# The Number Of Yeast Cells In A Suspension Biology Essay

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Density of cells in liquid is the number of cells per its unit volume. It are needed to be counted by the biologist. Therefore, the most convenient ways is by using Haemocytometer and microscope. It is the simplest and the cheapest to calculate the number of cells in a sample.

Haemocytometer consist of a heavy glass slide within the two counting chambers, which is 0.1 mm deep, each of which divided into nine large 1mm squares, on an etched and silvered surface separated by a through.

A cover slip sits on top of the raised support of the 'H' shaped toughs enclosing both chambers. There is 'V' or notch at either end where the cell suspension is loaded into the haemocytometer. When loaded with the cell suspension, it contains a declined volume of liquid.

The engraved grid on the surface of the counting chambers ensures that the number ofparticles in a defined volumeof liquid is counted.

The haemocytometer is placed on the microscope stage and the cell suspension is counted.

## RESEARCH QUESTION

What is the number of yeast cells per mm³ in five different dilutions of yeast suspension?

## HYPOTHESIS

As the concentration of yeast suspension increases, the number of yeast cells increases. This is due the density of yeast cells in the suspension increases.

## VARIABLES

## UNITS

## RANGE

## INDEPENDENT VARIABLE

The dilutions of yeast suspension

## -

0-1

## DEPENDENT VARIABLE

Number of yeast cell in every dilutions

## -

## -

TABLE 1 : Independent and Dependent Variable

## CONTROLLED

## VARIABLES

## UNITS

## POSSIBLE EFFECTS ON

## RESULTS

The temperature of surrounding

ËšC

Different surrounding temperature will effect the condition of the yeast

The period of cell to settle down (5minutes)

min

To ensure that all the yeast suspension dropped are distributed evenly

TABLE 2 : Controlled Variables

## MATERIALS AND APPARATUS

## Materials

## NO.

## MATERIALS

## QUANTITY

## VOLUME / SIZE

1.

Yeast solution

## -

5cm³

2.

Distilled water

## -

50cm³

TABLE 3 : Materials

## Apparatus

## NO.

## APPARATUS

## QUANTITY

## VOLUME / SIZE

1.

Test tubes

5

Standard size

2.

Dropper

1

Standard size

3.

Haemocytometer slide

1

## -

4.

Microscope

1

## -

5.

Coverslip

1

## -

6.

Soft tissue paper

1 roll

## -

7.

Measuring cylinder

2

5ml size

8.

Labelling paper

5

Standard size

9.

Stop watch

1

## -

TABLE 4 : Apparatus

## METHOD

Five test tubes are labelled with A, B, C, D and E respectively with labelled paper.

A sample of the standard yeast suspension provided is taken by using measuring cylinder about 5cm³. The yeast suspension is put into test tube A.

About 1cm³ of of the yeast suspension is taken out and put into test tube B. By using measuring cylinder, 9cm³ of distilled water is added into the test tube B. 1 in 10 dilution is made.

The procedure is continue until three more serial dilutions as follows are made :

## Test tubes

## Dilution

C

1 in 100

D

1 in 1000

E

1 in 10000

A coverslip is placed over the grid on the haemocytometer.

A small drop of the standard yeast suspension from the test tube A is placed at the edge of the coverslip.

5 minutes is waited untilfor the cells to be settle down.

The appropriate size square on the haemocytometer grid is chosen and the number of yeast cells in three separate squares are counted. The number of yeast cells are recorded.

These numbers are converted into the number of cells per mm³.

Steps 6 to 9 are repeated by using the same dilution.

Step 6 to 10 are repeated by using each of the serial dilutons in turn.

The control experiment are prepared.

The quantitative and qualitative data are recorded.

## DATE COLLECTION

## QUANTITATIVE DATA

Volume of standard yeast suspension sample = 5cm³

Volume of solutions in every test tubes = 10cm³

Number of yeast in every yeast suspension

## TEST TUBES

## DILUTION

## NUMBER OF YEAST PER mm³

## TRIAL 1

## TRIAL 2

## TRIAL 3

## 1

## 2

## 3

## 1

## 2

## 3

## 1

## 2

## 3

## A

## 1

2112

1936

1600

1920

1760

1728

3072

2640

2496

## B

## 1/10

176

288

336

192

96

320

160

256

192

## C

## 1/100

12

13

20

10

11

11

7

15

6

## D

## 1/1000

12

13

15

5

5

7

4

4

9

## E

## 1/10000

4

3

6

2

2

3

1

2

3

TABLE 5 : The Number of Yeast per mm³

## QUALITATIVE DATA

The colour of yeast suspension with the higher concentration is milky white

The colour of yeast suspension with the lower concentration is colourless.

