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INTRODUCTION TO BIOLOGY UNIT TWO Survey of the Plant Kingdom Plant Anatomy & Physiology Angiosperm Reproduction Photosynthesis Cellular Respiration CERRITOS COLLEGE SUMMER 2004 LECTURER – L. L. HARRIS Biology 120 Cerritos College INTRODUCTION TO PLANTS I. Beginnings – A Journey Out of the Water A. The Algae: Restricted to aquatic environments. Members of the Kingdom Protista GREEN ALGAE (Chlorophyta) RED ALGAE (Rhodophyta) BROWN ALGAE (Phaeophyta) B. Problems to Solve for a Terrestrial Life 1. How to Obtain and Transport Water 2. How to Prevent Evaporate Water Loss 3. How to Maintain a Moist Surface Area for Gas Exchanges 4. How to Support Body Against the Pull of Gravity 5. How to Carry Out Sexual Reproduction on Land No Water for a Flagellated Sperm Protect Zygote/Embryo from Dessication 6. How to Survive Despite Extreme Environmental Fluctuations II. Quick Survey of the Plant Kingdom A. Non-vascular Plants Out of the water, but they are restricted to moist areas 1) Because they have no true vascular tissue (no xylem, no phloem) 2) Because they have a “swimming sperm” – needs moisture to swim in! Perhaps the most common include: MOSSES (Bryophyta) LIVERWORTS (Hepatophyta) B. Vascular Plants Pterophytes: FERNS Successful transition onto land, but still require open water for sexual reproduction “Amphibians of the Plant Kingdom” – Only the Sporophyte is vascularized! For successful sexual reproduction, their swimming sperm must have water to swim in! Fern-Allies: HORSE-TAILS & others Gymnosperms: CONIFERS GINGKO CYCADS EPHEDRA Name means “Naked Seed” – Bear their seeds along their stems Non-swimming sperm Angiosperms: ANTHOPHYTA Name means “Vesseled Seed” – Bear their seeds in a fruit’ Non-swimming sperm Anthophytes are the Flowering Plants Two Classes: MONOCOTS & DICOTS (See Text Table for Distinguishing Characters) Alternation of Generations: (2N) Sporophyte (1N) spores meiosis (1N) Gametophyte mitosis (1N) gametes mitosis Sperm & Egg mitosis (2N) "ZYGOTE" FERTILIZATION Seen is a cycle of SPORIC MEIOSIS Important Trends: 1) Sporophyte becomes the dominant generation (the “obvious” plant) 2) Reduction in the size of the Gametophyte (becomes microscopic!) 2 II. Bodies of Higher Plants A. Roots & Shoots (Gymnosperms & Angiosperms) (If below ground → Roots / If above ground → Shoots) 1. Root Functions a. Absorb/Conduct water and dissolved minerals b. Store food c. Anchor (and may act as a structural support) 2. Shoots Two main organ types: STEMS & LEAVES a. Stem Functions i. Framework for upright growth. ii. P/S is possible in young green stems. iii. Storage sites (Ex. potatoes = stems) b. Leaf Functions i. The usual sites of P/S ii. Flowers & Cones are modified leaves III. Plant Tissues A. DERMAL TISSUES 1. EPIDERMIS – “skin” Outer covering of leaves, stem, and root. Typically only one cell layer thick! Often covered by a waxy CUTICLE – “water saving” Modifications of Epidermis: Guard Cells Root Hairs Lenticles Epidermal Hairs 2. PERIDERM – Replaces epidermis in those plants that experience Secondary Growth B. VASCULAR TISSUES 1. XYLEM – "roots to shoots" Conduct water and dissolved solutes from the soil Offers structural support for the plant as well (Xylos - Greek word for WOOD) Functional xylem tube is composed of DEAD CELLS Living cells do not transport water. Instead special properties of Water are responsible for assuring that water keeps moving up! COHESIVENESS & HIGH HEAT OF VAPORIZATION 2. PHLOEM – "shoots to roots" Conduct food and other plant products in shoots & roots Functional