BIG IDEA II Biological systems utilize free energy

BIG IDEA II Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2. A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2. A. 1 All living systems require a constant input of free energy. Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Essential Knowledge 2. A. 1: All living systems require a constant input of free energy. • Learning Objectives: – (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. – (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. – (2. 3) The student is able to predict how changes in free energy availability affect organisms, populations and ecosystems. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Organic +O molecules 2 Cellular respiration in mitochondria ATP powers most cellular work Heat energy

Life requires a highly ordered system. • The living cell is a chemical factory in miniature, where thousands of reactions occur within a microscopic space. – Order is maintained by constant free energy input into the system. – Loss of order or free energy flow results in death. – Increased disorder and entropy are offset by biological processes that maintain or increase order. • The concepts of metabolism help us to understand how matter and energy flow during life’s processes and how that flow is regulated in living systems. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Metabolism • Metabolism is the totality of an organism’s chemical reactions: – An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics. • Metabolism is an emergent property of life that arises from interactions between molecules within the cell. • A metabolic pathway begins with a specific molecule and ends with a product, whereby each step is catalyzed by a specific enzyme. • Bioenergetics is the study of how organisms manage their energy resources. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Overview: A Metabolic Pathway Enzyme 1 A Reaction 1 Enzyme 2 B Reaction 2 Starting molecule Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings Enzyme 3 C Reaction 3 D Product

Catabolism and Anabolism • Catabolic pathways release energy by breaking down complex molecules into simpler compounds: – Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway of catabolism. • Anabolic pathways consume energy to build complex molecules from simpler ones: – The synthesis of protein from amino acids is an example of anabolism. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Forms of Energy • Energy is the capacity to cause change. • Energy exists in various forms, some of which can perform work: – Kinetic energy is energy associated with motion. – Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules. – Potential energy is energy that matter possesses because of its location or structure. – Chemical energy is potential energy available for release in a chemical reaction. • Energy cannot be created or destroyed, but it can be converted from one form to another. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

A diver has more potential energy on the platform than in the water. Climbing up converts the kinetic energy of muscle movement to potential energy. Diving converts potential energy to kinetic energy. A diver has less potential energy in the water than on the platform.

The Laws of Energy Transformation • Thermodynamics is the study of energy transformations. • A closed system, such as that approximated by liquid in a thermos, is isolated from its surroundings. • In an open system, energy and matter can be transferred between the system and its surroundings. • Organisms are open systems. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The First Law of Thermodynamics • According to the first law of thermodynamics, the energy of the universe is constant: – Energy can be transferred and transformed, but it cannot be created or destroyed. • The first law is also called the principle of conservation of energy. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Second Law of Thermodynamics • During every energy transfer or transformation, some energy is unusable, and is often lost as heat. • According to the second law of thermodynamics: – Every energy transfer or transformation increases the entropy (disorder) of the universe. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Living systems do not violate the second law of thermodynamics, which states that entropy

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. • Energy flows into an ecosystem in the form of light and exits in the form of heat. • 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. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Free-Energy Change, G https: //paul-andersen. squarespace. com/gibbs-free-energy • The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously. • Biologists often want to know which reactions occur spontaneously and which require input of energy. • To do so, they need to determine energy changes that occur in chemical reactions. • A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Free-Energy Change, G • The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin (T): ∆G = ∆H – T∆S • Only processes with a negative ∆G are spontaneous. • Spontaneous processes can be harnessed to perform work. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Free Energy, Stability, and Equilibrium • Free energy is a measure of a system’s instability, its tendency to change to a more stable state. • During a spontaneous change, free energy decreases and the stability of a system increases. • Equilibrium is a state of maximum stability. • A process is spontaneous and can perform work only when it is moving toward equilibrium. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

• More free energy (higher G) • Less stable • Greater work capacity In a spontaneous change • The free energy of the system decreases (∆G < 0) • The system becomes more stable • The released free energy can be harnessed to do work • Less free energy (lower G) • More stable • Less work capacity (a) Gravitational motion (b) Diffusion (c) Chemical reaction

Free Energy and Metabolism • The concept of free energy can be applied to the chemistry of life’s processes: – An exergonic reaction proceeds with a net release of free energy and is spontaneous (∆G is negative). – An endergonic reaction absorbs free energy from its surroundings and is nonspontaneous (∆G is positive). Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Reactants Free energy Amount of energy released (∆G < 0) Energy Products Progress of the reaction (a) Exergonic reaction: energy released Free energy Products Energy Reactants Progress of the reaction (b) Endergonic reaction: energy required Amount of energy required (∆G > 0)

