2.1.1 Ron revisited In Case Report 1 you met Ron. Ron is 59 years old, has a BMI of 31 and a central obesity ratio of 0.96, indicating that he is moderately obese, with the fat concentrated in his abdomen, rather than his hips. Clearly a number of factors, some environmental, others relating to Ron's age and all interacting with Ron's genetic constitution, may help to provide an explanation. Let's look at some of these factors in a little more detail. It is clear that Ron enjoys a comfortable lifestyle with litt
1.6 Obesity treatment Obesity treatment is only successful if weight is reduced and maintained to within a desired range. There are three approaches to obesity treatment: changing behaviour and diet is the most common approach although drugs and surgery can be used in some severe cases of obesity. Behaviour and diet: it is important to be realistic about an obese patient's target weight as many patients have over-ambitious targets that they are unlikely to achieve. A severely obese patient probably ca
1.5 Obesity At the time of writing (2004) 20% of the adult population of the UK is classified as obese. The number of obese children has doubled since 1982, 10% of six year olds and 17% of fifteen year olds are now classified as obese. As shown in Table 4, obesity is recognized when the BMI exceeds 30 and occurs quite simply wh
1.4 Inadequate intake In the developed world inadequate intake of food, at least in terms of energy, is not common. Nevertheless, in many parts of the world starvation is a huge issue, and it is estimated that tens of millions of people face starvation, and well over 5 million, mainly children, die each year from inadequate nutrient intake. Importantly, lack of particular nutrients impairs our ability to carry out many functions. 1.3 Balanced energy intake There is a need for a certain daily energy intake to allow metabolism to occur in the body. Metabolism means all the chemical reactions occurring in the body and there are two types of process involved: catabolism breaks down larger molecules into smaller ones often with energy release and anabolism is the building up of larger molecules from smaller precursors, often requiring energy. The body requires energy to power anabolic, mechanical (for example, muscle contraction 1.2 Summary of Section 1.1 A balanced diet consists of six main nutrient groups; proteins, carbohydrates, lipids, vitamins, minerals and water. Dietary reference values (DRVs) comprise a range and an estimated average of recommended daily intake levels for nutrients and energy for males and females at different stages of their life. 1.1 The components of a balanced diet A balanced diet contains six key nutrient groups that are required in appropriate amounts for health. These groups are outlined below. Proteins are involved in growth, repair and general maintenance of the body. Carbohydrates are usually the main energy source for the body. Lipids or fats are a rich source of energy, key components of cell membranes and signalling molecules, and as myelin they insulate neurons (nerve cells 4.1 Natural stores of carbon The major natural stores of carbon (called ‘reservoirs’) are shown below in Figure 1.9. 4 Fossil fuels Part of the incoming solar energy becomes stored in fossil fuels (oil, gas and coal: 3.1 Solar radiation Over 99.9% of the energy available at the Earth's surface comes from the Sun. Solar energy emanat 7.5 Outstanding issues Evidence from rotation studies shows that some AGNs do indeed contain compact, supermassive objects within them, though there is no direct evidence that these are black holes. Quasars were most abundant at redshifts of 2–3 and have been declining in number for the last 10 billion years. It seems probable that AGNs fade with time as the supply of accreting material is used up. There is speculation that AGNs may be rejuvenat 7.7 Physical hazards In any laboratory, potential hazards arise from the use of electrical equipment. The legal requirements relating to the use and maintenance of such equipment are contained in the ‘Electricity at Work Regulations 1989’ (EAW). The regulations require certain safety objectives to be achieved but do not prescribe in detail the measures to be taken. Instead, precautions should be selected appropriate to risk depending on particular work activities. ‘Portable’ electrical equipment – 7.3 Disposal requirements When carrying out a risk assessment, you must consider disposal requirements. For example, any chemical d 5.2 Cryogenic liquids and ionising radiation safety There are a number of hazards associated with cryogenic liquids, the main one being that when accidentally released the liquid expands hugely to form a gas (600 times in the case of nitrogen). The formation of such a large volume of gas can lead to asphyxiation in confined areas. The other main hazard is cold burns (frostbite). 4.1 Vitamin A deficiency Vitamin A, more properly known as retinol, is an important chemical intermediate in a number of biochemical processes in mammals. It is involved in vision, and is found in the rod cells of the retina of the eye. These cells are particularly important in seeing at low light levels, and night blindness is a symptom of vitamin A deficiency (VAD). Vitamin A is also involved in the proper functioning of the immune system. Children suffering from VAD are prone to serious infections, and often die f 1 How do organisms acquire iron? Metals are an essential part of biological chemistry. Of all the trace elements, iron is the most important, especially as it is present in many essential enzymes and proteins. But how do organisms acquire the iron from their surroundings? Clearly, organisms need to absorb iron biochemically before it can be used in proteins. Also, some method of replacing lost iron quickly is needed: for instance, how is blood replaced once it has been lost through a cut? This prompts the question: what bioc 3.8 Review In this unit we have looked at some of the factors which infuence a couple's decision to have a child. For people who choose not to do so, at least for some part of their lives, a range of contraceptive practices is available. We have looked at the biological processes involved in producing gametes, and at the precise sequence of events necessary to produce a healthy, fertilized egg. We have seen how this egg develops, first as a pre-programmed, free-living embryo, then becomes buried within 1 What is development? In this unit we begin to look at the human being in the context of an individual life cycle, examining some of the processes that contribute to the formation of a new person. This is the first time that many of you will have encountered this level of biological detail; we would ask that you take the time to understand it fully at this stage. We hope to show you that, far from being a dry academic subject, the study of biology allows us to glimpse a dimension of dynamic sophistication and eleg 1.3.1 Helices A variety of helical structures can be identified in proteins using X-ray diffraction. A helix can be described by the number of units (amino acid residues) per turn (n) and by its pitch (p), which is the distance that the helix rises along its axis per turn. These parameters are indicated in Figure 8 for a number of helices 1.3 Protein secondary structure From our consideration of the steric constraints that apply to peptide bonds and amino acid residues in a polypeptide, we have already begun to discuss some of the factors that determine how the backbone of the polypeptide folds. The conformation adopted by the polypeptide backbone of a protein is referred to as secondary structure. Whilst it is true to say that all proteins have a unique three-dimensional structure or conformation, specified by the nature and sequence of their amino a
5.2.1 Cryogenic liquids
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