The cells distributed evenly in each square.

The magnification used to observe the number of cells isow 10 x 40.

## DATA PROCESSING

## Average Number of Yeast in each Dilutions

The average number of yeast cell in each dilutions is calculated by using this formula :

∑ (Number of yeast cells in each particular square) 9

For example, in test tube A,

∑ (Number of yeast cells in each particular square) 9

= 2112+1936+1600+1920+1760+1728+3072+2640+2496 9

= 19264 9

= 2140

The average number of yeast in each dilutions are calculated by using the same formula.

## DILUTION

## AVERAGE NUMBER OF YEAST PER mm³

1

2140

1/10

224

1/100

12

1/1000

8

1/10000

3

TABLE 6 : The average number of yeast in each dilutions

## The Average Yeast Density

The average density of yeast in every dilutions is calculated by using this formula :

Average number of yeast cells in each particular square Volume of square grid, V (mm³)

For example, in test tube A,

Average number of yeast cells in each particular square Volume of square grid, V (mm³)

= 2140 0.2x0.2x0.1

= 535000 yeast per mm³

The average density for all the dilutions are calculated by using the same formula.

## TEST TUBES

## DILUTIONS

## VOLUME OF SQUARE GRID (mm³)

## AVERAGE NUMBER OF YEAST PER mm

## DENSITY OF YEAST PER mm

A

1

0.2 X 0.2 X 0.1

2140

535000

B

1/10

0.2 X 0.2 X 0.1

224

56000

C

1/100

0.2 X 0.2 X 0.1

12

3000

D

1/1000

0.2 X 0.2 X 0.1

8

2000

E

1/10000

0.2 X 0.2 X 0.1

3

750

TABLE 7 : The density of yeast in every dilutions

## The Standard Deviation

The standard deviation of average number of yeast is calculated by using this formula,

∑ x² - Χ² where, x = number of yeast in particular square n Χ = average number of yeast n = 9

For example, the standard deviation of average number of yeast for test tube A,

( 2112²+1936²+1600²+1920²+1760²+1728²+3072²+2640²+2496²) - 2140² 9

= 43041369 - 4579600 9

= 450

The standard solution of average number of yeast for other dilutions are calculated by using the same formula.

## TEST TUBE

## DILUTIONS

## STANDARD DEVIATION

A

1

450

B

1/10

76

C

1/100

3

D

1/1000

4

E

1/10000

1

TABLE 8 : The standard deviation of average number of yeast cell in each dilutions

The standard deviation of average density of yeast is calculated by using this formula :

Δ Density = Δ Average of number of yeast cells Density Average number of yeast cells

:- âˆ† Density = Δ Average of number of yeast cells X Density Average number of yeast cells

For example, the standard deviation of density of yeast cells in test tube A,

âˆ† Density = Δ Average of number of yeast cells X Density Average number of yeast cells

= 450 X 535000 2140

= 112500

The standard deviation of average density of yeast cells for other dilutions are calculated by using the same formula.

## TEST TUBES

## DILUTIONS

## STANDARD DEVIATION

A

1

112500

B

1/10

19000

C

1/100

750

D

1/1000

1000

E

1/10000

250

TABLE 9 : The standard deviation of average density of yeast cells

## CONCLUSION AND EVALUATION

## DISCUSSION

From the graph, the higher the concentration of yeast suspension, the higher the number of yeast cells counted.

When the yeast suspension ir further diluted, the number of yeast cells decreases.

The number of yeast cells in the concentrated yeast suspension is higher that it in diluted yeast suspension.

Thus, the number of yeast cells increases when the concentration of yeast suspension increases.

## EVALUATION

## Limitations and Suggestions

## LIMITATIONS

## SUGGESTIONS

The amount of yeast suspension dropped onto the haemocytometer slide are not evenly for every dilutions

Estimate the amount of the yeast suspension dro onto the haemocytometer slide by using dropper

The dilutions are not stir evenly in the test tube before being dropped onto the haemocytometer slide

Stir the yeast suspension with the glass rod before taking it onto the haemocytometer slide.

Thehaemocytometer slide is not clean and disturbing the process of counting

Clean the cover slip with an alcohol.

## CONCLUSION

The density of yeast cells are vary with different concentration of yeast suspension. The hinger the concentration of the yeast suspension, the higher the density of the yeast cells. The density for yeast suspension concentration of 1 is 535000. The density for yeast suspension concentration of 0.1is 56000. The density for yeast suspension concentration of 0.01 is 3000. The density for yeast suspension concentration of 0.001 is 2000. The density for yeast suspension concentration of 0.0001 is 750.