∆G < 0 ∆G = 0 (a) An isolated hydroelectric system (b) An open hydroelectric system ∆G < 0 (c) A multistep open hydroelectric system

ATP & Energy Coupling https: //www. youtube. com/watch? v=Ahuq. Xwv. Fv 2 E H 2 O Energetically favorable exergonic reactions, such as ATP ADP, that have 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 exchange. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Structure of ATP • The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis • Energy is released from ATP when the terminal phosphate bond is broken • This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

NH 2 Glutamic acid NH 3 + Glu ∆G = +3. 4 kcal/mol Glutamine Ammonia (a) Endergonic reaction 1 ATP phosphorylates glutamic acid, making the amino acid less stable. P + Glu ATP Glu + ADP NH 2 2 Ammonia displaces the phosphate group, forming glutamine. P Glu + NH 3 Glu + Pi (b) Coupled with ATP hydrolysis, an exergonic reaction (c) Overall free-energy change

Membrane protein P Solute Pi Solute transported (a) Transport work: ATP phosphorylates transport proteins ADP + ATP Vesicle Cytoskeletal track ATP Motor protein Protein moved (b) Mechanical work: ATP binds noncovalently to motor proteins, then is hydrolyzed Pi

Energy-related pathways in biological systems are sequential and may be entered at multiple points in the pathway. • Illustrative Examples include: – Glycolysis – Krebs cycle – Calvin cycle – Fermentation Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Organisms use free energy to maintain organization, grow and reproduce. • Demonstrated understanding includes a knowledge of: – Strategies to regulate body temperature – Strategies for reproduction & rearing of offspring – Correlation between metabolic rate and size – Excess acquired free energy (storage/growth) – Insufficient acquired free energy (death) Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Bioenergetics of Animals • Animals use the chemical energy in food to sustain form and function. • All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction. • The flow of energy through an animal, its bioenergetics, ultimately limits the animal’s behavior, growth, and reproduction – which determines how much food it needs. • Studying an animal’s bioenergetics tells us a great deal about the animal’s adaptations. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Bioenergetics of an Animal

Quantifying Energy Use • An animal’s metabolic rate is the amount of energy it uses in a unit of time. • An animal’s metabolic rate is closely related to its bioenergetic strategy – which determines nutritional needs and is related to an animal’s size, activity, and environment: – The basal metabolic rate (BMR) is the metabolic rate of a nongrowing, unstressed endotherm at rest with an empty stomach. – The standard metabolic rate (SMR) is the metabolic rate of a fasting, non-stressed ectotherm at rest at a particular temperature. – For both endotherms and ectotherms, size and activity has a large effect on metabolic rate. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Organisms use various strategies to regulate body temperature and metabolism. Copyright © © 2008

Elevated Floral Temperature in Some Plant Species Copyright © 2008 Pearson Education, Inc. ,

Different organisms use various reproductive strategies in response to energy availability. Copyright © 2008

Seasonal Reproduction in Plants Copyright © 2008 Pearson Education, Inc. , publishing as Pearson

Metabolic Rate and Size of Organisms • There is a relationship between metabolic rate per unit body mass and the size of multicellular organisms – generally, the smaller the organism, the higher the metabolic rate. • Larger animals have more body mass and therefore require more chemical energy. • Remarkably, the relationship between overall metabolic rate and body mass is constant across a wide range of sizes and forms. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Metabolic Rate and Size of Organisms Copyright © 2008 Pearson Education, Inc. , publishing

Changes in free energy availability can result in changes in population size and disruption to an ecosystem. • For example, a change in the producer level can affect the number and size of other trophic levels. • A change in energy resource levels such as sunlight can affect the number and size of the trophic levels. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

