Big Idea 2 Cellular Processes in Biological systems

Big Idea 2: Cellular Processes in Biological systems Energy Growth Reproduction Dynamic Homeostasis

Learning Objectives: LO 2. 1 The student is able to explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow and to reproduce.

Learning Objectives: LO 2. 2 The student is able to justify a scientific claim that free energy is required for living systems to maintain organization, to grow or to reproduce, but that multiple strategies exist in different living systems.

Learning Objectives: LO 2. 3 The student is able to predict how changes in free energy availability affect organisms, populations and ecosystems.

Enduring understanding 2. A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter.

Energy is the capacity to do work or ability to cause change. Any change in the universe requires energy. Energy comes in 2 forms: – Potential energy is stored energy. No change is currently taking place – Kinetic energy causes change. This always involves some type of motion.

1 st Law of Thermodynamics: Energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe remains constant; it only changes from one form to another.

nd 2 Law of Thermodynamics: “In all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state. " This is also commonly referred to as entropy.

Entropy It is a measure of disorder: cells are NOT disordered and so have low entropy. In the process of energy transfer, some energy will dissipate as heat. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die.

Biological systems follow the laws of thermodynamics, and to offset entropy, energy input must exceed energy lost from and used by an organism to maintain order.

Carbohydrate Metabolism heat carbohydrate muscle contraction Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 13

Not only can energy deficiencies be detrimental to individual organisms, but changes in free energy availability also can affect population size and cause disruptions at the ecosystem level.

Organisms use various energy-related strategies to survive; strategies include different metabolic rates, physiological changes, and variations in reproductive and offspring-raising strategies.

Cells and Energy a. H 2 O energy Glucose • more organized • less stable • more potential energy low entropy CO 2 Carbon dioxide and water • less organized • less potential energy • more stable high entropy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 17

b. H+ channel protein energy H+ H+ H+ Unequal distribution of hydrogen ions • more organized • more potential energy • less stable low entropy H+ H+ H+ H+ + H Equal distribution of hydrogen ions • less organized • less potential energy • more stable high entropy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

All living systems require constant input of free energy a) Life requires a highly ordered system. 1. Order is maintained by constant free energy input into the system. 2. Loss of order or free energy flow results in death. 3. Increased disorder and entropy are offset by biological processes that maintain or increase order.

The First Law of Thermodynamics – Energy cannot be created or destroyed – Energy can be transferred and transformed Chemical energy For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement

Free Energy: It is the portion of a system’s energy that is able to perform work when temperature and pressure is uniform throughout the system, as in a living cell • Free energy also refers to the amount of energy actually available to break and subsequently form other chemical bonds

Free Energy: Gibbs’ free energy (G): in a cell, the amount of energy contained in a molecule’s chemical bonds Δ = change G = free energy Change in free energy= ΔG and it is calculated as: energy left in products – energy content of reactants -ΔG = products have less energy than reactants, and the reaction will occur spontaneously. +ΔG = products have more energy than the reactants, and the reaction will occur only if there is a constant input of energy

Free Energy: -ΔG reactions are exergonic (free energy releasing reactions) +ΔG reactions are reactions that requires an input of free energy Exergonic reactions (G < 0) or Endergonic reactions (G > 0) on the basis of whether the free energy of the system decreases or increases during the reaction.

Gibbs Free Energy http: //www. youtube. com/watch? v=DPj. MPe. U 5 Oe. M

Example 1:

Example 2 Find the change is Gibbs Free Energy for the reaction at 310 C: HCl(aq) + Na. OH(aq) H 2 O(l) + Na. Cl

Exergonic reactions (G < 0) or Endergonic reactions (G > 0)

Calculate ΔH° and ΔS° for the following reaction: NH 4 NO 3(s) + H 2 O(l) NH 4+ (aq) + NO 3 - (aq)

b) Living systems do not violate the second law of thermodynamics, which states that entropy increases over time. 1. Order is maintained by coupling cellular processes that increase entropy (and so have negative changes in free energy) with those that decrease entropy (and so have positive changes in free energy). 2. Energy input must exceed free energy lost to entropy to maintain order and power cellular processes. 3. Energetically favorable exergonic reactions, such as ATP→ADP, that have a negative change in free energy can be used to maintain or increase order in a system by being coupled with reactions that have a positive free energy change.

