effect of salt on the rate of respiration of yeast · effect of salt on the rate of respiration of...

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Effect of salt on the rate of respiration of yeast

Science

Year 10 2015 ASSESSMENT TASK 3

Chaltu Etana

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Contents

Logbook 3

Background 18

Aim 19

Hypothesis 19

Table of variable 20

Materials 21

Method 21

Result 24

Discussion 26

Conclusion 28

Appendix 29

Reference 30

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Student Research Project – Logbook

Name: Chaltu Etana

Teacher: Ms Chalmers 7/6/15 -Today I went through the assessment task and started really looking in to the requirements and understanding the task. I went through and choose my top four experiments that I was mostly interested in. I told mum that I got science assessment task and I was strictly told not leave it until last minute so I immediately started researching. Firstly I went through my year 8 book and found scaffold for practical report, which was little bit different so I compared it and thought to use booth. I also found my year 8 SRP that was simpler but still decided to use it as guidance. By the end of the night I kind had an idea on where to go from here and what to do. 9/6/15 -After setting up a foundation on Sunday I started researching on my top four chosen experiments. What is the effect of heat when dissolving sugar or salt? What is the best way to stop nails rusting? Does fruit keep better in the refrigerator? Compare samples of soils for soil quality. After looking through the experiments and researching, I made the decision to change my mind and look for different experiments that I really would enjoy and also challenge myself. Any thing in the field of chemistry, medicine and health were I was aiming at, which I’m looking forward to explore variety of challenges and knowledge. 10/6/15 -After long search of experiments while being in and out of my room I managed to find one in the field of medicine /health which I’m really excited about. Can’t wait to show my teacher and see what she thinks about it. The topic is to see the “effectiveness of garlic in fighting bacteria”, mum said garlic was good for health but I never knew it was this powerful to be used in fighting bacteria. For today I’m going to leave it here and research it tomorrow in little bit depth (http://www.all-science-fair-projects.com/project1098_39.html) 11/6/15 -Today I went little bit in depth in researching background information of the topic. So that I have a clear understanding of the effect that garlic has on bacteria but also the amount of antibiotics that it contains. I went through the materials I needed and laid out what I need from home and which material I have to get from school. I printed out the information so that it’s easy for me to work with and to highlight and take notes. 12/6/15 -I just emailed my teacher my topic and material list for the experiment. I include material needed so that she can give me a feedback on what she thinks and also if some of the materials I need from school are available. I have a feeling I might not find all materials I need after googling some of them just because I wasn’t really sure on what they are. I sent her the email because I didn’t want to research to much

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and find out I can’t continue with the chosen topic because I could find the right equipment. 13/6/15 -I got a reply from my teacher and she said that I couldn’t do the experiment the school doesn’t have two of the materials I needed for my experiment. So I started researching for new experiment to work on but still in the field of health/medicine or chemistry. I researched a lot for new one so that I can run one trial on next week and have enough time to work on the assessment and run one trial week ten. I got really lucky and found an experiment I thought will be great to work with, the materials needed are things I know we have at school. The topic is “Saturated fat levels in different types of cooking oil” Also I showed mum the new experiment and said to do the new one because knowing that the materials I need are found at school makes my assessment easier. So I’m going to tell my teacher on Monday that I have found new topic for my experiment and see what she thinks. 15/6/15 -Today in class my teacher went through how we should use our logbooks and what information should be included even though I’ve already started it was good to know what was expected in the logbook. We were told that we need to fill in our part one of the assessment task that helps the teacher know what we’re doing and to help us get started. Then Ms. Chalmers came to me and started talking to me about how we can change some aspect of my original and use anything we have at school to measure the grow of bacteria and fungi from different location. After she mentioned the new Idea I was so confused and lost. I got what she meant but I didn’t really understand it really well and my mind is divided on the two experiments. I thought the original experiment was really interesting than my new Idea as the new one was something I can understand and work with it really well. Since the conversation I had with her at school I really wanted to do my original experiment with little bit of change but also I like my new idea. I got home and spent so much time trying to choose which one I should do and also emailed Ms about it because it was just annoying and driving me crazy. I also researched about how a logbook should look like and what it should contain. I found some helpful information and saved them on my bookmark to work with it. I’m really confused right now because i’ve planned of doing my first trial thursday or friday but i don’t know if i can get my mind set in one them and do my background information and make a method by then. 16/6/15 -Today i had a talk with Ms. Chalmers about my two topics for the experiments; “ effectiveness of garlic in fighting bacteria” (old)“Saturated fat levels in different types of cooking oil”(new). She explained to me that we don’t have the material needed to undertake the test but that we can do it with little bit change. She drew on the whiteboard analysing how bacteria and fungus are measured, the equipments used. It was really interesting to see her explain but i figured it was a little complected and she agreed also. So we then looked through the new topic “Saturated fat levels in different types of cooking oil” and it sounded easy but it contained lots of interesting facts behind it. Ms. Chalmers talked about about cell membrane and the structure of the layer and how it is affected by saturated fat. High cholesterol has a straight block of saturated fat and medium cholesterol allows a right movement with

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zigzag shape. At the end of our talk i confidently choose to do “Saturated fat levels in different types of cooking oil”. http://www.all-science-fair-projects.com/project1143_129.html https://docs.google.com/presentation/d/1kXOw-mX_4dgQGG6BrHO6ydVKljv0Sx7I-v1bpG5QK1k/embed?hl=en&size=s&slide=id.g5cfbc7eae_05 http://www.nutristrategy.com/fatsoils.htm 17/6/15 - Today i filled in part one of the assessment task and looked more into the effect of iodine on saturated fat. Based on most of the information the structure of saturated fat contains lots of hydrogen and less carbon and when the iodine is added it replaces some of the hydrogen.

