Lecture 13: Metabolic pathways and energy production Chemistry - FALL 2016 Course lecturer : Jasmin Šutković 10 th January 2017

Contents Flow of energy ATP Metabolism How Enzymes work International University of Sarajevo Flow of energy ATP Metabolism How Enzymes work Cellular respiration

Energy: the capacity to do work -kinetic energy: the energy of motion Flow of Energy Energy: the capacity to do work -kinetic energy: the energy of motion -potential energy: stored energy Energy can take many forms: chemical, mechanical, electric current, heat, light

ATP - Energy Currency of Cells ATP is the molecule that cells use to store, transfer, and provide energy The energy from ATP is used to fuel anabolic reactions recall: for growth, repair, and reproduction ATP = Adenosine TriphosPhate Adenosine (same molecule from DNA and RNA) + Three inorganic phosphates (functional group PO4)

ATP - Energy Currency of Cells ATP = adenosine triphosphate the energy “currency” of cells ATP structure: ribose, a 5-carbon sugar adenine three phosphates

Photo Courtest of Dr. O’Steen

ATP - Energy Currency of Cells ATP - 1 PO4 = ADP (Adenosine Diphosphate) ADP - 1 PO4 = AMP (Adenosine Monophosphate) ADP + 1 PO4 = ATP 9

ATP is a molecule that is used as an Energy Currency in cells ATP’s can be broken down to provide energy for endergonic reactions Cells use energy to build ATP’s Enzymes of allow cells to efficiently build ATP’s - Cells can make ATP’s for less energy than ATP’s can provide

ATP - Energy Currency of Cells ATP stores energy in the covalent bonds between phosphates: Phosphates are highly negative, therefore: the phosphates repel each other much energy is required to keep the phosphates bound to each other Energy is released when the bond between two phosphates is broken

Energy Currency of Cells When the bond between phosphates is broken: ATP ADP + Pi energy is released ADP = adenosine diphosphate Pi = inorganic phosphate This reaction is reversible...

ATP/ADP Cycling

ATP regulates enzyme activity Other Functions of ATP ATP regulates enzyme activity Phosphorylation and dephosphorylation - process of adding or removing phosphate groups - can activate or deactivate enzymes ATP serves as a source of phosphate groups 14

Three rules to be considered an enzyme Enzymes Enzymes: molecules that catalyze - speed up - biochemical reactions in living cells Three rules to be considered an enzyme Most are proteins (some RNA enzymes) Lower the energy of activation required for a reaction to occur Are not changed or consumed by the reaction Cofactors, Coenzymes 15

Metabolism Enzymes catalyze cellular chemical reactions Metabolism - the chemical reactions in a cell: Two categories of cellular chemical reactions: Anabolic Reactions Build larger molecules for growth, repair, reproduction Dehydration Synthesis Reactions require energy and nutrients Catabolic Reactions Breakdown larger molecules Hydrolysis Reactions mobilize nutrients for energy making it available to the cell

Metabolism Metabolism is the sum total of all anabolic and catabolic reactions that occur in the cell The metabolism of cells is carried out and controlled by the enzymes There are catabolic enzymes – those that cleave larger molecules into smaller ones Ex. Hydrolysis Reactions There are also anabolic enzymes – those that assemble smaller molecules into larger ones Ex. Dehydration Reactions

Enzymes interact with substrates. substrate: molecule that will undergo a reaction active site: region of the enzyme that binds to the substrate Binding of an enzyme to a substrate causes the enzyme to change shape, producing a better induced fit between the molecules.

Enzymes lower the activation energy of biochemical reactions. How Enzymes Work Enzymes lower the activation energy of biochemical reactions. Enzymes make it easier for chemical reactions to occur: by destabilizing the bonds in the substrate by bringing substrates together so they react by decreasing entropy - disorder - in the system Enzymes make the chemical reactions possible in the cell’s environment Enzymes make cells very efficient 19

Enzymes make cells very efficient How Enzymes Work Enzymes make cells very efficient Through enzymes, cells can carry out anabolic and catabolic reactions and end up with a net profit of energy. Metabolic reactions and Cellular respiration 21

The Energy is in the form of ATP Cellular Respiration Cellular Respiration is a metabolic pathway that breaks down glucose and extracts the energy to produce energy C6H12O6 + 6O2 6H2O + 6CO2 + Energy Glucose Oxygen Water Carbon Dioxide The Energy is in the form of ATP

Metabolic Pathways Metabolic Pathways are series of chemical reactions carried out by separate enzymes It is a sequence of chemical reactions where each reaction is controlled by a separate enzyme The product of one enzyme serves as the substrate for the enzyme of subsequent reaction in the metabolic pathway

The metabolism of cells is carried out and controlled by ENZYMES There are catabolic enzymes – those that cleave larger molecules into smaller ones Ex. Hydrolysis Reactions There are also anabolic enzymes – those that assemble smaller molecules into larger ones Ex. Dehydration Reactions