Exercise 14 - Cellular Respiration in Yeast

Cellular Respirationin YeastDOMINGO,GALOS,GENUINO,HILVANO,LAPIRA,LOZANO

Abstract

Cellular Respiration, a process by which an organism

produces energy from energy molecules such as glucose or

fatty acids, occurs differently under certain conditions. This

report makes use of these differences by exposing yeast

suspension under different conditions.

5 Smith Fermentation tubes were

prepared and placed with glucose with

yeast, glucose, boiled yeast with

glucose, starch solution with glucose

and yeast respectively. The rates of

CO2 formed by the yeast in each tube

were compared for 40 minutes.

Abstract

It can be concluded that under the condition by which

yeast and a simple sugar such as glucose is present, the

production of CO2 will form more prominently than the

others.

I. Introduction

All organisms need energy to survive. Cells use a

process called Cellular Respiration to acquire the energy

needed. In Cellular Respiration an organism’s cells transforms

energy molecules like starch or glucose into an energy

currency called Adenosine Triphosphate or ATP.

I. Introduction

Cellular Respiration can be classified as Aerobic or

Anaerobic Respiration. In Aerobic Respiration, cells will

breakdown glucose in the presence of oxygen through certain

processes to produce CO2 and H2O. Aerobic Respiration

usually occurs within the cells of animals such as humans.

I. Introduction

On the other hand, Anaerobic Respiration which can be

divided further more into Alcoholic Fermentation or Lactic

Acid Fermentation occurs without any oxygen. The only

difference between the two processes is that Alcoholic

Fermentation produces ethanol, ATP and CO2 while Lactic

Acid Fermentation produces Lactic Acid and ATP.

I. Introduction

In terms of completeness in breakdown and production

of energy and CO2, Aerobic Respiration is complete and

produces 6 moles of CO2 and 36/38 ATP while Fermentation

produces 2 ATP and 2 moles of Lactic Acid (Lactic Acid

Fermentation) or 2 moles of CO2 and a mole of ethanol.

I. Introduction

The experiment conducted aims to study the cellular

respiration in yeast by observing the results and taking note

of the condition at which they occur. Also, this experiment

aims to enumerate factors in cellular respiration by analyzing

and varying the reagent in each smith fermentation tube.

II. Methodology

• 5 Smith Fermentation tubes were filled with 20 ml of different reagents. (Glucose for the first 3 tubes, Starch for the 4th and water for the test tube

• 20 ml water was added to each of the tubes.

• 20 ml of yeast suspension was added to tubes 1,4 and 5 while 20 ml of boiled yeast suspension was added to tube 3.

• Each tube were checked for air bubbles in the tube and titled the tube horizontally while covering the opening to remove them.

• The opening of each tube was covered with cotton.

• The evolution of CO2 in each tube were recorded and compared.

III. Results and Discussion

Cellular Respiration is spontaneous chemical process

wherein a cell makes energy by the transformation of energy

molecules such as sugars and fatty acids into ATP and certain

by-products. Cellular Respiration is divided mainly into

Aerobic Respiration and Anaerobic Respiration.


Aerobic Respiration is the creation of

36/38 units of ATP, 6 moles of CO2 and 6

moles of H2O from the breaking down of

glucose through certain processes. It is

given by the equation:

C6H12O6 + 6O2 6CO2 + 6H2O+ 36/38 ATP


Aerobic Respiration is divided into 3

major processes: Glycolysis, the Krebs

Cycle and the Electron Transport Chain.

The first step of any type of Cellular

Respiration is Glycolysis where the glucose

molecules are transformed into 2 moles of

pyruvic acid in the cytosol at the

consequence of using 2 units of ATP.The energy input and output of glycolisis


In this process, 4 units of ATP is produced for a

net total of 2 (subtracted from the 2 used), 2 units of

NADH+H and as said, 2 moles of pyruvic acid. The

pyruvic acid produced goes into a transitional stage

where the pyruvic acid is transformed into Acetyl CoA.