Figure: 1.0

18/06/15 -‐ Today i typed up my logbook because i have sometimes written it on my dairy so i transferred it to my word doc. After that i did a bit of researching looking for information on this topic from the people that have already done it. I compared them and the first website i have been using as a guide was misleading and done very poorly, the basic information like the aim and materials was good but the rest was just messed up even the method. comparing different websites got me confused even at the point where my variables were mumble jumbled. I had to even ask my teacher what if i should change my variables. I used two prezi presentation that students already did and they were helpful in

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some way but i had to make up my mind and take charge then to follow the information written by another student because they were not reliable and misleading sources. I asked my teacher if i can have my first trial tomorrow and she said she will look in to it but that it was too soon and might not work out. I understand if i can’t do it tomorrow because we were told that we need to be organised earlier. 19/06/15 -‐ My teacher came in in homeroom and told me that i can’t do my trial today which i accepted gladly because i was not prepared 100% but i decided to have my trail on monday. I changed some of the variables and hypothesis but when i showed my teacher she told me the independent variable needs to be types of oil and she looked at my hypothesis she gave me some feedbacks which helped me make up my mind. I did a bit of work in homework club and looked the saturated fat levels for different kind of oil and surprised myself because i always thought coconut oil was healthy but it was the least healthiest of all with 92% of saturated fat. Olive oil has more saturated fat than canola oil which i was stunned to find out as olive oil is always used as the healthiest oil. 21/06/15 -‐Today i went on my laptop to check and get things ready for tomorrow's first ever trail of my experiment and found out that my background information was gone. It didn’t save on word doc so i made new folder for science in google drive so that i can do all my work on that and never worry if it is saved or not. So that i can make up the loose i had to research and find information which was not that hard since i can remember certain things and my history on my laptop is still there. 22/06/15 -‐Today i did my first ever trial and it didn't go how i wanted or how it was meant to turn out. There were no changes that took places even after 19mins, i was so confused because in most of the research i did people who had done it said it worked. In the other hand the iodine in the coconut oil made no movement like it did in the rest of the oil which didn't surprise me because it contained the highest saturated fat which was 92%. Based on my research there should have been a change in less than 3mins but nothing happened after sitting there for 19 minutes, i thought there was a colour change but it was just because of the test tube. So tried mixing the oil and iodine but nothing happened. I told Ms Charmers and the lab technician that the iodine was supposed to be purple so we added the concentrated iodine and left it to see if there was any change overnight. During my morning class we through some components needed in our students research project. We looked at referencing and used an information on

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bbc website about accuracy and reliability, which we also used the information to learn about accuracy and reliability and how to summarize information when writing out report. We also went through Variables and errors and mistakes, Ms showed us a powerpoint on error and mistakes which i downloaded to help me with my research and writing the report. Trial one

Figure 1.1

23/06/15 -‐This morning i went to the science lab hoping there was something that happened in the mixture of iodine and the oils but instead the coconut oil turned to sold and there was no change whatsoever to the rest of the oils. The iodine just sata at the bottom and i was so confused and stunned on why there were no changes to the oil or the presence of the iodine in the oil. I was really upset a little but good thing i did the test before the holidays. I came to the conclusion that i have to find another experiment before the end of the week and reseach it so that i can get approval from my teacher. I went home and found some possible ideas but i needed to ask my teacher and talk to her. The ideas were “effect of salt on the rate of respiration of yeast” and “where are the most germs in the school”. I like the ideas but i really didn't want to drag this assessment any longer as i’m a slow workers. 24/06/15 -‐I had a talk with Ms chalmers about my two ideas and she told me to talk to the lab technician if i’m doing “where are the most germs in the school” that was because i needed the agar plate they need to save some for me before they pack the equipments away. So i thought about if i really wanted to do it next term or if i should work through the holiday put in perspective that i’m slow worker. So i made up my mind that i was going to do the “effect of salt on the rate of respiration of yeast”. I choose this because i really wanted to do some part of it in the holidays even though i’m away for half of the time but it’s really helpful for me to do this experiment as i have all the materials at home. At lunch

