BIOL 411 Fa24 Final Exam Review PDF

12/9/24 BIOL 411 Review for Final Exam 1 Grading Breakdown Homework Assignments 15% 1 left- Lowest 2 dropped Exams 30% Lowest 1 dropped Final Exam...

12/9/24 BIOL 411 Review for Final Exam 1 Grading Breakdown Homework Assignments 15% 1 left- Lowest 2 dropped Exams 30% Lowest 1 dropped Final Exam 15% Not dropped Discussion Boards/PLTL 10% Lowest 2 dropped iClicker 05% adjusted- 75% = full credit Lab 25% ** Grade > 0.9 will be rounded up to the next whole number** 2 1  12/9/24 Reminders HW10 closes at 1159pm Extra Credit Assignment for Final Exam closes at 1159pm Blue SEL Surveys close at 1159pm Final Exam is on Thursday 12 Dec from 8am-10am Last Names A-H will take the Final in Paul College G75 Last Names I-N will take the Final in HamSmith 205 Last Names O-Z will take the Final in HamSmith 210 3 Final Exam Cumulative- questions from every week 85 Multiple choice Questions Bring UNH ID Helpful Tools Previous Exams, homework assignments Make flashcards/quizlets Clicker question files Use the previous exams’ review files-pdf and topics files Online Practice assignments Reach out for help Find the BIG Picture 4 2  12/9/24 Exam 1 (b) A lens cell uses information in DNA to make crystallin proteins. Organization of Life- Molecules to Genetic material to The crystallin gene is a Crystallin gene macromolecules to cells section of DNA in a chromosome. DNA A C C A A A C C G A G T (part of the crystallin gene) T G G T T T G G C T C A Using the information in the sequence of DNA nucleotides, the cell makes (transcribes) Eukaryotic cell Prokaryotic cell TRANSCRIPTION a specific RNA molecule called mRNA. Membrane DNA U G G U U U G G C U C A Cytoplasm (no nucleus) mRNA Membrane The cell translates the information in the sequence of mRNA nucleotides to make a TRANSLATION protein, a series of linked amino acids. Chain of amino acids Nucleus PROTEIN FOLDING (membrane- The chain of amino acids folds into the Membrane- enclosed) specific shape of a crystallin protein. enclosed DNA (throughout Crystallin proteins can then pack together and nucleus) 1 µm Protein focus light, allowing organelles the eye to see. Crystallin protein 5 Exam 1 Hydrogen Helium Element and Atoms 1H 2 He Atomic number 2He Atomic mass 4.003 Element symbol First Chemical Bonds shell Electron distribution Covalent diagram Ionic Lithium 3Li Beryllium 4Be Boron 5B Carbon 6C Nitrogen 7N Oxygen 8O Fluorine 9F Neon 10Ne Hydrogen Second shell pH Scale Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar Third shell 6 3  12/9/24 Covalent Bonds A single bond, the sharing of one pair of electrons, is indicated by Name and Electron Structural Space- Molecular Distribution Formula Filling a single line between the atoms Formula Diagram Model – For example, !"! (a) Hydrogen (H2). Two hydrogen atoms share one pair of A double bond, the sharing of two pairs of electrons, is indicated electrons, forming H H H H by a double line between atoms a single bond. – For example, (b) Oxygen (O2). Two oxygen atoms share two pairs of O O O O Each atom that can share valence electrons has a bonding electrons, forming a double bond. capacity, the number of bonds that the atom can form (c) Water (H2O). Bonding capacity, or valence, usually corresponds to the number Two hydrogen atoms and one H of electrons required to complete the atom oxygen atom are O O H joined by single H bonds, forming a H molecule of water. (d) Methane (CH4). Four hydrogen H atoms can satisfy H the valence of H C H H C H one carbon atom, forming H methane. H Figure 2.8 Covalent Bonding in Four Molecules 7 Ionic Bonds Types of Bonds Formed between two oppositely charged ions. NaCl (salt) 8 4  12/9/24 Hydrogen Bonding Gives Water Properties That Help Make Life Possible on Earth All organisms are made mostly of water and live d+ in an environment dominated by water H d+ H The charged regions in a water Water molecules are polar molecules, with the O molecule are due to its polar covalent bonds. oxygen region having a partial negative charge!!" " d- d- !!+ " Because and the hydrogen region a partial positive charge of its electron arrangement, oxygen Regions of neighboring water molecules with opposite partial has two regions with d+ charges are attracted to each other, partial negative charge. forming hydrogen bonds. Two water molecules are held together by a H Each water molecule can hydrogen bond hydrogen-bond to several O d+ d- others; these associations At any instant, most of the water molecules are H are constantly changing. hydrogen-bonded to their neighbors d- d+ d+ d- Figure 2.16 Hydrogen Bonds Between Water Molecules 9 Acids and Bases pH Scale We use a pH scale to describe how acidic or basic a solution is. It tends to range from 0-14. It is a logarithmic scale. Each increase by one represents a 10x increase. 