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MODULE 01

CLIL for Chemistry - Associazione culturale CHIMICARE

AUTHOR: Teresa Celestino FATTY ACIDS AND FATS How the study of the chemical composition and properties of fatty acids and fats allows us to understand the cell membrane structure and to make cosmetic formulations.

Moduli CLIL per i l quinto anno degl i Ist ituti Tecnici e dei Licei

OVERVIEW

GENERAL INFORMATION VOCABULARY WORDS

ADDRESSED TO STUDENTS 18-19 YEARS OLD CLASS TIME: 10 HOURS OR MORE ENGLISH LEVEL: B1/B2 (EUROPEAN FRAMEWORK)

Fatty acid, fat, lipid, branched/unbranched chain, side chain, building block, ester, alcohol, glicerol, acyl residue, phospholipid, hydroxyl group, isprenoid, isoprene, steroid, cholesterol, axial, equatorial, aromatic plant, oil, essential oil, to heal, to enhance, ointment, poultice, perfume, flavour/flavouring product, fragrance, household product, flower, fruit, seed, leave, wood, bark, root, distillation, steam distillation, squeezing, hydrolysis, soap, soapy water, hydrophobic, hydrophilic, lipophilic, , head, tail, polar/non polar, salt, foam, grease, emulsifier/emulsion/emulsifying agents, to disperse, amphiphile, droplet, saponifiable oil, miscible/immiscibile, micelle, continuous/discontinuos phase, viscosity, layer, bilayer, membrane, self-assembled, extracelluar fluid, to scatter, cytoplasm, neutron scattering, collision, hydrogen, deuterium, trick, isotope, mixture, beaker, condenser, boling flask, mechanical stirring, foaming products …..

CONTENTS

- FATTY ACIDS AND FATS - ISOPRENOIDS AND STEROIDS - SOAP AND EMULSIONS - THE CELL MEMBRANE

LABORATORY EXPERIENCES

- ISOLATION OF (+)-LIMONENE FROM CITRUS RIND - SYNTHESIS OF EXOTIC SOAPS - FORMULATION OF JOJOBA OIL BODY EMULSION

OBJECTIVES SKILLS USED OR DEVELOPED

BY THE END OF THIS MODULE, STUDENTS SHOULD BE ABLE TO DEFINE VARIOUS TYPES OF CHEMICAL COMPOUNDS AND EXPLAIN IN ENGLISH LANGUAGE (SPEAKING OR WRITING) SOME OF THEIR CHEMICAL AND PHYSICAL PROPERTIES IN THE BIOLOGICAL SYSTEMS. THEY SHOULD BE ABLE TO CARRY OUT EXPERIMENTS RELATED TO EXTRACTION, SINTHESIS AND FORMULATION USING AN ENGLISH TECHNICAL LANGUAGE.

COMMUNICATION IN ENGLISH LANGUAGE (NOTE TAKING, ORAL AND WRITTEN EXPOSITION, INCLUDING SUMMARIZATION) COMPREHENSION (LISTENING, READING) OBSERVATION - MANIPULATION EXPERIMENTATION (CONDUCTING DATA ANALYSIS)

SUBJECTS USEFUL HINTS

CHEMISTRY, BIOCHEMISTRY BIOLOGY PHYSICAL SCIENCE GENERAL SCIENCE

Questions sheets could be used by the teacher to assign homeworks or as exercise to assess students’ level. If the teacher uses questions sheets during the lesson time, it is advisable to organize students two by two or in groups of three.