phloem is composed of LIVING CELLS – More on this Later C. GROUND TISSUES – This is the bulk of a plant’s body 1. Parenchyma – majority of GTs Functions: Photosynthesis, Storage, Secretions, Wound Healing 2. Collenchyma Functions: Support, Texture, Strength (with Flexibility) 3. Sclerenchyma Functions: Protection, Texture, Strength (with Rigidity) 3 IV. Plant Growth MERISTEMATIC TISSUES: Perpetually young tissues; undifferentiated tissue actively undergoing mitosis that will give rise to new cells for added growth A. Primary Growth Adds LENGTH to the plant feature – Occurs at tips of roots and shoots a. ROOT APICAL MERISTEM Region of root tip that is most actively undergoing mitosis b. SHOOT APICAL MERISTEMS & LATERAL AXILLARY BUDS Shoot Apicals: At the tips of shoots Lateral Axillary Buds: At nodes along stem; result in leaves, flowers, & lateral branches B. Secondary Growth Adds DIAMETER (girth) to the feature Woody Plants – extensive 2o growth for Dicots; very little (if any) in Monocots Non-Woody Plants (herbaceous) – little or no 2o growth Pattern of 2o Growth: Two Meristems: Vascular Cambium & Cork Cambium VASCULAR CAMBIUM – makes 2o Phloem & 2o Xylem On VC’s OUTER FACE 2o PHLOEM forms Most is crushed against the Cork Cambium On VC’s INNER FACE 2o XYLEM forms SAPWOOD – conducting xylem HEARTWOOD – non-conducting xylem ANNUAL RINGS – EARLY WOOD (Spring Wood) & LATE WOOD (Summer Wood) CORK CAMBIUM – gives rise to the Periderm [aka CORK] BARK: Those tissues outside the vascular cambium GIRDLING A TREE: Remove a strip of bark from tree’s circumference and also take a strip of VC Purpose: Kill the tree for its permanent removal C. Seasonal Growth Cycles Life cycle : Seed Germination -> -> -> Seed Formation 1. ANNUALS – (example: corn) Go through their entire life cycle in only one growing season Experience one season of primary growth. Very little secondary growth (if any) is noted 2. PERENNIALS – (examples: oaks, sycamores, "fruit trees") Live for more than one growing season Life cycle continues year after year before death Experience continued 1o and 2 o growth 3. BIENNIALS – (examples: foxglove & asparagus) Complete their life cycle in 2 growing seasons 1st season: Roots & Shoots 2nd season: Flowering, Fruit & Seed formation. 4 Biology 120 Cerritos College PLANT PHYSIOLOGY I. Water Absorption Root Hairs are the functional units of roots. Root Hairs are thin-walled epidermal ("skin") cells Water enters the Root Hair by Osmosis Water passes from Root Hair –> Cortex –> Endodermis Water passes between cells and through cells Passage to vascular tissue regulated – CASPARIAN STRIPS Waxy band of tissue around cells – water must travel through cells Water eventually funneled into Xylem II. Transpiration, Water Conduction, & Cohesion Theory A. Transpiration – loss of water due to evaporation Occurs primarily at leaves and stems Major Site – Stomata of leaves B. Water conducted upward by a constant negative pressure Tension extends downward from Leaf to Roots C. Negative Pressure & Transpiration assure that more soil water enters Xylem D. Summary of Cohesion Theory As long as water molecules vacate the transpiration sites, replacement water is sucked up through the xylem from the roots in continuous water columns as a result of hydrogen bonding between water molecules. III. Stomatal Regulation A. Stoma and Guard Cells Anatomy Stoma – hole, opening for gas exchange – flanked by Guard Cells Guard Cells – specialized epidermal cells; have chloroplasts B. Open State is Dependent on CO 2 & Water Levels in GCs P/S in GCs causes CO2 levels to