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time i printed out some information on the experiment and similar experiments done with different kind of aim. I’m looking at how salt effect the rate of respiration of yeast. so with the mixture of sugar, warm water and yeast i’m going add salt and see how it affect the producing of carbon dioxide. I had a talk with my teacher on how to measure the amount of Co2 produced and she said to use circumference and to use measuring type. 25/06/15 -‐ Today i had a talk with Mrs Hayden and Ms charmerce on how i should measure my result if i wanted to calculate the volume of Co2 produced and so i found out the formula for finding the volume of sphere. Then Ms Charmerce gave wrote down the formula to find the riduc of the sphere which i need to find the volume of the Co2 produced. After that i tried to look at my printed information and started to sort out what i need to buy from shops and what i have at home already as my class had a free period that lesson. 30/06/15 -‐Today i went through my method, aim and hypothesis to help me research for my background information as i want to start my trail as soon as i can. I went through lots of websites and one thing that stood out was that there is a yeast infection! https://www.exploratorium.edu/cooking/bread/bread_science.html This helped me understand about yeast and it’s properties and the website had lots of likes that lead me to different useful informations. Yeast belongs to the group of organisms called fungi. Yeast is tiny and one gram holds about 25 billion cells. That amount of fungi can churn out a significant amount of carbon dioxide. I’ve learnt so much interesting information which i’ll put it in my background information and i’m 100% grateful i choose this experiment. 2/7/15 -‐Today i finally got the time to undertake my first trial to test the effect that salt has on the rate of respiration of yeast. I had really good time see the changes and the effect of salt on production of carbon dioxide. Even though i’m still researching why this is happening it was so good to actually see the differences between each bottle. I had hard time setting up the area for the practical test, i didn’t know that i actually had that much equipments and materials i needed. To make it easier for me i used one of the laundry baskets to keep and hold my paperwork and all materials needed expect the water and the bottles and brought it with me to my study room just to feel safe from my little brothers. I actually took another basket to hold my bottles after a little bit of thinking and hid them in the dining room where no kid can see it because i don’t

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want have to loose them with their marking on them. Before even starting anything i started giving the balloons a stretch and one of them broke and that just scared me and got me worried what if that happened before i collect my measurements and then i noticed the measurement of the big jug and little judge was not equal as the big jug help more water than the little jug even though they were both measured 200ml. So i just went with the little jug and used to measure the waters to be used for the trail and used the big one to mix up the water. I’m not really sure if my results would be accurate due to parallax effect i think i might effect the result from hom i look at the jug, the side, the angle and the amount of concentration given to each read. I had waters spilling in the kitchen because there was a crack in the big jug and which actually nearly drowned my Ipad, which is hazard to electronics i use and my safety. other than that today's work could not have gone any better.

Figure: 1.2 Observation: During my 1 hour long trail i’ve found out that yes salt does effect that salt on the rate of respiration of yeast as there were changes when different amount of salt were put into mixture of sugar, warm water and yeast. Obviously the first bottle with no salt produced the most carbon dioxide (22 cm) with 3cm difference from the second bottle ½ teaspoon of salt that produced (19cm). The third bottle had thick foam than all of the bottles and produced (17cm. Bottle 4 and 5 has thin mist and produced very less Carbon Dioxide than the rest.

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Result table for trial 1 part 1( Bottle 1-‐5)

0 Teaspoons of salt (control)

½ Teaspoons of salt

1 Teaspoons of salt

1 ½ Teaspoons of salt

2 Teaspoons of salt

circumference of gas produced (cm)

22 19

18 11 12

Figure: 1.3 Result table for trial 2 part 1( Bottle 1-‐5) I did a second trial today and i’m really happy about this one as it really assured me that my hypothesis is in the right direction and my result decreased as it was meant to. This time there was more carbon dioxide produced throughout the five bottles but the first bottle still produced the largest amount.



1 Teaspoons of salt


2 Teaspoons of salt


23.5 17.5 17 15.5 14

Figure: 1.4 3/06/15 -‐Today i wanted to do my second trial of part one as did a trial last night and wanted to compare the result with today's outcome. Today i didn’t have much trouble as i knew where everything goes and had already done it last night and had every single material in good condition including jug and balloons. It only took me 5mins to start my first bottle and everything from that moment went very smoothly to the end of the 1 hour mark.

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Result table for trial 3 part 1( Bottle 1-‐5)



1 Teaspoons of salt


2 Teaspoons of salt


23 19.5 20.5 17 13.5

Figure: 1.5 Observation: On today's trail same changes took place but with a bit of twist as the third bottle with the 1 Teaspoons of salt produced more carbon dioxide then the second bottle with only had ½ Teaspoons of salt. I was surprised when i started measuring and got these results because this just proven to me why science experiments should be repeated at least 3 times specially this one. Even though it was only 1 bottle it could eventually mislead the true result if i only went with this trail. I found out that the more carbon dioxide is produced the thicker the mist is at the bottom of the bottle. 6/07/15 -‐Tonight i did my part two of the test which included bottle 6-‐10 which was more difficult to comprehend than the part one (1-‐5) as it was harder to produce carbon dioxide this time as the bottle have a lot more salt than before. I was really looking forward to today's experiment at the start because this is my first time completing bottle 6-‐10 than my mood changed as no change was shown for very long period of time. Today I’m going to undertake three trails, one test at a time as i have free time. Result table for trial 4 part 2( Bottle 6-‐10 )


4 Teaspoons of salt

6 Teaspoons of salt

8 Teaspoons of salt

10 Teaspoons of salt


7 4 nil nil inhaled

Figure: 1.6 Observation: I started doubting myself half way through the 1 hour mark as nothing much has changed, there was a change to bottle 6 and 7 but it was very very minimal. I was hoping that there were changes by the end of the 1 hour

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mark but nothing much changed and i ended up with no result for the last three bottle. It was understandable since they had very high amount of salt levels but i’m not convinced yet and the 10 bottle inhaled and sucked any air that was in the balloon and the bottle had irregular shape. I’m confused whether i should take it for negative or positive thought. So i’m did the next trial after 5 mins of cleaning up and getting everything i wanted back to normal. Result table for trial 5 part 2( Bottle 6-‐10 ) 3

