Energy and Metabolism Energy: kj- unit of work or kcal- heat energy Energy: kj- unit of work or kcal- heat energy the capacity to do work. Two types: the capacity to do work. Two types: PE vs KE Many types of energy… PE vs KE Many types of energy… Chemical Energy Chemical Energy PE stored in chemical bonds PE stored in chemical bonds Energy Conversions: Shooting an arrow.. Energy Conversions: Shooting an arrow.. Chem PE> Muscle KE> Mechanical E… Chem PE> Muscle KE> Mechanical E… Turning on a light? Turning on a light?

? H e a t Entropy (S) #1: Energy can be changed from one form to another, but it cannot be created or destroyed. #2: In all energy exchanges, if no energy enters or leaves the system, the PE of the final state will always be less than that of the initial state." (entropy)entropy

Metabolism Sum of all the chemical activities taking place in an organism. Two main types: Sum of all the chemical activities taking place in an organism. Two main types: Anabolism A + B AB *need energy Anabolism A + B AB *need energy Catabolism AB A + B *release energy Catabolism AB A + B *release energy Energy from where?? Energy from where?? Bond Energy = energy required to break a bond = Total PE = Enthalpy (H) Bond Energy = energy required to break a bond = Total PE = Enthalpy (H)

*Enthalpy H = Hproducts – Hreactants *Entropy = S = measure of randomness Disorganized energy, (ex- heat), -high entropy. Cars %, Cells, 60% ‘lost’ As Temp increases….increase random molecular motion….multiplies ‘disorder’ The only kind of energy that can do cell work. (Stored bond energy-PE) H = G + TS The total energy of a system (Enthalpy-H) Is equal to free energy (usable energy-G) plus entropy (the unusable ‘heat’ energy-S) *T As entropy (S) increases, what happens to G?

Use ‘G’ to predict if a reaction will release energy, or will require an input of energy ENTHALPY ENTROPY FREE ENERGY

ExergonicVsEndergonic?

Endergonic: Building There is a gain of free energy (+G) G products > G reactants

Exergonic: Breakdown There is a loss of free energy (-G) G reactants > G products “spontaneous”……slow……require AE

EXERGONIC vs ENDERGONIC

Coupled Reactions *Endergonic *Exergonic

ATP

Oxidation I s Loss of electrons (H) Reduction Is Gain of electrons (H) Chemical energy = energy stored in bonds. Chemical energy = energy stored in bonds. Some bonds require more energy to form than others. Some bonds require more energy to form than others. When these high energy bonds break, new lower energy molecules are formed. When these high energy bonds break, new lower energy molecules are formed. In a redox In a redoxreaction, the energy difference is released. *Supplies energy *For this reaction Oxidation Reduction (Redox) Reactions “OIL RIG”

Enzymes: Proteins that are used for chemical reactions (some RNA molecules) Enzymes can either break up or put together substrates Enzymes are specific – only work on certain substrates. Enzymes are biological catalysts that react on substrates Enzymes are NOT CHANGED in the reaction

Catalyst: A substance that causes a reaction to occur but does not itself get changed A substance that causes a reaction to occur but does not itself get changed Biological catalysts (enzymes) are found in ALL living cells Biological catalysts (enzymes) are found in ALL living cells

Activation Energy The energy required for a chemical reaction to start and continue on its own. The energy required for a chemical reaction to start and continue on its own. Similar to rolling a boulder downhill, it is the chemical ‘push’ that gets a chemical reaction going. (Enzymes lower the activation energy needed for chemical reactions. Less energy needed to start the reaction, can occur at lower temperatures, faster rates.)

Lowering the Activation Energy

How an enzyme works… Substrate: A substance that the catalyst (enzyme) acts on Substrate: A substance that the catalyst (enzyme) acts on Ex) Lactose = milk sugar (substrate) Ex) Lactose = milk sugar (substrate) Lactase = breaks down lactose (enzyme) Lactase = breaks down lactose (enzyme) Active Site: The specific region of the enzyme that combines with the substrate Active Site: The specific region of the enzyme that combines with the substrate

Liver/Potato Demo- Liver/Potato Demo- Reaction? Reaction? Enzyme? Enzyme? Multiple collisions…forever?? Multiple collisions…forever?? “Induced Fit”- stress on substrate bonds, weakens them…less AE needed “Induced Fit”- stress on substrate bonds, weakens them…less AE needed (text p 162,166) (text p 162,166)

Lock and Key: The lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).

Factors that affect the rate of Enzyme Action: TemperaturepHConcentration:  Increasing the amount of enzyme will increase the rate of reaction, but it will eventually stop- why?  For the same reason, increasing the substrate concentration will increase the rate of reaction, but it will eventually level off.

Enzyme Regulation: A cell can regulate enzymatic activity by controlling the amount of enzyme produced Can the amount of enzyme available for a reaction be changed?

Factors that affect the rate of Enzyme Action:  Temperature: There is an optimum (best) temperature that each enzyme works in. Increase temperature, increase molecule movement, increase rate of the reaction.  Temperature too LOW, decrease the effect of the enzyme  Temperature too HIGH- Protein Denatures (breaks down/changes shape)- the enzyme will not work.

Denatured Enzyme Weakened H-bonds….Alpha/Beta… unravels

Noncompetetive vs Competetive Inhibition

Allosteric Sites (Feedback Inhibition) A cell can regulate enzymatic activity by controlling the amount of enzyme produced A cell can regulate enzymatic activity by controlling the amount of enzyme produced

Metabolic Pathways

During feedback inhibition (negative inhibition and positive inhibition), the concentration of the end product(s) dictate the activity of the enzyme.

Allosteric Regulation: Inhibition or Activation

Enzymes as Activators or Inhibitors

Enzyme Animation html html nim_2.htm nim_2.htm

pH and the Rate of Enzyme Action

Lactose Intolerance Lactose Digestion in Infants.53 Lactose Digestion in Infants.53 Lactose Digestion in Infants.53 Lactose Digestion in Infants.53 Natural Selection of Lactose Tolerance.46 Natural Selection of Lactose Tolerance.46 Natural Selection of Lactose Tolerance.46 Natural Selection of Lactose Tolerance.46 Got Lactase? Got Lactase? Got Lactase? Got Lactase? 14.52

Presence of Glucose in Milk: Rice vs Soy vs Cow