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Tables

Table 6 Williams et al. (2001) 'Seasonal variation in
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4.3 Cellular changes

Hibernation can result in the deposition of fat in adipose tissue. In tissues of finite size which are important sources of energy and sites for fuel metabolism, changes in cell structure (redistribution of organelles involved in energy metabolism and protein synthesis) are the most likely adaptation to a state of torpor. Liver hepatocytes of the hibernating dormouse (Muscardinus avellanarius), are visibly different from those of arousing and euthermic dormice when viewed in thin secti
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Introduction

This unit is the third in a series of three on Animals at the extreme. In order to get the most from it you should have previously studiedAnimals at the extreme: the desert environment (S324_1)andAnimals at the extreme: hibernation and torpor

This unit is from our archive and is an adapted extract from Animal physiology (S324) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in <
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4.5.1 Introduction

In the UK, three-way catalysts must currently (1996) meet emission standards for a life of 50,000 miles; however, research efforts and legislation are set to double this requirement in the very near future to the current US standard of 100,000 miles. The catalysts do deactivate with use. Indeed the ability to withstand mild deactivation is built into the design of the catalyst, and into the entire emission control system in the vehicle. This is done by setting up vehicles at efficienci
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4.3.6 The role of CeO2

Figure 20 shows the effect on performance of adding CeO2 to a Pt catalyst for three-way catalytic conversion.

Figure 20
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4.4.1 Introduction

Since its development, the three-way catalyst has been exposed to the full spectrum of techniques available for the characterisation of catalytic materials. The data provided can be correlated with the results of activity tests and kinetic measurements, which provide information on the performance of the catalyst. This reveals that although the catalyst functions as a composite material, it can be divided into distinct groups of catalytic centres that provide several different types of site,
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4.1 Exhaust pollutants

The most important chemical reaction in a petrol engine – that is, the one that provides the energy to drive the vehicle – is the combustion of fuel in air. In an ‘ideal’ system, combustion would be complete so that the only exhaust products would be carbon dioxide and steam. In practice, the complete oxidation of the fuel depends on a number of factors: first, there must be sufficient oxygen present; second, there must be adequate mixing of the petrol and air; and finally, there must
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References

Blakemore, C. and Cooper, A. (1970) Development of the brain depends on visual environment, Nature, 228, pp. 477–8.
Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. and Poulton, R. (2002) Role of genotype in the cycle of violence in maltreated children, Science, 297, pp. 851–4.
Caspi, A., Sugden, K., Moffitt, T. E., Taylor
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8.3 Lissencephaly

Lissencephaly, literally meaning ‘smooth brain’, is characterised by the absence of sulci and gyri, and by a four-layered cortex, instead of the usual six layers, with the majority of cortical neurons in layer four (Figure 22). Babies born with lissencephaly have a very poor prognosis; the disease proving lethal be
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8.2 Wilson's disease

The effects of a protein that is absent, or present but not doing its job, may not be evident for many years. This is called late onset, and is exemplified by Wilson's disease. Many molecules within the body require small amounts of minerals such as iron, magnesium or copper to function properly. There are mechanisms for absorbing these minerals from the diet. However, in excess, these same minerals can be toxic, as is the case with copper. So there are also mechanisms for getting rid
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10.4 Key points about minerals

  1. Certain minerals are required in the body.

  2. Some minerals form essential structural components of tissues. For example, calcium, phosphorus and magnesium compounds are major components of bones and teeth. Fluoride is also important in protecting teeth from decay.

  3. Sodium, potassium, calcium and chloride ions are important in maintaining the correct composition of cells and of the tissue fluids around them (homeostasis). These
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10.3.2 Fluid gain

In a normal diet, fluid is gained via food as well as in drinks. The amount of water in various foods is shown in Table 6. As well as plain water, most drinks, such as tea, coffee, juices and milk drinks, hydrate the body, but alcoholic drinks may not. Alcohol is a diuretic, a substance that increases the output of ur
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4.3 Calcium (Ca)

About 40% of the total mineral mass of bones is calcium, making it the most abundant mineral in the body. In bone, it is combined with phosphorus, as well as oxygen and hydrogen, in a mineral compound called hydroxyapatite. Calcium is also present in the fluids in the body, and there it occurs in the form of dissolved ions. An ion is an atom that carries a very small electrical charge, which can be either positive (+) or negative (−), depending on the ion.

You may recall from our stud
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3.7 Vitamin C (ascorbic acid)

Activity 14

What is the condition that results from vitamin C deficiency and what are its symptoms?

Answer

You will probably remember from the start of this
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3.6.4 Vitamin B6 (pyridoxine)

Vitamin B6 is composed of pyridoxine and two closely related compounds. It is found in small quantities in many foods, though it can be destroyed in the cooking process. No clear deficiency disease has been recognised in humans as being directly caused by lack of this vitamin, since it is often found in conjunction with other B vitamins and their absence has greater effects. Its main role is in the conversion of some amino acids into other ones, depending on the requirements of the
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3.6.2 Riboflavin (vitamin B2)

Riboflavin or vitamin B2, which was originally known as vitamin G, is found in a wide variety of foods, including milk and dairy products. It is more stable to heat than some of the other B vitamins, but is destroyed by exposure to sunlight. Milk in a glass bottle exposed to sun, loses 10% of its riboflavin per hour. Riboflavin plays a crucial role in the metabolism of carbohydrates and proteins and is involved in many other metabolic reactions in the body.

Although riboflavi
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3.6.1 Thiamin (or thiamine, also known as vitamin B1)

The deficiency disease beriberi has been known for thousands of years. The name literally means ‘I can't, I can't’ in Sinhalese (a major language in Sri Lanka), and reflects the crippling effect on its victims, who suffer from neurological symptoms, including pain, fatigue and paralysis, and cardiovascular disease. The disease was most common in southeast Asia, where white or ‘polished’ rice was a major part of the diet. The main source of thiamin is in the outer layers of the grain,
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3.6 Vitamin B

Vitamin B, often called the vitamin B complex, consists of a whole range of different compounds, some of which have similar functions and work together. However, unlike the families of compounds forming vitamins E and K, the B vitamins are sufficiently different from one another to be given individual names or numbers, and to be listed separately on many food labels. Except for vitamin B12, the body can only store limited amounts of B vitamins and because they are all water-soluble
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3.5 Vitamin K

Like vitamin E, vitamin K is fat-soluble and composed of a series of related compounds. Vitamin K is widely distributed in the diet (see Table 1) and it is absorbed from the small intestine with the assistance of bile acids. Vitamin K is also manufactured by the bacteria that inhabit the human large intestine and appears to be absorbed there too. The main role of vitamin K is in blood clotting. This process requires the presence of a number of different chemicals, called clotting factors, in
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1.2.3 The transmission of genetic material

The full complement of 46 chromosomes in the human genome, the diploid number, is restored at fertilization. As Figure 3.1 shows, all the somatic cells and cells in the testes and ovaries arise from the same fertilized egg by the process of mitosis; the cells all contain copies of the same genetic material (with some exceptions).

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