THE EFFECT OF VARIOUS SUGAR TO YEAST FERMENTATION

Abstract

All living thing on earth can uptake energy from the environment to do biological work by cellular respiration and fermentation. Yeast breaks down glucose to conduct fermentation, release energy, and produce alcohol or other organic acid and carbon dioxide. This experiment is conducted to study the effective various forms of sugar that substitute to produce energy and influence the metabolic activities of yeast. Using five Ziploc bags with yeast and each with different solutions from varying sugar content, and one bag as the control analyzes the speed increase of fermentation of yeast and compare to each other. Throughout the experiment, the amount of CO₂ bubbles measures the bag thickness by a ruler, and measure the acidic of yeast production by pH indicator. From the experiment, the data gathered show that the higher sugar in a solution, the faster in the rate of fermentation. This means the amount of gas production and the acidic of the solution will be raised up.

Introduction

 Cellular respiration is the process of releasing energy in the form of adenosine triphosphate (ATP) from the glucose (C₆H₁₂O­₆) in the food. Cells need these energies for cellular work, all the activities of life. Cellular respiration occurs partially in the cytoplasm, and most of the steps occurs in the mitochondria. Cellular respiration involves four stages process: glycolysis, intermediate stage, Krebs cycle, and electron transport chain. Glycolysis occurs in the presence or absence of oxygen called anaerobic pathway. But the other stage requires the presence of oxygen called aerobic pathway. Substrate level phosphorylation includes glycolysis and Krebs cycle stage. Oxidative phosphorylation is the electron transport chain stage that produces ATP with oxygen as a terminal electron acceptor. The overall chemical reaction is

C₆H₁₂O­₆ + 6O₂  6CO₂ + 6H₂O + ~ 38 ATP

Fermentation is an anaerobic pathway for breaking down a glucose. Glycolysis is the only pathway to obtain energy in fermentation. Because of lacking the presence of oxygen, the pyruvate cannot continue to go the Krebs cycle and the electron transport chain. In fermentation, the electron transport chain isn’t functional, the NADH made in glycolysis cannot drop its electrons off, then it turns back into NAD⁺ and regenerates.

 There are few different types of fermentation. One of them is lactic acid fermentation (figure 1). After glycolysis, NADH transfers its electrons to pyruvate to generate lactate as a product. Lactate is the deprotonated form of lactic acid. Muscle cell also carries out lactic acid fermentation. Then, lactic acid is transported through the bloodstream to the liver that converted back to pyruvate and processed in the remaining reactions of cellular respiration.