The Rate Of Respiration In Yeast And

How It Is Affected By Temperature. Essay, Research Paper

Harry Fox 11ST Biology

Science 1 – Strand 1: Planning Aim??????????? In my experiment, my aim is to find out any correlation

between rate of respiration? of glucose

by yeast and the mixture?s temperature. I shall do this by conducting an

experiment which will involve the timing of the yeast, water and glucose which

has been mixed with a little methylene blue. I shall time how long it takes to

revert to the original colour using a control. This shall be done at various

temperatures. To obtain the best range of values to use in my final experiment,

I shall conduct a preliminary experiment. This will also aid accuracy of the

final experiment by uncovering potential flaws in the method.Hypothesis

and Theory ??????????? There are many ideas to suggest that the change in

temperature will cause an increase of respiration in yeast. Yeast is a single

celled fungus made up mostly of protein which has been used for its

applications in fermentation. Yeast, after activation creates the ferments

carbon dioxide and ethyl alcohol by secreting the enzyme zymase (a complex of

12 enzymes) in the yeast which acts on simple sugars such as glucose. The

alcohol produced has been used in making wines and beers and the carbon dioxide

produced has been used in baking as it gets trapped in the dough and causes it

to rise. ??????????? Enzymes are catalysts which speed up reactions, they are

made from protein and are specific as to which substrate they work on. Enzymes

basically work due to the ?lock and key? theory, where the substrate substance

(the ?key?) ?fits? into the active site on the enzyme and they bind together,

the reaction takes place and the substrate unlocks to form one or more new

substances leaving the enzyme ready to perform the binding again. An enzyme can

only bind with a substrate that fits the shape of the active site unique to

that kind of enzyme. A zymase-complex enzyme will only bind with a glucose

molecule to produce the ferments carbon dioxide and alcohol which brings about

the fermentation in my experiment. This ties in with the Induced Fit theory

which states that the substrate cannot bring about catalysis and the reaction

itself, but the active site, when it comes in to contact with the substrate

slightly changes its shape to form an effective fit and arrangement of

catalytic groups on its surface which brings about the catalysis reaction. To

display this, think of a hand in a glove where the hand acts as the key and

substrate, inducing a change? in the

shape of the glove which acts as the enzyme. When some substrate substances

induce a fit with the enzyme, the enzyme may not be able to ?accept? some other

substrate(s). These ideas tie in with my experiment to explain the formation of

the products of respiration of yeast. ??????????? Yeast have to make energy, stored as ATP to carry out all

cellular functions. To do this they can respire both aerobically when there is

plenty of oxygen, but where oxygen is short, they respire anaerobically; by

this, they are called partial anaerobes. This produces less energy, but keeps

the yeast alive. Pyruvic acid has to be broken down in respiration when formed

by breaking down of glucose molecules, this can?t be done in the same way as it

is aerobically when respiring anaerobically which is how the carbon dioxide and

ethanol is formed through the zymase. Here is the equation for anaerobic

respiration:??????????? ????? enzymes in

cytoplasm ??????????????? ?????????

(zymase complex) glucose???? —————–>??? ethanol???? +??? carbon dioxide??? +energy C6H12O6???????? ?????

????????????????? 2C2H5OH?????? ????????

CO2??????????? 210

Kj/mole210Kj/mole in anaerobic

respiration as aposed to 2890Kj/mole in aerobic respiration There is 2ATP from each

respired glucose molecule – in aerobic there is 38ATP.??????????? Kinetic theory states that, with an increase in

temperature, the rate of reactions will increase. This is due to the increase

of speed of the particles, brought about by the extra energy given to them by

heat. Faster particles will bring about more particle collisions and so the

reaction will take lace faster. Enzymes are sensitive to temperature changes up

until a certain temperature and will increase in their activity also. The

reactions that take place in the enzymes will be quicker and so will create

more of their products. As a general rule of thumb, it has been said that there

is a doubling of the rate of reaction for every 10?C rise this is called the

?Q10=2? theory. This should be evident when the concentration of the enzyme and

substrate are kept the same also. ??????????? Enzymes are sensitive to temperature up untill a certain

