Lecture 7A Introduction to Bioenergetics PDF

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Bioenergetics The study of energetic events in a biological world ○ We use chemical energy that we get in the form of ATP Energy for activity is based on two concepts ○ We do not create energy ○ Energy conversion happens at an efficiency ■ Its efficient for mechanical work but there is still a tremendous amount of energy that is lost as heat ■ About 20-40% efficient (this amount is going to be usable but the rest is used as heat) A dynamic change must occur to show that energy was present When it comes to exercise, that rate of conversion determines the rate of performance ○ If we want to increase amount of work being done we have to increase the rate of energy conversion Metabolism ○ The sum of all of the chemical reactions taking place within the body ■ The sum of all of the chemical reactions taking place within the body ● They either require energy or convert/ release it Fuel Substrates Thermodynamics ○ Potential energy: energy of position ■ Energy that is stored ○ Kinetic energy: energy of movement ○ PE + KE = total energy in the system ○ Follows law of thermodynamics (energy is neither created nor destroyed but just transformed into a different form) Biosynthesis ○ Anabolic: “to build”; it is an endergonic process ○ Endergonic: we have to add energy into the process ○ Ex: glucose + glucose → glycogen ; glycerol + fatty acids → triglycerides ; AA + AA → protein ■ This is an anabolic process These process normally occur when we have a surplus of supplies as well as energy to add to the process Biodegradation ○ Occurs when we need energy and want to perform work ○ Catabolic: “to break down” ○ Exergonic: We are releasing energy ○ Heat is a by product of these reactions (exothermic reactions) ■ This is energy that is lost CHO ○

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Preferred yet heavy fuel It is the ideal usable energy form but not the ideal storage energy form For every g of CHO we store we also store it with 3x its mass of water We store CHO in the liver but the majority of the body’s CHO is stored in the skeletal muscle Fats (lipids) ○ Built for efficiency ○ We store a lot more energy in fat ○ When we store fat we do not have to store it with any water storage associated with it which is what makes fat an ideal storage ○ We store the majority of fat in the subcutaneous and visceral fat; we do not have a lot of fat stored in muscle ○ Proteins ○ Fuel during starvation ■ We consider it an emergency fuel ○ We want to use proteins for building structures in the body not for energy ○ We normally have a low supply (4 kcal/g) ○ We use proteins when glucose from CHO is low ■ We take proteins and we convert them into glucose Figure 2.1

Controlling the Rate of Energy Production ●

Substrate availability ○ Mass action effect

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■ When we have more of a substrate available, we are more likely to use it Enzymatic activity ○ Enzymes: proteins that speed up (catalyze) a reaction ■ They lower the energy of activation needed for a chemical reaction to occur ■ They will dictate the rate that we can convert energy in the body ○ Coenzymes: organic molecules that will allow enzymes to perform their job ○ More enzyme activity = more product ○ Rate limiting enzymes ■ gatekeepers of a metabolic pathway that will control how fast we go from substrates to the end product

Enzyme Activity

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We reduce the amount of activation energy required to start a reaction with the enzyme

Rate Limiting Enzymes

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By product 3 we will have negative feedback to inhibit the RLE so that the fuel isn't being depleted...