fall as glucose is made Active Transport of Potassium into GCs when CO2 drops Potassium concentration gradient moves water into GCs High K+ means Low H2O inside GC. Water higher outside GC than in GC, therefore water moves into GC. Increased water in GCs –> Increased turgor –> Expose Stoma IV. Transport of Organic Substances in Phloem A. Translocation – Transport of Sucrose and other compounds through Phloem From "SOURCE" to SINK" regions Source – leaves and stems where P/S occurs (or where product is stored) Sink – where organic compound is being translocated B. Pressure Flow Theory (depends on pressure gradients between SOURCE & SINK region 1. Solutes actively transported out of Source cells and into Phloem "plumbing" 2. Result – water moves out of Source cells and into Phloem -> high Phloem pressure as result 3. Water & Solutes move by bulk flow from Source region toward Sink region Source Region is HIGH PRESSURE region – Sink Region is LOW PRESSURE region 4. Solutes reach Sink – Actively transported into Sink cells This lowers water pressure in sink cells – Water from phloem moves into Sink Cells 5 Biology 120 Cerritos College ANGIOSPERM REPRODUCTION I. INTRODUCTION Our discussion will be restricted to SEXUAL REPRODUCTION All other reproduction in plants is said to be VEGETATIVE II. THE REPRODUCTIVE SYSTEM A. DIVISION ANTHOPHYTA Characterized as: FLOWERING & FRUITING Characterized as having DOUBLE FERTILIZATION: 1. Formation of ZYGOTE → EMBRYO 2. Formation of ENDOSPERM → Starchy Food for the Embryo B. FLOWER ANATOMY 1. STEM (and PEDICLE) – for support and placement of flower 2. RECEPTACLE – Broadened region; base for ovary 3. SEPAL – for support and protection of developing flower 4. PETAL – Modified leaves. Function: Attract Pollinators via Colors, Patterns, Nectar, … 5. STAMEN (MALE) a. FILAMENT – Stalk that supports the anther b. ANTHER – Male Sporangium; Gametophyte production site 6. PISTIL (FEMALE) aka CARPEL a. STIGMA – Typically sticky; to hold & hydrate pollen grains b. STYLE – Stalk-like; will be site of the Pollen Tubes c. OVARY – Female sporangium; contains OVULES, Ovule – Gametophyte production site. Opening into ovule: MICROPYLE C. POLLINATOR ANYTHING that carries pollen from Anther to Stigma More specifically – many arthropods, mollusks, chordates, water, wind Gymnosperm Pollen and many Angiosperm Grasses – wings to catch the wind Angiosperm Pollen – without wings; majority rely on living pollinators III. GAMETOPHYTE PRODUCTION A. In the Ovule: MegaSpore –> 8-nucleated gametophyte (Embryo Sac) There is Unequal Cytokinesis: 8-nuclei divided among 7 cells 2 Important Cells: EGG (1n) & POLAR BODY (2n) B. In the Anther: Microspores –> 2-nucleated gametophyte “POLLEN GRAIN” TUBE NUCLEUS – Builds the pollen tube GENERATIVE NUCLEUS – mitosis –> 2 sperm cells 6 IV. POLLINATION & FERTILIZATION EVENTS 1. Pollen delivered to stigma 2. Tube Nucleus begins to bore a Pollen Tube 3. Generative Nucleus follows behind the Tube Nucleus 4. Generative Nucleus mitosis –> 2 sperm cells 5. Tube Nucleus finds the micropyle and enters ovary 6. Sperm cells enter too! 7. One Sperm fertilizes the Egg 1n + 1n –> 2n ZYGOTE 8. Other Sperm fertilizes Polar Body 1n + 2n –> 3n ENDOSPERM 9. Ovule becomes a Seed V. THE FRUIT Fate of ovary is to swell and form a fruit that surrounds the seed. Some ovaries form the CORE of some fruits – Receptacle forms the "fruit" part (APPLE, PEAR) 1o function of a fruit –> Dispersal of the seed Some fruits taste good! But, not all fruits taste good! Burrs: strategy is to stick onto a passing animal Nuts & Acorns: strategy is to roll Some fruits never need to come off the sporophyte Jacaranda – wind dispersal of seed 7 Biology 120 Cerritos College PHOTOSYNTHESIS I. Introduction A. Energy Source THE NEED TO RESIST ENTROPY!!! 