An investigation into the effect of temperature on the rate of respiration in yeast

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An investigation into the effect of temperature on the rate of respiration in yeast

There are two types of respiration in yeast:

Aerobic:

Anaerobic: Glucose  Carbon dioxide + ethanol + energy

Respiration is controlled by enzymes, which are proteins which speed up one or more biological reactions. Within any cell many chemical reactions are going on at any one time. Yeast has many different types of enzymes that speed up respiration.

Prediction

I predict that as temperature increases, the rate will also increase, until a certain optimum temperature, after which, the rate will decrease until the rate is zero as respiration has stopped completely.

REASON

As temperature increases, rate of respiration increases, because particles move faster and with more energy, which in turn means more particles collide with enough energy to react. However, as temperature increases, enzyme stability decreases, so at temperatures above the optimum temperature, the rate will decrease, until all the enzymes have been fully denatured and all the active sites have been lost.

Enzymes speed up reactions in organisms. Each enzyme works on a specific substance, called its substrate.

The diagram below shows an “E” (an enzyme) catalysing the breakdown of “S” (the substrate) into two different products (“P”). Catalysis occurs because substance S fits precisely into surface of the enzyme E, so this reaction and no others are speeded up.

As can be seen from the diagram, if the enzyme changes shape, the active site (the area where the substrate reacts) would no longer be able to fit the substrate. This would mean the enzyme would lose its effect; the substrate would not break down.

This happens when the temperature is too high; the process is called “denaturing”. When an enzyme reaches a certain temperature, it will have so much energy that it is de-shaped; it is “denatured”. This diagram shows how a denatured enzyme will not work:


The enzymes will hardly work at very low temperatures (they wont be active). As temperatures increases, so does the activity of enzymes. Each enzyme has an optimum temperature in which they are most active. When the temperature is too high for that particular enzyme, the enzymes are denatured.

In yeast, there is more than one type of enzyme involved in anaerobic respiration. This means that the yeast enzymes do not denature at the same time, so although yeast does have an overall optimum temperature, the decrease in the rate of respiration that occurs after this point is gradual, as the number of actives sites decreases.

This is the apparatus I will be using in my experiment.


This graph summarises how and why temperature affects enzymes:

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I will be changing the temperature of the yeast, and I intend to use these temperatures: 20, 30, 40, 50, 60, 70, and 80 (oC), although it does not matter what exact temperatures I use, as long as they are at a suitable range. I will just use the temperatures which are most convenient when I am making the water baths.

I will measure how much water will be displaced by Carbon Dioxide in 3 minutes, in ...

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This is a well written report that shows good understanding of the process of an investigation. 1. There are several subheadings missing that would improve the structure of the report. 2. Researched information needs to be directly referenced. 3. The conclusion explains the pattern well but should use data from the investigation to back it up. 4. The evaluation is the strongest section and includes a good amount of detail. ****