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Chapter

Cover Biological Science

Ratio and Proportion  

This chapter focuses on the expression and comparison of ratio and proportion. The ideas of ratio and proportion can be expressed using a variety of symbols. Their notation is often used interchangeably when describing these ideas. A part-to-whole ratio is often expressed as a fraction, especially since a diagram can be a helpful way to visualise ratio. The chapter also considers the notions of probability and the term concentration in relation to the notion that solutions can be expressed as the mass of a substance per volume. It then considers the dilution of a solution which is carried out to make the concentration ten times less.

Chapter

Cover Biological Science

Ratio and Proportion  

This chapter focuses on the expression and comparison of ratio and proportion. The ideas of ratio and proportion can be expressed using a variety of symbols. Their notation is often used interchangeably when describing these ideas. A part-to-whole ratio is often expressed as a fraction, especially since a diagram can be a helpful way to visualise ratio. The chapter also considers the notions of probability and the term concentration in relation to the notion that solutions can be expressed as the mass of a substance per volume. It then considers the dilution of a solution which is carried out to make the concentration ten times less.

Chapter

Cover Biomedical Science Practice

Preparing and measuring reagents  

Ian Graham

This chapter details the process of preparing and measuring reagents, which are essential and fundamental skills for all biomedical scientists. The use of balances for weighing and pipettors and other volume measurement methods for volume delivery are key techniques in the production of solutions and their dilution. For correct operation, balances must be appropriately sited and calibrated. Burettes, pipettes, and volumetric flasks provide high levels of accuracy if used correctly. However, pipettors are the volume measurement tool of choice for highly accurate and precise work. They use disposable tips for convenience, require calibration, and, being precision instruments, must be used with care. The chapter then looks at molar concentrations and alternative ways of expressing concentration.

Chapter

Cover Making the Transition to University Chemistry

Kinetics  

This chapter discusses rates of reactions in kinetics. The rate of reaction is based on the rate of change of concentration per unit time. The activation energy for a reaction is the minimum energy necessary for a collision to lead to a successful reaction. The rate of reaction, then, depends on the concentration of the reactants, temperature, presence of a catalyst, and state of subdivision. The Maxwell–Boltzmann distribution pins the number of molecules in a gas with given energy against energy. On the other hand, the Arrhenius equation measures the activation energy on how the rate constant depends on the temperature.

Chapter

Cover Biochemistry and Molecular Biology

Mechanisms of metabolic control and their applications to metabolic integration  

This chapter highlights metabolic pathways that must be regulated to avoid futile substrate cycling. It determines how enzyme activities may be controlled by changing the amount of enzyme or by changing the rate of catalysis of enzymes. Control points in metabolic pathways usually occur at irreversible steps in which the forward and backward reactions can be separately controlled. The chapter cites allosteric control, which is a powerful concept essential for cells to exist. Allosteric enzymes are multisub-unit proteins which contain allosteric sites to which molecules attach and affect the activity. The chapter notes the effect of substrate concentration on reaction rates which is sigmoidal rather than hyperbolic.

Chapter

Cover Essentials of Human Nutrition

Assessment of Nutritional Status  

A. Stewart Truswell

This chapter presents an assessment of nutritional status. Dietary intake estimation, described in the preceding chapter, cannot always prove that an individual or community is well nourished or poorly or overnourished. Food intake measurement—really, estimation—is ultimately subjective. It depends on the memory, cooperation, and honesty of individuals. Assessment of nutritional status is, by contrast, ultimately objective. A person's weight, height, and chemical concentration in blood or urine is measured by an outside observer and if a second and third observer repeats the measurement, they should obtain about the same result. The chapter then looks at the uses of nutritional assessment, before considering anthropometric assessment and the estimation of body composition.

Chapter

Cover Aqueous Acid-Base Equilibria and Titrations

Basic concepts  

This chapter discusses the basic concepts of acids, bases, and pH. The concept of acid and base can be generalized in several ways. The book uses the definition given by Brönsted, which emphasizes the complementary nature of acids and bases in aqueous solutions. It considers as an acid any substance that can donate a proton, and as a base any proton acceptor. In this nomenclature, an acid that loses its proton become a base, and vice versa, so that one can consider conjugate acid-base pairs. Meanwhile, the concept of pH was introduced by Sørensen as the negative logarithm of the hydrogen concentration. The chapter then looks at the mass action law, which is the fundamental law of chemical equilibrium. It also considers concentration fractions, logarithmic concentration diagrams, and the proton condition.