1. Chemiosynthetic Autotrophs At geothermal vents and in soil; bacteria that never see sunlight. Instead of (or in addition to) CO 2, they utilize inorganic compounds NH3 (ammonia), Fe (iron containing), & S (sulfur containing) 2. Photosynthetic Autotrophs – Able to trap and transform Sunlight Energy II. Photosynthesis Defined Trapping of solar E and its conversion to chemical ENERGY which is then used in manufacturing food molecules from CO2 and H2O. Solar E –> Chemical E –> Food E SUMMARY EQUATION OF P/S: LIGHT 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6H2O CHLOROPHYLL This is the fixation of CARBON (from CO2) into a form that living organisms can utilize We (and other organisms) can also use the O2! Aerobic Cellular Respiration – studied in future lecture And OZONE (O3) is made from O2 – Forms the “Ozone Layer” that protects cells from UV radiation III. The Mechanics A. P/S REQUIRES CARBON DIOXIDE Stomata – Avenue for obtaining CO2 and releasing O2 Most are located on underside of leaves Guard cells – cells of the leaf skin (epidermal cells) –The only epidermal cells w/ chloroplasts Bend like a banana when full of water (turgid) – Bending "creates" stoma between them If lose too much water they lose volume and lose their "bend" (become flaccid) Loss of turgidity –> closing off of the stoma B. Water is essential to P/S Water is brought to the leaves by xylem Water is conserved by the plant in various ways: Cutin Wax, Epidermal Hairs, Guard Cells C. Light is need for P/S Electromagnetic Spectrum: All Radiations Spectrum of Visible Light (white light) Gamma Rays X-rays UV <– violet blue green yellow orange red –> IR MW RADIO 380nm –- 500nm – 600nm – 760nm high E low E E = 1/wavelength Long wavelengths have lower E Short wavelengths have higher E 8 D. Pigments 1. Defined – Any substance (usually a protein) that absorbs light The color associated with a pigment though is due to the reflected wavelengths of white light 2. Excitation of Electron Absorption of light by pigments causes electrons of the pigment to get excited. Electron boosted to higher E level = Higher Potential E 3. Chlorophylls – Several kinds are recognized: a & b – most common Chlorophyll a is the major photosynthetic pigment Reflects (transmits) wavelengths of green & yellow Absorbs wavelengths of violet, blue, and red These wavelengths do P/S! AKA Absorption Spectrum of Chlorophyll Contains the Action Spectrum = Radiations Energies to do P/S! 4. Accessory Pigments Extend the range of light available for P/S by passing the energy absorbed (e -'s) to chlorophyll a Chlorophylls b, c, and d Carotenoids: red, orange, & yellow (Include the Carotenes and Xanthophylls) 5. Chloroplasts contain Chlorophyll Generalized anatomy of chloroplast: thylakoid, grana, stroma Photosystems: located along the THYLAKOID MEMBRANES Light-absorbing pigments are arranged in clusters called PHOTOSYSTEMS Plants utilize: Photosystem II (lower E, P680) and Photosystem I (higher E, P700) V. Non-cyclic Pathway of Photosynthesis 0f C3 Plants A. P/S is a 2 stage process Light-Dependent Rxns (Photochemical) B. Light-Dependent Rxns – Converts light energy to chemical energy Light-Independent Rxns (Enzymatic) (lo P.E.) ADP + Pi (hi P.E.) ATP H2O 1/2 O2 NADP+ (lo PE) NADPH (hi PE) Water splits in process called PHOTOLYSIS; releases e-'s & H+'s Electron transfers and H+'s make ATP and NADPH