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Lecture 6

BISC 101 - Lecture 6 - Cell Energy and Enzymes.docx

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Simon Fraser University
Biological Sciences
BISC 101
Christopher Kennedy

Biological Science 101 – General Biology Lecture Six: Cell Energy and Enzymes Ch. 8, Pgs. 142-160 Figs 8.8-8.21 Cell Energy and ATP Cell Energy (Metabolism): - All of the chemical reactions in the body. - Breakdown of complex molecules to simple ones = Catabolism (Cellular respiration). Cellular respiration -> Energy produced. - Build-up of complex molecules from simple ones = Anabolism, energy is required. Complex molecules -> Catabolism -> Energy is produced (exergonic) -> Energy captured -> Anabolism -> Energy is used (endergonic). Energy Captured -> Cells use energy. E.g. DNA replication, Protein synthesis and Membrane transport. Energy captured -> ATP (Adenosine triphosphate) Exergonic reaction -- ATP --> Endergonic ATP + H 02-> ADP + Pi (7.3 kcal/mole energy) Exergonic Muscle Cells -> require 10 million ATP/sec when working. - Energy from foods is converted to energy through cellular respiration. - Glucose + O 2> CO +2H2O (686 kcal/mole) Another energy molecule: NAD (Nicotinamide Adenine Dinucleotide) Oxidation -- Electrons --> Reduction - “High-energy foods”  Fats  Carbohydrates Enzymes Enzymes: - Involved in catabolism. - Food broken down. - Energy released. - Catalytic proteins that speed up the rate of a reaction, without altering the end products or change the reaction. Chemical reaction to start requires initial energy (activation energy), usually heat energy. Enzyme reduces the activation energy required. Characteristics of Enzymes: 1) Substrate Specific - Sucrase -> Sucrose - Sucrose binds to an active site on the enzyme. - Form enzyme + substrate complex. - Products released (glucose + fructose) - Reaction occurs at 1000 x per second. 2) Affected by Environment (Sensitive) - Temperatures can affect enzymes ability to function. - Each enzyme has its own optimal temperature. - pH can also affect enzymes. - Each enzyme has its own optimal pH. 3) Requires Cofactors or Co-enzymes - Assist with the catalytic activity. E.g. Zn, Cu, Co-enzyme A, Vitamins (function as cofactors or co-enzymes) 4) Activity of Enzymes are affected by Chemicals - This may cause enzymes to stop. - It can be reversible or irreversible: a) Competitive Inhibition: - Chemical inhibitor. - Competes for active site. - Reaction stop. - Reversible. b) Non-competitive Inhibition: - Chemical molecule binds to enzyme. - Alters active site. - Enzyme nonfunction
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