Senior Science HSC course Stage 6 Lifestyle chemistry Part 4: What s growing on your skin? IncorporatingOctober2002 AMENDMENTS
Number: 43168 Title: Lifestyle chemistry This publication is copyright New South Wales Department of Education and Training (DET), however it may contain material from other sources which is not owned by DET. We would like to acknowledge the following people and organisations whose material has been used: Cross section of human skin under a microscope, courtesy of Selby-Biolab Part 3 p 21 All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith. Published by Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). State of New South Wales, Department of Education and Training 2008.
Contents Introduction... 2 The microflora of skin... 3 Microbe colonisation...9 Breaking the barrier...10 Acidity and alkalinity... 11 The ph scale...12 The ph of skin... 14 Skin and hair products...16 Testing skin and hair products...17 Summary... 20 Appendix 1... 21 Appendix 2... 22 Suggested answers... 23 Exercises Part 4... 27 Part 4: What s growing on your skin? 1
Introduction Your skin is host to a great number of micro-organisms. They live on skin oils, proteins and sweat. Your first instinct might be Yuck! Get rid of them! However, these microbes play an important role in body defence. The skin and hair products you use must be compatible with the skin s natural defense or damage and infections can result. In Part 4, you will be given the opportunities to learn to: define the term microflora and discuss the role of the microflora on skin in different parts of the body discuss the term ph in terms of its ability to describe the acidity of a substance explain the relationship between the natural ph of the skin and the action of microflora natural oil produced by glands in the skin perspiration. In Part 4, you will be given opportunities to: perform first-hand investigations to measure the ph values of a range of skin and hair products. Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October 2002. The most up-to-date version is to be found at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/index.html 2 Lifestyle chemistry
The microflora of skin The term microflora is an odd term. You should understand the term micro. It means very small or microscopic in size. You are not able to see micro-organisms with the naked eye. The second part of the term microflora is flora. What would you normally associate the term flora with? Think about florists, floral patterns, flora and fauna. Have you decided what flora should mean? Your answer should have been plants. Automatically your brain should think that microflora means microscopic plants, right? Wrong! In this instance, flora appears to take on the meaning of an ecosystem or a group of organisms surviving together. For this reason, the term microflora is defined as microorganisms surviving as microscopic communities. 1 Write the correct definition for microflora in the box below. Your mouth, nose and ears all contain different varieties of microflora. Most microflora on and in the body are bacteria. You will be researching the natural microflora existing on the surface of your skin and what their effects are. Part 4: What s growing on your skin? 3
2 Use the glossary to define the following terms as they will help you understand the Microflora section of the Skin audio tape/internet audio files. bacteria staphylococci cocci microbes micro-organisms sebum epidermis keratin Think about the skin on different parts of your body. Colour the parts of the body below where you think bacteria might exist. Remember, you are focusing on where bacteria might exist on the surface of your skin. 4 Lifestyle chemistry
You will see how accurate your predictions were as you listen to the following audio. Listen to the Microflora section of the Skin audio tape/internet audio files, then carry out the activities which follow. You may need to listen to the tape several times in order to answer all the questions. 3 Why is skin not considered to be uniform? 4 What conditions favour the growth of micro-organisms? 5 All organisms require nutrients to live. What nutrients are available on the skin surface for micro-organisms to utilise? 6 Why is the skin an unstable site for microbes to colonise? 7 What effects can the action of microflora have on the skin surface? Appendix 1 contains a species list of microflora found on the surface of human skin. Use this list to help you spell the species names stated in the audiotape for the following question. Word processed genus and species names are italicized eg. Staphylococcus aureus. The first name is the genus name and must start with a capital letter. The second name is the species name and begins with a lower case letter. You might remember from preliminary work that when hand writing genus and species names, you must underline each separately eg. Staphylococcus aureus. Do this for the species column for question 8 on the following page. Part 4: What s growing on your skin? 5
