B3 Biological elements Flashcards
What are the key three biological molecules essential for all living organisms?
-Carbohydrates
-Lipids/fats
-Proteins
What are the chemical elements that make up carbohydrates?
Carbohydrates contain:
-Carbon
-Hydrogen
-Oxygen
What are the chemical elements that make up proteins?
Proteins contains:
-Carbon
-Hydrogen
-Oxygen
-Nitrogen
-Sulfur (sometimes)
What are the chemical elements that make up fats/lipids?
Fats contain:
-Oxygen
-Hydrogen
-carbon
What are large molecules made from?
Large molecules are made from smaller molecules.
What makes up carbohydrates?
Carbohydrates are:
-Long chains of simple sugars
e.g. Glucose is a simple sugar.
-When two glucose molecules join together, maltose is formed.
-When lots of glucose molecules join together, starch, glycogen or cellulose can form.
What makes up fats?
Fats/lipids are:
-Large molecules made from smaller units of fatty acids and glycerol.
-1 glycerol molecules is chemically bonded to 3 fatty acid chains.
-Lipids are divided into fats (solid at room temp) and oils (liquid at room temp).
What makes up proteins?
Proteins are:
-Long chains of amino acids whose order has been determined by genes.
-The amino acids can be arranged in any order, resulting in hundreds of thousands of proteins.
What is the first step of testing the presence of certain molecules in food?
Prepare food samples - e.g. crushing with a pestle and mortar before mixing with distilled water. The solution can then be strained or filtered to remove any pieces of solid food. This solution can then be tested using a specific reagent, and the solution may change colour.
What does it mean if the reagent remains unchanged in colour?
If the reagent remains unchanged in colour, it means there is a negative result.
How to test for starch?
To test for starch:
-Reagent: Iodine solution
1) Add food sample to a test tube.
2) Add a few drops of iodine.
3) Iodine solution will change from orange to blue/black colour if starch IS present.
4) Results are instant - qualitative.
How to test for glucose/ reducing sugars?
To test for glucose/ reducing sugars:
-Reagent: Benedict’s solution.
1) Add food sample solution into a test tube.
2) Add Benedict’s solution into the small solution (in test tube).
3) Heat at 60-60°C in a water bath for 5 minutes.
4) Take test tube out of water bath and observe colour.
5) A positive test will show colour change from blue to orange/brick red.
What are the safety precautions to take when doing the test for glucose/ reducing sugars?
- Handle test tube with tongs.
-Wear safety goggles.
-Wear heatproof gloves.
How to test for proteins?
To test for porteins:
-Reagent: Biuret solution.
1) Add food sample to a test tube.
2) Add drops of Biuret solution to the food sample.
3) A positive result will show a colour change from blue to purple/violet.
How to test for lipids?
To test for lipids:
-Reagent: Ethanol.
1) Mix food sample with 2cm3 of ethanol and shake.
2) Food sample is filtered.
3) Add the food sample to an equal volume of cold water/ distilled water.
3) A positive test will show a clear solution turning into a milky white/ cloudy emulsion forming.