BIG IDEA II Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2. A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2. A. 2 Organisms capture and store free energy for use in biological processes. Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Essential Knowledge 2. A. 2: Organisms capture and store free energy for use in biological processes. • Learning Objectives: – (2. 4) The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store and use free energy. – (2. 5) The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store or use free energy. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Autotrophs capture free energy from physical sources in the environment. • Photosynthetic organisms capture free energy present in sunlight. – 6 CO 2 + 6 H 2 O + light energy C 6 H 12 O 6 + 6 O 2 + 6 H 2 O – carbon dioxide + water + light energy sugar + oxygen + water • Chemosynthetic organisms capture free energy from small inorganic molecules present in their environment, and this process can occur in the absence of oxygen. – 6 H 2 S + 6 H 2 O + 6 CO 2 + 6 O 2 C 6 H 12 O 6 + 6 H 2 SO 4 – hydrogen sulfide + water + carbon dioxide + oxygen sugar + sulfuric acid Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Photosynthesis and Chemosynthesis Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin

Heterotrophs capture free energy present in carbon compounds produced by other organisms. • Heterotrophs may metabolize carbohydrates, lipids and proteins by hydrolysis as sources of free energy. – C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + energy (ATP + heat) – organic compounds + oxygen carbon dioxide + water + energy • Fermentation produces organic molecules, including alcohol and lactic acid, and it occurs in the absence of oxygen. – C 6 H 12 O 6 yeast 2 CH 3 CH 2 OH + 2 CO 2 + heat – sugar yeast ethanol + carbon dioxide + heat Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Respiration and Fermentation Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin

Different energy-capturing processes use different types of electron acceptors. • An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. • It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. – For example, NADP+ in photosynthesis – For example, oxygen in cellular respiration • Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Catabolic Pathways & ATP Production • Catabolic Pathways yield energy by oxidizing organic fuels. • Several processes are central to cellular respiration and related pathways. • The breakdown of organic molecules is exergonic: – Fermentation is a partial degradation of sugars that occurs without O 2. – Aerobic respiration consumes organic molecules and O 2 and yields ATP. – Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O 2. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates. • Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration. • Although carbohydrates, fats, and proteins can all be consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: • C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (ATP + heat) – The transfer of electrons during chemical reactions releases energy stored in organic molecules. – This released energy is ultimately used to synthesize ATP. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized, and O 2 is reduced: Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps. – Electrons from organic compounds are usually first transferred to NAD+, a coenzyme. – As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Stages of Cellular Respiration: A Preview • WATCH IT! http: //www. sumanasinc. com/webcontent/animations/content/cellularrespiration. html • Cellular respiration has three MAIN stages: – Glycolysis (breaks down glucose into two molecules of pyruvate) – occurs in cytosol. – The citric acid cycle (completes the breakdown of glucose) – occurs in mitochondrial matrix. – Electron Transport/Oxidative Phosphorylation (accounts for most of the ATP synthesis) – occurs across inner membrane of mitochondria. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Figure 9. 16 Review: how each molecule of glucose yields many ATP molecules during cellular respiration: http: //www. wadsworthmedia. com/biology/0495119814_starr/big_picture/ch 07_bp. html

Oxidative Phosphorylation • The process that generates most of the ATP during cellular respiration is called oxidative phosphorylation because it is powered by redox reactions of an electron transport chain. • Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Substrate-Level Phosphorylation • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Mitochondrion Structure & Function Copyright © 2008 Pearson Education, Inc. , publishing as Pearson

Visual Overview of Cellular Respiration Copyright © 2008 Pearson Education, Inc. , publishing as

Glycolysis rearranges the bonds in glucose molecules, releasing free energy to form ATP from ADP and inorganic phosphate, and resulting in the production of pyruvate. • WATCH IT! http: //highered. mcgrawhill. com/sites/0072507470/student_view 0/chapter 25/animat ion__how_glycolysis_works. html • Glycolysis harvests chemical energy by oxidizing glucose to pyruvate – it is the first stage of cellular respiration. • This means that glycolysis “splits sugar” into two molecules of pyruvate. • Glycolysis occurs in the cytoplasm and has two major phases: – Energy investment phase – Energy payoff phase Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Glycolysis “Need to Know” • Glycolysis occurs WITH or WITHOUT oxygen. • The first step is the phosphorylation of glucose (glucose molecule gains 2 inorganic phosphates) – this ACTIVATES the glucose to split. • The second step is the splitting of glucose – breaking it down into (2) 3 -carbon molecules called pyruvic acid. – This process is achieved by stripping electrons and hydrogens from the unstable 3 -C molecules (as well as the borrowed phosphates). • 2 ATPs are needed to produce 4 ATPs (energy investment and energy payoff phases). • A second product in glycolysis is 2 NADH, which results from the transfer of e- and H+ to the coenzyme NAD+. – Occurs in the cytoplasm – Net of 2 ATPs produced – 2 pyruvic acids formed – 2 NADH produced Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -8 Energy investment phase Glucose 2 ADP + 2 P 2 ATP used 4 ATP formed Energy payoff phase 4 ADP + 4 P 2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+ 2 Pyruvate + 2 H 2 O Net Glucose 4 ATP formed – 2 ATP used 2 NAD+ + 4 e– + 4 H+ 2 Pyruvate + 2 H 2 O 2 ATP 2 NADH + 2 H+

Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The “Intermediate” Step • The pyruvate produced during glycolysis is transported from the cytoplasm to the mitochondrion, where further oxidation occurs. • The conversion of pyruvate to acetyl Co. A is the junction between glycolysis (step 1) and the Krebs cycle (step 2). • If oxygen is present, Pyruvate (3 C each) from glycolysis enters the mitochondrion. • Using Coenzyme A, each pyruvate is converted into a molecule of Acetyl Co. A (2 C each). Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -10 CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate Transport protein 3 CO 2 Coenzyme A Acetyl Co. A

The Citric Acid Cycle http: //highered. mcgrawhill. com/sites/0072507470/student_view 0/chapter 25/animation__how_the_krebs_cycle_works__quiz_1_. html • In the Krebs cycle, carbon dioxide is released from organic intermediates. • ATP is synthesized from ADP and inorganic phosphate via substrate level phosphorylation and electrons are captured by coenzymes (NAD+ & FAD+). • The citric acid (Krebs) cycle completes the energyyielding oxidation of organic molecules – and its events take place within the mitochondrial matrix. • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH 2 per turn. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -11 Pyruvate CO 2 NAD+ Co. A NADH + H+ Acetyl Co. A Citric acid cycle FADH 2 2 CO 2 3 NAD+ 3 NADH FAD + 3 H+ ADP + P i ATP

Chemiosmosis & Electron Transport http: //highered. mcgrawhill. com/sites/0072507470/student_view 0/chapter 25/animation__electron_transport_system_and_atp_synthesis__quiz_1_. html • Following the Krebs cycle, the electrons captured by NADH and FADH 2 are passed to the electron transport chain: – The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP to ATP. – Every time high energy electrons are transported down the ETC, their energy is used to transport H+ across the inner membrane of the mitochondria…this creates a (+) charge on the inside of the membrane and a (–) charge in the matrix of the mitochondria. – As a result of this charge difference, H+ ions escape through channel proteins called ATP synthase causing it to rotate. – Each time it rotates, the enzyme ATP synthase grabs a low energy ADP and attaches a phosphate, forming high-energy ATP. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

NADH 50 2 e– NAD+ FADH 2 2 e– Free energy (G) relative to O 2 (kcal/mol) 40 FMN FAD Multiprotein complexes FAD Fe • S Q Cyt b 30 Fe • S Cyt c 1 IV Cyt c Cyt a 20 10 0 Cyt a 3 2 e– (from NADH or FADH 2) 2 H+ + 1/2 O 2 H 2 O

• The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes. • Electrons delivered by NADH and FADH 2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen. • The passage of electrons is accompanied by the formation of a proton gradient (a type of electrochemical gradient) across the inner mitochondrial membrane, with the membrane separating a region of high proton concentration from a region of low proton concentration. • The flow of protons back through membrane-bound ATP synthase by chemiosmosis generates ATP from ADP and inorganic phosphate (Pi).

Fig. 9 -14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX

Fig. 9 -16 H+ H+ H+ Protein complex of electron carriers H+ Cyt c V Q FADH 2 NADH FAD ATP synthase 2 H+ + 1/2 O 2 NAD+ H 2 O ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain Oxidative phosphorylation 2 Chemiosmosis

Fig. 9 -17 Electron shuttles span membrane CYTOSOL 2 NADH Glycolysis Glucose 2 Pyruvate MITOCHONDRION 2 NADH or 2 FADH 2 6 NADH 2 Acetyl Co. A + 2 ATP Citric acid cycle + 2 ATP Maximum per glucose: About 36 or 38 ATP 2 FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis + about 32 or 34 ATP

