1. Living Factories: Yeast

2. Saccharomyces cerevisiae
YEAST!!!

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

4. 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!

5. Looking at Yeast

6. 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

7. Do you remember the difference between aerobic and anaerobic respiration?

8. 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.

9. Aerobic Respiration Glucose + oxygen carbon dioxide + water + energy

10. 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

11. 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

12. Anaerobic Respiration (Fermentation)
Glucose carbon dioxide
+ ethanol energy

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

14. 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)

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

16. 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

17. Breadmaking

18. 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.

19. 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.

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

21. 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

22. 4. Kneading the dough

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

24. 6. Proving the dough Yeast releases CO2 bubbles making dough rise

25. 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