10 5  12/9/24 Chapter 2 Carbon-Hydrocarbons are organic molecules consisting of only carbon and hydrogen Macromolecules and their functions 11 ATP: An Important Source of Energy for Cellular Processes An organic phosphate molecule, adenosine triphosphate (ATP), has an important function in the cell ATP stores the potential to react with water, releasing energy that can be used by the cell 12 6  12/9/24 The Synthesis and Breakdown of Polymers Cells make and break down polymers by the same (a) Dehydration reaction: synthesizing a polymer mechanisms 1 2 3 A dehydration reaction occurs Short polymer Unlinked monomer when two monomers bond Dehydration removes a water together through the loss of a molecule, forming a new bond. water molecule Polymers are disassembled to monomers by hydrolysis, a (b) Hydrolysis: breaking down a polymer reaction that is essentially the 1 2 3 4 reverse of the dehydration 1 2 Longer 3 polymer 4 reaction Hydrolysis adds a water These processes are facilitated molecule, breaking a bond. by enzymes, which speed up chemical reactions 1 2 3 Figure 3.7 The Synthesis and Breakdown of Polymers 13 Carbohydrates Serve as Fuel and Building Material Carbohydrates include sugars and the polymers of sugars The simplest carbohydrates are monosaccharides, or simple sugars (b) Abbreviated ring structure. Each unlabeled corner represents a carbon. The ring’s thicker edge (a) Linear and ring form s. Chem ical equilibrium between the linear and ring structures greatly favors indicates that you are looking at the the form ation of rings. The carbons of the sugar are num bered 1 to 6, as shown. To form the ring edge-on; the com ponents glucose ring, carbon 1 (m agenta) bonds to the oxygen (blue) attached to carbon 5. attached to the ring lie above or below the plane of the ring. 14 7  12/9/24 Fats Fats made from saturated fatty acids are called saturated fats and are solid at room temperature Most animal fats are saturated Plant fats and fish fats are usually unsaturated (b) Unsaturated fat Fats made from unsaturated fatty acids, called unsaturated At room temperature, the molecules of an unsaturated fat such as olive oil fats or oils, are liquid at room temperature cannot pack together closely enough to solidify because of the kinks in some of (a) Saturated fat their fatty acid hydrocarbon chains. At room temperature, the molecules of a saturated fat, such as the fat in butter, are packed closely together, forming a solid. Structural formula of a Structural formula of an saturated fat molecule (Each hydrocarbon chain unsaturated fat molecule is represented as a zigzag line, where each bend represents a carbon atom; hydrogens are not shown.) Space-filling model of oleic acid, an unsaturated fatty Space-filling model of acid stearic acid, a saturated fatty acid (red = oxygen, black = carbon, gray = Cis double bond hydrogen) causes bending. Figure 3.14 Saturated and Unsaturated Fats and Fatty Acids 15 Proteins Include a Diversity of Structures, Resulting in a Wide Range of Functions Enzymatic proteins Defensive proteins Function: Selective acceleration of chemical reactions Function: Protection against disease Example: Digestive enzymes catalyze the hydrolysis of bonds in food Example: Antibodies inactivate and help destroy viruses and bacteria. Proteins account for more than 50% of molecules. Antibodies the dry mass of most cells Enzyme Virus Bacterium Storage proteins Transport proteins Protein functions include defense, Function: Storage of amino acids Examples: Casein, the protein of milk, is the major source of amino Function: Transport of substances Examples: Hemoglobin, the iron-containing protein of vertebrate storage, transport, cellular acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo. blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across membranes, as shown here. communication, movement, and Transport protein structural support Ovalbumin Amino acids for embryo Cell membrane Hormonal proteins Receptor proteins Function: Coordination of an organism’s activities Function: Response of cell to chemical stimuli Example: Insulin, a hormone secreted by the pancreas, causes other Example: Receptors built into the membrane of a nerve cell detect tissues to take up glucose, thus regulating blood sugar concentration. signaling molecules released by other nerve cells. Receptor protein High Insulin Normal blood sugar secreted blood sugar Signaling molecules Contractile and m otor proteins Structural proteins Function: Movement Function: Support Examples: Motor proteins are responsible for the undulations of cilia Examples: Keratin is the protein of hair, horns, feathers, and other skin and flagella. Actin and myosin proteins