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Chapter

Cover Chemistry for the Biosciences

Equilibria: how far do reactions go?  

This chapter focuses on equilibrium reactions, which can proceed in both forward and reverse directions simultaneously. At equilibrium, the rates of the forward and back reactions are equal: they continue to proceed, but there is no overall change in the system—this is called dynamic equilibrium. The relative position of an equilibrium reaction when equilibrium has been reached is represented by an equilibrium constant. The chapter explains the reaction quotient, before looking at binding reactions and how they represent a type of equilibrium reaction. When an equilibrium is perturbed, the system acts to counteract the change so that a state of equilibrium is re-established. There are three key ways to perturb an equilibrium: by changing the concentration of species present, changing the temperature, or changing the pressure. Finally, the chapter considers the impact of free energy on chemical equilibria.

Chapter

Cover Genetics

The Genetics of Populations  

This chapter delves into population genetics with a human focus and explores the assumptions of the Hardy—Weinberg equilibrium model. It reviews the many different types of evolutionary change which can operate in order to shape the genetic structure of a population and the imprints these leave at the level of the genome. It also features long-term studies of bacterial populations presented as a method to explore evolution experimentally. The chapter describes how transmission of alleles and genotypes within a population can be assessed, even when the individual matings cannot be monitored. It defines non-random mating as the main process that affects genotype frequencies without affecting allele frequencies directly, which can result in population stratification.

Chapter

Cover Thrive in Genetics

Genetics of Populations  

This chapter examines population genetics, which analyses the patterns of genetic variation shown by groups of individuals, i.e. by populations. This contrasts with the main concern of Mendelian genetics and, to a large extent, of quantitative genetics, as both focus on the genotype of individuals and the genotypes resulting from single mating. Population genetics explores the evolutionary processes that shape a population’s genetic variation, i.e. mating systems, migration, mutation, population size, and selective forces. The chapter then considers how the analysis of genetic diversity in populations of endangered species helps formulate conservation policies. Ultimately, the genetic variation within and between different populations is described in terms of frequencies of alleles and resulting genotypes. The chapter looks at the Hardy–Weinberg equilibrium, non-random mating, natural selection, and genetic drift.

Book

Cover Chemistry for the Biosciences
Chemistry for the Biosciences explores all of the essential chemical concepts that students of biology need to know and understand. It starts by looking at atoms as the foundations for life, and how chemical bonding brings together atoms to form molecules and compounds. It also considers the interactions that operate between molecules, and what the chemical and biological implications of these interactions are. After considering a range of quantitative concepts relevant to the study of biology – moles, concentrations, and dilutions – it discusses the molecular basis of organic chemistry by considering hydrocarbons and functional groups. The text moves on to consider isomerism, molecular shape and structure, and the structure and function of key biological macromolecules. After explaining why metals have an important role in biological systems, it goes on to explore what happens during chemical reactions, and introduces oxidation, and reduction. It then explores concepts from the field of physical chemistry that are vital our understanding of life: energy, equilibria, and kinetics. After exploring acids, bases and buffers and their importance to biological systems, it concludes with a review of how we can use chemical analysis to better understand biological molecules.

Chapter

Cover Conservation: A people-centred approach

Populations, Patchiness, and Movement  

This chapter describes how population sizes change. Understanding the dynamics of populations involves studying the key demographic processes of birth, death, immigration, and emigration. Much of twentieth-century population ecology concentrated on explaining population dynamics of closed populations, using the effects of density on births and deaths, while ignoring movement. The equilibrium theory of island biogeography changed this focus onto the study of movement as a key determinant of species richness. This focus was then transferred into the idea of the metapopulation, a set of extinction-prone populations on patches kept going by the movement of individuals. Natural landscapes consist of many patches of suitable habitat in a sea of unsuitable habitat. Movement across such landscapes is an important element in the population dynamics of many organisms.

Chapter

Cover Biochemistry and Molecular Biology

Energy considerations in biochemistrya  

This chapter looks at energy which changes during chemical reactions. Looking at this energy provides a reliable guide to the biochemistry of cells. The chapter describes free energy change (ΔG) as the most useful value as it expresses the amount of energy change in a reaction available to perform useful work. The ΔG value can be used to determine the equilibrium constant of a reaction. It also shows whether the reaction is likely to be reversible in cells. The chapter mentions free energy made available from food breakdown. This energy is used to synthesize adenosine triphosphate (ATP), the universal energy carrier of life. Catabolism or breakdown of food molecules drives anabolism or synthesis of molecules with ATP being the energy-carrying go-between.