Unit 4 - Lesson 10: Yeast & Beer Flashcards
What does biotechnology use to make useful products?
Microorganisms
What process is often involved in biotechnology?
Fermentation, which uses the respiration of microorganisms to make products.
What is yeast used for regarding bread?
Yeast is often used to make bread rise.
Is yeast a single celled fungus or a multicellular fungus?
Yeast is a single celled fungus.
How does yeast achieve/absorb nutrients?
It uses saprotrophic nutrition to secrete extracellular digestive enzymes, which breakdown organic matter (normally dead or decaying). It then absorbs the nutrients.
(a) What are the products when yeast mixes with sugar?
(b) Write the chemical equation.
(a) When mixed with sugar, yeast produces carbon dioxide and water by aerobic respiration.
(b) C6H12O6 + O2 –> H2O + ATP
Where does the CO2 build up in the bread and what effect does this have on the bread?
CO2 builds up in the bread creating pockets, which makes the bread rise and have a spongy texture.
What does leavened bread mean?
Leavened bread (with yeast)
What does unleavened bread mean?
Unleavened bread (without yeast)
If sugar is not mixed with yeast, can aerobic respiration still occur? If so, how?
Yes. The glucose is obtained from the starch in the flour. The flour contains enzymes to break down starch to maltose. The extracellular digestive enzymes from the yeast convert this to glucose for respiration.
When the oxygen runs out, how does the yeast respire?
The yeast respires anaerobically.
When yeast respires anaerobically (without oxygen), what does it produce?
Ethanol (a type of alcohol).
Give the word equation for what glucose produces when yeast respires anaerobically.
Glucose –> Ethanol + Carbon Dioxide + Energy
When the bread is baked, the temperature rises and does what to the yeast? What process stops due to this? How is ethanol affected by this?
The temperature kills the yeast, so FERMENTATION stops. The alcohol is evaporated away.
When the yeast dies, what happens to the bread?
The bread stops rising but the air pockets remain.
What is the 3 step method for making bread?
- Mix yeast with flour and water. Adding sugar is useful to provide the sugar for respiration. Without it, enzymes in the flour breakdown the carbohydrates to sugars.
- Knead the dough and leave in a warm place to rise.
- Bake in the oven.
How is wine made? What process?
Wine is made by the fermentation of grape juice sugars.
What is used to ferment the sugars when making wine?
Yeast
What is wine made in and why?
Wine is made in large, airtight containers. This maintains the anaerobic conditions needed to produce the ethanol.
What will happen if oxygen enters the airtight container when making wine?
If oxygen enters, the yeast will switch to aerobic respiration and ethanol production will stop.
As the alcohol levels increase, when making wine, what happens to the yeast? What process is effected by this and how?
The yeast is killed. At this point, fermentation will stop.
How is beer made? What process?
Beer is produced from the fermentation of barley.
What kind of biomolecule is barley?
Barley is a type of carbohydrate called ‘starch’ (polysaccharide).
What must starch be broken down into for respiration (when making beer)?
It must be broken down to a simple sugar for respiration.