Exergonic reactions • Reactants have more free energy than the products • Involve a net release of energy and/or an increase in entropy • Occur spontaneously (without a net input of energy) Free energy Reactants Amount of energy released (∆G <0) Energy Products Progress of the reaction (a) Exergonic reaction: energy released

Endergonic Reactions • Reactants have less free energy than the products • Involve a net input of energy and/or a decrease in entropy • Do not occur spontaneously Free energy Products Energy Reactants Progress of the reaction (b) Endergonic reaction: energy required Amount of energy released (∆G>0)

Energy supplied Energy released Product Reactant Endergonic Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Reactant Exergonic Product

Metabolic Reactions and Energy Transformations Metabolism: – Sum of cellular chemical reactions in cell – Reactants participate in reaction – Products form as result of reaction Free energy is the amount of energy available to perform work – Exergonic Reactions - Products have less free energy than reactants – Endergonic Reactions - Products have more free energy than reactants 35

ATP and Coupled Reactions Adenosine triphosphate (ATP) – High energy compound used to drive metabolic reactions – Constantly being generated from adenosine diphosphate (ADP) Composed of: – Adenine and ribose (adenosine), and – Three phosphate groups Coupled reactions – Energy released by an exergonic reaction captured in ATP – That ATP used to drive an endergonic reaction 36

P P P adenosine triphosphate Energy from exergonic reactions (e. g. , cellular respiration) Energy for endergonic reactions (e. g. , protein synthesis, nerve conduction, muscle contraction) a. ATP b. P P adenosine diphosphate Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 37 + P inorganic phosphate

Synthesis of ATP

Work-Related Functions of ATP: Primarily to perform cellular work – Chemical Work: Energy needed to synthesize macromolecules – Transport Work: Energy needed to pump substances across plasma membrane – Mechanical Work: Energy needed to contract muscles, beat flagella, etc. 39

Life Requires Energy http: //www. youtube. com/watch? v=JBmykor-2 k. U

Metabolic Pathways Reactions are usually occur in a sequence Products of an earlier reaction become reactants of a later reaction • Begins with a particular reactant • Proceeds through several intermediates • Terminates with a particular end product A B C D E F G “A” is Initial Reactant B, C, D, E, and F are Intermediates “G” is End Product 41

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c) Energy-related pathways in biological systems are sequential and may be entered at multiple points in the pathway. § § Krebs cycle Glycolysis Calvin cycle Fermentation

Biological Order and Disorder • Cells create ordered structures from less ordered materials • Organisms also replace ordered forms of matter and energy with less ordered forms • The evolution of more complex organisms does not violate the second law of thermodynamics • Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases

Biological Order and Disorder • Living systems – Increase the entropy of the universe – Use energy to maintain order – A living system’s free energy is energy that can do work under cellular conditions – Organisms live at the expense of free energy 50µm

Metabolism: Part 1 http: //www. youtube. com/watch? v=MUtf. F 2 qnz. Go

Equilibrium and Metabolism • Reactions in a closed system eventually reach equilibrium and then do no work • Cells are not in equilibrium; they are open systems experiencing a constant flow of materials

Equilibrium and Metabolism • A catabolic pathway in a cell releases free energy in a series of reactions

Equilibrium and Metabolism • Closed and open hydroelectric systems can serve as analogies

Equilibrium and Metabolism • Closed and open hydroelectric systems can serve as analogies (b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equlibrium. ∆G < 0

(c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucose is broken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium.