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FATTY ACIDS AND FATS The naturally occurring fatty acids are carboxylic acids with linear hydrocarbon chains of 4–24 carbon atoms. They are present in all organisms as components of fats and membrane lipids. They are usually esterified with alcohols (glycerol, sphingosine, or cholesterol). Fatty acids are also found in small amounts in unesterified form. In this case, they are known as free fatty acids (FFAs). Free fatty acids have strongly amphipathic properties. The Table 1. lists the full series of aliphatic carboxylic acids that are found in plants and animals. Longchain and unbranched fatty acids with either 16 or 18 carbon atoms are the most common in vascular plants and animals (e. g., palmitic and stearic acid). The number of carbon atoms in the longer, natural fatty acids is always even. This is because they are biosynthesized from C2 building blocks. Unsaturated fatty acids contain one or more isolated double bonds. Common unsaturated fatty acids include oleic acid and linoleic acid. Of the two possible cis–trans isomers, usually only the cis forms are found in natural lipids. Branched fatty acids only occur in bacteria.

Table 1 – Carboxylic acids


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Questions Sheet 1. Is the acetic acid a fatty acid? Why? ---------------------------------------------------------------------------------------------------------------- 2. Greek letters are also used to indicate fatty acids’ structure: α = C-2; β = C-3; ω = the last carbon; -3 = the third last carbon.

Linoleic acid is a − 6 fatty acid:

Search in the Table 1. -3, -9 and other -6 fatty acids: ---------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------

3. The arachidonic acid’s structure is indicated with a series of numbers. What does every number mean? 20 : 4 ; 5, 8, 11, 14

4. Essential fatty acids are fatty acids that have to be supplied in the diet (see Table 1.). Linoleic and linolenic acid can be converted into arachidonic acid by elongation, and they can therefore replace arachidonic acid in the diet. Identify at least four linoleic and linolenic acids rich foods. ---------------------------------------------------------------------------------------------------------------- -------------------------------------------------------- 5. Why fatty acids have amphipathic properties? ---------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------- --------------------------------------------------------


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Fats are esters of the trivalent alcohol glycerol with three fatty acids. When a single fatty acid is esterified with glycerol, the product is referred to as a monoacylglycerol. A fatty acid residue is an “acyl residue” (see Figure 1).

Figure 1 – Fats’ structure

When extracted from biological materials, fats always represent mixtures of very similar compounds, in which fatty acid residues may differ in terms of their chain length and the number of double bonds they contain. Phospholipids are the main constituents of biological membranes. Their common feature is a phosphate residue that is esterified with the hydroxyl group at C-3 of glycerol.

Questions Sheet 1. The length of the fatty acid residues and the number of their double bonds affect the melting point of the fats. The shorter the fatty acid residues and the more double bonds they contain, the lower their melting points. Explain changes in the melting points in terms of intermolecular interactions. ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… 2. After the answer to the first question, try to assume the difference between oils (liquid at room temperature) and fats at the molecular level. ………………………………………………………………………………………………………………………………………………………………………………………………………. 2. Why do the fats show optical activity? ………………………………………………………………………………………………………………………………………………………………………………………………………


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ISOPRENOIDS AND STEROIDS Isoprenoids structure can be derived from a single common building block, isoprene . Only few species of plants and animals have the ability to synthesize particular isoprenoids (see Figure 2).

Figure 2 ‐ Isoprenoids

Isoprene metabolism in plants is very complex. Plants can synthesize many types of aromatic substances and volatile oils from isoprenoids. Examples include menthol, camphor, and citronellol. These C-10 compounds are also called monoterpenes (two isoprene units). Similarly, compounds consisting of three isoprene units are termed sesquiterpenes, and the steroids (six isoprene units) are called triterpenes. The steroids molecular core structure consists of four saturated rings (A, B, C and D), sometimes coupled with a side chain. Substituents of the steroids can lie in the same plane as the ring (e = equatorial) or nearly perpendicular to it (a = axial). Substituents pointing toward the ob-server are indicated by an unbroken line, while bonds pointing into the plane of the page are indicated by a dashed line (see cholesterol structure, Figure 3)

Figure 3 – Cholesterol structure

Resources from “Color Atlas of Biochemistry”, J. Koolman and K.H. Roehm(second edition, 2005)


