)n (n = 200 - 1000)
starch macromolecules consist of residues of cyclic α-glucose molecules
4

STARCH - A MIXTURE OF 2 POLYSACCHARIDES
5
Amylose (10-20%) has a linear structure
Amylopectin (80-90%) forms a branched structure
Section of the amylose molecule
Section of the amylopectin molecule

The amylose macromolecule is a helix, each turn of which consists of 6 a-glucose units.
When amylose interacts with iodine in an aqueous solution, iodine molecules enter the internal channel of the helix, forming a so-called inclusion compound. This compound has a characteristic blue color.

GLYCOGEN – STARCH OF ANIMAL ORIGIN
7
Is a reserve substance
Formed in the liver of humans and animals
Has a more branched structure than amylopectin

MOLECULAR FORMULA OF CELLULOSE (C6H10O5)n (n = 400,000 to 2 million)
Cellulose is also a natural polymer. Its macromolecule consists of residues of glucose molecules. Why do starch and cellulose, substances with the same molecular formula, have different properties? The properties of polymers depend on the number of elementary units and their structure. The degree of polymerization of cellulose is much greater than that of starch. Cellulose macromolecules, unlike starch, consist of residues of the β-glucose molecule and have only a linear structure. Cellulose macromolecules are located in one direction and form fibers (flax, cotton, hemp).

THE STRUCTURE OF CELLULOSE DETERMINES ITS PROPERTIES
9

Chemical properties of starch
Starch is easily hydrolyzed: Stepwise enzymatic hydrolysis of starch. Starch → dextrins → maltose → glucose
10
Н2SO4
H2O
H2O
H2O
(C6H10O5)n
+ nH2O
→ nC6H12O6
Starch hydrolysis

Chemical properties of cellulose
Cellulose (fiber), unlike starch, is difficult to hydrolyze. At hydrolysis plants, wood waste (chips, sawdust) is processed into glucose and then into alcohol
Н2SO4
(C6H10O5)n
+ nH2O
→ nC6H12O6
(C6H10O5)n
→ С6Н12О6
→ C2H5OH
Hydrolysis of cellulose

FORMATION OF CELLULOSE ESTERS
12
Trinitrocellulose - explosive pyroxylin
cellulose

OBTAINING TRIACETYL CELLULOSE
13
OH C6H7O2 OH OH n
NOOS-CH3 + n NOOS-CH3 NOOS-CH3
O - COCH3 C6H7O2 O - COCH3 O - COCH3 n
+ 3nH2O
Cellulose
Triacetyl cellulose
Acetic acid