• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Fermentation project - I am trying to find out what effects respiration in yeast.

Extracts from this document...


Fermentation project Aim I am trying to find out what effects respiration in yeast. Introduction Yeast is any of a number of microscopic one-celled fungi used for their ability to ferment carbohydrates in various substances. Yeasts are extensive in nature, occurring in the soil and in plants. Most cultivated yeasts belong to the species Saccharomyces; those known as brewers yeast are strains of S. cerevisiae. Yeasts have been used since the early years for the making of beer, wines and bread and today are used furthermore in industrial processes. Pure yeast cultures are grown in a medium of sugars, nitrogen sources, minerals and water. The final product may take the form of dried yeast cells. In the making of wines and beers, the fermented medium is the desired product and the yeast itself is discarded or used to feed animals. Anaerobic respiration Because yeast respires in anaerobic way fermentation can take place. Anaerobic respiration is respiration without the presence of oxygen. The first step consists of breaking down glucose into pyruvic acid and the end product (in yeast respiration) will be ethyl alcohol. Theory of fermentation Fermentation is the chemical changes in organic substances produced by the action of enzymes. In alcoholic fermentation, the action of zymase (the enzyme) secreted by yeast allows anaerobic respiration to take place, converts simple sugars such as glucose and fructose into ethyl alcohol (ethanol) ...read more.


Conversely enzymes will still allow respiration at low temperatures, as they are very efficient. Minute quantities of an enzyme can accomplish at low temperatures what would require violent reagents and high temperatures by ordinary chemical means. As a catalyst cannot be used up, the rate of bubbles will be released at a constant speed. The rate at which the bubbles carbon dioxide is produced (how fast the bubbles emerge) will not alter with time. However enzymes are proteins and become denatured if the temperature becomes too high. The active site changes shape and the substrate will no longer fit. Most enzymes stop working at around 45 C. This will mean that the rate of respiration will increase as the temperature gets higher until a certain temperature (around 45 C). I predict the enzyme will then become denatured and respiration will not occur. No CO will be produced. Method Before the experiment, a set of control results need to be obtained to compare against these will be carried out in the same way as the final experiment only using water in place of yeast. Firstly a yeast suspension needs to be prepared. This can be achieved by pouring a packet of yeast into around 500ml of water at 20 adding glucose and stirring until the granules are dispersed. The solution will become cloudy and frothing will occur. This is the carbon dioxide. ...read more.


It was quite hard to keep the temperature constant throughout each test. The tin foil helped but the temperature sometimes dropped 1 or 2 degrees. To solve this, better insulation methods could be used such as more tinfoil or a layer of polystyrene as well. Then there was the accuracy in the amount of carbon dioxide being released. It was quite simple to count the number of bubbles, however each bubble was not the same size making it impossible to know the actual volume of carbon dioxide being released. To solve this, a more complicated experiment would need to be carried out using a piece of apparatus called the Ganongs respirometer. This is a u shape monometer with a tap to equalize the pressure. The tap is then closed and co pushes a salt solution through the tube. Depending on how much the solution has moved, the amount of co can be recorded. This allows the quantity of co in cm to be recorded giving more accurate results. My results are reliable as for both tests, similar results were achieved and the conclusion fitted both sets of results. However my conclusion is only valid to the range of values I have investigated. To get more accurate results I would use smaller steps between each temperature. I only know that the temperature of denaturing is between 45 and 50 C plus the enzyme isn't full denatured at 50 . Some bubbles are still being produced. I would have to extend my range to see what happens when the temperature is increased further. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. Marked by a teacher

    Effect of different substrates on fermentation by Yeast.

    4 star(s)

    After 10mins, read the amount of Carbon Dioxide collected in the measuring cylinder, and record you results. Do the same for the other substrates, and repeat your readings. Results: Sugar Carbon Dioxide collected (ml) 1st test Carbon Dioxide collected (ml) 2nd test Avg.

  2. The effect temperature has on the rate of anaerobic respiration in yeast.

    * Using a stop clock instead of counting * Using the water bath to heat the water instead of a kettle or Bunsen burner so the temperature of the water is consistent * Checking the temperature of the water bath with a thermometer to check the accuracy of the water

  1. Investigating the Factors Affecting Respiration in Yeast.

    Diagram of the apparatus Clamp Thermometer Syringe with yeast, glucose and air Water Bath Example of Result Table (One table for each Temperature) Test Period Of Time** Intended temperature Actual temp. at beginning Actual temp. at end Average temp.* No.

  2. What is the effect on the rate of respiration of yeast cells with glucose ...

    to products. Enzymes are very specific as they can only catalyse a reaction in which the substrate molecule has a complementary shape to that of its active site. The substrate molecules that react together on the active site are likened to a 'key' and the active site to a 'lock'.

  1. Factor affecting the rate of fermentation.

    concentration of the glucose solution, and the amount of the catalyst ( yeast). In this experiment, we keep the temperature of the glucose solution the same by putting all the boiling tubes into the same water baths, which fills the warm water, this is not only to keep the environment

  2. The effects of organic effluent from the seweage on the biodiversty in a freshwater ...

    Ammonia is toxic and may lead to a lower biodiversty in the water stream near the sewage. Hence a nitrate indicator will be used to check for the presence of nitrates in the fresh water stream and support my hypothesis.

  1. Investigating The Fermentation of Yeast

    When the fermentation is strong more gas will be made than when the fermentation is weak. I do not need to know exactly how much gas is produced - I will only need to be able to judge if more or less is being given off.

  2. How temperature affects the rate of photosynthesis.

    than its previous repeats even though the environmental temperature is still the same. Accuracy: Form the personal graph it is clear that most points lay very close to the line of best fit apart from the anomaly at 25 oC which lies above the line of best fit.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work