temperature where the shape of the active site is altered drastically, so much

so that binding hardly ever takes place. This is called denaturisation. Prediction ??????????? With reference to my theory, I predict that the rate and

speed of respiration of glucose by yeast will increase with temperature rise up

until a certain point where the enzyme used and secreted by the yeast will

become denatured and cease to function, reducing the rate significantly. This

is explained through Kinetic theory, yeast respiration and the nature of

enzymes. Initial

Investigation??????????? In my initial investigation, I simply counted the number

of bubbles released by the yeast in a 2 minute period. I did his because I only

wanted to uncover the general trend and temperatures where there was or wasn?t

notable activity so I could use this information when conducting my final

experiment. I used 1g of glucose and 1g of yeast, creating a 50:50 split, I

also used 10cm3 of distilled water. I mixed the three in a boiling

tube, warmed it a little and shook it to activate the yeast. I then left it for

one minute to let the mixture acclimatise to the temperature and then assembled

the apparatus as shown and counted how many bubbles were formed during 2

minutes. My independent variable was the temperature; the dependant being the

number of bubbles. I increased the temperature by 10?C each time. I took three

readings at each temp took their mean. I timed from the first bubble. Initial Investigation

Diagram

See Attatched Document Initial Investigation

Results

See Attatched Document

See Attatched Document

??????????? 0????????????????????????????????? 0????????????????????? 0????????????????????? 0????????????????????? 0

See Attatched Document

??????????? 10??????????????????????????????? 0????????????????????? 0????????????????????? 0????????????????????? 0?????????

See Attatched Document

??????????? 20??????????????????????????????? 4????????????????????? 6????????????????????? 4????????????????????? 4.7 ??????????? ??????????? 30??????????????????????????????? 11??????????????????? 9????????????????????? 10??????????????????? 10 ??????????? 40??????????????????????????????? 18??????????????????? 16??????????????????? 14??????????????????? 16 ??????????? 50??????????????????????????????? 22??????????????????? 20??????????????????? 19??????????????????? 20.3

See Attatched Document

??????????? 60??????????????????????????????? 4????????????????????? 10??????????????????? 6????????????????????? 5

See Attatched Document

At this last temperature, I

think the 10 bubbles at 60?C was an anomalous result. This may be due to

improper heating and will be discussed in my evaluation. It was not included in

my mean number of bubbles.

See Attatched Document

Graph Variables??????????? In my main experiment, I shall use the time taken for

methylene blue test tube with yeast and glucose solution to turn the colour of

the control as my dependant variable and the temperature as my independent

variable. ??????????? Here is a list of variables that can have an affect on my

experiment and also how I will control them if possible.Temperature Amount of methylene blue Amount of yeast Amount of glucose Volume of water Amount of shaking and

acclimatisation Light and atmospheric

conditionsTEMPERATURE??????????? Temperature of the experiment will have a great affect on

the results as explained by kinetic theory. Temperature will affect the rate of

yeast respiration. I shall keep the temperature of he mixture and water bath

under control by using a thermometer and checking it constantly. I shall also

keep swirling the thermometer to keep the heat distributed. Also, as it will

take longer for the temperature inside the test tube the same as the water

bath, I shall leave the apparatus for two minutes, keeping the temperature

constant.AMOUNT OF METHYLENE BLUE??????????? Methylene blue is sensitive to oxygen and will go blue

with contact with oxygen and colourless with the production of NADH during

glycolysis as the glucose is broken down. The amount of this would affect the

accuracy of the readings as the rate of NADH production affects the methylene

blue and a differing amount of methylene blue would not give fair and reliable

results. I shall keep the amount of drops of methylene blue the same at each

timing. AMOUNT OF YEAST??????????? The amount of yeast is crucial, more yeast means more

glucose will be respired and more products created. An imbalance will upset the

results. The amount of yeast will be weighed out on an accurate top-pan balance

each time.AMOUNT OF GLUCOSE??????????? The amount of glucose will affect the results also, as

more glucose means that there are potentially more products, which would make

the results accurate or the experiment fair. The glucose will be weighed out

each time using an accurate top-pan balance.VOL. OF WATER??????????? The volume of water may have a slight affect to the

