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Lecture 5 - Lecture 5 Where do living organisms get their...

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Lecture 5 Where do living organisms get their energy from? Autotrophs (plants) – use solar energy to synthesize food compounds. o Light energy to chemical energy, forming sugar. Heterotrophs (animals) – obtain energy by processing the chemical energy in organic compounds (food). Where do cells get their food from? Cells obtain energy by processing the chemical energy in organic compounds (food) Food can be sugar, proteins, or lipids. How does Glucose Oxidation Release Chemical Energy? Glucose – most common fuel in organisms. Other molecules are first converted into glucose or other intermediate compounds – proteins and lipids need to be broken down at different points in the pathway (not beginning at glycolysis). Principles of metabolic pathways: Chemical transformation occurs in a series of reactions. Each reaction has a specific enzyme The same type of pathways exists in both eukaryotes and prokaryotes. Eukaryotes – metabolic pathways are compartmentalized in organelles. Each pathway is regulated by key enzymes. Oxidation of glucose The pathways all have to deal with glucose oxidation (catabolism). NADH – where energy is captured and used to make ATP. The majority of energy is released in redox reactions. Pathways Photosynthesis – where you get your glucose molecule Glycolysis – where you get your pyruvate molecule Aerobic – Cellular Respiration o complete oxidation of glucose – waste products CO2 and H2O – 32 ATP Anaerobic – Fermentation o Incomplete oxidation – waste products organic compounds and CO2 – 2 ATP Redox Reactions Transfer of electrons Reduction – gain electrons or hydrogen atoms
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Lecture 5 Oxidation – loss of electrons or hydrogen atoms Terms apple if H atoms are gained or lost Oxidation and reduction always occur together Oxidizing agent – the reactant reduced Reducing agent – the reactant that is oxidized Energy is always with the reduced product. Glucose is the reducing agent and Oxygen is the final electron acceptor (oxidizing agent) NAD (nicotinamide adenine dinucleotide) Coenzyme NAD is an electron carrier in redox reactions (gives the most energy) Two forms: NAD + (oxidized) and NADH + H + (Reduced) Transfers involving NAD – what is actually transferred is an H- (a proton and two electrons) and a free proton (H+) ATP Exergonic reactions produce ATP ATP is used to power endergonic reactions (i.e. pumping of ions against the gradient; movement of substances around the cell) We first need the exergonic reactions to occur in order to get energy to make ATP. Glucose & ATP Production Two major categories: aerobic and anaerobic Five pathways: glycolysis, pyruvate oxidation, citric acid cycle, electron transport chain, fermentation.
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