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Chapter

Cover Biochemistry

Photosynthesis  

This chapter considers oxygenic photosynthesis as the most important biochemical process on earth. With a few minor exceptions, photosynthesis is the only mechanism by which an external abiotic source of energy is harnessed by the living world, and it is the source of O2, which sustains all aerobic organisms. It explains photosynthesis as the light-driven biochemical mechanism whereby CO2 is incorporated into organic molecules, such as glucose. The chapter refers to captured light energy that is used to synthesise adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), which drive the process. The reducing power of NADPH is necessary as a strong electron donor is required to reduce the fully oxidised, low-energy carbon atoms in CO2 to the carbon units of organic molecules.

Chapter

Cover Biochemistry and Molecular Biology

The basic molecular themes of life  

This chapter talks about living cells. These obey the laws of physics and chemistry. Energy is derived in cells from the breaking down of food molecules and released in a form that can drive chemical and physical work. The chapter considers adenosine triphosphate (ATP) as the universal energy currency in life. Energy from food breakdown is used to synthesize ATP from adenosine diphosphate (ADP) and phosphate. ATP breakdown can then be coupled to carry out biochemical work. The chapter analyses biological molecules which are based on the carbon atom bonded mainly to hydrogen, oxygen, nitrogen, and other carbon atoms. Noncovalent bonds are weak in comparison with covalent bonds but important in allowing interactions between molecules.

Chapter

Cover Animal Physiology

Aerobic and Anaerobic Forms of Metabolism  

This chapter details the aerobic and anaerobic forms of metabolism. It explains that both forms of metabolism are major categories of catabolic, biochemical pathways by which animal cells release energy from foodstuff molecules to synthesise adenosine triphosphate (ATP). The four mechanisms of ATP production are aerobic catabolism by the use of O2 acquired simultaneously from the environment, anaerobic glycolysis, anaerobic ATP production by the use of phosphagen, and aerobic ATP production by the use of internal O2 stores. The chapter also considers fatigue and muscle fibre types as the themes in exercise physiology. It cites the interplay of aerobic and anaerobic catabolism during exercise.

Chapter

Cover Biochemistry

Metabolism: Transforming Energy and Biomolecules  

This chapter evaluates the process of metabolism. Although there are many different sets of reactions, or metabolic pathways, involved here, only a small number are fundamental to all cells. The chapter focuses on two metabolic pathways that are particularly well understood by biochemists because of their importance for life: aerobic respiration and photosynthesis. To appreciate cellular metabolism, it is important to understand how energy is transferred between different molecules and converted to different forms. Moving and transforming energy is fundamental to how cells function, and the biochemists that study this topic describe it as bioenergetics. One of the key theoretical concepts that is particularly useful for understanding this biochemical topic is 'free energy'. This concept helps identify whether biochemical reactions are favourable or not. The chapter looks at adenosine triphosphate (ATP), as well as endosymbiosis.

Chapter

Cover Physical Chemistry for the Life Sciences

The Gibbs energy  

This chapter explores the procedure developed by American theoretician J. W. Gibbs, who laid the foundations of chemical thermodynamics towards the end of the nineteenth century. Gibbs discovered how to combine the two contributions needed in entropy calculations into one. Indeed, almost the whole of biochemical thermodynamics is now discussed in terms of the Gibbs energy. As this chapter shows, at constant temperature and pressure, the direction of spontaneous change is towards lower Gibbs energy. It also relates the Gibbs energy to work — particularly non-expansion work, which includes muscle contraction (for movement) and causing neurotransmitters to move across synapses to give rise to thought, or at least, neuronal response. Finally, the chapter examines the action of adenosine triphosphate in a case study.

Chapter

Cover Physical Chemistry for the Life Sciences

Coupled reactions in biochemistry  

This chapter explores coupled reactions. A spontaneous reaction may be able to drive forward a non-spontaneous reaction. In cells, every reaction is a part of a wider network of reactions and transmembrane transport processes. Here, inspection of metabolic pathways often reveals steps that can be considered to be a coupling between an energetically unfavourable process and an energetically favourable process. To better study these concepts, the chapter presents two case studies. The first involves the function of adenosine triphosphate, ATP (Atlas N3), which is to drive endergonic, energetically unfavourable processes such as protein synthesis, muscle contraction, and vision by the process of parallel coupling. The second concerns the oxidation of glucose and sequentially coupled reactions.

Chapter

Cover The Physiology of Training for High Performance

Biochemical Bases for Performance  

This chapter discusses adenosine triphosphate (ATP), which is the donor of the free energy that is used for muscle contraction, for the supporting ionic pumps that regulate muscle electrical activity, and for biosynthesis. It also talks about the molecule of ATP that is made up of a molecule of adenosine and consists of a purine base, a five-carbon sugar, and a chain of three phosphate groups. It also analyszes the phosphate groups that are attached by what are known as high-energy bonds, which means that considerable energy is required to produce the attaching reaction. The chapter points out that the formation of the high-energy bond is known as phosphorylation, while the breaking of the bond is known as hydrolysis. It details how adenosine diphosphate (ADP) is formed when a molecule of ATP is hydrolyzed and loses one of its phosphate groups.