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Questions Sheet 1. What is the meaning of “l = 2, 3, 4, ….” referred to isoprenoids? Look for the following isoprenoids in your textbook and write briefly their functions: - camphor …………………………………………………………………………………………………………………………………… - vitamin A …………………………………………………………………………………………………………………………………… - vitamin E …………………………………………………………………………………………………………………………………… - vitamin K …………………………………………………………………………………………………………………………………… - menthol …………………………………………………………………………………………………………………………………… - squalene …………………………………………………………………………………………………………………………………… 2. The acronyms HDL and LDL are referred to cholesterol. What are their estended names? Why our blood should contain HDL and LDL in an appropriate ratio?

The teacher reads slowly paragraph by paragraph. Students are organized two by two: every student l istens and takes notes; then, the couple of students writes together a summary of every paragraph. The day after, teacher asks students to expose the summary oral ly, without reading.

Aromatic plants Aromatic plants can be defined as plants containing substantially high levels of volatile oils. However, a plant can lack a typical odour in its natural state, but can generate an essential oil of high value if it is processed adequately. This is the case of patchouli, whose leaves must be fermented to give the famous essential oil. Thus, the concept of aromatic plant can be estended to plants which can generate an aromatic product by some physico-chemical processing. The use of aromatic plants seems to be as old as the human being. They have been used for thousands of years dating back to ancient civilizations, such as Egyptians, Greeks, Romans and Persians, that used them mainly to heal and enhance the body and spirit. Many ancient texts often describe the various procedures and rituals involved in the making of healing ointments, medicated oils, poultices and healing perfumes. Most probably aromatic plants were also known in ancient China, but very little is known. The plant kingdom provides a multitude of flavours and fragances which play different roles into everyday life. Essential oils are applied as flavouring for foods, soft drinks and confectionaries, in pharmaceutical products, as fragances in perfumes, cosmetics, household and industrial products. Plant species with aromatic properties are countless, including from superior plants to algae and lichens. According to different


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authors, approximately 3000 plant species contain essential oils, from wich only 250 are in the market. Aromatic plants grow all over the world, in different climates and environments although many of them tend to prefer certain geographical habitats. Essential oils are complex misture of volatile aromatic compounds which may be found in any part of a plant: flowers, fruits, seeds, leaves, woods, barks or roots. Essential oils contain hundreds of constituents with a large structural diversity. Many of them are terpenoids, mainly mono– and sesquiterpenes, wich can have aliphatic, cyclic or aromatic structures as hydrocarbons or with different oxygenated functions. The chemical composition of essential oils is extremely variable, not only due to ecological factors but also to genetic characters. The physical process by wich essential oils are obtained may also influence their chemical composition. Water distillation, steam distillation, squeezing and solvent extraction produce different essential oils from the same plant material, because not all components are extracted equally well by each process or because individual components may undergo changes during the process. Therefore, it can be concluded that the genetic variability of plants as well as ecological factors and agricultural and industrial methodologies, are responsible of an enormous richness of aroma diversity. The pharmaceutical and medicinal areas must take advantage of this diversity to provide the population with therapeutically useful materials in benefit of the human health. From: “Biodiversity of aromatic plants” - Course “Plant Biodiversity and Health” (Barcelona, July 2008) – Author: Dra. Roser Vila, Unitat de Farmacologia i Farmacognòsia/Facultat de Farmàcia, Universitat de Barcelona.

SOAPS AND EMULSIONS Soap is almost as essential as food, and is closely related in the sense that it is made from many of the same fats which are used for food. Any salt of a fatty acid is a soap, but common terminology provides a special meaning, since only the water-soluble salts have detergent properties. The simplest method of manufacturing soap is by neutralization of a fatty acid with an alkali, as follows: C17H35COOH + NaOH C17H35COONa + H2O stearic acid sodium hydroxide sodium stearate water

In this equation stearic acid is used to represent the mixtures of fatty acids always used commercially. Although this process appears simple it is never applied commercially on a large scale because of high cost.

