Summative Practice Chapter 5 – Question 5 – 8 (Form 4 Biology Textbook Exercise and Answer)

Question 5:
(a) If you are a food entrepreneur, suggest an enzyme that you can use to process meat and fish. State the function of this enzyme.
(b) Discuss how the characteristics of the enzymes can influence its action.

The enzyme that is used in meat processing is protease. Protease helps to tenderise meat. The enzyme that is used in fish processing is protease. Proteases can separate fish meat from its skin.

Enzyme is an organic catalyst that accelerates the rate of chemical reactions in living organisms.

Characteristics of enzyme that affect its reactions:
Enzyme is very sensitive to temperature. Each enzyme functions optimally within a certain temperature range. At temperatures too high, the protein structure in the enzyme will be denatured whereas at temperatures too low, the enzyme becomes less active.

Enzyme is sensitive to changes in pH. Each enzyme functions optimally within a certain range of pH value. If the pH value is not within the optimum range, the enzyme will become inactive. For example, pepsin reacts in the pH range of 1.5 to 2.

Enzymes are specific. Only substrate molecules that can complement the enzyme molecule will bind to it so that reaction can take place.

Question 6:
The enzymes that exist in the bacteria strain which live in hot spring areas can be extracted and added to laundry detergent. Suggest why enzymes from these bacteria are suitable to be used as laundry detergent.

The washing machine has a temperature control function. High temperatures can cause the enzymes in detergents to denature. Thus, if enzymes are extracted from live bacteria in hot springs, these enzymes are able to withstand high temperatures without denaturing.

Question 7:
Why does cyanide poisoning cause immediate death?

Cyanide can bind with one of the cellular respiration enzymes. Cyanide can block glucose oxidation and stop cellular respiration. Without cellular respiration, a person will die.

Question 8:
Fresh fruits can be processed to produce juice. Fruits are crushed and squeezed before the juice is extracted. Plant cells contain strong cellulose walls. However, if enzymes that contain pectinase enzymes are used, more juice can be extracted. Based on this information, suggest one laboratory experiment that can extract more fruit juice than the pressing method.

• A few apples are blended together.

• The blended apple mixture is divided equally into two different beakers, beaker A and beaker B.

• The blended apple mixture is left at room temperature for 30 minutes to allow the enzyme inhibitor that exists naturally in the apples to be oxidised to its inactive form.

• 2 ml of distilled water is added to beaker A while 2 ml of pectinase solution (enzyme solution containing cellulose and hemicellulose) is added to beaker B (pectinase is diluted with distilled water to a 50% concentration before added to beaker A).

• Both beakers are immersed in water at 30 °C for 30 minutes.

• The solution from both beakers are then filtered into two different measuring cylinders.

• The apple juice obtained from beaker B is 20% more than beaker A.

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