8 List the species of microflora in the table below and indicate where they are commonly found on the body. Disregard the centre column as you will complete this with question 9. The first one has been done for you. Species of microflora Group Part of body found Staphylococcus epidermidis upper body 9 Classify each of the micro-organisms identified above into groups. The classifications are: bacteria, fungi and mites. Write these names in the middle column in the above table. All cocci and bacilli are forms of bacteria. Mould and yeast are forms of fungus. Refer to Appendix 1 to help you classify each species. 10 Look at the diagrams of cocci, bacilli and moulds on the following page, then answer the following questions. 6 Lifestyle chemistry
coccus diplococcus staphlococcus Examples of cocci bacteria viewed under a high powered microscope. Examples of bacilli bacterium under a high powered microscope. Example of a mould under a light microscope (not as high powered). 10 a) What do the diagrams of cocci bacterium look like to you? b) Describe what bacilli look like in one sentence. Part 4: What s growing on your skin? 7
c) Explain the difference between moulds and bacteria when viewed under a microscope. 11 For each of the body parts inhabited by microflora in question 8, indicate the microflora present on the diagram of a person on the following page. The places where particular species of microbes are found on human skin. Check your answers. 8 Lifestyle chemistry
Microbe colonisation More recent studies have found that microflora of the skin can be divided into two groups: resident microflora and transient microflora. Resident microflora are found on the skin surface and are thought to reside in the sebaceous glands under the skin. Bacterial counts are higher where more oil is being produced by sebaceous gland activity. Resident bacteria such as Staphylococcus epidermidis are thought to play an important role in protecting the individual from more pathogenic or disease-causing bacteria. It has been found that an area of skin colonized by relatively harmless bacteria inhibits the growth of other microbes. In this way, the body is protected from skin diseases and disorders by the microbes living on the skin surface. Transient microflora have two sources. The first source is the external environment eg. soil, water and air. Contact with soil, water and air transfers any microbes present to the skin surface. The second source is the natural microflora that comes out of body orifices such as the nasal passages, ear canals and anus. Micro-organisms are transferred to various parts of the body by the hands. Once these organisms are transferred to a suitable site, they can flourish. Transient microbes can cause diseases such as diarrhoea and meningitis. Washing with soaps and detergents removes many surface microbes, along with a great deal of the oily protective layer. However the remaining resident microbes quickly grow and reproduce to colonise the clean skin, restoring the natural microflora of the skin. Part 4: What s growing on your skin? 9
Breaking the barrier Have you ever had a rash or skin irritation? Your skin defence could have been breached. Have you ever had tinea on your feet? If so, your skin defence has been breached. There are many ways your skin defense can be broken. You may have recently broken your skin defense barrier without realising. Have you burnt or cut yourself recently? You may have shaved an area of skin; grazed yourself; or handled chemicals such as turps without gloves. All these common activities can alter the protective layer of skin. A change in diet can cause a change in skin acidity, lowering your defense to harmful micro-organisms. Even washing can remove natural microflora, allowing more harmful microbes to colonise the area. Has your skin become damaged over the last two weeks? Record the damage, how it occurred, the part of the body and any resultant infections or skin irritations that occurred. Damage to skin How the skin was damaged Part of the body Resulting infections or irritations As you have seen, the protective skin barrier is easily damaged. Harmful microbes living on the skin surface can easily penetrate a wound, causing an infection. The use of products that are incompatible with the skin surface can cause skin damage, alter the natural acidity of the skin or alter the natural microflora of the skin. 10 Lifestyle chemistry