The principal method of production of soap is by the reaction of an aqueous solution of caustic soda with the commercial saponifiable oils. This reaction can be represented in an equation as: (R–COO)3C3H5 + 3 NaOH 3 R-COONa + C3H5(OH)3 oil sodium hydroxide soap glycerol e.g. glyceryl stearate e.g. sodium stearate (C17H35COO)3C3H5 C17H35COONa

or diagrammatically as:


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This representation shows that the soap is obtained by a basic hydrolysis reaction, in which the O-C bonds (green dashed lines --) are broken. The long covalent hydrocarbon chain gives rise to the hydrophobic (water hating) and oil-soluble (non-polar) properties of the soap molecule (represented in yellow). The charged carboxylate group (represented in blue) is attracted to water molecules (hydrophilic). In this way, soaps are composed of a hydrophilic head and a hydrophobic tail (Fig. 4)

Figure 4 – A soap molecule

The cleaning action of soap is determined by its polar and non-polar structures in conjunction with the solubility principles. The long hydrocarbon chain is non-polar and hydrophobic (repelled by water). The "salt" end of the soap molecule is ionic and hydrophilic (water soluble). When grease or oil (non-polar hydrocarbons) are mixed with a soap- water solution, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules. Since soap molecules have both properties of non-polar and polar molecules the soap can act as an emulsifier. An emulsif ier is capable of dispersing one liquid into another immiscible liquid. This means that while oil (which attracts dirt) doesn't naturally mix with water, soap can suspend oil/dirt in such a way that it can be removed. The soap will form micelles (see Fig. 5) and trap


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the fats within the micelle. Since the micelle is soluble in water, it can easily be washed away.

Figure 5 – A micelle

An emulsion is a mixture of two immiscibile liquid substances. One substance (the dispersed phase) is dispersed in the other (the continuous phase), forming droplets. The continuous phase is salso called external phase. The dispersed phase is also called internal or discontinuous phase. The dispersed phase forms droplets of a size between 0.1 – 30 µm. An emulsion is prepared by shaking strongly the mixture of the two liquids or by passing the mixture through a colloid mill known as the “homogenizer”. The emulsions thus prepared from the pure liquids are usually not stable and the two liquids separate out on standing. To get a stable emulsion, small quantities of other substances are added to stabilize the emulsions. These substances are called emulsifiers or emulsifying agents. The substances

commonly used as emulsifying agents are soaps of various kinds. There is affinity between emulsions and the skin, therefore emulsions are more used in cosmetics to carry the active ingredients through the skin. In cosmetics, the phases are:

- Water (W) and hydrophilic ingredients; - Oil (O) and lipophilic ingredients; - Emulsifier or emulgent.

The ingredients selection depends on: - properties: aspect (gloss, mat), stickiness, softness,

smoothness, etc..- - efficacy in carrying active ingredients and in allowing

perspiration. We have two types of emulsion:

- O/W: oil in water (external phase: water). Hydrophilic emulsion easy to remove with water.

- W/O: water in oil (external phase: oil). Hydrophobic emulsion occlusive (more than o/w), emollient, easy to remove with o/w milks or soapy water.

Considering viscosity, emulsions are: - milks (low viscosity, fluid emulsions); - creams (high viscosity, semisolid emulsions)


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THE CELL MEMBRANE Without a membrane, a cell could haven’t individual identity, and molecules required by the cell would just diffuse away into the environment. The phospholipids organize themselves in a bilayer to hide their hydrophobic tail regions and expose the hydrophilic regions to water (Fig.6). Highly hydrophobic core forms a barrier: protects content of the cell. This organization is a self-assembled system that results from a spontaneous, not requiring energy process. This structure forms the layer that is the wall between the inside and outside of the cell. (Fig. 7). Lipid bilayer participates to exchanges between extracellular fluid and cytoplasm. So, the properties of amphiphiles are vitally important for life. The structure and organization of the lipid bilayer component of membranes hold the key to understand the functioning of membranes.

