Experiments Included ( answered thoroughly with additional notes ):
1 Describe the role of anaerobic respiration in yeast during the production of ethanol for biofuels.
2 Describe the role of anaerobic respiration in yeast during bread-making.
3 Investigate and describe the use of pectinase in f...
1 Describe the role of anaerobic respiration in yeast during production of ethanol for biofuels.
When yeast cells are reproducing rapidly, the oxygen is used up. The yeast has to switch to using anaerobic
respiration to ensure it can survive. With fossil fuels being non-renewable and contributing to global warming, biofuels
are increasingly being considered as a possible alternative for the future. Bioethanol production uses yeast
to anaerobically ferment carbohydrate. When ethanol is made by fermentation, sugar is converted into ethanol and
carbon dioxide if conditions are anaerobic. Single-celled fungi, called yeast, contain enzymes that are
natural catalysts for making this process happen. In some countries, such as Brazil, the source of sugar is sugar cane
- which yeast can directly ferment into ethanol. (In other countries, plants such as maize are used. Because maize
contains starch rather than sugar, the enzyme amylase must first break down the starch into sugar before the yeast
can ferment it into ethanol). The ethanol produced by yeast only reaches a concentration of around 15 per cent before
the ethanol becomes toxic to the yeast. In order to make it sufficiently concentrated to be burnt as a fuel, the ethanol
must be distilled. https://www.bbc.co.uk/bitesize/guides/z8sb2p3/revision/4
2 Describe the role of anaerobic respiration in yeast during bread-making.
Yeast is a live, single-celled fungus. There are about 160 species of yeast, and many of them live all around us.
However, most people are familiar with yeast in its mass-produced form: the light brown granules that come in 8g foil
packets at the supermarket. This organism lies dormant until it comes into contact with warm water. Once reactivated,
yeast begins feeding on sugars in foods such as flour, and releases carbon dioxide that makes bread rise (although at
a much slower rate than baking powder or soda). Yeast also adds many of the distinctive flavors and aromas we
associate with bread. Yeast, on the other hand, is a live, single-celled fungus. There are lots of different types of flour
used in bread, but the most commonly used in raised bread is wheat flour. This is because wheat flour contains a
protein which, when combined with water, forms gluten. As you knead the dough, the gluten becomes more and more
stretchy. This gum-like substance fills with thousands of gas bubbles as the yeast goes to work during rising.
Starch, a carbohydrate that makes up about 70% of flour by weight, also gets in on the act. When starch granules are
attacked by enzymes present in flour, they release the sugars that yeast feeds on. Starch also reinforces gluten and
absorbs water during baking, helping the gluten to contain the pockets of gas produced by the yeast.
Sometimes, a baker will let the dough rise several times, allowing the gluten to develop more completely and the
yeast to add more of its flavors. When the dough is finally cooked—either in an oven, over a fire, or in a steamer,
depending on what kind of bread you’re baking—the yeast inside it continues feeding, and the pockets of gas in the
dough continue to expand. As the temperature of the cooking dough rises, the yeast eventually dies, the gluten
hardens, and the dough solidifies – and you end up with …Bread!
https://www.exploratorium.edu/cooking/bread/bread_science.html Check this practical: https://www.exploratorium.edu/cooking/bread/activity-
yeast.html
3 Investigate and describe the use of pectinase in fruit juice production.
Enzymes are an integral component of modern fruit juice manufacturing and are highly suitable for optimising
processes. Fruit juices are extracted using an enzyme called pectinase. Pectin is a substance which helps to stick
plant cells together. Fruits like apple or orange contain a lot of pectin. The braking down of pectin makes it much
easier to squeeze juice from the fruit. Pectinase is widely used in order to: (a) extraction of juice from raw material
(b) processing efficiency (pressing, solid settling or removal) (c) generate a final product that is clear and visually
attractive. http://igbiologyy.blogspot.com/2012/12/27-use-of-enzymes-in-food-industry.html
Check this practical: https://www.youtube.com/watch?v=Q3bJStyn80o
4 Investigate and describe the use of biological washing powders that contain enzymes.
Biological washing powders contain protease and lipase to remove protein stains and fat/grease from clothes. The
enzymes break down proteins or fats on the fabric, forming water-soluble substances that can be washed away.
Example: Blood contain the red protein Haemoglobin (Hb). The Proteases in biological washing powder break Hb
molecules into smaller molecules, which are not coloured and which dissolve in water and can be washed away.
This makes the washing powder more effective than detergent alone, especially at lower temperatures. This save
energy (no need to boil water), but if the temperature is too high, the enzyme will be denatured.
https://biology-igcse.weebly.com/use-in-biological-washing-powders.html
5 Investigate and explain the use of lactase to produce lactose-free milk.
When the enzyme lactase is mixed with milk which contains lactose, the lactase enzymes break the lactose down into
simple sugars that can be consumed by people who have intolerances to lactose The following link shows haw
lactase can be used to break lactose down into glucose and other monosaccharide sugars:
https://www.youtube.com/watch?v=P7e9Mj9ATpQ
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