Chapter

Cover Human Physiology

Acid–base balance  

This chapter explains how the body continually produces CO2 and non-volatile acids as a result of metabolic activity. The chapter refers to the blood hydrogen ion concentration [H+] which is normally maintained within the relatively narrow range of 40-45 nmol of free hydrogen ions per litre. This corresponds to a blood pH between 7.35 and 7.4, and the extreme limits that are generally held to be compatible with life range from pH 6.8 to pH 7.7. The chapter talks about hydrogen ions which are absorbed by other molecules in a process known as buffering, and acid products are subsequently eliminated from the body via the lungs and kidneys. The concept of acid-base balance refers to the processes that maintain the hydrogen ion concentration of the body fluids within its normal limits.

Chapter

Cover Clinical Biochemistry

Therapeutic drug monitoring  

Robin Whelpton, Nigel Brown, and Robert Flanagan

This chapter studies therapeutic drug monitoring (TDM), which is the term used to describe the measurement of the plasma concentrations of a drug and/or any pharmacologically active metabolite(s) attained during treatment. The aim of TDM is to help optimize treatment by, for example, selecting a dose that maximizes the desired effect(s) of a drug, while minimizing the risk of toxicity. For most drugs, there is a wide margin (so-called margin of safety) between the clinically effective dose and the dose associated with marked adverse effects. However, for some drugs the difference between a clinically effective dose and a potentially toxic dose is small. These drugs are said to have a small ‘therapeutic range’ or narrow ‘therapeutic window’, and the dose of the drug must be adjusted carefully for each patient. In order to appreciate the reasons for TDM and the decisions that may have to be made in dose adjustment, it is necessary to understand what is meant by a ‘drug’, how drugs are given, what the body does to a drug, and how the effect of dose adjustment on the plasma concentration of a drug may be predicted.

Chapter

Cover Clinical Biochemistry

Fluid and electrolyte disorders  

Tim James

This chapter looks at fluid and electrolyte balance from the viewpoint of the clinical biochemistry laboratory; it considers the major causes of each abnormality that may be encountered and provides guidance on the accurate reporting of these parameters. The plasma electrolytes sodium and potassium are the most frequently requested investigations in most clinical biochemistry laboratories. Ion-selective electrodes (ISEs) are the main analytical technique used for analysis of sodium and potassium. Two distinct types of ISE, direct and indirect, are used to measure electrolyte concentrations and these may produce different results when used for specimens in which the total protein and/or lipid contents are increased. Poor collection and handling of clinical samples can adversely affect plasma potassium test results. Ultimately, serious disturbances to plasma electrolyte concentrations can be life threatening and rapid communication of abnormal test results by laboratory staff to clinical teams is essential.

Chapter

Cover Making the Transition to University Chemistry

Chemical Equilibrium  

This chapter introduces equilibria and equilibrium constants. Equilibrium is recorded when the rate of the forward reaction equates to the rate of the backwards reaction. When equilibrium has been reached, the concentrations of all the substances remain constant. The thermodynamic equilibrium constant is devised when the standard Gibbs energy change is in line with the natural logarithm of the equilibrium constant. The chapter lists the equilibrium calculations mostly used in universities. Le Chatelier's principle refers to the small conditions changes subjected at a system in equilibrium as the equilibrium tends to shift to minimize the effect of the change.

Chapter

Cover Atkins’ Physical Chemistry

Activities  

This chapter describes how the extension of the concept of chemical potential to real solutions involves introducing an effective concentration called an ‘activity’. In certain cases, the activity may be interpreted in terms of intermolecular interactions; an important example is a solution containing ions. Such solutions often deviate considerably from ideal behaviour on account of the strong, long-range interactions between the charged species. The chapter shows how a model can be used to estimate the deviations from ideal behaviour when the solution is very dilute, and how to extend the resulting expressions to more concentrated solutions. It looks at the Margules equations, the Debye–Hückel theory, and the Debye–Hückel limiting law.

Chapter

Cover Chemical Structure and Reactivity

Chemical kinetics  

This chapter explores how rate laws are determined. This will involve looking at experimental methods, as well as at how the form of the rate law can be determined from data of concentration as a function of time. Concentration can be measured as a function of time by using various physical methods such as the measurement of absorbance, conductance, or pressure. The chapter then looks at two fundamental theories about the rates of reactions: collision theory, which is based on gas kinetic theory, and the more sophisticated transition state theory. Gas kinetic theory can be used to estimate the collision rate and hence the rate constant; however, in its simplest form, the theory massively overestimates the rate constant. Reactions can be thought of as taking place on a potential energy surface.

Chapter

Cover Chemical Structure and Reactivity

Electrochemistry  

This chapter studies electrochemistry. The cell potential is very simply related to the Gibbs energy change of the reaction taking place in the cell. Measuring the cell potential is a straightforward process: attaching a digital voltmeter to the cell enables one to make a precision measurement in seconds. As a result, such measurements give access to thermodynamic properties in a particularly simple way. Since cell reactions generally involve ions, these measurements of cell potentials are especially useful for finding the standard thermodynamic functions of ions in solution. Data derived from cells, in the form of standard electrode potentials, are very useful for understanding the relative oxidizing or reducing power of different species. The cell potential is related in a simple way, given by the Nernst equation, to the concentration of the species in the cell. This leads to important practical applications in which cell potentials are used to measure concentrations.

