Maintaining a Balance Notes - Biology Hsc

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9.2Maintaining a Balance
Contextual Outline
Multicellular organisms have specialized organ systems that are adapted for the uptake and transport of essential nutrients from the environment, the utilisation or production of energy and the removal of waste products arising from cellular activities.

The basis of healthy body functioning in all organisms is the health of their cells. The physical and chemical factors of the environment surrounding these cells must remain within narrow limits for cells to survive. These narrow limits need to be maintained and any deviation from these limits must be quickly corrected. A breakdown in the maintenance of this balance causes problems for the organism.

The nervous and endocrine systems in animals and the hormone system in plants bring about the coordinated functioning of these organ systems. They are able to monitor and provide the feedback necessary to maintain a constant internal environment. Enzyme action is a prime example of the need for this balance. Enzymes control all of the chemical reactions that constitute the body’s metabolism. As enzymes normally function only within a narrow temperature range, even a small rise in body temperature can result in the failure of many of the reactions of metabolism that are essential to life. This module increases students’ understanding of the applications and uses of biology, implications for society and the environment and current issues, research and developments in biology.

1. Most organisms are active in a limited temperature range

ENZYMES

Students learn to:
a) identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates

Role of Enzymes in metabolism – Enzymes speed up/govern the rate of reactions in the body, as they are biological catalysts in biological systems.
Metabolism: all chemical reactions that occur in the body

Description of Chemical composition – Enzymes are tertiary/globular proteins with a specific active site
– Made up of C, H, O, N
– Proteins made of polypeptide bonds
– Created in ribosomes for areas in which original enzymes have denatured
– Enzymes are highly specific – that is one enzyme to one substrate. They work by providing a surface or active site for the reaction to take place. The substrate bings to the active site and is either broken down or joined together.

Lock and Key Model
Lock and Key Model

Some common enzymes:
1. Maltase: Found in saliva and pancreatic juice, acts on maltose 2. Sucrase: Acts on the carbohydrate sucrose
3. Catalase: Found in all living cells, acts on the poison hydrogen peroxide (H2O2)

b) identify the pH as a way of describing the acidity of a substance
PH - pH is a measure of the acidity or basicity of a substance (measure of hydrogen/hydroxide ion concentration)
0 – Highly acidic7 – Neutral14 – Highly basic/alkaline

c) explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
There are various factors that affect enzyme activity. Some of these include:

Temperature: enzymes have an optimum temperature (about 370 in mammals) which is a temperature at which substrate and enzymes come into contact with sufficient energy for the reaction to occur. At low temperatures, there is insufficient energy and at temperatures above about 500C the enzyme denatures and its shape changes and will not work again even if temperature is lowered. At...
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