Teaspoons of salt (control)

4 Teaspoons of salt

6 Teaspoons of salt

8 Teaspoons of salt



6.5 5 nil nil nil

Figure: 1.7 Observation -‐I carefully placed the ingredients in all five bottles and hoped for the best. I got worried as no change was noticeable but i still took some photos. I did not notice any change until the last 15 minutes of the experiment and the last three bottles are flat unlike the the last trail. So when the time was up i measured them all and there was a bit of change as bottle seven (4 teaspoon of salt) had produced a little more carbon dioxide then the last trail. I’m hoping after conducting my last trail the mean of the whole result would actually reflect my hypothesis. Result table for trial 6 part 2( Bottle 6-‐10 ) 3

Teaspoons of salt (control)

4 Teaspoons of salt

6 Teaspoons of salt

8 Teaspoons of salt



6 5 nil inhaled inhaled *

Figure: 1.8 Placing the ingredients in all five bottles was fine so i just sat down hoping for the best. Throughout the one hour time frame i took some photos as usual but i took so many this time just to make sure i had an evidence in what took place

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throughout my trail. This time no change was seen until after 40mins from starting and but it started to expend little by little. By the end of the 1 hour mark the result i got was not satisfying and i thought it had the same amount of circumference when i look at it after tying it together and after measuring it, it had a little difference with my first trail. So that kind of convinced me to believe that if i got similar result in my two experiments than there is a chance that the result was meant to take place as it is lead by the reaction that took place than human era. Even though the results were similar this time the tenth bottle had inhaled more than the in the last trail. Also the ninth bottle had inhaled a little and as not flat like bottle 8. So i’ve made it my very noticeable on my whiteboard at home to talk to my teacher and see what she says about my results. 13/07/15 -‐ Today in my science period my teacher went through some important information that really guided me in what is expected of me from this report and conducting the whole assessment. This lesson we went through last years somes assessment task which helped me understand what level i had to push myself to to get an A level and the little things i need to do to get extra marks but it really gave me a great understanding of the layout of the report. My teacher talked about what we’re expected to include in out background information and showed us some possible questions that we should ask our self in order to have a great introduction. We talk about how to write hypothesis and aim which cleared my head as i’ve already done it. Ms chalmers talked about that when we write our discussion or background information we should aim to write in detail approximately one page but some might have the ability to explain well in less than a page. For me it help me to learn it’s a good thing answering a question in longer length as i’m that kind of person. At the end of the lesson we had a little talk and she said it’s okay that my last three bottles didn’t work as i did us large quantity of salt. 15/07/15 -‐I’m finally done my background information, i spent more time on it than any other part and hope it’s really good. I’m going to start laying out my report to clearly identify what i’ve completed and what i need to work on. Tomorrow i’m looking forward to talk to my teacher on how to write the discussion and hopefully i’m on the right track.

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16/07/15 -‐Today in class we were taught how to construct a table for our results which was really helpful, i’m waiting on until my teacher gives me feedback on my work so i know where to improve and keep things the same for my final report. My teacher also talked about how to write about our result and one thing she emphasised was “DO NOT EXPLAIN WHY” which i understand why as it is to be talked about in the discussion. We also looked at how to graph our results and the components involved when doing so. We were given a sheet with a table of results and were asked to graph it and i didn’t finish mine so i took it home to do for homework. Units (in brackets) Scale must! Even Graph type (line or column graph) Ruler Axes titles Pencils Heading Spreading Out 17/07/15 -‐Today was not where i wanted be as i missed out 2 hours of homework time due to family commitments, this really dragged me behind a bit but i’m hoping i catch up on the weekend. Today at school we went through how a method should be set and what features it should include. Then we went through the whole concept of accuracy, validity and reliability and how to discuss them in the discussion and the importance of including improvements in our discussion. The class had a discussion about why we might have different results when measuring the temperature of water and what factors may mislead the accurate results, which then got us thinking how human, parallaxe and equipment error have a huge impact on our results. We also went through worksheets that had really helpful information on how to prepare our discussion. At the end of the lesson we were though shown how to graph in excel and label them properly which i really appreciate as i’ve forgotten how to use excel. 19/07/15 -‐Today i went through my logbook and then filled my report up to the method. I had my information printed on a sheet because it is more easier to write on and make changes so i took some time to type it up on google doc. I need to ask my teacher to check my work as i might need to change some components of my written work.