Acidity and alkalinity Carry out the following activity to review ph in terms of acidity and alkalinity. 1 a) Write the numbers 0 to 14 on the scale below. b) On the line next to 7, after the arrow, write neutral ph. c) On the line next to 1, write strongly acidic. d) On the line next to 14, write strongly alkaline. e) Next to the arrow pointing up, write increasing acidity. f) Next to the arrow pointing down, write increasing alkalinity. 0 Æ Ø 14 Well done. You just created a ph scale. Part 4: What s growing on your skin? 11
The ph scale measures acidity and alkalinity from 0 to 14. From the previous activity you should understand that a ph number lower than 7 indicates an acid and a number greater than 7 indicates an alkali. A ph of 7 is neutral. Most organisms prefer to live in ph neutral conditions (7) as acids and alkalis tend to damage cells and destroy tissue. A ph of 4 is more acidic than a ph of 6. A ph of 10 is less alkaline than a ph of 12. The stronger the acid or alkali, the more dangerous it is as it has the ability to corrode substances. 0-2 is a strongly acidic; 3-4 is an acid; 5-6 is weakly acidic; 7 is neutral; 8-9 is weakly alkaline; 10-11 is alkaline; and 12-14 is strongly alkaline solution. 2 Indicate the acidity or alkalinity of the following ph values using the above information. a) 4 b) 6 c) 13 d) 10 e) 7 f) 9 g) 1 Check your answers. The ph scale You may have received some ph paper from your teacher with this part. ph paper turns a different colour depending on the acidity or alkalinity of the substance it is testing. You will be investigating the ph range 1-11. You will need to match your ph paper with a colour to determine the ph of the substance you are testing. 12 Lifestyle chemistry
You are about to create a colour scale by which you can gauge colour changes in the ph paper. Use coloured pencils or textas to colour in the blank boxes below with the shade indicated below each box. You may need two different colours to create the correct shade in each box. Colour maroon red deep orange orange light orange yellow/mustard light green grass green dark green deep blue/green dark blue Shade ph 1 2 3 4 5 6 7 8 9 10 11 You will be using the colour scale you just made for experiments later in this part. You may need some practice to read the correct ph from the scale and determine if it indicates acidity or alkalinity or neutrality. State the ph of the following shades of ph paper and the acidity or alkalinity they indicate. You may use the boxed information on page 12 to help you determine acidity and alkalinity. The first one has been done for you as a guide. Shade of ph paper ph Acidic/alkaline dark green 9 weakly alkaline orange deep blue/green deep orange light green maroon yellow/mustard Check your answers. Part 4: What s growing on your skin? 13
The ph of skin Do you recall seeing lipsticks in shops that are green or blue, but change colour when you apply them? The lipsticks change colour due to the acidity of the skin. Often two people can apply the same lipstick, but it will turn a different colour on each person due to the different acidity levels of each person s skin. This lipstick is not to be confused with normal lipstick which stays the same colour when applied. Many factors can affect the ph of your skin. Listen to the Skin ph section of the Skin audiotape/internet audio files. You may need to listen to the tape several times to answer the following questions. 1 What is the normal ph range of human skin? 2 Explain the normal ph range in terms of acidity and alkalinity eg. strongly acidic to alkaline. _ 3 What main factor causes skin to become acidic? 4 What parts of the body have different ph values? 14 Lifestyle chemistry
5 Are the ph values that are commonly associated with the parts of the body outlined in question 4 higher or lower than the rest of the body? Does this mean they are more acidic, more neutral or more alkaline? 6 Are more or fewer microbes associated with the underarms, forehead, toe webs and the soles of the feet? 7 There are two theories why the underarms, forehead, toe webs and the soles of the feet have higher ph values. Explain those two theories below. a) b) 8 What is the acid mantle? 9 What is thought to be the function of the acid mantle? 10 Some scientists believe that the acid mantle has little to do with the microflora of skin. What do they suggest has a greater impact on microbe populations on the skin surface? Check your answers. Part 4: What s growing on your skin? 15
