An investigation in to how enzyme ripeness in pineapple affects the setting of gelatine.

Authors Avatar

An investigation in to how enzyme ripeness in pineapple affects                   the setting of gelatine

Gelatine, more commonly known as Jelly, is a substance that consists mainly of collagen, a protein found in animal tendons and skin. The gelatine used for cooking purposes is usually in the form of granules. These granules swell when they are re-hydrated in water, but only fully dissolve in hot water. As this solution cools it sets to a moisture holding gel. This gel forms due to the proteins in gelatine joining to form a web like structure.

In Module 1 A-level Biology, we learn about the structure of a protein molecule. A protein molecule is formed when amino acids join together by condensation, forming a peptide bond and water as a bi-product. A chain of many amino acids is known as a polypeptide and a protein can consist of one or more of these. The opposite of condensation is hydrolysis. When hydrolysis occurs a peptide bond is broken and water is used up in the reaction. There are specific enzymes called proteases (Module 2), which can be found in fruits such as pineapple, that speed up the hydrolysis reaction that breaks down protein molecules. From research I have found that it is a protease called bromelain found in pineapple, which in the scenario is preventing the gelatine from setting by breaking up the proteins forming the web like structure.

It is also in Module 1 that we learn how enzymes perform such tasks, and the conditions that best suit them. Enzymes are proteins which act as catalysts. They have a tertiary structure that provides them with an active site; a groove in the enzyme surface that combines precisely with a substrate of a specific shape and charge. The lock and key hypothesis states that the substrate binds to the active site to form an enzyme substrate complex. The substrate is then altered to form the product of the reaction and is released from the active site. The induced fit hypothesis is a more recent theory which suggests that the active site actually changes shape to mould itself to the substrate.

The tertiary structure of enzymes also causes them to be sensitive to temperature and pH, and an enzyme will denature in extremes of these conditions. When an enzyme denatures it is no longer functional because the active site has changed shape and consequently the substrate molecule will not be able to combine with the enzyme. Increasing the temperature gives molecules more kinetic energy, so they collide more frequently and the rate increases. This is also true for enzymes up to a certain point: the optimum temperature. Above this temperature, enzymes vibrate so much that their structure is damaged and the active site altered. A change in pH disrupts the charges; consequently the active site cannot bind to the substrate.

Plants produce fruit to acts as a delivery system for seeds. Fruit consist of carbohydrates that make them taste sweet (Module 1), providing attractive food for animals, which will help aid the dispersion of the seeds. Ageing of fruit is known as ripening, and this process is designed to stop animals from eating the fruit before the seeds are fully developed. When under-ripe, pineapples would not be appealing to animals because they are green in colour, tough to eat and acidic.

Join now!

There are enzymes responsible for the ripening of fruit which break down the starch content to produce more sweet sugars and make the fruit softer, making it more edible. Therefore, altering the conditions which effect enzyme rate of reaction, will effect how quickly a pineapple will ripen. Other enzyme activity increases in the fruit during ripening, due to certain hormones (such as ethylene). Applying this rule to pineapple: the bromelain enzyme activity will increase as the pineapple ripens. If I were to put a pineapple in cold conditions, this would slow down the ripening process because the enzymes responsible would have ...

This is a preview of the whole essay