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20/07/15 -‐Today in class my teacher went around helped people with their assessment and questions they have. I didn’t say anything as i was waiting for her to comment of my work on google do but she said she still didn’t get it so i asked people to help me share my work with my teacher. I’ve completed my work up to the method but my background information is one page long and i’m not confident with the amount of work in it as i’ve tried to bring in lots of things together. I’m hoping for the best until i get a feed back from my teacher. So i just worked on my background information while she went around and used the time to correct information and add anything to my information. 21/07/15 -‐Today i edited most of my work that my teacher gave feedback on and i’m little worried as i’ve confused my self with lots of information. I’ve made to do list as it helps me keep track of where i am, it’s just that i’m buzzy at home but if i just have a day to myself i could sort things out and work to the best of my ability. Even though i’ve written down everything i just feel that i should go over and fix up my scientific language as it help me convey my ideas a little more. 22/07/15 -‐Today at school Ms chalmers gave the whole class a feed back after going through our work. We were told what NOT to do when writing our method, aim and hypothesis, specially not to use first person when writing our aim and hypothesis. We were also told to have a detailed method that clearly sets out what we’re doing. As my teacher was going through the class and helping other students and set up equipments for others, i went through my background information and started editing from the feedback she gave me. Then i left editing as some things she wrote didn’t make sense so i tried creating graph for my result but whenever i type in the results they automatically change into dates and months. Even though i tried to fix it i couldn’t but Ms chalmers came over and helped me create my graph. The we discussed about what my background information i’ve included in it, we talk about fermentation and respiration and how i should talk about them separately and what kind of information i should include. Ms chalmers also told me to make my background information stricture flow and not mix when it comes to the layout. I also fixed up my background information and did more research to help me talk about fermentation and respiration. http://www.paec.org/biologypartnership/assets/february%2022/Cellular%20Respiration%20Protocol%20-‐%20Balloon%20Lab.pdf ( Cellular Respiration in Yeast) http://www.bbc.co.uk/education/guides/zqn82hv/revision (revision on fermentation and respiration, got my respiration formula from here) 25/07/15 -‐Today i went through the feedback i got from my teacher on my background information and corrected them according. For the last few days i’ve been i’ve been a bit buzzy with subject selection and little ill so i was unable to

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work on my SRP but i do look over then when ever i can. Today i edited and changed my Background information/ Introduction in more detail to help me with my discussion writing and to help me convey my experimental aim comprehensively. I had a question on what the difference is between respiration and cellular respiration is even though i knew what they meant, i didn’t know which one to use in my background information. After sending my teacher the email i started writing the summary of the result table to help explain the result in more understandable way. I then took note on a piece of paper to help me outline the layout of my final report and note down “to do list” to help me keep track of timing. I did some draft on writing my discussion so i can write most of it tomorrow. 26/07/15 -‐Today i worked on my discussion and it was not how i expected, i thought i had everything figured out what to put in and what to discuss but it’s not easy. It needs lots of interpreting and explaining in detail with an excellent scientific languages. I made a start on the areas i’m clear about and took some notes down for some areas so i can finish them tomorrow. I’ll also as my teacher to check what i’ve started and give me feedback if it’s possible so i can make some changes tonight and work on them. There are few things that needs to be completed in the background information and results, other than that i need to finish my discussion and put in my photos, complete the reference and set everything up in an appropriate layout. 27 -‐Today i fixed up my background from feedback i got from my teacher which was so helpful as i made lots of mistakes or what i wrote didn’t make sense to others. I also worked on factors that affect the rate of respiration as i had put it off until last night but i finished it all. It’s sometimes hard to find an information that i can work with and it’s time consuming. 28 -Today i worked on the background as my teacher has edited needed to fix up the structure so it flows. it and my graph was not made in a great quality and i had to fix that and it was little tricky as the units and the axis shift. I also went through the report and edited my method to tring and make it more clear and also needed to fix y result table as i needed to change some things around. I also worked on my discussion and hoping it’s good this time but i would love to get a feed back if there are any mistakes. It was a little difficult but i think i did well. 29/07/15 -‐ Today i did a really good job in completing my SRP on time as it took me longer to put everything together and editing from the feedback i got. I edited and fixed up my background information and my report as my teacher told me

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to, which really was helpful. I sette out the report by inserted photos, diagrams that goes with my work and labeled them to help me with referencing them in the discussion. I also created a reference page with the websites and book that i found helpful. I also made a cover, content and appendix page to the report other than that i’m happy with my work and i think i still need to edit my grammar.

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Introduction: Yeast are microscopic one-celled organisms belonging to the group of organisms called fungi. Yeasts are found in the soil, in water, on the surface of plants, and on the skin of humans and other animals. Yeasts are eukaryotic single celled fungi, which reproduce by budding or fission. To obtain the energy they need for their life activities, yeast carry out several processes, one of which is fermentation. Fermentation is a metabolic process in which an organism converts a sugar (glucose) solution containing yeast and turns into alcohol (ethanol). In the absence of oxygen, they can obtain this energy through the process fermentation, which breaks down sugars and produces alcohol and carbon dioxide as by-products. People use yeast to bake because during fermentation carbon dioxide forms bubbles in the dough and expand it. Yeast is necessary to make leavened bread, beer, cheese, wine, and whiskey. Since baking is done at high temperatures, yeast ultimately dies and nearly all the ethanol evaporates. It is rich in B vitamins; a form of yeast called brewer's yeast is used as a diet supplement. Yeast is also used in genetic engineering to produce large quantities of certain hormones and enzymes, which are used for such medical purposes as healing wounds and reducing inflammation. Some types of yeast however cause disease like candidiasis and skin infection. Chemical reaction of fermentation: glucose ethanol + carbon dioxide

Yeast can use oxygen to release the energy from sugar in the process called "respiration". So, the more sugar there is, the more active the yeast will be and the faster its growth. Cellular respiration is the controlled breakdown of carbohydrate to carbon dioxide and water withcapture of some of the energy in the form of ATP. The yeast uses the sugar and warm water to grow. Warm water provides heat to the yeast reaction and accelerates it. As yeast grows it expands and gets bubbly. By being “bubbly” the yeast gives off carbon dioxide, the same gas that your body produces when you breath. Respiration provides organisms with the energy to do cellular work that helps them grow, function, and live. During respiration, yeast cells prefer to use sugar as an energy source. They release the energy stored in food (sugar) molecules and use this energy to produce ATP molecules that power the yeast cells’ chemical reactions. The waste products of respiration in yeast are carbon dioxide and water. The chemical reactions in cellular respiration are controlled by enzymes. Respiration: Glucose (sugar) + 6 Oxygen → 6 Carbon Dioxide + 6 Water + energy for cell

