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

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 when it comes to Biology

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. C6H12O6 + 6O2  6CO2 + 6H2O + Energy 300 J + 200 J  100 J + 100 J + 300 J

Laws of Thermodynamics 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.

Categories of Metabolic (cellular) Reactions 1. ANABOLIC 2. CATABOLIC

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 8

Substrates (Reactants) Anabolic Reactions Products Anabolic reactions consume energy. ENDERGONIC or ENDOTHERMIC Energy Supplied Substrates (Reactants) Energy Released 9 Menu

Energy is released when bonds are broken – CATABOLIC Reactions (Exothermic/exergonic) 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 8 Menu

Energy is released when bonds are broken. 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. 8 Menu

Catabolic Reactions Energy Supplied Substrate (Reactant) Catabolic reactions release energy. EXERGONIC EXOTHERMIC Energy Released When bonds are broken, energy is released. 10 Menu

Video Clip – Endothermic vs Exothermic https://www.youtube.com/watch?v=XYRCXoFWPZw

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

Catabolic and Anabolic Reactions An anabolic reaction A catabolic reaction ATP ADP + Pi Energy Catabolic and Anabolic Reactions 8 Menu

ENTROPY Calculation G = Eproducts - Ereactants 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 = Eproducts - Ereactants 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 = Eproducts - Ereactants So 300 J – 500 J = - 200 Joules. A negative number indicates a exothermic/exergonic reaction

Go Over Ch. 6 Worksheet Question #11 Then we will see why ENZYMES Are so important

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!

Enzymes in Action – video clip https://www.youtube.com/watch?v=qgVFkRn8f10 Enzymes in Action – video clip

Enzymes 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.

Metabolic reactions use enzymes

1 3 2 Enzymes Menu Enzymes are organic catalysts. Substrate Active Site Enzyme Product Enzyme-Substrate Complex 3 2 Enzyme 15 Menu

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.

Coenzymes Cofactors that are organic molecules are coenzymes. Coenzymes are usually vitamins.

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

STOP For the day

How do Enzymes Speed Up Reaction Rate ?? Activation Energy In either kind of reaction, additional energy must be supplied to start the reaction. This energy is called “Activation Energy. Energy Supplied Activation Energy Energy Released 21 Menu

Enzymes Lower Activation Energy Enzymes lower the amount of activation energy needed for a reaction. Enzymes Lower Activation Energy Activation energy without enzyme Energy Supplied Activation energy with enzyme Energy Released 22 Menu

TWO THEORIES ON HOW AN ENZYME BONDS WITH ITS SUBSTRATE Induced Fit Theory Locak and Key Theory

Induced Fit Theory – Most current 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.

Lock and Key Theory 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

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

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

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

A B C D Feedback Inhibition The goal of this hypothetical metabolic pathway is to produce chemical D from A. A B C D enzyme 1 enzyme 2 enzyme 3 B and C are intermediates. The next several slides will show how feedback inhibition regulates the amount of D produced. 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. 34

X X A B C D X Feedback Inhibition C and D will decrease because B is needed to produce C and C is needed to produce D. X The amount of B in the cell will decrease if enzyme 1 is inhibited. A B C D X enzyme 1 enzyme 2 enzyme 3 Enzyme 1 is structured in a way that causes it to interact with D. When the amount of D increases, the enzyme stops functioning. 35

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

A B C D X Feedback Inhibition enzyme 1 enzyme 2 enzyme 3 As D begins to increase, it inhibits enzyme 1 again and the cycle repeats itself. 42

The End