Turn to Exercise 4.1 at the back of this part to discuss the role of microflora in different parts of the body.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Skin and hair products 1 Fill in the missing words in the passage below. Imagine you are a microbe living on a person s face. You are comfortable living with a ph of 6. Suddenly, the person their face with a substance that has a ph of 8. The skin has changed from weakly to weakly. You and your friends cannot survive above a ph of 7.5. You die, along with your friends. The skin surface is no longer acidic. The mantle has been altered. Different are more able to colonise the area you were living on. They may cause on the skin surface. Write the questions for the following answers. 2 Your clean skin could become colonised by different, microbes if the ph was changed. These microbes could cause disease. 3 Products used on the skin should have a similar ph to that of skin to minimise disruption of the acid mantle. The acid mantle protects the skin from colonisation by harmful organisms. 4 Substances that are acidic or alkaline have the ability to destroy living tissue. Products used on the skin with a ph below 5 or above 9 have the ability to damage the skin. The protective layer of skin can allow the entry of harmful organisms once damaged. Rashes, skin irritations, infections and disease can result. Check your answers. 16 Lifestyle chemistry
Testing skin and hair products 1 Next to the bullet points below, write down all the skin and hair products you have at home. Include as many as you can such as: soaps; cleansers; shampoos; deodorant, hair spray; ointments; heat rub; shaving cream; moisturisers; perfume; sunscreen after shave; and lipsticks. You may need to ask your family what products they use on their skin. Do not include dry substances such as eye shadow and blusher as they are not moist enough to change the colour of the ph paper. Were you surprised at the range of hair and skin products in your house? Did you have enough room to record them all? Skin and hair products are used by people on a daily basis. Have you ever thought about how compatible these substances are with your skin? Do you think they could have the ability to damage your skin or lower your defence to infection? You are about to test the ph of skin and hair products in your home and evaluate their compatibility with skin ph. Aim To measure the ph values of a range of skin and hair products. Apparatus Approximately 20 cm of universal ph paper from your teacher. The ph colour scale from page 13 or the one supplied with ph paper Ten skin and/or hair products. Ten cotton buds or pop sticks (ice cream sticks). Part 4: What s growing on your skin? 17
Method 1 Collect ten or more skin and hair products from around the house. You listed these earlier. Record the product type and brand for each of the substances. 2 Being careful not to wet or contaminate the ph paper, roll it out on top of a sheet of paper or absorbent paper. The paper will protect the table surface. You may need to weigh down each end of the ph paper to keep it flat. If you have pieces of ph paper instead of a length of paper, place these on a clean A4 sheet of paper. You will need to keep track of what substance is being tested on what part of ph paper. Write the substance on the paper next to the ph paper. Refer to the diagram opposite. 3 Dip a cotton bud or a pop stick into the first substance to be tested. Remove any excess and dab the substance onto the place allocated on the ph paper. Be careful to apply only a small amount of the substance as the substance may spread, contaminating other sections. Use a different cotton bud or pop stick for each substance being tested. Some substances may need to be wetted first or lathered before sampling eg. soap. If so, be careful not to contaminate the ph paper with water drops or wet hands. 4 Repeat step three with the remaining substances. 5 When all substances have been applied, use your ph colour scale from page 13 to determine the ph of each substance. Record these in the results table. Some substances such as foundation may mask the ph colour. Try turning the ph paper over to observe the colour absorbed underneath. 18 Lifestyle chemistry
Results Complete your results in the table below. An example is provided. Skin or hair product Brand ph colour ph soap sunlight yellow/mustard 6 Discussion Fill in the missing ph values and product names based on your results. a) The substances tested ranged from to in ph. b) was the most acidic substance with a ph of and was the most alkaline substance with a ph of. c) Generally the hair products tested range in ph from to. d) ph values of the skin products tested range from to. Turn to Exercise 4.2 at the back of this part to draw your conclusions on the ph values of a range of skin and hair products.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 4: What s growing on your skin? 19