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Factors that affect the rate of respiration are temperature, pH, types of food (sugar), the concentration of yeast and glucose. As temperature increases, rate of respiration increases, because particles move faster and with more energy, which in turn means more particles collide with enough energy to react. The effect of pH is that when increased or decreased dramatically will denature the enzyme that helps fuel the reaction, and will in effect, decrease the rate at which the reaction occurs. Yeasts reproduce rapidly, and they grow especially well in substances containing sugar. Depending of the type of sugar the yeast respiration outcome will have different production. Maltose comes from grains and is used with yeast to make beer. Fructose comes from fruits and with yeast makes wine. Sucrose from sugar cane, rum and lactose which comes from milk, nothing. Glucose is the simplest sugar but glucose is has proper enzymes capable of breaking the food’s chemical bonds in a useful way. Glucose concentration can affect the rate of respiration as the greater the concentration of glucose the faster the rate of respiration will be. The rate of respiration increases as the amount of yeast concentration in the increases. This happens because yeast provides the enzymes and glucose is the reactant. This experiment was conducted to investigate the effect of increasing salt concentration on yeast. When salt was added the yeasts made less carbon dioxide, inflating the balloon less than when only sugar was used. This is because the addition of salt changed the environment and made it less ideal for the yeasts. By adding salt increased the salinity of the environment and trapped the the carbon dioxide produced. Based on previous research, increasing the amount of salt added to a mixture of sugar, yeast and water will decrease the amount carbon dioxide produced (Duke University student 2010). Yeasts are facultative anaerobe, which means that they can respire or ferment depending upon environmental conditions. In the presence of oxygen, respiration takes place. Without oxygen present, fermentation occurs. Both processes require sugar to produce cellular energy. In this experiment the yeast breaks down the sugar and it releases a gas called carbon dioxide as a by-product. The gas fills the bottle and then fills the balloon as more gas is created. This experiment sought to validate this claim by testing to see if salt has a negative effect as yeast can churn out a significant amount of carbon dioxide, provided it has the simple sugars it uses as food.

Aim: To investigate the effect of increasing the amount of salt on yeast respiration. Hypothesis: Increasing the amount of salt added to a mixture of sugar, yeast and water will decrease the rate of respiration and therefore, decreases the amount of gas (carbon dioxide) produced.

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Table of variables:

Independent variable

Dependent variable Controlled variable

● Amount of salt ● Circumference of the balloon (amount of gas produced)

● Amount of yeast added

● Amount of warm water added

● Amount of sugar added

● Type and brand of the salt, sugar and yeast

● Size and shape of bottle

● Time (Length of time of the experiment)

● Type, brand and size of the balloon

● Temperature of water

Figure: 1.9 Risk Assessment:

Risk/Hazard Control/solution Hot water ● Burns ● Scalds

Wear your lab coat and an enclosed leather shoes to avoid any burns. This experiment needs to be done away from children or busy area. Make sure you use lab gloves to avoid any burn. Take caution when handling hot water, Do not place on the edge of the bench. Do not lend over the hot water.

Water spills Wear your lab coat and an

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● Falling over and being hurt ● falling over with dangerous

equipment (knife, scissors, glass, hot kettle)

enclosed leather shoes to avoid water spills on your body or your clothe. Do not place water on the edge of the bench, do not lend over water and mop up all spills straight away to avoid injury.

Knife ● Hurting yourself or others

around. ● Infection

Make sure your knife is in a the right condition (not rusted) and use it slowly with caution. Do not rush to get it over and done with and always cut away from yourself.

Kettle ● Burn ● Being electrocuted ● Damage the electric cord and

the electric board.

Always handle the kettle with caution and carefully to avoid any burn from the heat. Make sure the area that the kettle is situated is always dry and away from any wear equipments, liquids and taps. Make sure the end of the cord always has it’s safety cover to prevent any connection with water.

Figure: 2.0 Materials: ● 500g Sugar ● 500g Salt ● 12 sachets Yeast ● 10 plastic bottles 1.25L ● Water ● 1x Dress type measure ● 1x Funnel ● 30x balloons ● 1x ½ teaspoon ● Teaspoon ● Tablespoon ● 1x Knife ● 1x Kettle ● 1x Measuring Jug -‐ 500ml

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● 1x Measuring Jug -‐ 250ml ● 1x Measuring Syringe in mls ● 1x Spoon ● 1x Timer ● 1x Large Bowl ● Writing Utensils : Pen, book, Laptop and marker

Method:

1. Gather all materials and lay them out in an appropriate area. 2. Grab the kettle and fill it with tap water and boil the water. 3. Measure out 500ml of boiling water using the 500 ml measuring jug and

pour in a large bowl. 4. Measure out 500ml of cold water using the 500 ml measuring jug. 5. Carefully combine the cold water with the boiling water in the large bowl.