Chapter

Cover Interfacial Science

The gas-liquid interface: adsorption; films and foams; aerosols  

This chapter describes some of the most obvious and dramatic effects of adsorption that can be seen at the air-solution interface. It talks about liquid drops that change their shape, foams that can be formed on liquids that otherwise will not foam, and the rise of liquids in capillaries that is reduced. It also analyses the enhanced spreading of liquids over solid surfaces, the reduction of the ability of light winds to ruffle the surface of water in a pond, and soils that are wetted more readily by water. The chapter deals with the measurement of adsorption by analysis of the surface or by change in bulk phase concentration that is usually not feasible as the area of a gas-liquid interface is usually small and sample collection is often difficult. It explains how adsorption is normally determined from surface tension data using the Gibbs equation.

Chapter

Cover Elements of Physical Chemistry

The equilibrium constant  

This chapter assesses the equilibrium constant, which expresses the composition of an equilibrium mixture as a ratio of products of activities. It is a succinct summary of the equilibrium composition of a reaction mixture, but special techniques have to be applied in order to extract individual concentrations of the reactants and products. The chapter then explains how to set up and use an equilibrium table that does the task systematically. An equilibrium table is a table with columns headed by the species and, in successive rows, the changes in composition needed to reach equilibrium. Ultimately, the equilibrium constant of a gas-phase reaction may be expressed as a ratio of products of pressures or, after the appropriate conversion, concentrations.

Chapter

Cover Fundamentals of Plant Physiology

Photosynthesis: Physiological and Ecological Considerations  

This chapter explores some physiological and ecological considerations concerning photosynthesis. Physiologists wish to understand the direct and indirect responses of photosynthesis to environmental factors. The dependence of photosynthetic processes on environmental conditions is also important to agronomists because plant productivity, and hence crop yield, depends strongly on prevailing photosynthetic rates in a dynamic environment. To the ecologist, photosynthetic variation among different environments is of great interest in terms of adaptation and evolution. The chapter focuses on how naturally occurring variation in light and temperature influences photosynthesis in leaves and how leaves in turn adjust or acclimate to such variation. It also describes how atmospheric CO2 influences photosynthesis, an especially important consideration in a world where CO2 concentrations are rapidly increasing as humans continue to burn fossil fuels for energy production.

Chapter

Cover Making the Transition to University Chemistry

Redox Reactions  

This chapter looks into redox reactions: oxidation, and reduction. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. The oxidation number of an element is the number of electrons that need to be added to the element needed to make a neutral atom. Thus, oxidation numbers should change during redox reactions. Half-equations help focus the attention on a single element to showcase the breakdown of an equation of a redox reaction. Most of the complicated half-equation calculations involve acid as a source of hydrogen ions. Finally, the chapter notes the Nernst equation which allows quantitative prediction on what happens when concentrations differ from the standard value.

Chapter

Cover Clinical Biochemistry

Diabetes mellitus and hypoglycaemia  

Allen Yates and Ian Laing

This chapter examines diabetes mellitus and hypoglycaemia. Diabetes mellitus is a consequence of the failure of glucose and lipid handling, two of the main energy sources for the body. This is precipitated by either a complete lack (type 1), or a defective action (type 2), of insulin. The release of insulin by endocrine β cells of the pancreatic islet is controlled by the integrated interplay of glucose, lipid, and incretins. Wide excursions in the blood glucose concentration are normally prevented by insulin and its counter-regulatory hormones glucagon, cortisol, adrenaline, and growth hormone. This balance is disrupted in diabetes. Long-term complications of diabetes, resulting from poor blood glucose control, are severely debilitating and include increased risk of heart attack and stroke, kidney disease, blindness, and limb amputations. The chapter then looks at the wide range of therapies and treatments for diabetes, including bariatric surgery.

Chapter

Cover Organs, Systems, and Surgery

The Story of Anaesthesia  

This chapter focuses on the effects and development of anaesthesia. It explains that nearly all drugs in anaesthesia act on two basic principles of activation or suppression of cellular receptors and dependence on a concentration gradient. Modern anaesthesia involves precise doses of specially designed drugs that obliterate consciousness and provide pain relief. The chapter then looks at the equipment and techniques concerned with the anaesthetist at work. It looks into the debates surrounding anaesthetic drugs and how they work, and it references the relationship between GABA receptors with globally decreased neurone transmission within the brain and other organ systems.