Figure 6 ‐ Bilayer's structure Figure 7 ‐ Bilayer in a cell membrane

The teacher reads slowly paragraph by paragraph. Students are organized two by two: every student l istens and takes notes; then, the couple of students writes together a summary of every paragraph. The day after, teacher asks students to expose the summary oral ly, without reading.

Neutron scattering to investigate cel l membranes

Neutron scattering is an essential tool for the study of structure at the nanometer level of self-assembled systems like cell membranes. Why neutrons? In neutron spectrometry experiments to measure dynamics (how atoms move in a substance), the neutrons in the beam collide with the atoms to be studied, like billiard balls bouncing off each other (Fig. 8). Neutrons and atoms exchange energy and momentum – the neutrons are scattered. Thus, measuring how these values change for the neutrons after the collision gives us an indication of the energy and momentum of the atoms they encountered, and therefore of how these atoms move.

Figure 8 ‐ Neutron reflection gives direct access to detailed microscopic

information about the structure of the phospholipid bilayers and other

components of the cell membranes.

But how can we distinguish between the motions of different atoms in a complex sample, such as a cell that contains not only water but


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also many other molecules whose atoms move in different ways? Neutrons are scattered with different power by different atoms. To study complex systems, scientists use a trick to reduce the scattering power of everything they do not want to measure. Hydrogen(H) scatters neutrons much more strongly than all other atom types (about 10-100 times, depending on which atom type you compare it with). In contrast, deuterium (D), a heavy isotope of hydrogen (its nucleus contains one neutron in addition to one proton), scatters neutrons about 40 times more weakly than hydrogen. Exploiting this property, scientists replace hydrogen with deuterium in the components of a complex system they are not interested in and render them practically ‘invisible’. The contributions to the scattering signal by the molecules that contain deuterium are negligible; we ‘see’ only the motions of the molecules that contain hydrogen. Sensitiveness to isotopes H and D are very different . Playing with deuteration without being invasive, we can evidence components in the lipid matrix such as cholesterol. Work on lipid bilayers has benefited and will continue to benefit from studies on surfactant systems. This has importance both in detergency and pharmaceutical industries. Perspectives in biology are very numerous. From: “Physics and chemistry of life” - Presentation “From soap bubbole to cell membranes” (Grenoble, October 2011) – Author: Dr. Giovanna Fragneto, senior scientist at ILL (Laue-Langevin Institute, Grenoble) Giuseppe Zaccai, “The intracellular environment: not so muddy waters” – Science in school, Issue 13, Autumn 2009

LABORATORY ISOLATION OF (+)-LIMONENE FROM CITRUS RIND Materials: One orange Water Steam distillation apparatus as shown below:

Procedure: Peel the skin off one orange and weigh it. Place the peel in a blender with about 150 ml of water and blend for about 30 sec. Transfer the slush to the 500 ml distillation flask, using an additional 50 ml of water as a rinse. The flask should be no more than half full or it may boil over during distillation. Heat the mixture to a boil and begin the


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distillation. Record the temperature after the first drop is collected and again after around 20 drops have been collected. At the beginning of the distillation, the mixture may come over cloudy as limonene separates from the water. Continue the distillation until at least 25 ml has been collected and the distillate coming over is clear. The continued presence of limonene in the distillate can best be determined by collecting approximately 1 ml in a test tube and looking for small oil droplets as the test tube is agitated. From: http://www.uwlax.edu/faculty/koster/limonene.htm

SYNTHESIS OF EXOTIC SOAPS

Materials: 10 g of oil or fat ∗ Sodium hydroxide, NaOH 95% ethanol , EtOH Solution 25 wt % sodium chloride, NaCl 250 ml beaker Double boiler apparatus Vacuum filtration apparatus ∗The fats or oils you can use are listed below with the resulting soaps :

Procedure: Dissolve 5 g of NaOH in 40 mL of a 50/50 water – 95% EtOH mixture. CAUTION: Aqueous sodium hydroxide solution is corrosive and it is very dangerous to the eyes. Skin burns are possible. Appropriate safety precautions must be ob- served.


