(9) Plant cells have a large, fluid filled space in the centre this is known as a vacuole. It contains cell sap – this is made up of a watery solution of sugars, salts and sometimes pigments. The substrate Catechol can be found in the vacuoles of the plant cells. Catechol oxidase on the other hand can be found in the cytoplasm
If the cell becomes damaged so does the vacuole the knockon effect is:
Cell damaged catechol released into cytoplasm substrate and enzyme meet to convert catechol into o.quinine.
Melanines are produced to give the cell its brown colour
Catechol oxidase therefore acts as a defense mechanism and it protects damaged cells from bacterial and fungal disease.
(3) The pigment melanin has an important function in both human skin pigment and plants. It Protects from UV radiation as it absorbs the harmful rays. The Black/brown colour means it doesn’t allow any energy to escape. Its acts as a protective defence against invading organisms in plants and animals.
Melanin is a water-insoluble polymer of various compounds derived from the amino acid . It is one of two pigments found in a banana and adds brown to skin color; the other pigment is , which contributes yellow coloring. The synthesis of melanin reactions is catalyzed by the enzyme tyrosinase; an inherited lack of tyrosinase activity results in one of the forms of albinism. Tyrosinase is found in only one specialized type of cell, the melanocyte, and in this cell melanin is found in membrane-bound bodies called melanosomes. Melanosomes can be transferred from their site of synthesis in the melanocytes to other cell types. Besides it role in pigmentation, melanin, which absorbs ultraviolet light, plays a protective role when skin is exposed to the damaging rays
(4) ‘The protective aspect of melanin is seen as resulting from its high concentration and its confinement to ellipsoidal and densely packed organelles that can effectively shield the nucleus.’
(2) The enzyme catechol oxidase and the substrate Catechol will bind to form an enzyme substrate complex.
As with all enzymes the activity of Cathechol Oxidase depends very much on temperature, they work slowly at a low temperature and can also be denatured at high temperatures. pH also effects the arte at which the enzymes work. Both these factors would change the enzymes 3 dimensional shape. Enzymes can also be inhibited by substances such as metals.
Substrate and enzyme concentration effects the rate of reaction of experiments involving enzymes.
(6)Determining the levels of substrates and enzyme and the dynamics of natural enzymic browning as affected by cultivar, physiological age and environmental factors such as temperature.
Both potatoes and apples exhibit lowest browning rates at harvest. In apples, the rate increases during storage; however, in potatoes the rate was lower after 6 months storage.