are responsible for the contrac- appendages. Insects and spiders use silk fibers to make their cocoons tion of muscles. and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues. Actin Myosin Collagen Figure 3.17 An Overview of Protein Functions Muscle tissue 30 µm Connective tissue 60 µm 16 8  12/9/24 Levels of Protein Structure 17 Nucleic Acids Store, Transmit, and Help Express Hereditary Information DNA The amino acid sequence of a polypeptide is programmed by a unit of 1 Synthesis inheritance called a gene of mRNA in the nucleus mRNA Genes are made of DNA, a nucleic acid made of monomers called nucleotides NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via cytoplasm Ribosome 3 Synthesis of protein using information carried on mRNA Amino Polypeptide acids Figure 3.26 Gene Expression: D N A → R N A → Protein 18 9  12/9/24 The Components of Nucleic Acids NITROGENOUS BASES The sugar in DNA is Pyrimidines deoxyribose; in RNA it is ribose Sugar-phosphate backbone A prime (′) is used to 5¢ end (on blue background) Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) identify the carbon 5¢C atoms in the ribose, 3¢C Purines such as the 2′ carbon or Nucleoside 5′ carbon Nitrogenous base A nucleoside with at Adenine (A) Guanine (G) 5¢C least one phosphate attached is a nucleotide 1¢C SUGARS Phosphate 3¢C 5¢C group Sugar (pentose) 3¢C (b) Nucleotide monomer in a polynucleotide Deoxyribose (in DNA) Ribose (in RNA) 3¢ end Figure 3.27 Components of Nucleic Acids (a) Polynucleotide, or nucleic acid (c) Nucleoside components 19 Chapter 5 Cells: Eukaryotic vs Prokaryotic Organelle- Functions 20 10  12/9/24 Comparing Prokaryotic and Eukaryotic Cells In a eukaryotic cell most of the DNA Fimbriae: attachment structures on the surface of some prokaryotes is in the nucleus, an organelle that is (not visible on TEM) Nucleoid: region where the bounded by a double membrane cell’s DNA is located (not enclosed by a membrane) Prokaryotic cells are characterized Ribosomes: complexes that synthesize proteins by having Plasma membrane: membrane enclosing the cytoplasm No nucleus Bacterial chromosome Cell wall: rigid structure outside the plasma membrane DNA in an unbound region called Glycocalyx: outer coating of many prokaryotes, 0.5 µm the nucleoid (a) A typical consisting of a capsule or a slime layer (b) A thin section through the bacterium Corynebacterium rod-shaped bacterium Flagella: locomotion No membrane-bound organelles organelles of some prokaryotes diphtheriae (colorized TEM) Both types of cells contain cytoplasm bound by the plasma membrane Figure 4.4 A Prokaryotic Cell 21 A Panoramic View of the Eukaryotic Cell A eukaryotic cell has extensive internal membranes that divide the cell into compartments—organelles The plasma membrane and organelle membranes participate directly in the cell’s metabolism Nuclear envelope: double ENDOPLASMIC RETICULUM (ER):network membrane enclosing the Flagellum: motility of membranous sacs and tubes; active in nucleus; perforated by Rough structure present in membrane synthesis and other synthetic pores; continuous with ER Nuclear envelope endoplasmic NUCLEUS some animal cells, and metabolic processes; has rough Nucleolus reticulum Smooth (ribosome-studded) and smooth regions Nucleolus: nonmembranous Chromatin composed of a cluster of structure involved in production endoplasmic microtubules within an NUCLEUS reticulum Rough ER Smooth ER of ribosomes; a nucleus has extension of the plasma one or more nucleoli membrane Chromatin: material consisting of DNA and proteins; visible in Centrosome: region a dividing cell as individual Ribosomes (small brown dots) where the cell’s condensed chromosomes microtubules are Central vacuole: prominent organelle Plasma membrane: in older plant cells; functions include storage, initiated; contains a membrane Golgi apparatus breakdown of waste products, and hydrolysis pair of centrioles enclosing the cell CYTOSKELETON: of macromolecules; enlargement of the reinforces cell’s shape; vacuole is a major mechanism of plant growth functions in cell movement; components are made of Microfilaments Ribosomes (small brown Microtubules CYTOSKELETON protein. Includes: Microfilaments dots): complexes that Intermediate filaments make proteins; free in Microtubules cytosol or bound to Microvilli: rough ER or nuclear projections that Mitochondrion envelope Peroxisome increase the cell’s surface area Golgi apparatus: organelle active Plasma membrane Chloroplast: photosynthetic in synthesis, modification, sorting, organelle; converts energy of Peroxisome: organelle with and secretion of cell products sunlight to chemical energy various specialized metabolic Cell wall: outer layer that maintains Lysosome: digestive cell’s shape and protects cell