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Role of Enzymes
- Enzymes are made out of protein, which control all the chemical processes of living systems (metabolism) and are produced within living cells.
- They are organic catalysts Catalysts are any substance that speeds up or brings about a chemical change without itself being used up in the reaction.
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Chemical Composition of Enzymes
They work by providing an active site (surface) where the reaction can take place. They act on molecules known as the When the substrate molecules bind to the active site, a temporary chemical change in the shape of an enzyme occurs, where the substrate is changed. When the product leaves, more substrate can be catalysed.
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Simple Model
- The model shows that the enzyme is specific for only one type of substrate The enzyme can only react with a substrate that is reciprocal to the shape The substrate binds to the enzyme at the active site whereby a reaction occurs Once the reaction is complete the enzyme returns to its regular state and the two products are formed.
- The substrate fitting to the enzyme is similar to a key going in a lock
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Identify the pH as a way of describing the acidity of a substance
pH is a way of describing the acidity of a substance It is a measure of the concentration of hydrogen ions that are released by acids A pH of 7 is neutral – neither acidic nor alkaline A pH of 1-6 is acidic which has a large amount of hydrogen ions present in solution A pH of 8-14 is alkaline which has very little hydrogen ions Any variation of the specific level of acidity may reduce the rate of activity for enzymes
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Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
- Temperature, pH and substrate concentration can affect the rate of an enzyme-catalysed reaction and efficiency.
- Benefits of having a constant internal environment is essential for optimal metabolic efficiency as:
- - Enzymes regulate metabolism by regulating rates of reaction
- - Optimal enzyme activity is achieved under certain conditions of temperature and pressure
- - Therefore, optimal metabolic efficiency is achieved in a constant internal environment
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Describe homeostasis as the process by which organisms maintain a relatively stable internal environment
- Homeostasis is the process by which organisms maintain a relatively stable internal environment despite changes in the external environment
- Homeostasis is important for optimal metabolic efficiency – if the internal environment is relatively stable this allows for a high level of efficiency of the enzymes within the cells
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Explain that homeostasis consists of two stages:
- Detecting changes form the stable state
- Counteracting changes from the stable state
- A feedback mechanism is a self-regulating mechanism that maintains balance or homeostasis
- Stage 1: Detecting Changes from the Stable State
- Any information that provokes a response is called a stimulus. Environments contain many stimuli and organisms have receptors that detect them.
- Stage 2: Counteracting Changes from the Stable State
- When a change affects the organism’s stable state, a homeostatic response occurs to counteract the change to ensure a stable state is maintained
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Outline the role of the nervous system in detecting and responding to environmental changes
- The nervous system acts as a control centre to coordinate all the organism’s responses in detecting and responding to environmental changes
- Central Nervous System (CNS) coordinates all responses, where the received information, interprets it and initiates a response
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Identify the broad range of temperature over which life is found compared with the narrow limits for individual species
Individual organisms cannot survive this wide range of temperatures. Most organisms survive and be active in between 0˚C and 45˚C as living cells are restricted to a narrow range of temperatures
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Compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
- Endotherms
- Animals that can generate their own body heat and generally maintain a constant body temperatureBody temperatures are controlled largely by metabolic processes and by adaptive mechanisms that control the rate of heat exchange with the environment.
- Ectotherms
- Animals that cannot generate their own body heat or maintain a constant body temperature. When environmental temperatures are low, the activity of the ectotherm is low and metabolic rate is low. Hence, they use the energy from the environment to regulate their body temperature.
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Identify some responses of plants to temperature change
- On land, where temperature fluctuates, plant responses may include:
- The ability to orientate leaves vertically to reduce the surface area exposed to the sun, reducing heat absorptions and supporting convective cooling
- Ability to drop leaves if temperature becomes too cold
- Germination may occur if seeds have been exposed to a minimum number of hours of cold conditions
- Budding as temperature and length of day increase in spring
- Closing stomates in response to high temperatures to reduce water loss
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