Economic Importance of Anaerobic Respiration

Yeast is a

single-celled fungus

What type of respiration can yeast carry out

Yeast can carry out both aerobic and anerobic respiration

In bread-making what happens to the yeast?

The yeast starts of respiring aerobically, producing water and CO₂ (Carbon Dioxide makes the dough rise)

When the air runs out, the yeast begins to respire anaerobically. The sugar (glucose - coming from the breakdown of the starch in flour) isn’t fully oxidized to produce CO₂ and water, but instead produces CO₂ and ethanol.

What is alcoholic fermentation?

Is when sugar (glucose) is partially broken down by yeast (or a certain bacteria) into CO₂ , ethanol and ATP in the absence of oxygen

Why is the alcohol in bread not present after baking

The alcohol evaporates because of the high temperatures in the oven

How does yeast use the energy it gets from respiration

For growth and other living processes (7 vital functions)

How are alcoholic drinks like wine and beer produced?

By alcoholic fermentation by yeast, which breaks down sugars (depends on diff types of sugars)

Where do the sugars come from in beer and wine production?

Beer - Sugars come from germinating barley seeds (maltose) - Hops is added too

Wine - Sugars come from grapes

Thus, the yeast respires ___________, breaking down the sugars from the ______ or _____ (depending on whether beer or wine is going to be produced) into _______ and ______ and also some energy. The yeast uses this energy for _______ and ________

anaerobically

barley or grapes

ethanol and CO₂

growth and other living processes

To make yogurt you need

bacteria

What is the souring of milk

A fermentation process, known as lactic acid fermentation

What does fresh milk contain

sugars and some bacteria

What is this bacteria known as

Lactobacillus

What does this bacteria, lactobacillus, do?

It uses the sugars, known as lactose (from the milk) as its energy source.

Lactose is then converted into

Lactic acid

What effect does lactic acid have on milk

It causes the proteins in the milk to coagulate (curd/clump up) making the milk thicker and more sour

What is the step by step process for making yogurt?

1. Heat the milk at 80C for 15secs to kill pathogenic bacteria

2. Cool the milk down to 40C and add Lactobacillus bacteria

3. Keep the milk at 40C for 3hrs

4. Lactose is turned into lactic acid, and the milk proteins coagulate (clump up)

What is the word equation for lactic acid fermentation?

Lactose → Lactic acid + Energy