Intro to Metabolism

Learning Goals To understand that metabolic pathways are multistep, enzyme-catalyzed transformations To see how catabolism and anabolism free- up and use energy and raw materials to provide the cell with what it needs

Metabolism The set of enzyme catalyzed life-sustaining chemical transformations that allows an organism to grow, reproduce, maintain structures, and respond to their environment.

Catabolism and Anabolism More specifically, the food we eat is broken down to obtain materials and energy through catabolic pathways. These materials and energy can then be used to build things the cell needs through anabolic pathways.

Metabolic Pathways Chemical reactions of metabolism are organized into metabolic pathways: one chemical is transformed into another through a series of steps, catalyzed by a sequence of enzymes. https://primalmeded.fi les.wordpress.com/20 11/05/metabolism.jpg

Conserved Metabolic Pathways Some enzymes, and pathways are conserved across the domains of life, while others can differ dramatically. Eg. Glycolysis is a 10 step reaction that almost every organism on Earth can undergo in some form.

Overall Reactions Two metabolic pathways you have likely heard of are cellular respiration and photosynthesis. We will be studying each of these in this unit. They are often represented by their overall reactions: C6H12O6 + 6O2         6CO2 + 6H2O + ATP 6CO2 + 6H2O + ATP              C6H12O6 + 6O2 In reality, each of these are pathways that have many reactions and intermediates.

Warm-Up Explain at your table what metabolism is. What do you think a metabolic disorder is? How do you think biochemical pathways factor into metabolism?

Time to think… Individually answer the following question, then share with your group: 1.ATP, or Adenosine Triphosphate, is a molecule that is used by virtually every living cell. What role might a molecule like this have? How could its structure be suited for its function? 2. What is a coenzyme?

ATP (Adenosine Triphosphate) The energy currency of the cell Major product of many catabolic pathways Major source of energy for many anabolic pathways Also involved in generating electric impulse through our nerves, muscle contractions, moving things through a cell, and more!

Where is the Energy? ATP can have its terminal phosphate group cleaved through a hydrolysis reaction, releasing energy This reaction is highly exergonic with ΔG = -30.5 kJ/mol

Coupled Reactions Cells use ATP to drive endergonic reactions (products possess more free energy than their reactants) If the cleaving of ATP’s terminal high-energy bond releases more energy than the other reaction consumes, the two reactions can be coupled so that the energy released by hydrolysis of ATP can be used to supply the endergonic reaction with energy.

Where Does ATP Come From? We break down food to use the energy in its bonds to produce ATP. This is accomplished through metabolic pathways ATP is constantly recycled through hydrolysis to ADP + Pi and reformation

What is Different About Plants? Plants have another way to make ATP aside from breaking down food: USING ENERGY FROM THE SUN!!

What Are Energy Carriers? More commonly referred to as electron carriers, these are coenzymes that can carry electrons to locations where their energy will be used, primarily to produce ATP. You can think of them as more minor players in energy exchanges in metabolism.

Oxidation/Reduction When a molecule loses electrons (and thus energy) we say it has been oxidized (because we used to think it was only the really electronegative oxygen that could cause this) When a molecule gains electrons (and thus energy) we say it has been reduced. Reduced forms of molecules have higher energy than their oxidized form. REMEMBER: L E O says G E R or O I L R I G

More Coupled Reactions Oxidation and Reduction can also be thought of as coupled reactions, because when one molecule is losing electrons, another is gaining them. We call these redox (reduction/oxidation) reactions. For example: C6H12O6 + 6O2                         6CO2 + 6H2O

Homework Is an anabolic reaction more likely to be exergonic or endergonic, and would this type of reaction have a positive or negative value for ΔG? Explain. Draw a diagram of a molecule of ATP. Label the different groups that make up this molecule. Use labelled diagrams to illustrate the ATP energy cycle (use diagrams to show how it is used and recycled) Distinguish between oxidation and reduction reactions. Why are these reactions linked? Why is the recycling of electron carriers and ATP important for the cell?