Mix these two in a large bowl to create warm water. 6. Using the 250 ml measuring jug, measure 200 ml of warm water and pour

into a bottle. 7. Repeat Step 6 ninetimes on the other bottles (4) 8. Place 2 teaspoon of sugar carefully into each bottle. 9. Add salt carefully to each bottle as per table below:

First bottle 0 tsp salt

Second bottle ½ tsp salt

Third bottle 1 tsp salt

four bottle 1 ½ tsp salt

Fifth bottle 2 tsp salt

sixth bottle

3 tsp salt

seventh bottle 4 tsp salt

eight bottle 6 tsp salt

nine bottle 8 tsp salt

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tenth bottle

10 tsp salt

10. Write down that each bottle contains and place it near the experiment or label it on the bottle using the marker.

11. Carefully place a teaspoon of yeast in every bottle. 12. Carefully place a balloon on each of the bottles (ensure they’re on tight so

gas doesn’t escape)

Figure: 2.1

13. Start the timer or clock as soon as each balloon is on, and leave it for an

hour. 14. when the time is up tie up the balloons, make sure no gas escapes. (If gas

escapes then that measurement will be unreliable and can’t be used. 15. Clearly label each balloon with it’s number ( Bottle 1, 2, 3..). 16. Measure the circumference of the balloon using dress type measure and

label the balloon with the measurement. 17. Record the results in a result table. 18. Repeat the experiment 3 times to increase the reliability of the result. 19. Carefully collect and pack up the equipments and clean the area used.

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Results: Test results for each trial

Salt (Teaspoons)

Circumference of balloon. (cm)

1st reading

2nd reading

3rd reading

Averages

0 (control) 22.0 23.5 23.0 22.8 ½ 19.0 17.5 19.5 18.7 1 18.0 17.0 20.5 18.5 1 ½ 11.0 15.5 17.0 14.5 2 12.0 14.0 13.5 13.2 3 7.0 6.5 6.0 6.5 4 4.0 5.0 5.0 4.7 6 0.0 0.0 0.0 0.0 8 0.0 0.0 0.0 0.0 10 0.0 0.0 0.0 0..0

Figure: 2.2

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Graph:

Figure: 2.3

The data Figure 2.2 shows the average circumference in cm for each salt concentration tested. As can be seen from the graph and averages in the results table the amount of gas (CO2) produced declines as more salt is added. The circumference decreased and therefore the amount of gas also decreased. The average line declined fairly rapidly and then slow down after around 2 teaspoons of salt has been added. It still declines after this but a slower rate than before. This produces a slight curve in the graph which seems to start to level out, and because the experiment was conducted up to 10 teaspoons of salt it is likely that the levelling would continue if more tablespoons of salt concentrations were added. The rate of reaction decreases as the amount of salt concentration increases the circumference of gas (carbon dioxide) produced decrease.

Figure: 2.4

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Figure: 2.5 Discussion: This experiment aimed to determine the effect of different salt concentrations on the rate of respiration in yeast by comparing the production of carbon dioxide, a by-product of respiration for each different salt concentration. It has been shown previously that carbon dioxide production declines with increasing salt concentration.Yeast are unicellular eukaryotic fungi that use organic compounds (compounds containing carbon and hydrogen) as a source of energy. Yeast obtain this energy through the process of cellular respiration: the process of breaking down sugar (glucose) to make energy in the form of ATP. The experimental question being tested in this lab exercise waswhat is the effect of salt on the rate of yeast respiration? The objective of this experiment was to measure yeast respiration rate for 10 different concentration of salt: 0 tsp, ½ tsp, 1 tsp, 1 ½ tsp, 2 tsp, 3 tsp, 4 tsp, 6 tsp, 8 tsp and 10 tsp. By measuring CO2 production for each concentration, it was predicted that CO2 production would decline with increasing salt concentration. The results obtained in the experiment support the hypothesis as carbon dioxide production sharply declined with increasing salt concentration as indicated by the data Figure 2.3. This relationship is consistent with the studies previously conducted. Because of the observed decline in gas production, it can be concluded that salt affects or stops the rate of respiration and consequently the growth of the yeast. Since growth requires energy, if the rate of respiration is reduced, then so to is the growth rate. This maybe caused because of the high concentration of salt outside the cell, the water inside the cell will move out of the cell due to the difference in salt concentration causing the cell to shrink and wilt. As can be seen from date figure 2.3(graph) and figure 2.2 (result table) averages in the results table the amount of gas (CO2) produced declines as more salt is added. The average line declined fairly rapidly and then slowed down after around 2 teaspoons of salt has been added. It still declines after this but a slower rate than before. This produces a slight curve in the graph which seems to start to level out, and because the experiment was conducted up to 10 teaspoons of salt it is likely that the levelling would continue if more concentrations were added. By repeating the experiment three times while increasing the amount of salt used by more than a few teaspoons, It increased the reliability of the experiment. As the result

