krit.club logo

Biotechnology and Genetic Engineering - Biotechnology and yeast

Grade 11IGCSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Biotechnology is the use of living systems and organisms to develop or make products, or any technological application that uses biological systems to modify products or processes for specific use.

•

Yeast (SaccharomycesSaccharomyces cerevisiaecerevisiae) is a single-celled fungus used widely in biotechnology because it is easy to grow, reproduces rapidly, and can respire both aerobically and anaerobically.

•

Anaerobic respiration in yeast, also known as fermentation, is the process of breaking down glucose (C6H12O6C_6H_{12}O_6) in the absence of oxygen to produce ethanol (C2H5OHC_2H_5OH) and carbon dioxide (CO2CO_2).

•

In bread making, yeast is mixed with flour and water. The CO2CO_2 produced during fermentation gets trapped in the dough's gluten network, causing the bread to rise. The ethanol evaporates during the baking process.

•

In the production of alcoholic beverages, yeast ferments sugars from fruit (like grapes for wine) or grains (like malted barley for beer) to produce ethanol.

•

Biofuels involve using yeast to ferment sugars from crops like sugarcane or maize. The resulting ethanol (C2H5OHC_2H_5OH) is purified and used as a renewable energy source to reduce reliance on fossil fuels.

•

The rate of fermentation in yeast is influenced by temperature and the concentration of the glucose (C6H12O6C_6H_{12}O_6) substrate.

📐Formulae

C6H12O6→2C2H5OH+2CO2+EnergyC_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2 + \text{Energy}

C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

💡Examples

Problem 1:

Explain why the temperature must be carefully controlled when using yeast to produce ethanol in a fermenter.

Solution:

Temperature must be kept at an optimum level, usually around 25∘C25^{\circ}C to 35∘C35^{\circ}C.

Explanation:

Yeast activity is controlled by enzymes. If the temperature is too low, the rate of reaction is slow because the molecules have less kinetic energy. If the temperature exceeds the optimum (above 40∘C40^{\circ}C to 50∘C50^{\circ}C), the enzymes in the yeast will denature, changing the shape of the active site and stopping the fermentation process.

Problem 2:

A baker notices that a batch of dough failed to rise. Suggest a reason involving the yeast and the environment.

Solution:

The water added to the yeast may have been too hot (e.g., above 60∘C60^{\circ}C).

Explanation:

High temperatures cause the denaturation of essential enzymes within the yeast cells. This kills the yeast, preventing it from performing anaerobic respiration to produce CO2CO_2 gas, which is necessary for the dough to expand.

Problem 3:

Calculate the mass of CO2CO_2 produced if yeast ferments 180g180g of glucose (C6H12O6C_6H_{12}O_6), given that the molar mass of glucose is 180g/mol180g/mol and CO2CO_2 is 44g/mol44g/mol.

Solution:

88g88g of CO2CO_2.

Explanation:

From the equation C6H12O6→2C2H5OH+2CO2C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2, 11 mole of glucose produces 22 moles of CO2CO_2. Since 180g180g of glucose is 11 mole, it will produce 2×44g=88g2 \times 44g = 88g of carbon dioxide.

Biotechnology and yeast - Revision Notes & Key Diagrams | IGCSE Grade 11 Biology