results as it may cause less accuracy when distributing the heat in the test

tube. The volume of water will be kept constant by using a measuring cylinder

at each preparation.ACLIMATISATION AND SHAKING??????????? Acclimitisation and shaking will help to activate the

yeast and prepare the solution for timing. If it is improperly mixed,

acclimatised to temperature or activated, the results would not be fair and

inaccurate. I will shake the test tube thoroughly each time until I can see

bubbles being created well and I shall do this while it is warm to aid

activation. I shall also leave this in the water bath at the required heat for

two minutes, regulating the temperature with the Bunsen.LIGHT + ATMOSPHERIC

CONDITIONS??????????? These would not have a great deal of affect on my

experiment and are beyond my control. Some of the substances may be sensitive

to these, but I doubt they are sensitive enough to affect the results.?Diagram of final experimentApparatus Bunsen Burner Stopwatch Yeast Glucose Stand and Gauze Methylene-blue Syringe Pipette Boiling tubes (x2) Beaker Bungs Method??????????? In my final experiment, I shall use methylene blue in the

solution. I shall time how long it takes for methylene blue to go colourless in

the solution, constantly checking against a control which contains a little

methylene blue for continuity. To avoid unfair contact to Oxygen in the air, I

will? put a layer of oil over the

mixture. I shall weigh out 2g of glucose and 2g of yeast this time and 25cm3

of water to aid accuracy.? My

independent variable is the temperature and the dependant is the time taken to

change colour of control. ??????????? I shall take readings from 20?C to 60?C at 10?C

intervals. I will start from 20?C as I found out from my initial investigation

that there was no respiration activity below this temperature. I shall proceed

in this sequence as it is the easiest way of collecting results and will help

to find out other flaws at a lower temp.?

Also to aid accuracy, I shall take three readings at each interval and

take the mean.Results

headingsTime (s)????????????????????????????????? t1???????? t2???????? t3???????? T(mean)???? Rate (S-1)Temp (?C)????????????????????????????? Safety

See Attatched Document

HAZARD?????? ??????

DANGER(0-3)?? ? LIKELIHOOD(0-3)???? SCORE???? ACTION

See Attatched Document

Burn (Bunsen,??????????? 1????????????????????????????????? 2????????????????????????????????? 2????????? ?

Goggles, care hot water)?????? ?????

????????????????????????????????????????????????????????????????????????????????????????? ???when heating ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?? and handling,? ???????????????????????????????? ??????????????????????????????????????????????????????????????????????????????????? ????orange flame ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?? when not used.

See Attatched Document

Broken glass????????????? 2????????????????????????????????? 2

???????????????????????????????? 4????????? ?

Goggles, care ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?? when hot and ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?handling, clean ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? up

all fragments Broken ?????????????????????? 3????????????????????????????????? 1????????????????????????????????? 3????????? Care when using thermometer??? ????????????????????????????????????????????????????????????????????????????????????????????? don?t

hit hard, or ??????????????????????????????????????????????????????????????????????????????????????????????? ????????????? leave to roll off desk.Biology

Science 1 – Strand 2: Obtaining Revised

Method??????????? I have made only slight alterations to my proposed method

in the planning. I have kept everything the same, except that I shall take

multiple readings of smaller intervals around the ?plateau? of my results so as

to gain a more accurate understanding of what is happening and where the peak

in activity happens. This will also help me to analyse my hypothesis.Variables??????????? ??????????? ????? ??Time taken for solution to decolourise : Dependant Variable ??????????????????????? ???????? Temperature of solution : Independent

VariableRange: 20?C – 60?C in 10?C intervals mapping out plateau in 2?C

intervals from 42?C – 56?C. Measurements for both variables have been taken and

I have calculated the mean after taking three readings at each interval.ResultsSee Attatched Document Time(s)?????????? t1???????????????????? t2???????????????????? t3???????? ???

T(mean)?? Rate (S-1)???? x103

See Attatched Document

At 60?C the solution started to decolourise but with the last two, it

didn?t fully decolourise showing eventual denaturisation of the yeast?s

enzymes. Converting and manipulating data usually proves useful and aids

analysis and I have been able to calculate the rates for my results with my

dependant variable using 1/t. As this is inverse, and rates should

always be in seconds, the unit I shall use is?