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were not based on one trail but on three and this contributes how reliable the test was. The variation between the results makes the reliability of the experiment questionable even though it clearly seen on average amount of gas produced decreases with increasing salt concentration. This experiment is scientifically unreliable as all of the tests had different result for each trail, mostly caused by not controlling the temperature but also measuring the pH would have given the experiment more reliability on the results. As exact measurement can’t be estimated, hence the variation between results are caused due to not measuring the temperature using appropriate equipment. Hence the experimental design may not have been valid. Even though setting up several bottles at the same time would reduce the variation in the temperature for the replicates. Tap water was used instead of refrigerated water to increase the temperature of the water in the mixture by adding boiling and cold water together to make warm water. An uncontrolled variable lead to unreliable experiment as the correct equipment was not used. the difference in the temperature of the water is why the measurement varied so much. Using an appropriate equipment could have minimised the error. Possible errors may have occurred while measuring the water by using measuring cups as they may have been labeled an incorrectly or an even (faulty products). Parallax error might be one factor as it is caused by not having the eye directly line with the measurement of the jug. This may be accounted for by the fact that all bottle replicates did not show the same measurement of carbon dioxide produced as all of the tests had different measurements for each of salt concentration. Hence, this experiment was not reliable as the data on the carbon dioxide produced from each trial was varied on a small-scale. Although the experiment was conducted three times and it clearly supports the hypothesis as increasing the amount of salt added to a mixture of sugar, yeast and water decreased the amount of carbon dioxide produced. Which significantly provides a reasonable response to the aim and as supported by the background research. Salt causes the yeast to dehydrate by osmosis as water moves out of the yeast into the surrounding area. This reduces respiration of the yeast and so reduces the amount of CO2 produced (Duke University student 2010). The errors above cause variation in the validity of the experiment as all of the variables were not controlled. Not controlling the temperature had great effect on the validity of this experiment. Therefore the method was not completely valid even though it clearly tested the aim of the experiment. Not measuring the temperature made the validity of the experiment questionable which produced variation in the result. Even though the experiment was not 100% valid or reliable it absolutely supported the hypothesis and previous experiments and background information validated the result of the experiment. As it is proven that by increasing the amount of salt added to a mixture of sugar, yeast and water, this decreases the amount of carbon dioxide produced. As it can be seen from the data of the graph and table. The main improvement which can be done to experiment is using a thermometer to

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make sure that the temperature of the water is always constant. Having a more accurate measurement of the gas produced would also improve the experiment however, better scientific equipment would be needed. Using thermometer would have minimized any error and give a better result. More caution is need in the preparation and administration in future experiment as well as greater accuracy in measurements. One of the conventional uses of yeast in bread baking. Bread baking is an exact science that depends on the biological power of yeast to leaven the bread as it converts the fermentable sugars present in dough to carbon dioxide gas. In bread making, yeast initially respire aerobically producing carbon dioxide and water. Society benefits greatly from this experiment in making the process of bread making more efficient, but also in learning cellular respiration. Furthermore, there are implications of this experiment that extend to help in future research; ecosystem of the natural environment as yeast serve as vital decomposers in the earth's ecosystem.

Conclusion:

From the data presented it can be seen that the amount of carbon dioxide produced by respiring yeast slowly decreases as salt concentration increases even though there was variation between the trials. The hypothesis that states increasing the amount of salt added to a mixture of sugar, yeast and water will decrease the amount of carbon dioxide produced is supported by the experiment and the trends in the graph.

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Appendix:

Yeast

●

● Baker's Yeast (98%

● Emulsifier (491)

● Ascorbic Acid. ● Store in a cool ● Dry place. ● Use product in

its entirely after opening sachet.

● Do not store opened sachet.

● white sugar -

cane sugar

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Reference

BBC Bitesize. (2014). Fermentation or anaerobic respiration. Retrieved from: http://www.bbc.co.uk/bitesize/standard/biology/biotechnology/living_factories/revision/3/ BBC Bitesize. (2015). Respiration. Retrieved from: http://www.bbc.co.uk/education/guides/zq349j6/revision/1 Duke University. (2010). Broderick AP Biology. Retrieved from: https://sites.google.com/site/broderickapbiology/

Elise, M. (2006). Science handbook years 9-10. Sydney, Australia. Vivienne Petris Joannou. Iupui. (2004). Cellular Respiration. Retrieved from: http://www.biology.iupui.edu/biocourses/N100/2k4ch7respirationnotes.html Jim,K. (1997). Carbon Dioxide. Retrieved from: http://www.hallman.org/plant/CO2.html Science Clarified. (2015). Yeast. Retrieved from: http://www.scienceclarified.com/Vi-Z/Yeast.html Scientificamerican. (2014). Single-Celled Science Yeasty Beasties. Retrieved from: http://www.scientificamerican.com/article/single-celled-science-yeasty-beasties/ University of Sydney. (1997). How to Write a Laboratory Report. Retrieved from: http://sydney.edu.au/stuserv/documents/learning_centre/lab.pdf

Acknowledgements: Chloe Chalmers (Ms Chalmers): Chloe Chalmers (my science teacher) has been my mentor during the whole process of my Student research project(SRP). She has been my guide and encourager as well as my teacher who has linked me with those I need. She has also being my biggest helper and supporter throughout the SRP by doing everything in her power to help me achieve my goal.

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Pauline Bonfield (Mrs Bonfield): Pauline Bonfield has been so very helpful and willing to help me on my quest to complete my Student research project by providing equipments needed but also by giving very helpful advice when making decisions. Aem, Bekere and Yeshi: My family who have been unrelentingly supportive in every possible way. They have supported me in every decision i made but also gave me very insightful information to help me with my research and findings. Deborah Pawsey (Mrs Pawsey): Mrs Pawsey has been helpful by giving me ideas and helping me understand properties of Iodine but has given up her time to help me run my tests and guide me throughout the test. She has given me very insightful informations to help me many scientific facts and information.

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