Generation of Oxygen Gas Occurs along the THYLAKOID MEMBRANE Photosystem II: Excited electrons are taken up and fed through an Electron Transport System. ETS – along thylakoid membrane, special membrane proteins and enzymes Energy released from the ETS takes ADP + P → ATP This is PHOTOPHOSPHORYLATION H+ are released and pool in the thylakoid compartment. Electrical and H concentration gradient created between compartment (high) and stroma (low). Used to phosphorylate the ADP to ATP out in the stroma CHEMIOSMOTIC THEORY: Proton gradient across membrane drives the formation of ATP The ETS electrons are delivered to Photosystem I 9 Photosystem I: Light E excites a P-I electron and it is picked up by another electron acceptor that passes it to a second ETS E released from ETS takes NADP+ + H+ (2e-) → NADPH Therefore, ultimate e- & H+ acceptor is NADP+ → NADPH Majority of ATP that are made go to the DARK RXN C. Light-Independent Rxns – AKA Dark Rxns The Calvin-Benson Cycle (FIXES CO2) (From Light Rxn) ATP ADP + Pi 6CO2 C6H12O6 + H2O NADPH NADP+ (From Light Rxn) Energy released is used to fix CO2 into molecules that will form Carbohydrates (glucose) Occurs in the STROMA 10 PHOTOSYNTHESIS Photosynthesis – The conversion of carbon dioxide and water by light energy (sun) into a food energy Occurs in the presence of chlorophyll. There is carbohydrate synthesis and O 2 gas is generated; an autotrophic process Summary equation: light energy 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H2O chlorophyll This process is a complex series of reactions that may be divided into 2 parts, the Light Reactions (Light-Dependent) and the Dark Reactions (Light-Independent). The Light-Dependent Reactions (AKA Light Rxns; AKA Hill Rxns) Sunlight energy is used to split water molecules and, thereby, release oxygen gas. (Photolysis) sunlight 12 H2O 6 O2 + 12 H+ + ATP MR. SUN visible light energy CHLOROPHYLL e(energized chlorophyll) H2O (photolysis) | O2 released into the atmosphere e- & H+ ADP + P (photophosphorylation) ATP (goes to Dark Rxn) + NADP (electron acceptor) NADPH (Nicotinamide Adenine Dinucleotide Phosphate) (goes to Dark Rxn) Summary of Light Reactions: 1. Absorption of light energy by chlorophyll pigment 2. Photolysis of water molecule – Oxygen gas released & NADPH generated 3. Photophosphorylation – light energy stored in ATP 4. Molecules of NADPH and (most of the) ATP go to the Dark Reaction 11 The Light-Independent Reactions – (AKA Dark Rxns, AKA Calvin Cycle) This is the process that converts CO2 from the atmosphere into the sugar glucose. This is called carbon-fixing; taking an "unusable" form of carbon and putting the carbon into a "usable" form! 6 CO2 + 24 H+ + ATP C6H12O6 + 6 H2O CO2 + RuBP Ribulose Biphosphate (CO2 acceptor in chloroplast) C6 sugar (splits) 2 PGA Phosphoglycerate (C3 compound) ATP from light energy -> rxn ADP NADPH from light H+ -> rxn NADP Phosphoglyceraldehyde used immediately by the cell or converted to: PGAL H2O -> released as a by-product C6H12O6 Glucose RuBP Summary of Dark Reactions: 1. Uptake of atmospheric CO2 2. Receive and use energy of NADPH and ATP from Light Rxn 3. Make PGAL –> Synthesis of the glucose ("carbon-fixing") and the regeneration of RuBP (now available for the next round of the Calvin Cycle) 12 KINGDOM PROTISTA CHARACTERISTIC KINGDOM PLANTAE Algae Bryophytes & Hepatophytes Pterophytes Gymnosperms Angiosperms no no no no yes Phototrophic Vascular Tissue Seeds Swimming Sperm Dominant Generation Sori Cones Flowers Major Divisions Major Classes Common Names 13 Biology 120 Cerritos College CELLULAR RESPIRATION