SvS Biology 2000 - HSC module
9.2.1
Maintaining a Balance
1. The following diagram shows a type of enzyme reaction.
(a) What type of reaction is it?
(b) What is represented by the red smaller particles located at the top of the picture?
(c) What is represented by the larger purple particle located towards the base of the picture?
(d) Other than temperature, list three factors that may alter the rate of this reaction.2. Enzymes are unchanged by the reaction in which they participate, but they often require the assistance of cofactors and coenzymes.
(a) Construct a table to show the properties of these two molecules with regard to:
(i) whether they are changed or unchanged by the reaction
(ii) which one is minerals and which is a vitamin(b) Why are minerals only needed in small quantities (trace elements) in the body?
3. Temperature affects the rate at which an enzyme may function.
(a) Draw a freehand graph to show the effects of increasing temperature on enzyme activity. No plotted points nor scales are required, but label the axes.
(b) Why is the functionality of the enzyme poor at low temperatures? (What's wrong with the enzyme molecule?)
(c) Why is the functionality of the enzyme poor at high temperatures? (What's wrong with the enzyme molecule?)
(d) What term is given to describe the state of an enzyme molecule affected by excessively high temperatures?4. Define "homeostasis"
5. Nerves play a large role in homeostasis. Some reactions to stimuli are called REFLEX actions.
(a) What is a reflex action - how does it differ from other stimulus/response models?
(b) The diagram below is an example of a reflex, which involves both nerves and hormones.
Using this example, answer the following questions:
(i) What is the stimulus?
(ii) Where does the afferent (sensory) neurone travel from and to?
(iii) Where does the efferent (motor) neurone travel from and to?
(iv) How is the message in nerves transmitted?
(v) How is the effect of hormones transmitted to its target tissues?
(vi) Is the Hypothalamus part of the CNS or PNS?
6. Construct a table to show 4 responses of the human body to both high and low temperatures in order to maintain a balance. In the table state whether the adaptation is structural, physiological or behavioural.
7. Look at the following pictures of two Australian native animals. On the left is the Thorny Devil, a diurnal lizard. On the right is the Bilby, a nocturnal marsupial.
(a) Which of the two is an endotherm?
(b) State a way that each behaviourally acts to reduce its body temperature.
(c) State a way that the bilby physiologically (functionally) reduces its body temperature.
8. Plants also respond to the ambient temperature in various ways.
(a) The structure here is found predominantly on the underside of leaves.
(i) What is it called?
(ii) How does it function to counteract the heat of the day?
(b) State one behavioural and one structural adaptation of Eucalyptus pilalaris leaves to cope with the high temperatures in summer.
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S. van Strien