Fermentation/Anaerobic Respiration • Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen • Most cellular respiration requires O 2 to produce ATP • Glycolysis can produce ATP with or without O 2 (in aerobic or anaerobic conditions) • In the absence of O 2, glycolysis couples with fermentation or anaerobic respiration to produce ATP – Anaerobic respiration uses an electron transport chain with an electron acceptor other than O 2, for example sulfate – Fermentation uses phosphorylation instead of an electron transport chain to generate ATP Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -18 2 ADP + 2 Pi Glucose 2 ATP Glycolysis 2 Pyruvate 2 NAD+ 2 NADH + 2 H+ 2 CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 Pi Glucose 2 ATP Glycolysis 2 NAD+ 2 Lactate (b) Lactic acid fermentation 2 NADH + 2 H+ 2 Pyruvate

Fermentation and Aerobic Respiration Compared • Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate. • The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O 2 in cellular respiration. • Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Anaerobes • Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O 2. • Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration: – In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -19 Glucose CYTOSOL Glycolysis Pyruvate No O 2 present: Fermentation O 2 present: Aerobic cellular respiration MITOCHONDRION Ethanol or lactate Acetyl Co. A Citric acid cycle

The Versatility of Catabolism • Glycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways. • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration. • Glycolysis accepts a wide range of carbohydrates. • In addition to carbohydrates, heterotrophs may metabolize lipids and proteins by hydrolysis as sources of free energy. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -20 Proteins Amino acids Carbohydrates Sugars Glycolysis Glucose Glyceraldehyde-3 - P NH 3 Pyruvate Acetyl Co. A Citric acid cycle Oxidative phosphorylation Fats Glycerol Fatty acids

Fig. 9 -21 Glucose Glycolysis Fructose-6 -phosphate – AMP Stimulates + Phosphofructokinase – Fructose-1, 6 -bisphosphate Inhibits Pyruvate ATP Citrate Acetyl Co. A Citric acid cycle Oxidative phosphorylation

Energy Coupling H 2 O Following cellular respiration or fermentation, free energy becomes available for metabolism by the conversion of ATP ADP, which is coupled to many steps in metabolic pathways. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Photosynthesis is the process whereby light energy is converted to chemical energy and carbon is fixed into organic compounds. • In the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen: – Photosynthesis uses the energy of sunlight to convert water and CO 2 into O 2 and high energy sugars – 6 CO 2 + 6 H 2 O + light → C 6 H 12 O 6 + 6 O 2 – carbon dioxide + water + light → sugar + oxygen • Plants then use the sugars to produce complex carbohydrates such as starches: – Plants obtain carbon dioxide from the air or water in which they grow. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Inside a Chloroplast

Photosynthetic Pigments • Photosynthetic pigments absorb light energy and use it to provide energy to carry out photosynthesis. – – Chlorophylls (absorb light in the red, blue, and violet range): • Chlorophyll a - directly involved in transformation of photons to chemical energy • Chlorophyll b - helps trap other wavelengths and transfers it to chlorophyll a Carotenoids (absorb light in the blue, green, and violet range): • xanthophyll - Yellow • beta carotene - Orange • Phycobilins – Red – Chlorophyll b, the carotenoids, and the phycobilins are known as ANTENNA PIGMENTS – they capture light in other wavelengths and pass the energy along to chlorphyll a. – Chlorophyll a is the pigment that participates directly in the light reactions of photosynthesis! Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

During photosynthesis, chlorophylls absorb free energy from light, boosting electrons to a higher energy level in photosystems I and II.

Different types of organisms use different photosynthetic pigments to harvest energy. Copyright © 2008

Figure 10. 9 Location and structure of chlorophyll molecules in plants The pigment molecules have a large head section that is exposed to light in the surface of the membrane; the hydrocarbon tail anchors the pigment molecules into the lipid bilayer.

Photosystems Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Stages of Photosynthesis • The reaction that occurs during photosynthesis can be broken into 2 stages: 1. 2. Light Dependent Reactions • Take place within the thylakoid membranes inside a chloroplast • “PHOTO” phase – make ATP & NADPH…USE LIGHT ENERGY TO PRODUCE ATP & NADPH Light Independent Reactions (Calvin Cycle) • Take place in the stroma of the chloroplast • “SYNTHESIS” phase – coverts CO 2 to sugar…PRODUCE SUGAR Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Light Reactions: -carried out by molecules in thylakoid membranes -convert light E to chemical E of ATP and NADPH -split H 2 O and release O 2 to the atmosphere Calvin Cycle Reactions: -take place in stroma -use ATP and NADPH to convert CO 2 into the sugar G 3 P -return ADP, inorganic phosphate, and NADP+ to the light reactions