This product then goes into the Kreb’s cycle

where Acetyl CoA goes through numerous

transformations which will result into 8 units of NADH,

2 units of FADH2 and 4 units of ATP. This whole process

occurs inside the mitochondrial matrix of the cell.

Overview of pyruvate oxidation and Citric Acid Cycle


Lastly, the units of NADH and FADH2 proceed to

the cristae of the mitochondria where these products

are passed through certain pigments called cytochrome.

These carriers are then transformed into ATP.

The total units of ATP produced is 36 or 38 units

this is called the Electron Transport Chain. The reason for

the difference is due to the transportation of the NADH

produced in the cytosol to the mitochondrion of the cell.

There are 2 transportation systems: malate aspartate and

glycerol phosphate.

Free-energy change during electron transport


Under malate aspartate NADH can pass through the complete

Transport chain thus producing 6 for the two NADH while in glycerol

phosphate it will produce 4.

Anaerobic Respiration on the other hand is the production of

Energy from the enzymatic breakdown of Glucose to produce energy

this process is done without oxygen.


Unlike its oxygen using counterpart, Anaerobic Respiration is much

more inefficient in the production of ATP producing just 2 units of ATP. In

Anaerobic Respiration, only glycolysis takes place and the NADH produced

will be used in the repetition of glycolysis. This process has two different

types: Alcoholic Fermentation and Lactic Acid Fermentation. Alcoholic

Fermentation is the production of Ethyl Alcohol, 2 moles of CO2 and 2 units

of ATP.

C6H12O6 2CO2 + C2H5OH + 2 ATP

This type of respiration occurs in yeast and some plant cells.


The other type of Anaerobic Respiration is Lactic acid Fermentation

which is the enzymatic breakdown of glucose into Lactic acid and 2 units of

ATP. It is given by the equation:

C6H12O6 → C3H6O3 + 2 ATP

This type of respiration is seen in bacteria and muscle cells. This is

the main reason for cramping in our muscles

III. Results and DiscussionIn Cellular Respiration, there are two processes which can be observed in the

production of energy. The first is called substrate phosphorylation. It occurs when a

molecule of ADP reacts with a phosphate group from a substrate to produce ATP. This

type of Phosphorylation is seen in Glycolysis and also in the Kreb’s Cycle.

The other type of phosphorylation is called Oxidative Phosphorylation. This is

the process that creates the most number of ATP. This is only seen in Aerobic

Respiration and it occurs when an ADP combines with a phosphate group in the

electron transport chain.

In the experiment, mixtures were placed in separate Smith Fermentation tubes. The diameter of the circle was measured to compare the amount of carbon dioxide formed.

Tube No. Contents (excluding H2O)

1 Glucose +Yeast

2 Glucose

3 Boiled Yeast + Glucose

4 Starch Solution + Yeast

5 Yeast

min. 1 2 3 4 5

5m 0.02mm n/a 0.15mm 0.08mm 0.1mm

10m 0.03mm n/a 0.18mm 0.10mm 0.1mm

15m 0.04mm n/a 0.20mm 0.10mm 0.1mm

20m 0.05mm n/a 0.21mm 0.14mm 0.1mm

25m 0.05mm n/a 0.24mm 0.15mm 0.1mm

30m 0.05mm n/a 0.25mm 0.15mm 0.1mm

35m 0.5mm n/a 0.25mm 0.20mm 0.1mm

40m 0.5mm n/a 0.26mm 0.20mm 0.1mm


After shaking vigorously, spontaneous

production of CO2 was observed. Since it

produced bubbles instead of one big bubble, the

amount was then just compared to one another.

Content Amt. of bubbles

Glucose +Yeast Large production

Glucose No Bubbles

Boiled Yeast + Glucose 1 small bubble

Starch Solution + Yeast 2 large bubbles with a

small prod of bubbles

Yeast No Bubbles


The production of CO2 was observed in

Tube 1, Tube 3 and Tube 4.