Summary 1 Write three things you are unsure of about skin microflora _ 2 What do you need to do to gain an understanding about those points outlined in question 1? 3 Write three questions you would ask your teacher about the ph of skin if you were in class and did not fully understand the concept. 4 What do you need to do to gain an understanding about those points outlined in question 3? 5 a) What ph ranges do the skin and hair products have that you tested? b) How compatible are these ph ranges with skin ph? 20 Lifestyle chemistry
Appendix 1 Microbes commonly detected on human skin Gram-positive cocci Staphylococcus aureus Staphylococcus auricularis Staphylococcus capitis Staphylococcus cohnii Staphylococcus epidermidis Staphylococcus haemolyticus Staphylococcus hominis Staphylococcus saccharolyticus Staphylococcus saprophyticus Staphylococcus simulans Staphylococcus warneri Staphylococcus xylosus Micrococcus luteus Micrococcus lylae Micrococcus nishinomiyaensis Gram-positive bacilli Corynebacterium jeikeium Corynebacterium urealyticum Corynebacterium minutissimum Propionibacterium acnes Propionibacterium avidum Propionibacterium granulosum Brevibacterium epidermidis Gram-negative bacilli Acinetobacter calcoacaticus Yeasts (Fungi) Malassexia furfur Moulds Trichopyton mentagrophytes Mite Demodex folliculorum Micrococcus kristinae Micrococcus sedentarius Micrococcus roseus Micrococcus varians Part 4: What s growing on your skin? 21
Appendix 2 Example answer to Exercise 4.2 1 Include your used ph paper as shown above. 3 The skin and hair products tested ranged in ph from 5 to 7. Products within a ph range of 4 to 8 are compatible with skin as skin has a ph range of 4 to 8, however most skin has a ph of 5.5 to 6. The moisturisers, deodorants, soaps and hand creams tested are compatible with skin. Any substances used on skin with ph values below 4 and above 8 have the potential to change skin ph, thus altering the acid mantle. This could allow colonisation of the skin surface by harmful micro-organisms and result in skin irritation or infection. This answer is fictitious and does not indicate actual ph ranges of skin and hair products. 22 Lifestyle chemistry
Suggested answers The microflora of skin 1 Microflora means micro-organisms surviving as microscopic communities. 2 Bacteria: single-celled procaryotic organisms belonging to the protist kingdom. Staphylococci: cocci bacteria appearing in grape-like formations. Cocci: sphere-shaped bacteria. Microbes: micro-organisms. Micro-organisms: microscopic, often single-celled, organisms. Sebum: oil produced by sebaceous glands in the dermis. Epidermis: outermost layer of the skin which protects the underlying tissue, forms a barrier from heat loss, water loss and micro-organisms. Keratin: tough protein present in the epidermis of vertebrate organisms. 3 Skin varies from dry areas to moist areas and wet areas, therefore conditions on the skin surface are not uniform. 4 Micro-organisms prefer moist environments. 5 Sweat from sweat glands contains sodium chloride and lactate. Sebum, an oily substance from sebaceous glands next to hair follicles, also provides nutrients that encourage micro-organisms. 6 The skin surface is constantly losing clumps of dead skin. Any microbes on the skin surface are lost. The ph of skin is slightly acidic at 5.5 ph. Most microbes prefer a ph neutral environment of 7. For these reasons, only specific microbes are able to survive on the skin surface. 7 The action of microflora on the skin causes the oil on the skin to become acidic. Microbial action on sebum releases smelly gases, commonly referred to as body odour. Part 4: What s growing on your skin? 23
8,9 Species of microflora Group Part of body found Staphylococcus epidermidis bacteria upper body and face Staphylococcus hominis bacteria legs and arms Micrococcus luteus bacteria head, legs and arms Corynebacterium jeikeium bacteria arm pit Propionibacterium acnes bacteria face and shoulders Propionibacterium avidum bacteria arm pit Propionibacterium granulosum bacteria side of nose Brevibacterium epidermidis bacteria in between toes Acinetobacter calcoaceticus bacteria groin and front of elbow Malassezia furfur fungus scalp, ear and back Trichophyton mentagrophytes fungus feet Demodex folliculorum mite face 10 a) Cocci look like small round spheres like ball bearings. Staphylococci resemble a bunch of grapes. (Other answers are acceptable.) b) Bacilli look like small rods. One bacillus resembles a chain with rods linked together. (Other answers are acceptable.) c) Moulds have threads joining each mould head containing spores. Bacteria are much smaller, needing a higher power microscope for viewing and are individuals or groups of spheres or rods. 11 Refer to the table above to locate areas particular species of microbes are found. 24 Lifestyle chemistry