Equilibrium and Metabolism Cells in our body experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium

Energy Coupling • Living organisms have the ability to couple exergonic and endergonic reactions: • Energy released by exergonic reactions is captured and used to make ATP from ADP and Pi • ATP can be broken back down to ADP and Pi, releasing energy to power the cell’s endergonic reactions.

The Structure and Hydrolysis of ATP • ATP (adenosine triphosphate) – Is the cell’s energy shuttle – Provides energy for cellular functions Adenine NH 2 N O O - O O O - Phosphate groups O C N HC O O C N CH 2 - O H N H H H OH CH C OH Ribose

The Structure and Hydrolysis of ATP Energy is released from ATP when the terminal phosphate bond is broken P P P Adenosine triphosphate (ATP) H 2 O P i + Inorganic phosphate P P Adenosine diphosphate (ADP) Energy

Cellular Work • A cell does three main kinds of work – Mechanical – Transport – Chemical • Energy coupling is a key feature in the way cells manage their energy resources to do this work • ATP powers cellular work by coupling exergonic reactions to endergonic reactions

Energy Coupling - ATP / ADP Cycle • Releasing the third phosphate from ATP to make ADP generates energy (exergonic): • Linking the phosphates together requires energy - so making ATP from ADP and a third phosphate requires energy (endergonic), • Catabolic pathways drive the regeneration of ATP from ADP and phosphate ATP hydrolysis to ADP + P i yields energy ATP synthesis from ADP + P i requires energy ATP Energy from catabolism (exergonic, energy yielding processes) ADP + P Energy for cellular work (endergonic, energyconsuming processes) i

How ATP Performs Work? • ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant • The recipient molecule is now phosphorylated • The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP

ATP drives endergonic reactions by phosphorylation, transferring a phosphate to other molecules - hydrolysis of ATP: mechanical

ATP drives endergonic reactions by phosphorylation, transferring a phosphate to other molecules - hydrolysis of ATP: transport

ATP drives endergonic reactions by phosphorylation, transferring a phosphate to other molecules - hydrolysis of ATP: chemical

Activation Energy • All reactions, both endergonic and exergonic, require an input of energy to get started. This energy is called activation energy • The activation energy, EA – Is the initial amount of energy needed to start a chemical reaction – Activation energy is needed to bring the reactants close together and weaken existing bonds to initiate a chemical reaction. – Is often supplied in the form of heat from the surroundings in a system. A B C D Free energy Transition state A B C D EA Reactants A B ∆G < O C D Products Progress of the reaction Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Reaction Rates • In most cases, molecules do not have enough kinetic energy to reach the transition state when they collide. • Therefore, most collisions are non-productive, and the reaction proceeds very slowly if at all. • What can be done to speed up these reactions?

Increasing Reaction Rates • Add Energy (Heat) - molecules move faster so they collide more frequently and with greater force.

Increasing Reaction Rates • Add a catalyst – a catalyst reduces the energy needed to reach the activation state, without being changed itself. Proteins that function as catalysts are called enzymes. Energy released Energy supplied Activation Energy and Catalysis Activation energy Reactant Product Uncatalyzed Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Product Catalyzed

Peroxidase Enzyme Activity Advanced Inquiry Lab Peroxidase enzymes are widely distributed in plants and animals, including bacteria, to protect cells against the effects of oxidative stress and cell damage due to hydrogen peroxide. Certain enzymes within the peroxisome, use O 2, and remove hydrogen atoms from specific organic substrates in an oxidative reaction, producing hydrogen peroxide (H 2 O 2)

Peroxidase Enzyme Activity Advanced Inquiry Lab Peroxidases are easily extracted from turnips and other root vegetables and provide a model enzyme for studying enzyme activity—how the rate of an enzyme-catalyzed reaction depends on biotic and abiotic factors. Enzyme activity studies reflect enzyme structure and function and provide the foundation for understanding the mechanism or theory of enzyme action.

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