S-1. I have made my rate results positive by multiplying them

by 103 so making it easier for me to plot and use.To aid the final analysis and to certify precise and reliable results,

I decided to map out the top plateau of results at 2?C intervals. The values

used cover the rise, peak and fall of the plateau. The results for this are

shown below. This will allow me to form an accurate optimum temperature for the

respiration of yeast.? had taken all the

precautions that I had done previously and used the same method. I will talk

about the validity of all my results in my Evaluating.See Attatched Document

Temp(?C)?? t1(s)???? t2??????

t3????? Time(mean)????? Rate (S-1)???????? x103??????

See Attatched Document

42??????? ?????? 125????? 109???? 116????????? 117???????????????? 0.00855????????? ?

8.55

See Attatched Document

44??????? ??????? 96?????? 107????? 105???????? 102???????????????? 0.00980????????? ?

9.80

See Attatched Document

46??????? ??????? 100????? 92?????? 95?????????? 96??????????????????? 0.0104??????????? ?

10.4See Attatched Document

??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????? I have ensured that my results are accurate by controlling all the

variables stated in my Planning. I also took care when using the equipment so

as to retain continuity throughout the experiment. For this, I checked

everything was set up correctly at each reading and prepared my solution in the

same way. I did not prepare a ?batch? of solutions as this would have given

some more time to acclimatise and more time to react and respire, changing the

conditions. When weighing out glucose and yeast on the top pan balance, I

checked that the air bubble was always centered and adjusted it accordingly, if

left uncentered, this could cause biased results. When measuring out distilled

water, I carefully checked that the bottom of the water?s meniscus sat

horizontal with the required gradient on the measuring cylinder when looked at

from 90? at the side. I also kept the same water in the water bath so as to

keep fair the distribution of heat to the test tubes, I mixed this as well.To further manipulate my results I shall record logs of my results so I

can plot this in my analysis. This will also display my results in such a way

that will allow me to easily find an optimum temperature for anaerobic

respiration in yeast. It will also allow me to calculate the Q10 mean value for

my experiment. This would go some way to see the accuracy of my results, but

mostly to see whether the reaction is in line with the Q10 theory and

regularity of the rate of reaction. I will plot log temp against log rate? to generate my log graph. This is one of

many data manipulation methods I shall use in my analysis to find out as much

as I can from my data. Here are my log tables including the results taken when

plotting out the plateau:See Attatched Document

??? 20?? 1.301?????????????? ???? 2.36???

?????? 0.373????????????? ??? 30?? 1.477?????????????? ???? 3.31???

?????? 0.198 ??? 40?? 1.602?????????????? ?? ??7.41??? ?????? 0.870 ??? 42?? 1.623?????????????? ???? 8.55???

?????? 0.932 ??? 44?? 1.643?????????????? ???? 9.80???

?????? 0.991 ??? 46?? 1.663?????????????? ???? 10.4???

?????? 1.017 ??? 48?? 1.681?????????????? ???? 11.2?????????? 1.049??? ??? 50?? 1.699?????????????? ???? 11.6?????????? 1.065? ??? 52?? 1.716?????????????? ???? 12.2?????????? 1.086 ??? 54?? 1.732?????????????? ???? 10.7?????????? 1.029 ??? 56?? 1.748?????????????? ???? 10.2?????????? 1.009

See Attatched DocumentBiology Science 1 – Strand

3: Analysis Summary????????? I found that as the

temperature increased, the rate of respiration increased with it. I also found

that the rate of respiration dropped of completely after a certain point,

highlighting the denaturisation of the yeast?s enzymes.

