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Yeast and hymocytometer

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Introduction

NAME : NUR SAKINAH BINTI ISMAIL CLASS : M12F TEACHER`S NAME : PUAN MAZDIYAH BINTI SUBJECT : BIOLOGY HIGH LEVEL TITLE : Yeast cells and haemocytometer AIM : To investigate the effect of five different dilutions of yeast suspension on the number of cell per mm3 RESEARCH QUESTION : How do the five different dilutions of yeast suspension effect the number of cell per mm3 INTRODUCTION :Yeast are tiny single-celled (unicellular) fungi. The organisms in the Kingdom Fungi are not capable of making their own food. Fungi, like any other organism, need food for energy. They rely on sugar found in their environment to provide them with this energy so that they can grow and reproduce. Yeast, like bacteria grow in or on their food source. They produce and release digestive proteins (enzymes) into their environment where the sugar molecules are found. Complex sugar molecules then break down into monosaccharides that can be absorbed by the yeast and used for food (energy). There are many species of yeast, and each has a particular food source. Certain yeast feed on a variety of natural sources of sugar such as fruits, nectar from plants, and molasses from the plant crop called sorghum. Others break down wood and corn stalks. ...read more.

Middle

Special cover slip are been push on the slide as shown in diagram, the outside edges of the coverslip are been pressing down at the same time until the newton`s rings can be seen (see diagram 2). It is likely to break if you push the centre of the coverslip. Loading the haemocytometer The yeast cell suspension areshaked gently. The end of the capillary tube are inserted into the suspension. The liquid inside the tube will be rise. The end of the capillary tube has been run along the edge of the coverslip between the arms of the `H`. The area between the coverslip and the top half of the `H` are been filled with the suspension (shaded in diagram 3 below). Clean the slide if the yeast suspension flows into the troughs ( the lines of the `H` ) and start again. The slide through 180 degree are turned and for the opposite edge of the coverslip are been repeated (diagram 4). The haemocytomer are been placed on a damp tissue in a petri dish for at least two minutes to equilibrate. Counting the cells The microscope stage are been placed with the haemocytometer. The haemocytometer are been focused on the grid lines using the 10 X objective of the microscope. ...read more.

Conclusion

If less than 90% of the cells are free from contact with other cells, the count should be repeated with a fresh sample. Improper filling of chamber The chamber and cover slip should be cleaned first with distilled water, then by ethanol and wiped dry with a Kimwipe. Failure to adopt a convention for counting cells in contact with boundary lines or each other Develop a convention on which you do not count half of the cells that touch a border. For example, you only count the cells that touch the top border and left border, but do not count the cells that touch the bottom and right border. You should be consistent to increase the accuracy of your results. Statistical errors With careful attention to detail and by counting systematically and clearly, the overall error in counting can be reduced to between 10% and 15%. Parallax errors Make sure your eye is parallel with the level of the meniscus. Impurities in the suspension Clean all the apparatus thoroughly before beginning the experiment. Use a higher power of objective lens on the microscope to ascertain whether it is a yeast cell or not before counting a certain particle if you are unsure. Movement of yeast cells Wait a few second till the liquid suspension has stopped flowing and the yeast cells have stabilised before counting. ...read more.

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