BIOL 2401-Chapter 3 - Energy, Chemical Reactions, and Cellular Respiration PDF

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Energy, Chemical Reactions, and Cellular Respiration...

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ANATOMY AND PHYSIOLOGY CHAPTER 3 Energy: the capacity to do work and exists in two states: Potential energy= stored energy (energy of position) Kinetic energy= energy of motion:

Energy can be converted from one state to another Chemical energy: energy stored in a molecule's chemical bonds Used for movement, molecule synthesis, establishing concentration gradients Molecules function in chemical energy storage Triglycerides - long-term energy storage in adipose tissue Glucose - glycogen stores in liver and muscle ATP - stored in all cells; produced continuously and used immediately Protein - can be used as a fuel molecule but has more important functions

Kinetic Energy Forms Electric energy: movement of charged particles Mechanical energy: exhibited by objects in motion Sound energy: molecule compression caused by a vibrating object Radiant energy: energy of electromagnetic waves (Figure 3.2) Heat: kinetic energy associated with random motion of atoms, ions, and molecules

Measured as the temperature of a substance First law of thermodynamics: Energy can neither be created nor destroyed; it can only change in form. Second law of thermodynamics: When energy is transformed, some energy is lost to heat.

Metabolism: Collective term for all chemical reactions in the body Chemical reactions: Occur when chemical bonds in existing molecular structures are broken

Components of chemical equations Reactants: the substances present prior to start of a chemical reaction written on left side of equation Products: the substances formed by the reaction written on right side of equation A + B  C A and B reactants; C, the product Classification Based on Changes in Chemical Structure Catabolism: Collective term for all decomposition reactions Anabolism: Collective term for all synthesis reactions -

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Metabolism: Collective term for all chemical reactions in the body Decomposition reaction: Initial large molecule broken down into smaller structures Synthesis reaction: Two or more structures combined to form a larger structure Exchange reaction: Groups exchanged between two chemical structures Oxidation-reduction reaction (redox reaction): Electrons moved from one chemical structure to another

Structure that loses an electron oxidized during oxidation Structure that gains an electron reduced during reduction Exergonic reactions: Reactants with more energy within their chemical bonds than products Endergonic reactions: Reactants with less energy within their chemical bonds than products ATP cycling: The continuous formation and breakdown of ATP Irreversible reaction: Net loss of reactants and a net gain in products over time Reversible reaction: No net change in concentration of reactants and products Reaction rate: Measure of how quickly a chemical reaction takes place Activation energy (Ea): Energy required to break existing chemical bonds

Enzymes: catalysts that accelerate normal chemical activities by decreasing the activation energy of cellular reactions . Uncatalyzed reactions: chemical reactions that occur without an enzyme. Catalyzed reactions: chemical reactions that occur by means of an enzyme. Active site: Region of enzyme accommodating the reaction substrate (Figure 3.9). Cofactors: Molecules or ions required for normal enzyme function.

Cofactors may have non-protein organic or inorganic structure s. Organic cofactors called coenzymes. Six major classes of enzymes: oxidoreductase, transferase, hydrolase, isomerase, ligase, lyase (Table 3.2). Effect of Enzyme and Substrate Concentration: increases only up to point of saturation. Effect of Temperature: Human enzymes function best at the optimal temperature 3 7 o C

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Severe increases in temperature cause protein denaturation with loss of function. E:ffect of pH: Enzymes function best-at optimal pH between pH of 6 and 8 for most enzymes. Competitive inhibitors: Resembles and compete with substrate for occupation of active site. Noncompetitive inhibitors (allosteric inhibitors): Do not resemble substrate and bind to a site other than active site

(allosteric site) which induce conformational change to enzyme and active site. Metabolic pathway: Product of one enzyme becoming substrate of the next. Multienzyme complex: Group of attached enzymes. Phosphorylation: addition of phosphate group performed by protein kinases. Dephosphorylation: removal of phosphate group performed by phosphatases. Glucose oxidation: Step by step breakdown of glucose with energy release; Carbon dioxide and water formed

Direct synthesis of ATP called substrate-level phosphorylation. Indirect method: energy first released to coenzymes (e.g., NAD+, FAD) that energy then transferred to form ATP called oxidative phosphorylation; Involves oxygen as final acceptor. Stages of glucose oxidation : Glycolysis (anaerobic cellular respiration), intermediate stage, citric acid cycle, and electron transport system. Glycolysis (Figure 3.16 Metabolic pathway): Anaerobic process in the cytosol, Glucose broken down into two pyruvate molecules, Net production of 2 ATP (2 invested, 4 formed) and 2 NADH molecules Intermediate Stage and Pyruvate Dehydrogenase (Figure 3.17): This stage is the "link" between glycolysis and citric acid cycle; Pyruvate and coenzyme A (CoA) combined to form acetyl CoA and CO2 Citric Acid Cycle (Figure 3.18): 2 CO2, 1 ATP, 3 NADH, and 1 FADH2 formed during one cycle The electron transport system (Figure 3.20}: Collective group of proteins in the cristae, located in the inner membrane

of mitochondria, that "catch" electrons from NADH and FADH2 released. Proteins act as H+ pump: transport H+ from matrix to outer membrane compartment ATP synthetase allow for passage of H+ from outer compartment back into matrix; Flow of H+ harnessed to bond Pi to ADP to form ATP. Stage/Total Substrate level phosphorylation Glycolysis 2 ATP Intermediate Stage Citric Acid Cycle 2 ATP Total

4ATP

Oxidative phosphorylation 2 NADH to 6 ATP 2 NADH to 6 ATP 6 NADH to 18 ATP 2 FADH2 to 4 ATP 34ATP

Transport of NADH during glycolysis takes 1 ATP per NADH Total= 4 ATP+ 34 ATP-2 ATP= 36 ATP for one molecule glucose. Under conditions of insufficient oxygen, cell becomes more dependent on anaerobic process of glycolysis, requires NAD+ to continue; Glycolysis eventually shuts down due to lack of NAD+....