from stored in sugar molecules functions; produces hydrogen organelle where mechanical damage; made of cellulose, Plasmodesmata: cytoplasmic peroxide as a by-product and macromolecules are other polysaccharides, and protein channels through cell walls then converts it to water Mitochondrion: organelle where hydrolyzed W all of adjacent cell that connect the cytoplasms cellular respiration occurs and of adjacent cells most ATP is generated Figure 4.7 Exploring Eukaryotic Cells 22 11  12/9/24 The Evolutionary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts display the following Endoplasmic Nucleus similarities with bacteria that led to the endosymbiont reticulum theory: Nuclear Engulfing of oxygen- Enveloped by a double membrane envelope using nonphotosynthetic prokaryote, which, over Contain ribosomes and multiple circular D N A molecules many generations of cells, becomes a mitochondrion Grow and reproduce somewhat independently in cells. Ancestor of eukaryotic cells (host cell) The endosymbiont theory is widely accepted: An early ancestor of eukaryotic cells engulfed a Engulfing of Mitochondrion nonphotosynthetic prokaryotic cell, which formed an Photosynthetic prokaryote relationship with its host Chloroplast The host cell and endosymbiont merged into a single Mitochondrion At least one cell Nonphotosynthetic organism, a eukaryotic cell with a mitochondrion eukaryote At least one of these cells may have then taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts Photosynthetic eukaryote Figure 4.16 The Endosymbiont Theory of the Origins of Mitochondria and Chloroplasts in Eukaryotic Cells 23 A slice of a plant cell’s interior is illustrated in the center panel, with all structures and molecules drawn to scale. Selected molecules and structures are shown above Figure 4.30 Visualizing the This figure introduces a cast of characters that you will learn more about as you and below, all enlarged by the same factor so you can compare their sizes. All study biology. Be sure to refer back to this protein and nucleic acid structures are based on data from the Protein Data Bank; figure as you encounter these molecules. regions whose structure has not yet been determined are shown in gray. Scale of the Molecular Receptor Membrane proteins (Chapter 5) Proton Calcium Aquaporin pump channel Proteins embedded in cellular membranes help transport substances and conduct signals across membranes. They also participate in other Machinery in a Cell crucial cellular functions. Many proteins are able to move within the membrane. Enzyme in signaling pathway Transport Signaling Plasma membrane Cell wall Chloroplast Mitochondrion Phosphofructokinase Rubisco Stroma ATP synthase Complex III Complex IV Inner mitochrondrial ATP synthase NADP+ Cyt reductase membrane Cytochrome Cyto- complex Fd Q plasm Photosystem II Photosystem I Pq Matrix Complex II Thylakoid Thylakoid Hexokinase Isocitrate membrane Complex I Pc dehydrogenase Cellular respiration (Chapter 7) respiration, a multi-step Cellular Photosynthesis (Chapter Photosynthesis 8) produces sugars that process, generates ATP from food molecules. The first two stages are carried provide food for all life on the planet. The process begins with large out by enzymes in the cytoplasm and mitochondrial matrix; a few of these complexes of proteins (pink and purple) and chlorophyll (green) embedded enzymes (pink proteins) are shown. The final stage is carried out by proteins in the thylakoid membranes. These complexes trap light energy in molecules (purple) that form a "chain" in the inner mitochondrial membrane. that are used by other proteins (pink) in the stroma to make sugars. 24 12  12/9/24 Transcription (Chapter In the 14) nucleus, the Translation(Chapter 14) In the cytoplasm, the information information contained in a DNA sequence is transferred in mRNA is used to assemble a polypeptide with a specific to messenger RNA (mRNA) by an enzyme called RNA sequence of amino acids. Both transfer RNA (tRNA) molecules polymerase. After their synthesis, mRNA molecules leave the and a ribosome play a role. The eukaryotic ribosome, which includes nucleus via nuclear pores. a large subunit and a small subunit, is a colossal complex composed of four large ribosomal RNA (rRNA) molecules and Figure 4.30 Visualizing mRNA more than 80 proteins. Through transcription and translation, the RNA nucleotide sequence of DNA in a gene determines the amino acid polymerase sequence of a polypeptide, via the intermediary mRNA. Nuclear pore the Scale of the Molecular DNA Polypeptide Ribosome The nuclear pore complex made of regulates molecular traffic in amino and out of the nucleus, which acids is bounded by a double membrane. Among the largest tRNA Large subunit Machinery in a Cell Nucleosome: DNA wrapped structures that pass through around 8 histone proteins the pore are the ribosomal subunits, which are built in Small subunit the nucleus. mRNA DNA Nucleus Nuclear pore Endoplasmic Nuclear reticulum envelope Scale within cell 25 nm Microfilament 25 nm Vesicle Scale of enlarged structures 1. List the following structures from largest to smallest: proton pump, nuclear pore, cyt c, ribosome. Tubulin protein Microtubule Microfilament 2. Considering the structures of a nucleosome subunit Motor and of RNA polymerase, speculate about what (a + b protein must happen before RNA polymerase can dimer) (myosin) transcribe the DNA that is wrapped around the histone proteins of a nucleosome. CytoskeletonCytoskeletal structures are 3. Find another myosin motor protein walking on polymers of protein subunits. Microtubules are hollow Motor proteins, Such as a microfilament in this figure. What organelle structural rods made of tubulin protein subunits, while myosin, are responsible for transport of microfilaments are cables that have two chains of actin vesicles and movement of organelles is being moved by that myosin protein? proteins wound around each other. within the cell. 25 Chapter 5 Membrane Transport Fibers of extra- cellular matrix (ECM) Glyco- Carbohydrates protein Glycolipid EXTRACELLUL AR SIDE OF MEMBRANE Phospholipid Cholesterol Microfilaments Peripheral of cytoskeleton proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE 26 13  12/9/24 Membrane Proteins and Their Functions Six major functions (a) Transport. Left: A protein that spans the membrane may provide a (d) Cell-cell recognition. Some glyco- of membrane hydrophilic channel across the membrane that is selective for a proteins serve as identification tags that are specifically recognized by membrane proteins particular solute. Right: Other transport proteins shuttle a substance from one proteins of other cells. This type of cell-cell binding is usually short-lived Glyco- Transport side to the other by changing shape (see Figure 5.14b). Some of these compared with that shown in (e). protein Enzymatic activity proteins hydrolyze ATP as an energy source to actively pump substances ATP across the membrane. Signal (b) Enzymatic activity. A protein built into Enzymes (e) Intercellular joining. Membrane transduction the membrane may be an enzyme with its active site (where the reactant binds) proteins of adjacent cells may hook together in various kinds of junctions, exposed to substances in the adjacent Cell-cell solution. In some cases, several enzymes such as gap junctions or tight junctions (see Figure 4.27). This type of binding recognition in a membrane are organized as a team that carries out sequential steps of a is more long-lasting than that shown in (d). metabolic pathway. Intercellular (c) Signal transduction. A membrane Signaling molecule joining protein (receptor) may have a binding site with a specific shape that fits the Receptor (f) Attachment to the cytoskeleton and extracellular matrix (ECM). Microfilaments or other elements of the Attachment to the shape of a chemical messenger, such as a hormone. The external messenger cytoskeleton may be noncovalently cytoskeleton and (signaling molecule) may cause the protein to change shape, allowing it to bound to membrane proteins, a function that helps maintain cell shape and extracellular matrix relay the message to the inside of the stabilizes the location of certain membrane proteins. Proteins that can (ECM) cell, usually by binding to a cytoplasmic protein (see Figure 5.22). Signal transduction bind to ECM molecules can coordinate extracellular and intracellular changes (see Figure 4.26). Figure 5.7 Some Functions of Membrane Proteins 27 Passive Transport Is Diffusion of a Substance Across a Membrane with No Energy Investment Molecules of dye Membrane (cross section) Diffusion is the tendency for molecules to spread out evenly into the available space WATER Substances diffuse down their concentration Net diffusion Net diffusion Equilibrium gradient, from where it is more concentrated to (a) Diffusion of one solute. Molecules of dye can pass through membrane pores. Random movement of dye molecules will cause some where it is less concentrated to pass through the pores; this happens more often on the side with more dye molecules. The dye diffuses from the more concentrated side to the less concentrated side (called diffusing down a concentration Substances move down their own concentration gradient). A dynamic equilibrium results: Solute molecules still cross, but at roughly equal rates in both directions. gradient, unaffected by concentration gradients of other substances The diffusion of a substance across a biological Net diffusion Net diffusion Equilibrium membrane is passive transport because no Net diffusion Net diffusion Equilibrium energy is expended by the cell to make it happen (b) Diffusion of two solutes. Solutions of two different dyes are sepa- rated by a membrane that is permeable to both. Each dye diffuses down its own concentration gradient. There will be a net diffusion of the purple dye toward the left, even though the total solute concentration was initially greater on the left side. Figure 5.10 Diffusion of Solutes Across a Synthetic Membrane 28 14  12/9/24 Review: Passive and Active Transport Passive transport Active transport ATP Diffusion. Facilitated diffusion. Hydrophobic Many hydrophilic molecules and substances diffuse (at a slow rate) through membranes very small un- with the assistance of charged polar transport proteins, molecules can either channel diffuse through proteins (left) or carrier the lipid bilayer. proteins (right). Figure 5.16 29 Chapter 6 Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting Product molecule 30 15  12/9/24 Metabolic Pathways Catabolic pathways release energy by breaking down complex molecules into simpler compounds The energy is then available to do cellular work For example, in cellular respiration glucose and other organic fuels are broken down into carbon dioxide and water Anabolic pathways, called biosynthetic pathways, consume energy to build complex molecules from simpler ones For example, proteins are synthesized from simpler molecules called amino acids Energy is fundamental to all metabolic processes Bioenergetics is the study of how energy flows through living organisms 31 The Second Law of Thermodynamics According to the second law of thermodynamics Every energy transfer or transformation increases the entropy of the universe Entropy is a measure of molecular disorder Scientists use the term “disorder” to describe how dispersed energy is in a system and how many energy levels are present Heat CO2 H2O Chemical energy Kinetic energy in food (a) First law of thermodynamics: Energy can be (b) Second law of thermodynamics: Every energy transfer or transformation increases transferred or transformed but neither created nor the disorder (entropy) of the universe. For example, as the bear runs, disorder is destroyed. For example, chemical reactions in this increased around its body by the release of heat and small molecules that are the brown bear will convert the chemical (potential) by-products of metabolism. A brown bear can run at speeds up to 35 miles per hour energy in the fish into the kinetic energy of running. (56 km/hr)—as fast as a racehorse. Figure 6.3 The Two Laws of Thermodynamics 32 16  12/9/24 Free Energy and Metabolism The concept of free energy can be applied to the chemistry of life’s processes Exergonic and Endergonic Reactions in Metabolism An exergonic reaction proceeds with a (a) Exergonic reaction: energy released, spontaneous net release of free energy and is spontaneous; ΔG is negative Reactants The magnitude of ΔG represents the maximum amount of work the reaction Amount of energy can perform Free energy released (DG < 0) Energy Products Figure 6.6 Free Energy Changes (ΔG) in Exergonic and Endergonic Reactions Progress of the reaction 33 The Activation Energy Barrier The reactants AB and CD must absorb After bonds have enough energy from the surroundings broken, new bonds to reach the unstable transition state, form, releasing energy where bonds can break. to the surroundings. Course of A B EA reaction without without EA with C D Transition enzyme enzyme enzyme state is lower Free energy Reactants A B EA DG is unaffected C D Course of by enzyme energy reaction Free Reactants with enzyme A B DG < 0 C D Products Products Progress of the reaction Figure 6.12 Energy Profile of an Exergonic Reaction 34 17  12/9/24 Figure 6.15 The Active Site and Catalytic Cycle of an Enzyme Substrates enter the Substrates are held active site; enzyme changes in the active site by shape such that its active weak interactions, such site enfolds the substrates as hydrogen bonds and (induced fit). ionic bonds. E+S ES E+P Substrates The active Enzyme-substrate complex site lowers EA and Active speeds up site is the reaction avail- (see text). able for two new substrate molecules. Enzyme Products are released. Substrates are converted to Products products. 35 Enzyme Inhibitors (a) Normal binding A substrate can Substrate Enzyme activity is often regulated by molecules that bind normally to the active site of an Active site selectively inhibit enzyme function enzyme. Enzyme Competitive inhibitors bind to the active site of an enzyme and prevent the substrate from binding (b) Competitive inhibition Noncompetitive inhibitors bind to an alternate site on A competitive inhibitor mimics the