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Biology – HSC Online

Extract from Biology Stage 6 Syllabus (Amended October 2002) © Board of Studies, NSW 9.2 Maintaining a balance: 1. Temperature range
Background: All organisms are adapted to a particular environment with its characteristic temperature range. The temperature range allows the organism's enzymes to control its metabolism by operating at their optimum efficiency within this range. Some organisms are adapted to live at high temperatures (80 - 100oC) and these are called thermophiles. At the other end of the scale, there are organisms that are adapted to extremely cold temperatures (0-4oC), termed psychrophiles. Most mammals and microbes are adapted to a temperature range 30 - 45oC, averaging around 37oC. The optimum temperature for plants is around 25oC. identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates • Enzymes are biological catalysts. This means that they lower the energy required to start a chemical reaction within a cell but do not get used up by that reaction. Every reaction and process within a cell (metabolism) is controlled by a specific enzyme. • Enzymes are globular proteins whose shapes are specialised so that other chemicals (substrates) can form a temporary bond with them. There are two models used to show how an enzyme work: • One model used to illustrate the action of an enzyme is the lock-key model. This is where only one small part of the enzyme molecule can form a complex with the substrate. This part of the molecule is called the active site. Only a specific substrate(s) can bond in that site and this makes the enzyme specific to that substrate.

• The induced fit model, a more recent modification on the lock-key model, proposes that the active site slightly changes its shape to accommodate the substrate perfectly.

identify the pH as a way of describing the acidity of a substance • pH is a scale related to the concentration of hydrogen ions in a solution. • A pH value of 0 - 6 indicates an acid solution, where 0 is more acidic than 6, e.g. lemon juice has a pH value of 2, hydrochloric acid has a pH value of 1. • A pH value of 7 indicates a neutral solution, e.g. water. • A pH of 8 - 14 indicates a basic solution, where 14 is far more basic than 8, e.g. sodium hydroxide (drain cleaner) has a pH of 14, sodium bicarbonate has a pH of 8.

identify data sources, plan, choose , equipment or resources and perform a first-hand investigation to test the effect of: – increased temperature
– change in pH
– change in substrate concentration
on the activity of named enzyme(s)
• For this investigation, you need data that will assist you to determine appropriate ways in which each aspect may be researched. Enzymes that could be used include salivary amylase, trypsin and rennin. Rennin is an enzyme found in the stomachs of young mammals that are still being fed on milk. The rennin 'curdles' or sets the protein in the milk separating it into curds (solids) and whey (liquid). • Plan your investigation using the procedure provided below. • When choosing resources, you should be able to buy rennin as a junket tablet from supermarkets.

|Procedures to investigate the activity of an enzyme | |To demonstrate the effect of increased temperature: | |Make a rennin solution by dissolving a junket tablet in distilled water. | |Add the same amount of rennin solution to a number of test tubes of milk. | |Place test tubes in a number of different water baths at temperatures ranging from 0oC to...
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