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2.a.1 – All living systems require constant input of free energy (8.1-8.3). 4.b.1 – Interactions between molecules affect their structure and function (8.4 & 8.5). The totality of an organism’s chemical processes Concerned with managing the material and energy resources of the cell Pathways that break down complex molecules into smaller ones, releasing energy Example: Cellular respiration DOWNHILL! Pathways that consume energy, building complex molecules from smaller ones Example: Photosynthesis, condensation synthesis UPHILL! Energy cannot be created or destroyed It 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 Some usable energy dissipates during transformations and is lost During changes from one form of energy to another, some usable energy dissipates, usually as heat The amount of usable energy therefore decreases Ability to do work The ability to rearrange a collection of matter Forms of energy: › Kinetic › Potential › Activation Kinetic: › Energy of action or motion › Ex: heat/thermal energy Potential: › Stored energy or the capacity to do work › Ex: chemical energy Energy needed to convert potential energy into kinetic energy Activation Energy Potential Energy The portion of a system's energy that can perform work Known as ΔG ΔG = Δ H - T Δ S Δ = change (final-initial) ΔG = free energy of a system ΔH = total energy of a system (enthalpy) T = temperature in oK ΔS = entropy of a system If the system has: › more free energy=less stable (greater work capacity) › less free energy=more stable (less work capacity) › As rxn moves towards equilibrium, ΔG will decrease These are the source of energy for living systems They are based on free energy changes Two types: exergonic and endergonic Exergonic: › chemical reactions with a net release of free energy › Ex: cellular respiration › - ΔG , energy out, spontaneous Endergonic: › chemical reactions that absorb free energy from the surroundings › Ex: Photosynthesis › + ΔG , energy in, non-spontaneous - ΔG +ΔG Couples an exergonic process to drive an endergonic one ATP is used to couple the reactions together Types: mechanical, transport, chemical Adenosine Triphosphate Made of: 1. Adenine (nitrogenous base) 2. Ribose (pentose sugar) 3. 3 phosphate groups* *bonds can be broken to make ADP Three phosphate groups and the energy they contain Negative charges repel each other and makes the phosphates unstable › Tail is unstable = more free energy = more instability Works by energizing other molecules by transferring phosphate groups Hydrolysis of ATP = free energy is released as heat (can be adv or not adv) Energy released from ATP drives anabolic reactions Energy from catabolic reactions “recharges” ATP Very fast cycle › 10 million made per second Coupled RXN Takes place in cytoplasm and mitochondria Using special process called substrate-level phosphorylation › Energy from a high- energy substrate is used to transfer a phosphate group to ADP to form ATP Biological catalysts made of protein Speeds up rxn without being consumed Cause the speed/rate of a chemical rxn to increase › By lowering activation energy AB + CD AC + BD *AB and CD are “reactants” *AC and BD are “products” *Involves bond forming/breaking *Transition state: can be unstable Unstable state Energy is released as heat Lower the activation energy for a chemical reaction to take place Why do we need enzymes? › Cells can’t rely on heat to kick start rxns › Why? Denaturation, heat can’t decipher between rxns › Enzymes are selective! Can only operate on a given chemical rxn Substrate – › the material the enzyme works on Enzyme names: › Ex. Sucrase › “- ase” name of an enzyme › 1st part tells what the substrate is (i.e. Sucrose) Some older known enzymes don't fit this naming pattern Examples: pepsin, trypsin The area of an enzyme that binds to the substrate Structure is designed to fit the molecular shape of the substrate Therefore, each enzyme is substrate specific Enzyme + Subtrate EnzymeSub complex Enzyme + Product Notice: Complex becomes product, but enzyme stays the same! Enzyme is NOT CONSUMED! Lock and Key model 2. Induced Fit model 1. Reminder: Enzymes and substrates are usually held together by weak chemical interactions (H/ionic bonds) Substrate (key) fits to the active site (lock) which provides a microenvironment for the specific reaction Substrate “almost” fits into the active site, causing a strain on the chemical bonds, allowing the reaction Usually specific to one substrate Each chemical reaction in a cell requires its own enzyme Don’t change during rxn Always catalyze in direction towards equilibrium 1) 2) 3) 4) Active site is template for enzyme Enzymes may break/stretch bonds needed to be broken/stretched Active site is microenvironment Active site directly participates in chemical rxn Environment Cofactors Coenzymes Inhibitors Allosteric Sites Factors that change protein structure will affect an enzyme. Examples: › pH shifts (6-8 optimal) › Temperature (up, inc activity) › Salt concentrations Cofactors: › Non-protein helpers for catalytic activity › Examples: Iron, Zinc, Copper Coenzymes: › Organic molecules that affect catalytic activity › Examples: Vitamins, Minerals, usually proteins Inhibitor video Competitive › mimic the substrate and bind to the active site (compete for active site) › Toxins/poisons – Ex: DDT › Can be used in medicine – painkillers, antibiotics Noncompetitive › bind to some other part of the enzyme › Causes active site to change shape Identify forms of energy and energy transformations. Recognize the Laws of Thermodynamics. Recognize that organisms live at the expense of free energy. Relate free-energy to metabolism. Identify exergonic and endergonic reactions. Identify the structure and hydrolysis of ATP. Recognize how ATP works and is coupled to metabolism. Recognize the ATP cycle Relate enzymes and activation energy. Recognize factors that affect enzymes specificity and enzyme activity.. Recognize factors that control metabolism.