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AICE Biology Lab Review: Biological Molecules Enzymes

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AICE Biology Lab Review: Biological Molecules Enzymes

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    1. AICE Biology Lab Review: Biological Molecules & Enzymes Prepared by Ms. Evans at GHSPrepared by Ms. Evans at GHS

    2. B. Biological Molecules (a) carry out tests for reducing and non-reducing sugars (including semi-quantitative use of the Benedict’s test), the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins;

    3. Benedict’s Test: Reducing & Non Reducing Sugars, Round 1

    4. Benedict’s Test: Reducing & Non Reducing Sugars, Round 2 A Negative result in round one DOES NOT mean an absence of carbohydrates!!

    5. Sample Procedure for Benedict’s Test for Non Reducing Sugar In a test tube place 5 cm3 solution, add 3 cm3 Benedict's reagent to the solution in the test tube and place the tube in the boiling water bath for five minutes. Add 1 cm3 dilute hydrochloric acid to the solution solution in your test tube. Note the time and place in the water bath After 10+ minutes, remove the tube from the water bath & cool it under the tap. Neutralize the acid by adding solid sodium bicarbonate, a little at a time, until the addition of one portion produces no fizzing. With a dropping pipette place 3 cm3 Benedict's solution in test tube & return to the water bath and heat for five minutes. A color change indicates that there was Non reducing sugar present. How would you verify that your solution was sucrose & not starch???

    6. Benedict’s Testing: Sample Question 1 Solutions of four food substances are tested for sugars. The table shows the colours of the solutions after testing.

    7. Benedict’s Testing: Sample Question 2 Four sugar solutions were tested with a standard Benedicts solution. The table shows the colour of the solutions after testing.

    8. Testing for Starch IKI (Iodine in Potassium Iodide)

    9. Emulsion Testing for Lipids Sample Procedure: Add 2cm3 fat or oil to a test tube containing 2cm3 of absolute ethanol. Dissolve the lipid by shaking vigorously. Add an equal amount of cold water. Observation: A cloudy white suspension.

    10. Testing for Polypeptides (proteins) Biuret’s Reagent Left to right: Biuret's reagent (BrR), water + BrR, egg albumin solution, egg albumin solution+ BrR.

    11. Identify each sample Food tests are carried out on four unknown chemicals. The chart below shows the results of each test.

    12. C. Enzymes (c) follow the time course of an enzyme-catalysed reaction by measuring rates of formation of products (for example, using catalase) or rates of disappearance of substrate (for example, using amylase)

    13. Enzymes

    14. Enzymes Practice Question 2 The graphs show the effects of temperature and pH on enzyme activity.

    15. Enzymes Practice Question 3 The graph shows the effect of substrate concentration on the rate of an enzyme-controlled reaction. The enzyme concentration is constant.

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