Acidity and alkalinity 1 0 strongly acidic 1 2 3 4 5 6 increasing acidity 7 neutral ph 8 9 10 11 12 13 Æ Ø 14 strongly alkaline 2 a) 4 is acid b) 6 is weakly acidic c) 13 is strong alkaline d) 10 is alkaline e) 7 is neutral f) 9 is weakly alkaline g) 1 is strongly acidic increasing alkalinity The ph scale Shade of ph paper ph Acidic/alkaline orange 4 acidic deep blue/green 10 alkaline deep orange 3 acidic light green 7 neutral maroon 1 strongly acidic yellow/mustard 6 weakly acidic Part 4: What s growing on your skin? 25
The ph of skin 1 The normal ph range of human skin is 4 8. 2 The normal ph range of human skin is acidic to weakly alkaline. 3 Sweat released from sweat glands is released at a ph of 5, causing the skin to have an acidic surface. 4 The underarms, forehead, between the toes and the soles of the feet have different ph values than the skin on the rest of the body. 5 The underarms, forehead, between the toes and the soles of the feet have slightly higher ph values, meaning they are more neutral than the rest of the body. 6 More microbes are associated with the underarms, forehead, toe webs and the soles of the feet than the rest of the body. 7 a) The high microbe populations metabolise sweat, sebum and keratin. Their wastes cause the higher ph levels. b) Sites such as the underarm are moist and separate to the rest of the body. For this reason, the ph is higher and more microbes are able to survive there as a result. 8 The acid mantle is the protective layer on the surface of the skin. 9 The acid mantle is thought to prevent more microbes from colonising the skin surface, as most microbes prefer a neutral ph. 10 Some scientists suggest that electrostatic forces between the skin surface and microbes determines skin microflora populations more than the acidity of skin. Skin and hair products 1 Imagine you are a microbe living on a person s face. You are comfortable living with a ph of 6. Suddenly, the person washes their face with a substance that has a ph of 8. The skin has changed from weakly acidic to weakly alkaline. You and your friends cannot survive above a ph of 7.5. You die, along with your friends. The skin surface is no longer acidic. The acid mantle has been altered. Different microbes are more able to colonise the area you were living on. They may cause disease on the skin surface. 2 What could happen to your skin if the ph was changed due to cleaning products? 3 Why is it important that products used on the skin be a similar ph to the skin surface? 4 What result could products used on the skin have if they have a ph lower than 5 or greater than 9? 26 Lifestyle chemistry
Exercises - Part 4 Exercises 4.1 to 4.2 Name: Exercise 4.1 Choose two of these body parts: face arm underarm scalp back feet (and toes). For each of the two body parts you chose: state all the species of microflora present on the skin in that part of the body (if you chose the arm, you must include the species existing on the inside of the elbow) clearly draw an example of one of those species, indicating the species name (the species name must be scientifically written) explain the source of nutrients for the micro-organisms on that part of the skin explain the effects of microorganism activity eg. smell, acid environment. a) body part species of microflora present diagram and label of one microorganism present at this site. Part 4: What s growing on your skin? 27
source of nutrients effects of micro-organism activity b) body part _ species of microflora present diagram and label of one microorganism present at this site source of nutrients effects of micro-organism activity _? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. 28 Lifestyle chemistry
Exercise 4.2 a) Attach your ph paper with this section complete with product names. Appendix 2 includes a graphic showing what your teacher expects. Put the ph next to the name of each substance tested or include a results table with this information. b) Comment on the accuracy of your ph readings of different substances used on the skin given that you made your own ph scale. c) Most skin has a slightly acidic ph of 5.5 or 6. You have tested the ph values for a range of skin and hair products. In the space provided: outline the range of ph values you observed discuss the compatibility of skin and hair products with regards to ph outline possible consequences of skin and hair products that are too acidic or too alkaline. You may refer to Appendix 2, which provides an example answer to this exercise. Part 4: What s growing on your skin? 29