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Monday, 16 April 2012

Biological molecules


Specification:
2.5 recall the chemical elements present in carbohydrates, proteins and lipids (fats and oils)
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up of smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol
2.7 describe the tests for glucose and starch
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
2.9 understand how the functioning of enzymes can be affected by changes in temperatures
2.11 describe how to carry out simple controlled experiments to illustrate how enzyme activity can be affected by changes in temperature



2.5 recall the chemical elements present in carbohydrates, proteins and lipids (fats and oils)

Carbs and lipids: carbon, hydrogen, oxygen
Protein:
  • Carbon
  • Hydrogen
  • Oxygen
  • Sulphur
  • Phosphorous
  • Nitrogen 
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up of smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol 

Simple sugars e.g. glucose, maltose, galactose Starch, glycogen
Amino acids Protein
Fatty acids + glycerol Lipids

      2.7 describe the tests for glucose and starch


Test for glucose

Benedict's solution-blue solution containing copper (II) sulphate.
Reducing sugars such as glucose, maltose, fructose and lactose can reduce the copper (II) in Benedict's solution to copper (I).
-produce a brick-red precipitate of copper (I) oxide when boiled with Benedict's solution.
Benedict's test:
  1. Add 2 cm3 of Benedict's solution to 2 cm3 of glucose solution in a test tube and shake the mixture. Leave the test tube in a beaker of boiling water for five minutes.
  2. As a control experiment, repeat step 1 using 2 cm3 of distilled water in place of glucose solution.
  3. What do you observe after five minutes for both experiments? Is glucose a reducing sugar?
  4. Yes, we already know that, but this test just proves it. The colour change seen is the blue Benedict's solution turning brick-red or orange-red precipitate.
    Test for starch
    Iodine test:
    Starch can be detected by the iodine test. A few drops of iodine solution added to any substance containing starch will produce a blue-black colour.
  5. Add a few drops of iodine solution to a piece of potato on a white tile.
  6. What do you observe?
    Plants store glucose in the form of starch. For example, starch is abundant in vegetable such as potato and tapioca.
2.8 understand the role of enzymes as biological catalysts in metabolic reactions

Enzymes are biological catalysts made of proteins that speed up chemical reactions without being used up/chemically altered. They lower activation energy-which is the energy needed to start a chemical reaction.

2.9 understand how the functioning of enzymes can be affected by changes in temperatures

High temperatures denature enzymes so they do not function anymore.
To explain this in more detail:
The chains of amino acids are coiled/folded up to give the protein a three-dimensional shape. The coils are held in place by weak bonds (hydrogen bonds).
An increase in temperature increases vibrations in the atoms of the enzyme. At high temperatures (Above 65°C for many human proteins), the vibrations are so violent that they break the hydrogen bonds in the enzyme, causing it to lose its shape.
When the active site changes shape, the substrate

2.11 describe how to carry out simple controlled experiments to illustrate how enzyme activity can be affected by changes in temperature

http://askmichellebiology.blogspot.com/2012/04/effect-of-temperature-on-amylase.html

21 comments:

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    ReplyDelete
    Replies
    1. Hi I didn't include any Single Science specification points in my posts..sorry!

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  12. where is 2.11?

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    Replies
    1. Here http://askmichellebiology.blogspot.com/2012/04/effect-of-temperature-on-amylase.html
      :)

      Delete
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