Light Dependent Reactions - Overview • The light-dependent reactions of photosynthesis in eukaryotes involve a series of coordinated reaction pathways that capture free energy present in light to yield ATP and NADPH, which power the production of organic molecules in the Calvin cycle (dark reactions). – require presence of light – occur in thylakoids of chloroplasts – use energy from light to produce ATP and NADPH (a temporary, mobile energy source that helps store even more energy) – water is split during the process to replace electrons lost from excited chlorophyll – oxygen gas is produced as a by-product Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Light Independent Reactions - Overview • The energy captured in the light reactions as ATP and NADPH powers the production of carbohydrates from carbon dioxide in the Calvin cycle. – do not require light directly – so also known as the Dark Reactions or the Calvin Cycle – take place in the stroma of chloroplasts – ATP and NADPH produced during light dependent reactions are used to make glucose Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

LIGHT REACTIONS: How electron flow during the light reactions generates ATP and NADPH

Figure 8 -10 Light-Dependent Reactions Section 8 -3 Go to Section:

Figure 10. 15 Comparison of chemiosmosis in mitochondria and chloroplasts http: //bcs. whfreeman. com/thelifewire/content/chp 08/0802002. html

The Dark Reactions (Calvin cycle) • Calvin cycle can be divided into 3 phases: – Phase 1: Carbon Fixation – Phase 2: Reduction – Phase 3: Regeneration of CO 2 Acceptor (Ru. BP) • REMEMBER: The Calvin cycle is an ANABOLIC process – and therefore requires ENERGY – this energy is provided by the ATP and NADPH made during the light reactions!!! Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Figure 10. 17 The Calvin Cycle

BIG IDEA II Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2. A Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential Knowledge 2. A. 3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization. Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Essential Knowledge 2. A. 3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization. • Learning Objectives: – (2. 6) The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion. – (2. 7) The student is able to explain how cell size and shape affect the overall rate of nutrient intake and the rate of waste elimination. – (2. 8) The student is able to justify the selection of data regarding the types of molecules that an animal, plant or bacterium will take up as necessary building blocks and excrete as waste products. – (2. 9) The student is able to represent graphically or model quantitatively the exchange of molecules between an organism and its environment, and the subsequent use of these molecules to build new molecules that facilitate dynamic homeostasis, growth and reproduction. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Molecules and atoms from the environment are necessary to build new molecules. • Carbon moves from the environment to organisms where it is used to build carbohydrates, proteins, lipids or nucleic acids. Carbon is used in storage compounds and cell formation in all organisms. • Nitrogen moves from the environment to organisms where it is used in building proteins and nucleic acids. • Phosphorus moves from the environment to organisms where it is used in nucleic acids and certain lipids. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Biological and geochemical processes cycle nutrients between organic and inorganic parts of an ecosystem. • Life depends on recycling chemical elements. • Nutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles: – Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally. – Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 55 -13 Reservoir A Reservoir B Organic materials available as nutrients Organic materials unavailable as nutrients Living organisms, detritus Assimilation, photosynthesis Fossilization Coal, oil, peat Respiration, decomposition, excretion Burning of fossil fuels Reservoir C Reservoir D Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Atmosphere, soil, water Weathering, erosion Formation of sedimentary rock Minerals in rocks

Biogeochemical Cycles • In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors: – Each chemical’s biological importance – Forms in which each chemical is available or used by organisms – Major reservoirs for each chemical – Key processes driving movement of each chemical through its cycle – How humans are impacting each cycle Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 55 -14 a Solar energy Transport over land Net movement of water vapor by wind Precipitation Evaporation over ocean from ocean Precipitation over land Evapotranspiration from land Runoff and groundwater Percolation through soil

Fig. 55 -14 b CO 2 in atmosphere Photosynthesis Cellular respiration Burning of fossil fuels Phytoand wood plankton Higher-level consumers Primary consumers Carbon compounds in water Detritus Decomposition

Fig. 55 -14 c N 2 in atmosphere Assimilation Nitrogen-fixing bacteria NO 3– Decomposers Ammonification NH 3 Nitrogen-fixing soil bacteria Nitrification NO 2– NH 4+ Nitrifying bacteria Denitrifying bacteria Nitrifying bacteria