The evolution of CO2 is very fast and the

bubbles were numerous in tube 1 this was

because glucose was readily available for the

respiration of the yeast. In tube 3, there should

be no CO2 because yeast dies in high

temperature. The presence of CO2 in tube 3 is

probably due to the incomplete heating of the

yeast suspension.


Lastly, in tube 4 there was little evolution of CO2 this is because

to respire, yeast must secrete amylase to break down the starch into

glucose and not all yeast can produce amylase and even if they could

this will take more time. For tubes 2 and 5 Respiration was not present

because one of the essential factors was absent (yeast in tube 2 and

glucose in tube 5).


There are several factors in which respiration will occur, let’s

discuss them one by one:


Amount of Nutrients

The more nutrients that is available to transform, the

more energy results in the cellular respiration process. The

types of nutrients that can go through the cellular respiration

process and transform into energy are namely fat, proteins

and carbohydrates. This also includes amino acids and fatty

acids. The carbohydrates converts to glucose, the fats go

through the citric acid cycle and the proteins break down and

go through glycolysis. The amount of nutrients available to

transform into energy depend on the diet of a person. The

nutrients go through three processes in cellular respiration.

The processes are glycolysis, Kreb’s cycle and the cytochrome

system.


Temperature

Another factor affecting the cellular

respiration is the temperature of the

environment. Usually, the rate of cellular

respiration quickens if the temperature is

warmer. The lower the temperature, the slower

the rate of cellular respiration is. People who live

in warmer environments find it easier to restore

their energy as long as there are nutrients

available to convert in the body.


Temperature

The reason for this is the enzymes that

are present in the cellular respiration process.

Enzymes break down easier and then transform

into energy quicker when the temperature is

higher. Although the temperature affects the

rate of cellular respiration, there are no studies

that prove more energy production with higher

temperatures. The temperature factor just

affects the rate of the cellular respiration

process.


State of Cell

The state of a cell undergoing the cellular respiration

process is a factor that affects the rate of transforming

nutrients into energy. Working cells, such as neurons or roots

of the human hair, have a higher cellular respiration rate

compared with dormant cells like seeds. This is because

working cells can store extra energy in the body while dormant

cells tend to stay non-motile. For this reason, plant cells do

not need to store as much energy as human cells or animal

cells do. This is the reason why cellular respiration in plants is

a bit different from the cellular respiration process human

and animal cells go through.


Substrate Present

As seen with the experiment the type of

substrate to be used in Respiration is quite

important. As for the case of the yeast, if glucose,

starch and maltose are placed in different tubes,

glucose will still be the fastest. Though there are

numerous glucose molecules in both maltose and

starch, the yeast will need to release enzymes which

may not be available to them and even if they are it

would take time compared to an environment

where glucose is readily available.


Substrate Present

In the experiment, yeast was observed to use

energy through Alcoholic Fermentation.

Though yeast can produce through both

Aerobic and Alcoholic Fermentation, it can be

deduced that it is anaerobic because the cotton was

placed to block any oxygen had there been oxygen

the amount of CO2 would have been much greater.

IV. Conclusion

The rate of cellular respiration is affected by the conditions in

which it takes place. When yeast and a simple sugar such as glucose is

present during the cellular respiration, the production of CO2 will form

more prominently than the others

References

Biology 10 (General Biology) Laboratory Manual. Department of Biology - College of Arts and Sciences - University of the Philippines,

Manila. Print.

Campbell, N.A., Reece, J.B. & Meyers, N. (2006). Biology. FrenchsForest: Pearson Education

Delos Reyes, J. (2006). Introduction to Biology: Principles and Processes (6th ed.). Department of Biology, College of Arts and

Sciences, University of the Philippines Manila.

Exercise 14 - Cellular Respiration in Yeast

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Transcript of Exercise 14 - Cellular Respiration in Yeast