Chapter

Cover The Physiology of Training for High Performance

Training for Anaerobic Events and Team Sports  

This chapter reviews a wide range of sports that require maximal efforts over a period as brief as two seconds or less or as long as two minutes. It looks at the relative contribution of energy-delivery pathways that depends upon the duration of the event. It also analyszes explosive events such as throwing, jumping, or weightlifting, which require maximal power output over only a few seconds and are derived from resting muscle stores of adenosine triphosphate (ATP) and from hydrolysis of phosphocreatine (PCr). The chapter illustrates team sports that typically require bursts of maximal effort separated by lower-intensity intervals or stoppages in play for rule infractions. It mentions ice hockey or soccer, wherein the intense activity may be sustained for up to 60 seconds without a stoppage in play or a slowing in tempo.

Chapter

Cover Animal Physiology

Energy Metabolism: Generating Energy from Food  

This chapter discusses energy metabolism in animals. It focuses on how animals meet their bodies' demands for energy and on the common processes involved in the flow of energy. This process starts with the acquisition of food and sees the transfer of energy from food to molecules of adenosine triphosphate (ATP), the common currency for energy transfer and utilization in animal cells. Metabolism can be broadly subdivided into catabolism and anabolism. Most animals extract the bulk of their energy from the oxidation of carbohydrates and fats in the presence of molecular oxygen—a process called aerobic respiration. Oxidation of carbohydrates in the absence of oxygen can also provide energy through anaerobic respiration. The chapter then looks at the diverse feeding strategies that animals adopt.

Chapter

Cover The Biochemical Basis of Sports Performance

The weightlifter  

This chapter discusses skeletal muscle structure and function. Muscular strength is, to a large extent, determined by the size of the muscles and the ability to fully activate the muscles in a coordinated manner. Successful weightlifting requires a large muscle bulk and the ability to generate high power for a very limited period, usually less than a few seconds. Technique is also obviously important because, in competition, the weightlifter is required to demonstrate control of the posture and stance when lifting and holding the weight above the head. Muscle proteins provide the framework of the contractile machinery, and the chapter considers the structural and functional characteristics of these important biomolecules. It also looks at the energy needs for lifting heavy weights, with emphasis on the role of adenosine triphosphate (ATP) as the energy currency of the muscle (and all other) cells.

Chapter

Cover Biochemistry and Molecular Biology

Glycolysis, the TCA cycle, and the electron transport system  

This chapter looks at glycolysis, which is stage 1 in the complete oxidation of glucose or glucosyl units of glycogen. It splits the lysis of the C6 glucose molecule into the two C3 molecules of pyruvate. The chapter looks at how glycolysis produces a net gain of only two adenosine triphosphate (ATP) molecules and prepares the glucose for the next stage, the tricarboxylic acid (TCA) cycle. Since nicotinamide adenine dinucleotide (NAD+) is limited in amount it must be reoxidized via the mitochondrion or glycolysis would halt. The chapter points out that the TCA cycle is stage 2 of the oxidation of glucose. Pyruvate is transported into the mitochondrial matrix where it is converted by pyruvate dehydrogenase into acetyl-CoA, which enters the TCA cycle.

Chapter

Cover Biochemistry and Molecular Biology

An alternative pathway of glucose oxidation: the pentose phosphate pathway  

This chapter examines the pentose phosphate pathway, which is a pathway of glucose oxidation which does not generate adenosine triphosphate (ATP) nor oxidize a molecule of glucose completely. The chapter considers the pentose phosphate pathway as a versatile pathway that produces ribose-5-phosphate for nucleotide synthesis, supplies nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) for fat synthesis and other reductive systems, and provides a route for the metabolism of surplus pentose sugars coming from the diet. The pathway has an oxidative section converting glucose-6-phosphate into ribose-5-phosphate and it produces NADPH. The chapter explores how the nonoxidative section manipulates ribose-5-phosphate according to the needs of the cell. If a cell requires equal amounts of ribose-5-phosphate and NADPH, only the oxidative section is required.

Chapter

Cover Biochemistry

Aerobic Metabolism I: The Citric Acid Cycle  

This chapter discusses modern aerobic organisms that transduce the chemical bond energy of food molecules into the bond energy of adenosine triphosphate (ATP). It examines how aerobic organisms perform this feat where oxygen is used as the terminal acceptor of the electrons extracted from food molecules. The capacity to use oxygen to oxidise nutrients, such as glucose and fatty acids, yields a substantially greater amount of energy than does fermentation. The chapter recounts the accumulation of atmospheric O2 on Earth about 2 billion years ago, when existing organisms were confronted with a serious problem: molecular oxygen forms toxic oxygen ions and peroxides called reactive oxygen species (ROS). ROS react with and damage or destroy biomolecules. Consequently, exposure to O2 acted as a severe selection pressure.

Chapter

Cover The Biochemical Basis of Sports Performance

The sprinter  

This chapter examines anaerobic metabolism. The sprinter has to sustain a very high-power output over a relatively short period of time. As the intramuscular supply of adenosine triphosphate (ATP) is sufficient to last only about two seconds, there is a pressing need to resynthesize ATP extremely quickly, and this is achieved by the breakdown of intramuscular stores of phosphocreatine and the rapid activation of glycolysis. Both of these processes occur without the utilization of oxygen; that is, they are anaerobic means of regenerating ATP. However, sprinting is not entirely anaerobic. There is a contribution of carbohydrate oxidation to ATP resynthesis during sprinting that increases as the duration and distance of the sprint increases. The chapter then describes the concept of the cellular energy charge and explains why there is a loss of adenine nucleotides during very high-intensity exercise.