Page 142 - Knowledge Organiser Yr9 24-25

Knowledge Base: Science B2: Organisation in animals Year 9
3. Food Tests
3.1
How can you prepare a sample of food for a food test?
Crush the food (using a pestle and mortar), add a few drops of water and mix well.
3.2
What is the name of the chemical used when testing for starch in a food sample?
Iodine solution.
3.3
What colour is iodine and what colour does it turn in the presence of starch?
Brown, turns black/ dark blue if starch is present.
3.4
What is the name of the chemical used when testing for lipids in a food sample?
Ethanol.
3.5
What colour is ethanol and what happens to it in the presence of lipids?
Colourless, solution turns cloudy if lipids are present.
3.6
What is the name of the chemical used when testing for sugar in a food sample?
Benedict's solution.
3.7
What colour is Benedict's solution and what colour does it turn in the presence of sugar?
Blue, turns orange/ red if sugar is present.
3.8
What extra experimental step is required when testing for sugar?
Heat the solution in a boiling water bath at 75°C for 5 minutes.
3.9
What is the name of the chemical used when testing for protein in a food sample?
Biuret solution.
3.10
What colour does biuret solution turn in the presence of protein?
Purple.
4. Enzymes
4.1
What is an enzyme?
A biological catalyst which is a protein.
4.2
Name the three different groups of enzymes involved in digestion.
Carbohydrases, proteases, lipases.
4.3
Which group of enzymes break down carbohydrates?
Carbohydrases.
4.4
Which group of enzymes break down proteins?
Proteases.
4.5
Which group of enzymes break down lipids?
Lipases.
4.6
What products are carbohydrates broken down into?
Simple sugars, e.g. glucose.
4.7
What products are proteins broken down into?
Amino acids.
4.8
What products are lipids broken down into?
Fatty acids and glycerol.
4.9
What are the products of digestion used for, in the body?
To build new carbohydrates, proteins and lipids, some glucose is used in respiration.
4.10
What is the lock and key model?
The specific shape of the active site matches the specific shape of its substrate molecules.
4.11
What does denatured mean?
When the shape of the enzymes active site changes and the substrate no longer fits.
4.12
Name two environmental conditions that cause an enzyme active site to change.
Temperature increase, increase or decrease in pH.
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