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Process Skills in Science Science- A body of knowledge and a process by which we learn the knowledge (scientific method). Scientific Method: Problem: question you are trying to answer Background Information: Information required to help answer the question Hypothesis: Materials: An educated guess (If, then and because statement) stuff we use Procedure: explains steps in detail (must be simplified enough for anyone to follow but precise enough to ensure that it can be replicated) Observation Analysis: and Results: what did you see/observe relating the results to the problem with background information Conclusion: hypothesis Answering the problem and supporting/disproving your Variables: things that are changed in an experiment Manipulated: independent Responding: Dependent Controlled Manipulated: changed by the experimenter Responding: changes because of the manipulated variable Responds to your changes Controlled: Kept constant The results depend on what you’ve done here We use it to compare our results Control of an Experiment: A control group is used as a comparison to the experimental group. Controlled Experiment: A controlled experiment is one where A) all of the variables are kept the same except for one B) There is only one manipulated variable and one responding variable Graphing Techniques: Don’t forget a title for the graph Don’t forget to label the axis X-axis: manipulated variable Y-axis: responding variable Lines of best fit used to describe a relationship that we see in a graph Straight line: ONLY if you see a straight line Curved Line: ONLY if you see a curved line Cell Energy Why do we care about this? We need energy to keep cells alive Activities require energy Energy Requirements: Energy is released from foods The digestion process breaks down food into molecules Molecules are absorbed by cells Two uses of food by cells: 1) Anabolism: synthesis of larger molecules required by the cell Example: Enzymes 2) Catabolism: broken down into smaller molecules to release energy for cellular activities Example: contraction of muscle cells Metabolic Activities: Sum of the chemical reactions that occur in cells Two type of chemical reactions: Exergonic Endrogenic Exergonic Reactions: Example: Cellular Respiration Reactants Products + Energy Endrogenic Requires Reactions: energy Example: Photosynthesis Reactants + Energy Products Energy Conversions All cells must have a constant supply of energy Energy is trapped and released by two processes: Photosynthesis Cellular The Respiration Basics: Photosynthesis: Light energy is changed into chemical energy and stored in glucose Respiration: to the cell Glucose is broken down to release energy Photosynthesis Happens only in green plants in the presence of chlorophyll which is found in chloroplasts Chemical Energy Equation: stored in the form of glucose Cellular Respiration Happens in ALL cells whereby energy is released to perform life processes Chemical Equation: Involves burning of organic fuels by oxygen Energy is released Photosynthesis and Cellular Respiration Biology 20- Unit 3 Let’s Review Plants and animals are made up of eukaryotic cells (have a nucleus) In spite of varied size, shape and appearance, cells have several things in common. All cells digest nutrients, excrete wastes, synthesize needed chemicals and reproduce. 12 Cellular Anatomy All cells are made up of parts known as organelles Although both plant & animal cells share many common types of organelles there are also organelles which are unique to each type See pgs 154 - 155 13 The Cell Membrane Separates the internal environment of the cell from its external environment Made of a double layer of phospholipid molecules Membranes also have other proteins and molecules and molecules that are embedded within them. Create passageways through the membrane Membranes Two are semi-permeable ways molecules and ion move through the membrane are diffusion and osmosis (passive transport) Diffusion Natural movement of molecules or ions from an area where they are more concentrated to an area of less concentration (moving down its concentration gradient) Does not require energy Osmosis Diffusion of water across a membrane Movement of water depends of different things If water concentration of either side is equal than equal amounts of water move in and out (isotonic) If the water concentration is more outside the cell than in the water will move into the cell (hypotonic) If water concentration inside the cell is greater than outside water moves out (hypertonic). -Does not require energy Facilitated Diffusion Substances that need help to move in and out of the cell (example: glucose) Particular transport proteins will recognize and help move a specific type of dissolved molecule or ion (carrier protein) Channel proteins also carry molecules across but they must be small enough to fit through the tunnel. Active Transport Needs ATP- energy to move things in and out of the cell adenosine triphosphate Endocytosis and Exocytosis Used for substances too large to move across a membrane Example: Cholesterol Can use endocytosis- folds in on itself to create a membrane enclosed sac (vesicle) to “eat” the substance Types of Endocytosis 3 Type of Endocytosis: 1. Pinocytosis: intake of small amounts of liquids or small particles 2. Phagocytosis: intake of large amounts of liquids or larger particles 3. Receptor- assisted endocytosis: intake of specific molecules that attach to special proteins in the membrane Exocytosis Removing Vesicles substances from the cell from inside the cell moves to the membrane and “bursts” releasing its contents Cell Wall-Plant Cells A surrounding layer outside the cell membrane Composed of small fibres (microfibrils) of cellulose 25 Animal cells Animal Cell Parts Mitochondria: provide the energy a cell needs to move, divide, reproduce Power Centre of the cell Cristae are folded to increase surface area Parts of an Animal cell Cytoplasm: fluid that fills the cell Distributes materials such as oxygen and food to different parts of the cell Also helps support all the other parts of the cell Parts of an Animal Cell Nucleus: large dark nucleus is often the most easily seen structure in the cell Controls the cell activities Contains the chromosomes Enclosed in a nuclear membrane which controls what enters and leaves the cell Parts of an Animal Cell Nucleolus: prominent structure in the nucleus Produces ribosomes Parts of an Animal Cell Vacuoles: Storage places for surplus food, wastes and other substances that the cell cannot use right away. Parts of an Animal Cell Lysosomes: digestion Parts of An Animal Cell Golgi Apparatus: important in packaging proteins for transport elsewhere in the cell Parts of An Animal Cell Rough Endoplasmic Reticulum: Appears pebbled due to the presence of ribosomes. Synthesizes proteins Parts of An Animal Cell Smooth Endoplasmic Reticulum: Appears smooth Functions: lipid and steroid synthesizes Parts of an Animal Cell Ribosome: Site of protein synthesis Animal cells What You Need to have in an Animal Cell Nucleus Cell Membrane Cytoplasm Vacuoles Ribosomes Golgi Apparatus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Lysosomes Mitochondria Nucleolus Plant cells Parts of a Plant Cell Lucky for you plants have many of the same structures 1)Nucleus 2) Nucleolus 3) Cytoplasm 4) Golgi Apparatus 5) Lysosome 6) Mitochondria 7) Vacuole 8) Cell Wall 9) Smooth ER 10) Rough ER 11) Chloroplast Parts of a Plant Cell Cell Wall: are much thicker and more rigid than cell membranes and are made mostly of a tough material called cellulose. Provide support for the cell Parts of a Plant Cell Chloroplasts: Structures where photosynthesis takes place Photosynthesis & Cellular Respiration ATP and Cellular Activity How does ATP supply energy for cellular activity? ATP Supplies the energy for cellular activities Used rapidly so cells must be constantly creating it Used for: Active transport Movement of chromosomes Movement of muscles Cilia or flagella etc. Photosynthesis Needed in order for life to survive on Earth Photosynthesizing organisms contain chloroplasts that trap the Sun’s energy Converted into chemical energy and stored as sugars and carbohydrates Other products produced by the Sun’s energy are oxygen. ATP and heat Cellular Respiration Used by plants, animals and other multicellular organisms The break down of energy-rich compounds to release stored energy Broken down inside the mitochondria This makes ATP Photosynthesis – Chemical reaction Energy from the sun is captured by green plants by the process called photosynthesis (P/S) 6 CO2 + 6 H2O + E (light) C6H12O6 + 6 O2 48 Photosynthesis - Pigments For light energy to be used by living systems it must first be absorbed. A pigment is any substance that absorbs light. (Some pigments absorb all light and thus appear black. Others absorb light in the violet-blue and the orange-red spectrum and reflect green light.) 49 Photosynthesis - Pigments Various pigments absorb energy of different wavelengths. (absorption spectrum) 50 Photosynthesis - Pigments All photosynthetic organisms contain chlorophyll Different types of plants use various pigments in P/S. 51 Photosynthesis - Pigments Chlorophyll a (blue-green) and chlorophyll b (yellowgreen) are the most common pigments but most plants also contain a pigment group called carotenes (Example: beta-carotene) They absorb photons with energies in the blue-violet and red regions and reflect everything else 52 Chlorophyll a and b Chlorophyll a is the only pigment that can transfer the energy from sunlight to photosynthesis Chlorophyll b acts as an accessory pigment “helper” to catch the photons a misses and transfer the energy absorbed to a There are other compound, carotenoids , are also “helper” pigments. Photosynthesis - Pigments In green leaves carotenes are masked by chlorophyll, thus when chlorophyll production slows in the fall the leaves change color to show the carotenes. 54 Photosynthesis - Chloroplast Chlorophyll pigments reflect green and absorb blue and red wavelengths. Carotenoids absorb violet and blue wavelengths reflecting yellow. Pigments absorb light of the correct wavelength to excite electrons to a higher energy level 55 Photosynthesis - Plastids Plastids are structures that contain pigment and give plants their colour. The most common plastid is the chloroplast in which the chemical reactions of P/S occur. 56 Cellular Respiration Produces ATP energy by the combustion reaction of glucose called cellular respiration. C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + E (ATP) 57 Mitochondrial structure Respiration occurs at the mitochondrian Mitochondrian is composed of 4 regions: 1. outer membrane - smooth and freely permeable; contains enzymes to catabolize fats 58 Mitochondrial structure 2. inner membrane – folded membrane in the mitochondria (cristae); made mostly of protein including the enzyme that makes ATP; impermeable to most small molecules and ions 59 Mitochondrial structure 3. Intermembrane space - contains enzymes which use ATP 60 Mitochondrial structure 4. matrix - control region; mixture of proteins including enzymes which oxidize major compounds 61 Metabolic Pathways In a metabolic pathway the product of one reaction is the starting reactant for another The Role of Enzymes Metabolism refers to all the chemical reactions that occur within a cell to support and sustain life functions Can be broken into two distinct types of reactions: 1. Anabolic reactions & pathways create larger molecules from small subunits and require energy 2. Catabolic reactions & pathways break down large molecules into smaller pieces and release energy Energy required to start a reaction is known as activation energy Catalysts Allows and enzymes reduce the activation energy the reactions to proceed more rapidly Enzymes are specialized proteins that lower the energy needed to activate biological reactions Activation Energy Catalyzed vs. Uncatalyzed Reactions Oxidation & Reduction Oxidation is a reaction where an atom or molecule loses electrons LEO – Loses Electrons = Oxidation Reduction is a reaction where an atom or molecule gains electrons GER – Gains Electrons = Reduction Free electrons from oxidation cannot exist on their own Electrons that are lost through oxidation of one substance cause the reduction of another compound Molecules energy in their reduced form contain large amounts of Example: X + Y --> X+ + Yreducing oxidizing oxidized reduced agent agent agent agent Adenosine Triphosphate The cell obtains its energy requirements through cellular respiration which is an exothermic reaction manufacturing ATP 68 ATP produces energy by breaking a bond to a phosphate group This produces ADP (adenosine diphosphate) and a free phosphate group ATP ADP + Pi This process works in reverse to create more ATP Adenosine Triphosphate Adenosine triphosphate (ATP) consists of: nitrogenous base adenine (1/5 types of nitrogenous bases) an attached ribose sugar. attached to the sugar are 3 phosphate groups. 70 Adenosine Triphosphate The terminal phosphate is bonded by a covalent bond of unusually high energy. 71 Adenosine Triphosphate During cellular respiration a free phosphate group is attached to a molecule of ADP to make ATP in a process called phosphorylation 72 Adenosine Triphosphate ATP is used to provide the activation energy needed to power cell reactions (Energy is liberated by detaching the terminal phosphate group) 73 Review Cellular respiration is the process by which cells break down high-energy compounds and generate ATP. Review Adenosine triphosphate, or ATP, is the direct source of energy for nearly all types of energy-requiring activities of living organisms. Mitochondria Review Mitochondria have outer and inner membranes that surround a fluid-filled region called the matrix. The inner membrane has many deep infoldings called cristae. Review The chemical reactions of photosynthesis and cellular respiration take place in a series of step-by-step reactions called metabolic pathways. Enzymes are biological catalysts that reduce the amount of startup energy needed for the reactions in the metabolic pathways. In the absence of enzymes, the reactions could not occur at temperatures at which living organisms thrive. Review When a compound is oxidized in a chemical reaction, it loses electrons. When a compound is reduced in a chemical reaction, it gains electrons. Compounds contain more chemical energy in their reduced form than they do in their oxidized form. Photosynthesis Transforms the energy of the sun into chemical energy in glucose, ATP and NADPH Involves over 100 individual chemical reactions that work together These reactions can be summarized in two groups: 1. 2. Light-Dependent Reactions – generates high energy compounds ATP and NADPH Light-Independent Reactions – energy of ATP and reducing power NADPH are used to reduce carbon dioxide to make Light Dependent Light Independent 81 Light-Dependent Reactions Requires sunlight in order to work During these reactions, the pigments contained inside the thylakoid absorb light energy Although plants have a number of pigments, the most important for photosynthesis is chlorophyll Photosystems Within the thylakoid membrane, chlorophyll and other pigments are organized into photosystems. Chloroplasts of plants have two photosystems: Photosystem I (PSI) Photosystem II (PSII) Each system is made of pigment molecules that include chlorophyll and carotenoid molecules All the pigment molecules in each photosystem can absorb various wavelengths of light energy The various pigment molecules produce free electrons when light hits them These free electrons are passed along to the reaction center, a specialized chlorophyll a molecule When the electron in the reaction center is “excited” by the addition of energy, it passes to the electron-acceptor molecule This reduces the electron acceptor and puts it at a high energy level A summary of the Steps: The light reactions use the solar power of photons absorbed by both photosystem I and photosystem II to provide chemical energy in the form of ATP and reducing power in the form of the electrons carried by NADPH. Takes place in the thylakoid membranes of the chloroplast 86 Light Dependent Reaction – The Details: Photosystem II (PSII) Light enters PSII and is trapped by Pigment-680 (P680) An electron from P680 is boosted to a higher energy level where it is passed to an electron acceptor molecule This electron passes down an electron transport chain (cytochromes) to PSI forming ATP from ADP in a process called photophosphorylation 87 Light Dependent Reaction – The Details: Photosystem II (PSII) The lost electrons from P680 are replaced by electrons produced by the lysis of water photolysis, which liberates O2 as a waste product 88 Light Dependent Reaction – The Details: Photosystem I (PSI) The electron arriving from PSII is boosted to another electron acceptor molecule As it is passed along it releases energy This energy pulls hydrogen ions from the stroma into the thylakoid lumen 89 Light hits photosystem 1 An electron in this photosystem is “excited” and passed onto the smaller electron transport chain The excited electron from photosystem 1 passes down a chain of coenzymes (cytochromes) to make NADPH molecules from NADP Light Dependent Reaction 91 http://www.youtube.com/watch?v=BK_cjd6Evcw ATP Production - Chemiosmosis The energy from the electrons in photosystem II is used to produce ATP indirectly The H+ ions in the thylakoid lumen are unable to escape except through special proteins called ATP synthase complexes As the H+ ion moves though this complex they release energy The complex uses some of this energy to combine ADP and Pi making ATP This ATP then moves onto the light-independent reaction to make glucose Chemiosmosis Linking the movement of hydrogen ions to the production of ATP Occurs in a series of steps: 1. To return to the stroma, the H+ ions must move through a structure known as ATP synthase which provides the only pathway for H+ ions to move down their concentration gradient 2. ATP synthase uses the movement of the H+ ions to run a mechanism that bonds together ADP and free phosphates to form ATP Your Task Case Study page 184 questions 1 and 2 optional Section Questions page 185 questions 1-4 somewhat optional Practice Questions page 187 #1-3 getting less optional Practice Questions page 188 #4-6 not really a choice Practice Questions page 190 # 7-10 I wouldn’t ignore these Practice Question page 191 # 11-14 Do or suffer the consequences Expect a Quiz next class 94 Light Independent Reactions Does Also not require light known as the Calvin-Benson Cycle Occur in the stroma of the chloroplast Glucose is synthesized which requires: a. energy in the form of ATP and NADPH (there has to be enough) b. H since each glucose molecule has 12 H atoms http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html The Calvin-Benson Cycle The Calvin cycle regenerates its starting material after molecules enter and leave the cycle CO2 enters the cycle and leaves as sugar The cycle spends the energy of ATP and the reducing power of electrons carried by NADPH to make the sugar The actual sugar product of the Calvin cycle is not glucose, but a three-carbon sugar, glyceraldehyde-3-phosphate (PGAL) Each turn of the Calvin cycle fixes one carbon. For the net synthesis of one PGAL molecule, the cycle must take place three times, fixing three molecules of CO2. To make one glucose molecules would require six cycles and the fixation of six CO2 molecules. The Calvin cycle has three phases. Calvin - Benson Cycle http://www.youtube.com/watch?v=ixpNw6mx3lk Calvin Benson Cycle–The General Details The Calvin-Benson cycle can be thought of as having three stages: Carbon fixation Chemical reshuffling Reforming RuBP 99 Light Independent Occurs Step in 3 stages: 1: Carbon Fixation RuBP (ribulose biphosphate) joins with CO2 (catalyzed by Rubisco) to form an unstable 6 carbon molecule which splits to become PGA (phosphoglyceric acid) Light Independent Step 2: Reduction The 3 carbon compounds are activated by ATP (given energy) and then reduced by NAPDH (given more energy) The molecule now become 12 molecules known as PGAL 2 PGAL molecules move on to make glucose, 10 go to step 3 Light Independent Step 3: Replacing RuBP Remaining ATP PGAL will be used to make more RuBP will help break and reform the chemical bonds to make the 5-carbon RuBP Calvin-Benson Cycle - Simplified 103 Calvin Benson Cycle – more details 104 105 Let’s Put It All Together… http://www.youtube.com/watch?v=FoCS3EpUdV4 Photosynthesis Stores Energy in Organic Compounds Review Photosynthesis consists of two separate sets of chemical reactions: light-dependent and light-independent reactions. light-dependent reactions NADPH ATP chemiosmosis light-independent reactions Photosynthesis Stores Energy in Organic Compounds Review Chlorophylls a and b and the carotenoids are photosynthetic pigments that absorb light. Photosynthesis Stores Energy in Organic Compounds Review Light energy trapped by a pigment molecule excites electrons. When an electron in photosystem II is excited, it is transferred to and then passed along an electron transport system. Photosynthesis Stores Energy in Organic Compounds Review Energy released during electron transport is used to force hydrogen ions across the thylakoid membrane and create a concentration gradient. Energy from the concentration gradient is used to generate ATP from ADP and phosphate by means of chemiosmosis. As hydrogen ions move down their concentration gradient, they drive the reaction that generates ATP. Photosynthesis Stores Energy in Organic Compounds Review An electron from water replaces the electron that was lost from photosystem II. The oxygen from the water molecule is converted to molecular oxygen. When an electron from photosystem I is excited, it is eventually used to reduce NADP+ to NADPH. Photosynthesis Stores Energy in Organic Compounds Review • The series of reactions that synthesize carbohydrates is the Calvin-Benson cycle, which occurs in the stroma. • In this cycle, carbon dioxide combines with RuBP to form a six-carbon compound that immediately splits into two three-carbon compounds. Photosynthesis Stores Energy in Organic Compounds Review ATP and NADPH from the light-dependent reactions provide energy and reducing power to form PGAL from the newly formed three-carbon compounds. Six cycles produce 12 PGAL molecules, 10 of which regenerate RuBP and 2 of which are used to make glucose. http://www.youtube.com/watch?v=X-ZZETT6F-s http://www.youtube.com/watch?v=gTv9y5dol-A http://www.youtube.com/watch?v=ncEHa-ZwX3M http://www.youtube.com/watch?v=hqF5JOXi_K8 Cellular Respiration The cell obtains most of its energy requirements through the cellular respiration of glucose (glycogen, glycerol & amino acids may also be used) Releases the energy that is stored in carbohydrates Glucose is oxidized to form carbon dioxide, water and energy Releasing Stored Energy There are 3 ways of releasing the energy stored in food: 1. Aerobic cellular respiration is carried out by organisms that live in aerobic environments Examples: 2. fungi, bacteria, plants, animals Anaerobic cellular respiration is carried out by organisms that live in anaerobic environments Examples: 3. nitrogen fixing bacteria, deep ocean producers Fermentation - modified form of anaerobic cellular respiration Examples: Yeast, bacteria that cause milk to sour Aerobic Cellular Respiration The controlled process of respiration can be divided into three groups: 1. Glycolysis - anaerobic process which converts glucose to pyruvic acid (aka pyruvate) 2. Kreb's (Citric Acid) cycle - aerobic process in which the breakdown of pyruvic acid yields energy in the form of ATP and NADH/FADH 3. Respiratory (Electron Transport) Chain - an electron transfer system that produces ATP 117 Aerobic Cellular Respiration Glycolysis Anaerobic reaction that occurs in the cytoplasm Occurs in all living cells Does not provide enough energy to sustain life Animation http://www.youtube.com/watch?v=PowpbzBaTM0 Stage of Glycolysis Summary 1. Glucose (6 C sugar) enters respiration pathway 2. Two ATP from cytoplasm provide the activation energy to begin the reaction ( - 2 ATP ) which converts glucose to glucose phosphate (6 carbon molecule) 120 Stage of Glycolysis Summary 3. Glucose phosphate is split into 2 PGAL (phosphoglyceraldehyde) (3 carbon molecule) 4. Each PGAL continues through glycolysis to yield: 1 NADH, 2 ATP & 1 H2O forming the 3 carbon molecule - pyruvate 121 122 Stage 1 of Glycolysis Glucose ↓ (ATP -> ADP) [phosphorylation] Glucose phosphate ↓ [rearranged] Fructose phosphate ↓ (ATP -> ADP) [phosphorylation] Fructose diphosphate ↓ [split] PGAL PGAL 123 Stage 2 Glycolysis PGAL ↓ NAD -> NADH DPGA ↓ ADP -> ATP PGA ↓ ADP -> ATP Pyruvate PGAL ↓ NAD -> NADH DPGA ↓ ADP -> ATP PGA ↓ ADP -> ATP Pyruvate 124 Energy Gained from Glycolysis Glycolysis nets: 2 ATP (PGAL - -> pyruvic acid) X 2 = 4 ATP 2 ATP (activation energy) = - 2 ATP 2 ATP Also 2 NADH 125 The Fate of Pyruvate Pyruvate can proceed to two processes dependent on the availability of oxygen: Aerobic Cellular Respiration Pyruvate Anaerobic is transported from the cytoplasm into the mitochondria Cellular Respiration - Fermentation Pyruvate remains in the cytoplasm Preparation for the Kreb’s Cycle Transition Reaction (aka oxidative decarboxylation) Occurs in the mitochondria Pyruvate combines with coenzyme A (CoA) Remaining 2 carbon molecule attaches to CoA to form acetyl CoA Loses a carbon atom in the form of CO2 Coenzyme A “tows” the acetyl group (2 carbon compound) into the Krebs cycle During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are reduced to NADH and FADH2, and a small amount of ATP is produced. Krebs Cycle The NADH and FADH2 from the Krebs cycle donate their electrons to the electron carriers in the electron transport chain. As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient. The energy stored in the gradient is used to generate ATP by chemiosmosis. Krebs Cycle Citric Acid Cycle Occurs in the mitochondria Cycle must be completed 2x per glucose molecule Net gains per glucose molecule: 2 ATP 6 NADH 2 FADH2 Animation Reduced compounds – carry electrons need for electron transport system Kreb’s Cycle Steps The 2 C acetyl group from the transition reaction combines with a 4 C oxaloacetic acid to produce a 6 C called citric acid Citric acid steps through a number of reactions, losing a CO2 and forming NADH to become a 5C ketoglutaric acid 132 Kreb’s Cycle Ketoglutaric acid proceeds through a number of reactions losing CO2 and producing NADH and ATP to become a 4C - succinyl acid Succinyl acid becomes fumeric acid (4 C) producing FADH Fumeric acid is transformed to oxaloacetic acid forming NADH 133 Kreb’s Cycle The oxaloacetic acid molecule the cycle ends with is not the same molecule with which the cycle began [proven using radioactive markers in glucose entering - markers end up in oxaloacetic acid] 134 135 Video – The Kreb’s Cycle 136 Electron Transport Provides large quantities of ATP during aerobic cellular respiration Electrons are passed down a chain of protein complexes imbedded in the inner membrane Energy is pump hydrogen ions, H+, from the matrix into the intermembrane space Against concentration gradient Requires oxygen to function Oxygen is the final electron acceptor of the electron transport system producing water 2H+ + ½ O2 H2O Animation http://www.youtube.com/watch?v=JPCs5pn7UNI Electron Transport System Oxidative phosphorylation has these high energy electrons being passed step by step to a lower energy acceptor -> oxygen In oxidative phosphorylation a series of electron carriers, each holding the electron at a slightly lower energy level, pass the electrons along the pathway to make ATP At the top of the energy hill, the electrons are held by NADH and FADH 138 Cytochromes The principle components of the electron transport chain are cytochromes Composed of a protein enclosing an atom of iron each with a different capacity for holding electrons at different energy levels The enclosed iron atom alternately accepts and releases an electron passing it along to the next cytochrome at a slightly lower level of energy 139 Electron Transport System At the end of each chain the electrons are accepted by oxygen which then combines with protons (H+) from the solution to produce water For each NADH entering the electron transport chain a yield of 3 ATP is realized For each FADH entering the electron transport chain a yield of 2 ATP is realized 140 Role of Oxygen Video – Oxidative Phosphorylation 141 C/R - Energy Harvest Glycolysis ATP produced 4 ATP ( - 2 ATP activation E) Net Gain = 2 NADH Transition Rxn. 1 glucose molecule Net gain = 2 ATP 1 NADH/pyruvate Net Gain = 2 NADH Krebs cycle 3 NADH/cyle Net Gain = 6 NADH 1 FADH/cycle Net Gain = 2 FADH 1 ATP/cycle Net Gain = 2 ATP Total before ETC 4 ATP; 8 NADH & 2 FADH 142 C/R - Energy Harvest ETC 2 ATP for each NADH from glycolysis 2 3 ATP for each NADH after glycolysis 3 x 2 = 4 ATP x 8 = 24 ATP 2 ATP for FADH 2x2 = 4 ATP ATP from glycolysis and Krebs 4 ATP Total E Harvest – 36 ATP 143 Aerobic Cellular Respiration Net gain of 36 ATP molecules per 1 glucose during cellular respiration Majority of ATP is produced using Electron Transport System and Chemiosmosis Cellular Respiration Song Link ATP Sythase Video http://www.youtube.com/watch?v=00jbG_cfGuQ 146 Anaerobic Cellular Respiration No oxygen available Only produces the amount of ATP generated by glycolysis Converts excess pyruvate that cannot be processed in the Krebs cycle to lactate or ethanol Fermentation – pathway taken by pyruvate to produce ATP in anaerobic conditions Two types: Lactate Fermentation Ethanol Fermentation Lactate Fermentation Occurs in the cytoplasm Occurs when energy demands exceed oxygen supply Cells convert pyruvate molecules into lactate or lactic acid Use NADH as energy source Lactate is stored When oxygen levels increase lactate is converted back to pyruvate Pyruvate proceeds to Krebs cycle Ethanol Fermentation Anaerobic Occurs process in the cytoplasm of cells Process in which yeasts and some bacteria convert pyruvate to ethanol and CO2 Used to produce alcoholic beverages and aid in the rising of bread Anaerobic Respiration Both types of fermentation use energy but free NAD+ to accept H+ supplying a small amount of energy and preventing the cell from becoming acidic Various other chemical pathways exist which allow some organisms to thrive in anoxic and hypoxic conditions 150 Summary Cellular Respiration Releases Energy from Organic Compounds Review A. B. C. Three metabolic pathways make up aerobic cellular respiration. Cellular Respiration Releases Energy from Organic Compounds - Review The first set of reactions in aerobic cellular respiration is called glycolysis. It is an anaerobic process. During glycolysis, a small amount of ATP is generated, and NAD+ is reduced to NADH. Stage 1 of Glycolysis Glucose ↓ (ATP -> ADP) [phosphorylation] aglucose . phosphate ↓ [rearranged] fructose phosphate b. ↓ (ATP -> ADP) [phosphorylation] c.fructose diphosphate ↓ [split] d.PGAL PGAL 154 Stage 2 Glycolysis PGAL PGAL ↓ NAD -> NADH ↓ a.PGA PGA ↓ ADP -> ATP ↓ b. PGA ↓ ADP -> ATP c.Pyruvate NAD -> NADH ADP -> ATP PGA ↓ ADP -> ATP Pyruvate 155 Cellular Respiration Releases Energy from Organic Compounds - Review The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen (anerobic and aerobic) and on the type of organism. When oxygen is available, pyruvate enters the matrix of the mitochondrion. A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced to NADH. Transition Reaction Cellular Respiration Releases Energy from Organic Compounds - Review Acetyl-CoA enters the Krebs cycle by combining with a fourcarbon compound. During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are reduced to NADH and FADH2, and a small amount of ATP is produced. citrate Cellular Respiration Releases Energy from Organic Compounds - Review The NADH and FADH2 from the Krebs cycle donate their electrons to the electron carriers in the electron transport chain. As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient. The energy stored in the gradient is used to generate ATP by chemiosmosis. Cellular Respiration Releases Energy from Organic Compounds - Review Organisms that carry out anaerobic cellular respiration use inorganic chemicals other than oxygen as the final electronacceptor. This produces ATP for the cell, but not as much as in aerobic respiration. breakdown of glucose in the presence of oxygen 36 ATP breakdown of glucose by lactate or ethanol fermentation 2 ATP Cellular Respiration Releases Energy from Organic Compounds - Review In muscle that is functioning anaerobically, pyruvate is converted to lactate and the reduced NADH is reoxidized so that glycolysis can continue. This process is called lactate fermentation. Cellular Respiration Releases Energy from Organic Compounds - Review In yeast growing anaerobically, pyruvate is converted to carbon dioxide and ethanol. This process is known as ethanol fermentation. Cellular Respiration Releases Energy from Organic Compounds - Review Fermentation is used on an industrial scale to produce ethanol. Ethanol is used as an additive to gasoline to reduce some environmental contaminants. Selected Fermentation Products and their Uses Chapter Concept Organizer Chapter Summary P/S and C/R proceed through many different rxns to produce energy-rich compounds and break them down to release their stored energy (ATP) When the bond to the last phosphate group is broken, leaving ADP and a free phosphate group, the energy released is available to do cellular work. In P/S the CO2 and H2O are involved in two separate sets of reactions: H2 O is split into hydrogen ions, electrons, and oxygen in the lightdependent reactions CO2 is incorporated into carbohydrates in the light-independent reactions. Chapter Summary (cont’d) light-dependent rxns (thylakoid membranes) capture light energy and use it to excite electrons to produce ATP and NADPH. light-independent reactions (stroma) use the chemical potential energy of ATP and the reducing power of NADPH to reduce carbon dioxide and form glucose via the Calvin-Benson cycle. Glucose is processed to release energy through glycolysis, the Krebs cycle, and electron transport Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks down glucose into pyruvate Pyruvate enters the mitochondria, where it is broken down into carbon dioxide and acetyl CoA. Chapter Summary (cont’d) Acetyl CoA enters the Krebs cycle (matrix) and energy released from breakdown of compounds in the Krebs cycle is used to reduce NAD -> NADH and FAD -> FADH NADH & FADH donate electrons to the ETC on the inner mitochondrial membranes Energy, released as electrons, is passed along the chain & used to create a hydrogen ion gradient that powers chemiosmosis, which generates ATP. Glycolysis is the only source of energy for some organisms. Pyruvate is broken down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate fermentation). This process occurs anaerobically. Chapter Review What molecule provides energy for most cellular processes? Would photosynthesis and respiration be able to proceed without enzymes? Why or why not? Where are chlorophyll molecules found? What happens when a compound is oxidized? Reduced? Which form contains more energy? What occurs during chemiosmosis? Where does it occur? What metabolic pathways are involved in cellular respiration? Where do they occur?
