4.5.3 The effect of poisons The use of catalytic converters was one of the major contributors to the phasing-in of unleaded petrol. Lead in petrol is a severe poison for the catalyst, and there have been many stories, particularly in the early days of the converter, of people disabling the catalyst by misfuelling. Figure 25 shows how the activity
References 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 7.4 Elixirs of the nervous system: neurotrophins According to Section 7.2 axons obtain an elixir from targets at their synapses. Confirmation that there is indeed an elixir came from a series of events that reveals how much of science really works. Elmer Bucker, working with Hamburger in the mid-1940s, had removed a limb bud from a chick and replaced it with a tumour from 5.4 Retinoic acid The retinoic acid story is both distressing and illuminating. It is distressing because with hindsight it is possible to see how the suffering of many people could have been averted. It is illuminating because we now understand much about how retinoic acid works. Retinoic acid is a natural product of vitamin A. It had been known since the 1930s that a lack of vitamin A, a vitamin A deficiency, led to fetal abnormalities. Subsequent studies in animals showed that an excess of vitamin A a 3.1 Introduction We each begin life with a unique genome. As we grow and develop, we are each subjected to a range of factors that influence the way development proceeds. Most of those factors are common to us all, the intracellular and intercellular signals, hormones, birth, milk. But the precise combination and the range and duration of those factors varies between individuals, such as the duration of gestation or the composition and quantity of a mother's milk, for example. In addition we each undergo diff 2.9 Iron (Fe) The ability of blood to carry oxygen is due to the presence of the red pigment, haemoglobin, present in red blood cells. Haemoglobin is a protein formed from four polypeptide chains called globins, in the centre of each of which is a small non-protein part called a haem group (haima is Greek for ‘blood’). Each of the haem groups has an iron atom within it (Author(s): 1.6.2 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 9 Summary In this unit you have found out that: The sensation of pain is caused by the release of a chemical (prostaglandin) that stimulates the nerve endings and sends an electrical message to the brain. Pain can be reduced if the formation of prostaglandin can be inhibited. Prostaglandin is formed, from arachidonic acid, in a cavity in the active site of the enzyme cyclooxygenase (COX). Geometrical isomerism can be 1.4.1 Salicylic acid The structural formula of salicylic acid, 2.1, looks quite complicated. However, it becomes less daunting if you unpack it a bit. One of the first things to do when confronted with an unfamiliar structure is to check that all the valencies are correct (four for carbon, two for oxygen and one for hydrogen). If any atoms have the wrong valency, it follows that there is a mistake somewhere and the molecule does not exist as drawn. It looks OK for the structure of salicylic acid. You proba Learning outcomes After studying this course, you should be able to: understand the basic composition and structure of DNA understand what is meant by complementary DNA base pairing understand how base pairing allows a mechanism for DNA replication understand the number of DNA molecules within a chromosome. 1 Using information stored in DNA One important property of DNA is that it carries genetic information in the simple coding language of just four bases. These bases, which can be arranged in a huge variety of sequences, represent a vast potential store of information. In this course, we consider how this information is used by the cell. The key structural feature of complementary base pairs, which plays an important role in both stability and replication, is also the basis for how DNA functions as genetic material. How Conclusion Section 1 Superconductivity was discovered in 1911, and in the century since then there have been many developments in knowledge of the properties of superconductors and the materials that become superconducting, in the theoretical understanding of superconductivity, and in the applications of superconductors. Section 2 A superconductor has zero resistance to flow of electric current, and can sustain a current indefinitely. The magnetic flux remains constant in a completel 2.3 The Meissner effect The second defining characteristic of a superconducting material is much less obvious than its zero electrical resistance. It was over 20 years after the discovery of superconductivity that Meissner and Ochsenfeld published a paper describing this second characteristic. They discovered that when a magnetic field is applied to a sample of tin, say, in the superconducting state, the applied field is excluded, so that B = 0 throughout its interior. This property of the superconducting s References Optional reading If you are interested in considering the role of the internet on science communication practices, you may find the following references are of interest: Wulf (1999), Rzepa (1999) and Rowland (1999a). So far, you have been asked to reflect on your experiences of science communication both as a receiver and as a producer. You have also considered a definition for communication in terms of different types of media, noting how this influences the context for science communication (e.g. ‘f 3.1 Introduction In 2000, the House of Lords Select Committee on Science and Technology produced an influential report that highlighted the complex and increasingly problematic relationship between contemporary science and society, particularly in the field of biotechnology (House of Lords Select Committee on Science and Technology, 2000). The report argued that many of these concerns were seen by the public to be the result of a perceived lack of transparency in the relationship between science, industry, pu 1.5 Key dissertation ingredients A number of ingredients are essential for a satisfactory dissertation: a thesis, i.e. one coherent overriding ‘story’ or argument situation in existing knowledge, i.e. a critical review of prior research which motivates and justifies the research question contribution of something new appropriate voice and argument, i.e. the provision of clear and explicit evidence, substantiation, and chain of in 1.6.2 Metamorphic recrystallisation To consider metamorphic recrystallisation at its simplest, let's begin by imagining a sedimentary rock composed entirely of quartz grains – a quartz sandstone. Sandstone is a sedimentary rock and so has a fragmental texture (see Figure 7b). When it is subjected to high temperature and high pressure n 1.4 The formation of igneous rocks Igneous rocks are defined as having solidified from a molten state, either inside the Earth or on the surface at volcanoes.