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This alkaline solution was combined with 10 g of the fat source in a 250 ml beaker. Heat the mixture by partially submerging the beaker in a larger beaker of boiling water for 45′. During this heating period, stirr frequently the mixture. Then, add 40 mL of additional water–95% EtOH solution to make up for evaporation of the solution. The saponification mixture was poured directly into a cooled solution of 25 wt % aqueous NaCl. Stirr the mixture vigorously and allow cooling to room temperature. Collect the precipitated soap by vacuum filtration and wash with ice-cold water. The solid was allowed to air-dry and was then inspected for color, texture, and smell From: Otto Phanstiel IV, Eric Dueno, Queenie Xianghong Wang, “Synthesis of Exotic Soaps in the Chemistry Laboratory” - Journal of Chemical Education, Vol. 75 - No. 5, May 1998

FORMULATION OF A JOJOBA OIL BODY EMULSION

Notes: Dosage example: for 200 g the quantity of Montanov 68 is 10 g; so, the quantity weight could be 10,07 g (not necessarily 10,00 g). Every student signs in relation to the operation carried out.

MANUFACTURING GUIDELINE

OBJECTIVE : cosmetic formulation FORMULATION : jojoba oil body emulsion MANIFACTURING DATE : ..../…./........ EXPIRY DATE : ..../…./........ LABORATORY : N. ….. High school: …………………………………………………….

Manifacturing operations Signature

1. Heat A and B separately (70 °C).

2. Add B to A, under mechanical intense stirring. Carry on this process for 1 minute. 3, Begin the cooling process (at room temperature), under moderate mechanical stirring. 4. At 60 °C add C, and continue the cooling process under moderate mechanical stirring. 5. At 40 °C add D and F. Continue the stirring until the product be at room temperature.

Stage Raw materials Quantity (% weight)

Quantity for ….. g

Quantity weight (g)

Signature

A Montanov 68 5,00

Jojoba oil 10,00

Mentol 0,05

B Deionized water 77,95

Phenonip 0,50

C Sepigel 305 0,30

D Allantoin 1,00

Deionized water 5,00

E Parfum 0,20

Quality control: organoleptic characterist ics of f inished product Signature

……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………...

Operating technician (student) Approval of the person in charge of the laboratory (teacher)

Name and Surname: Name and Surname: Date and Signature: Date and Signature:


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From: “Biodiversity of aromatic plants” - Course “Plant Biodiversity and Health” (Barcelona, July 2008).

Task for the student: carry out a research to describe nature and functions of every component of the emulsion.

Exercise

In cosmetics, the foaming products have the primary function to eliminate dirty deposits located over the cutaneous surface and hair using detergents and/or emulsifiers. It is important to eliminate the dirt without damaging the natural cutaneous hydro-lipidic emulsion, a “barrier” necessary to guarantee healthy skin conditions and a nice external aspect. Below are listed some common components of the foaming products (left) and their functions (right) in the wrong order. Connect every component on the left column with the correspondant function on the right:

Components

Functions

Foam stabilizers They confer texture and appropriate flow characteristics to the finished product.

Rheological agents They adjust the pH product to values closest to skin pH

Conditioning agents They minimize the delipidization produced by frequent washing (fragility, loss of hair brightness as consequences)

Emollient They modify the final appearance of the product, giving it a pearly or an opaque aspect.

pH regulators (weak acids or basis) They stabilize of the foam volume and texture (creamy, smooth, persistent, very small bubbles ….).

Chelants They prevent the photodegradation of dyes, perfumes, ect ….. they avoid the formation of coloured complex.

Opacifiers/pearly agents They improve the easy combing, brightness and tact of hair.

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