See Attatched Document

??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

????????? ???????????????????????????????????????????? ?????????????????????????????????????????????????? This shows that

the temperature

See Attatched Document

??????????????????????????????????????????????????????????????????????????????????????????????????????????????? a certain point

where respiration ??????????????????????????????????????? ??????????????????????????????????????????????? stops.??????????????????????????????????????????????????????????????? Temp

(?C)To calculate the Q10 gradient of my results so I can gain information

about the nature of the reaction, I shall create a graph of my logs given in my

Obtaining. From my log graph I can give the optimum temperature for yeast

respiration and calculate the Q10 reading for my experiment.I can calculate my Q10 value as shown: ? See Attatched Document See Attatched Document

See Attatched Document Conclusion ??????? I have found that as I

increased the temperature of the yeast solution, the rate of respiration of the

yeast increased to a certain point where, as the temperature rose to a certain

level, (in my case about 58?C) the rate of respiration eventually cut off. I

have also found that my Q10 value is 1.43. Seeing as the most accurate value

for a Q10 reaction is 2 (the rate of reaction doubling for every 10?C rise)

this makes my reaction look a bit inaccurate yet with positive signs of

correlation. A Q10 reading as low as 1.43 suggests there were either faults

with the method or apparatus or that the reaction was not a true Q10=2

reaction; this reaction should be a typical Q10=2 reaction, so my method or

apparatus? probably give the

inaccuracies. I will talk further about this in strand iv to suggest reasons. ??????????? My hypothesis and

prediction can be backed up with the findings; from looking at my results and

graphs you can see the rise and fall of respiration, further displayed by the

reaction?s Q10 reading which, although quite a lot less than 2, it still gives

the presence of the reaction?s ?sensitivity? (through zymase) to temperature.

Thus my hypothesis and prediction are shown to be present and displayed to a

large extent. They are explained due to the theories of enzyme-substrate with

lock and key and kinetics. Where these meet is when kinetic theory states that

an increase in temperature means more particle collisions between reactants and

so a faster rate of reaction; and in enzyme-substrate where the enzyme is

sensitive to heat, and about a certain temperature, the active site will begin

denaturing, so slowing and eventually stopping the reaction. This will give an

area where the rate of respiration drops off and goes to nothing instead of a

precise ?cut-off? point. These both apply to my experiment and were described

in my planning. ??????????? Biology Science 1 – Strand 4: Evaluation My Method??????????? The experiment went

quite well as I was able to obtain sets of recordings and calculate means,

rates and logs, and my Q10 value from them.I did not find any results to be anomalous when looking at the results

table. This could be explained by the small spread of results at each interval

and that the reaction could not be totally accurately controlled with the

apparatus used.I think that the method I used, whilst giving results, was also quite

sensitive to changes and didn?t allow to tap the full potential of the

experiment. I would suggest using equipment which would not allow any biased

results or ignore anything that is happening in the solution. I would want to

spread out the solution in something like a pert dish to give maximum surface

area to help conduct heat and to evenly spread the methyl blue. I would

consider either not using the methyl blue colour change technique at all or use

a substance which is more precise as I felt that the method did not allow

accurate use of methyl blue because of how it was used and what it acted on.

This added to the slight ?unpredictability? of the experiment.My Results ??????????? ??????????? To make sure that the

results were as reliable as I could make them, I calculated the mean of three

results at each interval when dealing with the rate and also used these to

produce my log values. ??????????? I took all precautions

to make the apparatus used to be reliable and give good values so I think the

slight unreliability was caused by the preparation of the solution and the ?unpredictability?

of how the reaction went that came with it. To obtain more reliable results I

would want complete continuity with preparations, maybe arranging ?sets? of

substances to create multiple solutions beforehand or preparing them but not

actually activating the yeast so as to prevent any getting a ?head start? over

the others. This would ensure that all the preparations are the same and would

give continuity. I would want to be more strict and thorough with preparing

solutions and mixing them up. I would want each one to be thoroughly

acclimatised to the surroundings and had the same amount of methyl blue and

same activating and mixing time. This would help give more reliable results

throughout. ??????????? If I were to further

investigate this experiment and my results, I would probably want to calculate

the point where the enzymes begin to denature for respiration in yeast. I could

also examine the change in rate between the intervals to determine validity and

continuity, also running them through maybe more intricate calculations

involving log. At this stage, I shouldn?t think there is to be much more I

could do. I wouldn?t want to investigate any other variables or reactions at

this time.