Fig. 55 -14 d Precipitation Geologic uplift Weathering of rocks Runoff Consumption Decomposition Plankton Dissolved PO 43– Uptake Sedimentation Leaching Soil Plant uptake of PO 43–

Decomposition and Nutrient Cycling Rates • Decomposers (detritivores) play a key role in the general pattern of chemical cycling. • Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition. • The rate of decomposition is controlled by temperature, moisture, and nutrient availability. • Rapid decomposition results in relatively low levels of nutrients in the soil. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Ecosystem type EXPERIMENT Arctic Subarctic Boreal Temperate Grassland A Mountain G M T U H, I S N L D B, C P E, F O J K R Q RESULTS 80 Percent of mass lost Fig. 55 -15 70 60 K J 50 40 D 30 20 10 0 – 15 C A – 10 BE F I G H U R O Q N M L P T S – 5 0 5 10 Mean annual temperature (ºC) 15

Fig. 55 -16 (a) Concrete dam and weir Nitrate concentration in runoff (mg/L) (b) Clear-cut watershed 80 60 40 20 4 3 2 1 0 Deforested Completion of tree cutting 1965 Control 1966 (c) Nitrogen in runoff from watersheds 1967 1968

Human activities now dominate most chemical cycles on Earth. • As the human population has grown, our activities have disrupted the trophic structure, energy flow, and chemical cycling of many ecosystems • In addition to transporting nutrients from one location to another, humans have added new materials, some of them toxins, to ecosystems • Disruptions that deplete nutrients in one area and increase them in other areas can be detrimental to ecosystem dynamics. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 55 -17: Agriculture & Nitrogen Cycling Copyright © 2008 Pearson Education, Inc. ,

Algae Blooms & Eutrophication Copyright © 2008 Pearson Education, Inc. , publishing as Pearson

The Role of Matter in Living Organisms Experiments were carried out to determine the plant’s photosynthetic capacity by measuring the net uptake of carbon dioxide and changes in tissue starch concentration over a 32 -hour period with 8 hours of dark at the start and end of the measurement period and 16 hours of moderate light between the two dark periods. Epiphytic Plant from Rain Forest Canopy The changes in the rate of carbon dioxide uptake and the concentration of tissue starch are shown graph. • What is an appropriate title for this graph? • What was the IV of this experiment? The DV? • What variables should have been controlled during this experiment? • The photosynthetic pattern of this plant species is unusual. Explain. • A useful control for the experiment would have included what? Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Living systems depend on properties of water that result from its polarity and hydrogen bonding. • Four of water’s properties that facilitate an environment for life are: – Cohesive/Adhesive behavior – Ability to moderate temperature – Expansion upon freezing – Versatility as a solvent – http: //www. sumanasinc. com/webcontent/anim ations/content/propertiesofwater/water. html Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The polarity of water molecules results in hydrogen bonding. • The water molecule is a polar molecule: The opposite ends have opposite charges • Polarity allows water molecules to form hydrogen bonds with each other – Water is polar because the oxygen atom has a stronger electronegative pull on shared electrons in the molecule than do the hydrogen atoms Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Cohesion & Adhesion • Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion – the attraction of water molecules to other water molecules as a result of hydrogen bonding – Cohesion due to hydrogen bonding contributes to the transport of water and dissolved nutrients against gravity in plants • Adhesion is the clinging of one substance to another – Adhesion of water to cell walls by hydrogen bonds helps to counter the downward pull of gravity on the liquids passing through plants Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 3 -3 Adhesion Water-conducting cells Direction of water movement Cohesion 150 µm Cohesion and adhesion work together to give capillarity – the ability of water to spread through fine pores or to move upward through narrow tubes against the force of gravity.

