Menu 1 CH. 6 (Unit H) Metabolism : Energy and Enzymes

Menu 2 Forms of Energy  These forms of energy are important to life: – chemical – radiant (examples: heat, light) – mechanical – electrical  Energy can be transformed from one form to another.  Chemical energy is the energy contained in the chemical bonds of molecules. It is the main energy form we are interested in studying.  Energy that is stored is called potential energy.

Menu 3 Laws of Thermodynamics  1st law: Energy cannot be created or destroyed. –Energy can be converted from one form to another. The sum of the energy before the conversion is equal to the sum of the energy after the conversion. –Example: A light bulb converts electrical energy to light energy and heat energy. Fluorescent bulbs produce more light energy than incandescent bulbs because they produce less heat. C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy 300 J J  100 J J J

Menu Laws of Thermodynamics 4 2nd law: Some usable energy dissipates (leaves) during transformations and is lost as heat. During changes from one form of energy to another, some usable energy dissipates, usually as heat. The amount of remaining usable energy therefore decreases.

Menu 5 Energy is required to form bonds – ANABOLIC Reactions (endothermic/endergonic) Atoms or molecules Energy + Energy Larger molecule The energy that was used to form the bonds is now stored in the bonds of this molecule. Example: Taking amino acids and building them into a protein. Synthesis requires energy input

Menu 6 Energy Supplied Energy Released Anabolic Reactions Anabolic reactions consume energy. ENDERGONIC or ENDOTHERMIC Substrates (Reactants) Products Menu

7 Energy is released when bonds are broken – CATABOLIC Reactions (Exothermic/exergonic) Menu Larger macromolecules are hydrolyzed to give rise to smaller monomers. Energy is released. Example : When the body take triglycerides and breaks them into Glycerol and Three Fatty Acids

Menu 8 Energy is released when bonds are broken. Energy When bonds break, energy is released. It may be in a form such as heat or light or it may be transferred to another molecule. Menu

9 Energy Supplied Energy Released Catabolic reactions release energy. EXERGONIC EXOTHERMIC Catabolic Reactions Substrate (Reactant) When bonds are broken, energy is released. Menu

10 Catabolic and Anabolic Reactions  The energy-producing reactions within cells generally involve the breakdown of complex organic compounds to simpler compounds. These reactions release energy and are called catabolic reactions.  Anabolic reactions are those that consume energy while synthesizing compounds.  ATP produced by catabolic reactions provides the energy for anabolic reactions. Anabolic and catabolic reactions are therefore coupled (they work together) through the use of ATP.  Diagram: next slide

ATPADP + P i Energy Menu An anabolic reaction A catabolic reaction Catabolic and Anabolic Reactions

Menu ENTROPY Calculation 12 Entropy = is a mathematically- defined thermodynamic quantity that helps to account for the flow of energy through a thermodynamic process such as a chemical reaction G = E products - E reactants Example : if Reactants have 500 Joules of usable energy but your products end up only having 200 Joules of usable energy. Then 300 Joules were released. According to the example: G = E products - E reactants So 300 J – 500 J = Joules. A negative number indicates a exothermic/exergonic reaction

Menu 13 One very important energy storing and releasing molecule is ATP A Base (adenine) Sugar (ribose) 3 phosphate groups

Menu 14 A ATP ATP Stores Energy The phosphate bonds are high-energy bonds. A Energy ADP + P i + Energy Breaking the bonds releases the energy.

Menu 15 ATP ADP + P i Energy (from glucose or other high-energy compounds) ATP is Recycled – In the “ATP CYCLE”  ATP (Adenosine Triphosphate) is an energy-containing molecule used to supply the cell with energy. The energy used to produce ATP comes from glucose or other high- energy compounds.  ATP is continuously produced and consumed as illustrated below.  ADP + P i + Energy  ATP + H 2 O (Note: P i = phosphate group)

ATP ATPADP + P i Energy Menu In this diagram, energy from breaking bonds in this molecule is used to form ATP. The ATP Cycle can be coupled to drive other anabolic reactions, or coupled with catabolic reactions to form ATP from ADP + P.

ATP ATPADP + P i Energy Menu The energy in ATP can be used to form bonds in other molecules.

Menu 18 CH N C C C NH 2 N HC N N C C C C O C O P O P O P O CH 2 O O O O - O - O - - H OH H ATP (Adenosine Triphosphate) 3 phosphate groups Base (adenine) Ribose

Menu 19 METABOLISM : THE SUM OF ALL THE ANABOLIC AND CATABOLIC REACTIONS THAT TAKE PLACE INSIDE ALL THE CELLS OF AN ORGANISM. - The rate of these reactions gives rise to one’s METABOLIC RATE

Menu 20Enzymes  Catalysts are substances that speed up chemical reactions. Organic catalysts (contain carbon) are called enzymes.  Enzymes are specific for one particular reaction or group of related reactions.  Many reactions cannot occur without the correct enzyme present.  They are often named by adding "ase" to the name of the substrate. Example: Dehydrogenases are enzymes that remove hydrogen. – Helicase, Maltase, DNA Polymerase, Reverse Transcriptase etc.

