Living Factories: Yeast www.assignmentpoint.com

Saccharomyces cerevisiae YEAST!!! www.assignmentpoint.com

Yeast Single celled microorganism Type of fungus Exist on all living matter 16 chromosomes Hundreds of different species! www.assignmentpoint.com

Did you know? We may not look much like yeast or they like us, but many of the 6,000 genes in yeast have counterparts in humans! www.assignmentpoint.com

Looking at Yeast www.assignmentpoint.com

Yeast as a Living Organism As a living organism, just like us, yeast needs the following to survive and flourish: -sugars -water -warmth Respiration is the process by which a living organism releases energy from its food www.assignmentpoint.com

Do you remember the difference between aerobic and anaerobic respiration? www.assignmentpoint.com

Aerobic Respiration Humans produce energy through aerobic respiration In aerobic respiration glucose reacts with oxygen in the mitochondria of the cells to release energy. Carbon dioxide and water are by-products of the reaction. www.assignmentpoint.com

Aerobic Respiration Glucose + oxygen carbon dioxide + water + energy www.assignmentpoint.com

Anaerobic Respiration Anaerobic respiration occurs when oxygen is not available. In anaerobic respiration the glucose is only partially broken down, and lactic acid is produced www.assignmentpoint.com

Fermentation Living yeast cells in the absence of oxygen are still able to use sugar as their source of food to make energy This is known as fermentation In this case ethanol (alcohol) is produced instead of lactic acid www.assignmentpoint.com

Anaerobic Respiration (Fermentation) Glucose carbon dioxide + ethanol + energy www.assignmentpoint.com

Aerobic Vs. Anaerobic Respiration -oxygen always required -efficient method of respiration -sugar completely broken down to carbon dioxide and water www.assignmentpoint.com

Aerobic Vs. Anaerobic Respiration -oxygen never required -inefficient method of respiration -releases a small amount of energy -much of the energy remains locked up in the molecules of the end product (e.g. the alcohol) www.assignmentpoint.com

Quick Quiz Can you sort out the following statements into aerobic or anaerobic respiration? Just fill them into your table! www.assignmentpoint.com

Glucose + oxygen carbon dioxide + water + energy Glucose reacts in the mitochondra of cells Much of the energy remains locked up in the molecules of the end product Inefficient method of respiration Sugar completely broken down to carbon dioxide and water Only releases a small amount of energy Glucose carbon dioxide + ethanol + energy Oxygen always required Oxygen never required Efficient method of respiration www.assignmentpoint.com

Breadmaking www.assignmentpoint.com

Bread Basics! Bakers use two simple facts of life to create soft, spongy, moist bread: First, they use the fact that yeast (a single-cell fungi) will eat sugar: -from the sugar yeast creates alcohol and carbon dioxide gas as waste products -the carbon dioxide gas created by yeast is what gives bread its airy texture, and -the alcohol, which burns off during baking, leaves behind an important component of bread's flavor. www.assignmentpoint.com

Bread Basics! Second, wheat flour, if mixed with water and kneaded, becomes very elastic. -the flour-and-water mixture in bread becomes stretchy like a balloon because of a protein in wheat known as gluten -gluten gives bread dough the ability to capture the carbon dioxide produced by yeast in tiny flour balloons. www.assignmentpoint.com

Gluten http://www.exploratorium.edu/cooking/bread/bread_science.html www.assignmentpoint.com

How to make bread…. You will need: Flour with added salt and lard rubbed in to make dough Yeast added to warm sugar solution and allowed to grow to produce bubbles Mix the yeast and the flour together in a bowl www.assignmentpoint.com

4. Kneading the dough www.assignmentpoint.com

5. Leaving the mixture to rise Mixture left in warm place covered by damp cloth www.assignmentpoint.com

6. Proving the dough Yeast releases CO2 bubbles making dough rise www.assignmentpoint.com

7. Baking bread After dough rises a couple of hours in a warm place, it's ready to go into the oven. There, heat causes pockets of gas in the dough to expand www.assignmentpoint.com