Moderation of Temperature • Water moderates air temperature by absorbing heat from air that is warmer and releasing the stored heat to air that is cooler • Water can absorb or release a large amount of heat with only a slight change in its own temperature • The ability of water to stabilize temperature stems from its relatively high specific heat – This is the amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Water’s High Specific Heat • Water’s high specific heat can be traced to hydrogen bonding – Heat is absorbed when hydrogen bonds break – Heat is released when hydrogen bonds form • High specific heat of water is due to hydrogen bonding – H-bonds tend to restrict molecular movement, so when we add heat energy to water, it must break bonds first rather than increase molecular motion. – A greater input of energy is required to raise the temperature of water than the temperature of air! – Minimizes temperature fluctuations to within limits that permit life Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evaporative Cooling • Evaporation is transformation of a substance from liquid to gas • Heat of vaporization is the heat a liquid must absorb for 1 g to be converted to gas • As a liquid evaporates, its remaining surface cools, a process called evaporative cooling • The high amount of energy required to vaporize water has a wide range of effects: – Helps stabilize temperatures in organisms and bodies of water Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 3 -6 Insulation of Bodies of Water by Floating Ice Hydrogen bonds are stable Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings Liquid water Hydrogen bonds break and re-form

The Solvent of Life • A solution is a liquid that is a homogeneous mixture of substances – Solvent (dissolving agent) – Solute (substance that is dissolved) • An aqueous solution is one in which water is the solvent Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Hydration Shell http: //www. sumanasinc. com/webcontent/animations/content/propertiesofwater/water. html • A hydration shell refers to the sphere of water molecules around each dissolved ion in an aqueous solution – Water will work inward from the surface of the solute until it dissolves all of it (provided that the solute is soluble in water) Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Threats to Water Quality on Earth • Acid precipitation refers to rain, snow, or fog with a p. H lower than 5. 6. • Acid precipitation is caused mainly by the mixing of different pollutants with water in the air and can fall at some distance from the source of pollutants. • Acid precipitation can damage life in lakes and streams. • Effects of acid precipitation on soil chemistry are contributing to the decline of some forests. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Threats to Water Quality on Earth • Human activities such as burning fossil fuels threaten water quality • CO 2 is released by fossil fuel combustion and contributes to: – A warming of earth called the “greenhouse” effect – This can cause acidification of the oceans; leads to a decrease in the ability of corals to form calcified reefs Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 3 -11 EXPERIMENT Calcification rate (mmol Ca. CO 3 per m 2 per day) RESULTS 40 20 0 150 200 [CO 32–] (µmol/kg) 300

Surface area-to-volume ratios affect a biological system’s ability to obtain necessary resources or eliminate waste products. • As cells increase in volume, the relative surface area decreases and demand for material resources increases; more cellular structures are necessary to adequately exchange materials and energy with the environment. • As the surface area increases by a factor of n 2, the volume increases by a factor of n 3 - small cells have a greater surface area relative to volume. • These limitations restrict cell size. Illustrative examples include: – Root hairs – Cells of the alveoli – Microvilli Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 6 -8: Limits to Cell Size Surface area increases while total volume remains constant 5 1 1 Total surface area [Sum of the surface areas (height width) of all boxes sides number of boxes] Total volume [height width length number of boxes] Surface-to-volume (S-to-V) ratio [surface area ÷ volume] 6 150 750 1 125 6 1. 2 6

Root Hairs • An increased surface area to volume ratio means increased exposure to the environment. The higher the SA: Volume ratio for a cell, the more effective the process of diffusion. • Root hairs are long, thin hair-like cells that emerge from the root tip to form an important surface over which plants absorb most of their water and nutrients via diffusion. • They present a large surface area to the surrounding soil, which makes absorbing both water and minerals more efficient using osmosis. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Cells of the Alveoli • The ratio between the surface area and volume of cells and organisms has an enormous impact on their biology. Individual organs in animals are often shaped by requirements of surface area to volume ratio. • The numerous internal branchings of the lung and alveoli increase the surface area through which oxygen is passed into the blood and carbon dioxide is released from the blood. • Human lungs contain millions of alveoli, which together have a surface area of about 100 m 2, fifty times that of the skin. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Microvilli & Other Cell Types • Large animals require specialized organs (lungs, kidneys, intestines, etc. ) that effectively increase the surface area available for exchange processes, and a circulatory system to move material and heat energy between the surface and the core of the organism. • The intestine has a finely wrinkled internal surface, increasing the area through which nutrients are absorbed by the body. • A wide and thin cell, such as a nerve cell, or one with membrane protrusions such as microvilli has a greater surface-area-tovolume ratio than a spheroidal one. • Likewise a worm has proportionately more surface area than a rounder organism of the same mass does. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Plasma Membrane • The surface area of the plasma membrane must be large enough to adequately exchange materials; • Smaller cells have a more favorable surface area-tovolume ratio for exchange of materials with the environment. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings