Biology Essay Research Paper Fermentation InvestigationPlanningAs a

Method

Label five fermentation tubes 1-5, writing the numbers with a wax pencil upside down near the bottom of each tube. Pipette the following into each tube (10 drops of distilled water, glucose, fructose, pentose, hexose). Set up the fermentation tubes as follows. Hold the filled tube in your hand and insert it into an inverted test tube. With a pencil, or some other suitable instrument, push the small tube into the inverted test tube as far as it will go and then invert the whole assemblage. Tap the outer tube firmly to release any bubbles (CO2) trapped as the mouth of the inner tube. When all fermentation tubes have been set up, record the height of the fluid in mm in each one. Do this by holding the test tube vertically on a table ands placing a millimetre ruler alongside it. Now place all the test tubes in a constant-temperature water bath at 37 0C for at least 45 minutes. Remove the test tubes from the constant-temperature bath, and re-measure the height of the fluid in each fermentation tube. If enough gas has collected in the fermentation tube to make it buoyant, you must push it down when taking your reading. Record the difference in height between the initial and final reading for each of the tubes.

Background knowledge

FERMENTATION is the breakdown of sugars by bacteria and yeast using a method of respiration without oxygen (anaerobic respiration). It involves a culture of yeast and a solution of sugar, producing ethanol and carbon dioxide with the aid of the enzymes. This is an 8-10 step process requiring different enzymes each time, but it can be simplified like this.

This process can be slowed down by DENATURATION of the enzymes at a certain temperature.

All the ENZYMES are protein chains of amino acids. They exist in the form of ?-helix structure with hydrogen bonds holding the pitches together. On the amino acid molecules, there is R a group. They react with each other to form peptide bonds, transforming the chain into a 3-dimensional structure. Along the chain there are active sites where interaction between the enzyme and the substrate happens. These sites are sensitive to heat, like the hydrogen bonds that hold the 3D molecule together. When heat is applied to the enzyme, energy is given into the molecule. The active sites deform and the hydrogen bonds break, denaturing this enzyme. It would not be able to function as usual, and this is not reversible. This is called DENATURATION. The 3D-helix structure would breakdown and the active sites would change in shape; they would not be able to accommodate the substrate any more. The analogy of this is to compare a key to a keyhole. If the keyhole has changed, the same key would not fit in any more, and the lock would not be unlocked. The same thing happens here, and fermentation could not continue after this has occurred. Also when the temperature is too low, the enzymes would not work because there is not enough energy for activities to happen.