Menu 21 Rate of Reaction  Reactions with enzymes are up to 10 billion times faster than those without enzymes.  Enzymes typically react with between 1 and 10,000 molecules per second. Fast enzymes catalyze up to 500,000 molecules per second.  Substrate concentration, enzyme concentration, Temperature, and pH affect the rate of enzyme reactions.  They increase reaction rate by lowering the amount of Ea required!

Menu 22 Metabolic reactions use enzymes A high-energy molecule (substrate) is used to transfer a phosphate group to ADP to form ATP.

Substrate Enzyme Active Site Enzyme-Substrate Complex Product Enzyme Enzymes Enzymes are organic catalysts. Menu

24 Cofactors  Many enzymes require a cofactor to assist in the reaction. These "assistants" are nonprotein and may be metal ions such as magnesium (Mg++), potassium (K+), and calcium (Ca++).  The cofactors bind to the enzyme and participate in the reaction by removing electrons, protons, or chemical groups from the substrate.

Menu 25 Coenzymes  Cofactors that are organic molecules are coenzymes.  Coenzymes are usually vitamins.

Menu 26 Vitamins are Coenzymes VitaminCoenzyme Name NiacinNAD + B 2 (riboflavin)FAD B 1 (thiamine)Thiamine pyrophosphate Pantothenic acidCoenzyme A (CoA) B 12 Cobamide coenzymes

Menu 27 Coenzymes  Coenzymes are cofactors that are non protein.  They bind to the enzyme and also participate in the reaction by carrying electrons or hydrogen atoms. Enzyme Coenzyme

Menu 28 Activation Energy Energy Supplied Energy Released Activation Energy In either kind of reaction, additional energy must be supplied to start the reaction. This energy is called activation energy. Menu

29 Activation Energy Energy Supplied Energy Released Activation Energy An example of activation energy is the spark needed to ignite gasoline. Menu

30 Enzymes Lower Activation Energy Energy Supplied Energy Released Activation energy without enzyme Activation energy with enzyme Enzymes lower the amount of activation energy needed for a reaction. Menu

31 When studying enzymes in upcoming units remember to watch your S.T.E.P.P s S = SUBSTRATE NAME T = OPTIMAL TEMERATURE E = ENZYME NAME P = PRODUCT NAME P = pH – OPTIMAL pH

Menu 32 Induced Fit Theory – Most current  An enzyme-substrate complex forms when the enzyme’s active site binds with the substrate like a key fitting a lock.  The substrate molecule does not fit exactly in the active site. This induces a change in the enzymes conformation (shape) to make a closer fit.  After the reaction, the products are released and the enzyme returns to its normal shape.  Only a small amount of enzyme is needed because they can be used repeatedly.

Menu Lock and Key Theory 33 The older theory of how enzymes work was that the enzyme has an already perfect active site shape for that particular substrate. Just like only the perfect key will fit the complimenting lock

Menu 34 Metabolic Pathways  Metabolism refers to the chemical reactions that occur within cells.  Reactions occur in a sequence and a specific enzyme catalyzes each step.

Menu 35 Metabolic Pathways enzyme 1enzyme 2enzyme 3enzyme 4 F enzyme 5 A B C D E Enzymes are very specific. In this case enzyme 1 will catalyze the conversion of A to B only. Notice that C can produce either D or F. This substrate has two different enzymes that work on it.

Menu 36 A Cyclic Metabolic Pathway B C D F A E A + F  B B  C  D D  F + E In this pathway, substrate “A” enters the reaction. After several steps, product “E” is produced.

Menu 37 Enzyme regulation by negative feedback inhibition is similar to the thermostat example. As an enzyme's product accumulates, it turns off the enzyme just as heat causes a thermostat to turn off the production of heat. Feedback Inhibition A B C D enzyme 1enzyme 2enzyme 3 The goal of this hypothetical metabolic pathway is to produce chemical D from A. B and C are intermediates. The next several slides will show how feedback inhibition regulates the amount of D produced.

Menu 38 Feedback Inhibition A B C D enzyme 1enzyme 2enzyme 3 X Enzyme 1 is structured in a way that causes it to interact with D. When the amount of D increases, the enzyme stops functioning. X The amount of B in the cell will decrease if enzyme 1 is inhibited. XX C and D will decrease because B is needed to produce C and C is needed to produce D.

Menu 39 A B C D X Feedback Inhibition enzyme 1enzyme 2enzyme 3 XX When the amount of D drops, enzyme 1 will no longer be inhibited by it. B CD B, C, and D can now be synthesized.

Menu 40 Feedback Inhibition A B C D enzyme 1enzyme 2enzyme 3 X As D begins to increase, it inhibits enzyme 1 again and the cycle repeats itself.

Menu 41 The End