I. External Respiration vs. Internal Respiration A. External Respiration The inhale/exhale cycle that brings in O2 and blows off CO2 Performed by most multicellular organisms A "whole" organism phenomenon B. Internal Respiration = Cellular Respiration Release of Energy from organic compounds via metabolic processes Performed by all living cells of all organisms A "cellular" phenomenon II. The Two Pathways of Cellular Respiration A. Anaerobic Respiration Performed in the absence of O2 Occurs in cytoplasm (anaerobic condition) Some bacteria can only take this pathway B. Aerobic Respiration Performed in presence of O2 Preferred path of most organisms – More Energy Efficient! If O2 supply is low or depleted Animals will utilize the anaerobic path. (but it is limited) III. Steps for Aerobic Respiration For eukaryotic organisms: Aerobic Pathway can be discussed as having 5 Major Events cytoplasmic 1. GLYCOLYSIS mitochondrial 2. 3. 4. 5. PREPARATORY/TRANSITION RXN KREB'S CYCLE ELECTRON TRANSPORT SYSTEM ATP GENERATION via CHEMIOSMOTIC THEORY IV. Summary Equation of Aerobic Pathway enzymes C6H12O6 + 6 O2 ENERGY 6 CO2 + 12 H2O + ENERGY = 36 ATP (skeletal muscle yield) (38 ATP [liver, kidney, heart muscle]) Know where/how the reactants are acquired – Know where the products appear along the pathway 14 V. Closer Look at Glycolysis A. Glycolysis = The Breaking of Sugar 2 ATP C6H12O6 (glucose) (GLUCOSE) 2 ADP + 2 Pi \_______/ \ 4 ATP 2 C3H4O3 \ (pyruvate) 2 NAD –> 2 NADH Taken to an ETS –> ATP Glycolysis Summary: 1. Anaerobic process – involves several enzymatic steps 2. Occurs in the cytoplasm (Compartmentalization) 3. Generation of 4 Substrate Level ATP (gross; net is 2 ATP) 2 ATPs are spent for glycolysis and 4 ATPs are made during glycolysis 4. Generation of 2 NADH – e- and H+ carrier 5. 2 molecules of PYRUVATE for each molecule of glucose VI. Closer Look at the Mitochondrial Reactions A. Mitochondrion General Anatomy: 1) OUTER MEMBRANE 2) INNER MEMBRANE: a. CHRISTAE – folds that greatly increase surface area b. ELECTRON TRANSPORT SYSTEM – NADH & FADH2 Series of embedded Cytochromes, Enzymes, & Coenzymes c. LOLLIPOPS – Channels containing ATP Synthetase 3) OUTER COMPARTMENT – High H+ gradient established 4) INNER COMPARTMENT (aka Matrix) – Prep Rxn & Kreb's Cycle B. Preparatory Rxn (aka Transition Rxn) 1. Pyruvate moves into the MATRIX of mitochondrion. And for each molecule of pyruvate: NAD+ NADH \_______/ C3H4O3 + Coenzyme A C2H3O-CoA (pyruvate) (acetyl-CoA) CO2 2. Enzymatic rxns takes PYRUVATE → ACETYL-CoA 3. DECARBOXYLATION occurs – Carbon Dioxide is released 4. REDUCTION of NAD+ to NADH NAD+ – Nicotinamide Dinucleotide; electron acceptor NADH carries electrons and a Hydrogen 15 C. Kreb's Cycle [Hans Krebs – 1930's] 1. Occurs in the MITOCHONDRIAL MATRIX (Kreb's Cycle aka Citric Acid Cycle) Starting Reaction: Acetyl-CoA + Oxaloacetate (2-C) (4-C) Citrate (Citric Acid) (6-C) 2. Decarboxylations occur (formation of CO2) 3. Substrate Level ATP is made (1/PYRUVATE; 2/GLUCOSE) 4. Electron Carriers are generated – NADH and FADH2 NAD – Nicotiamide Dinucleotide FAD – Flavin Adenine Dinucleotide D. Electron Transport System [aka Electron Transport Chain] 1. CRISTAE MEMBRANE of the mitochondrion 2. OXIDATIONS of NADH & FADH2 (to NAD+ & FAD) e- s are accepted – passed through the system H+ refused by ETS – H+ are moved to outer compartment to establish a high H + gradient 3. O2 is the final electron acceptor –> water E. Chemiosmotic Theory for Generation of ATP 1. H+s pool in the OUTER COMPARTMENT of mitochondrion 2. Sets up a concentration gradient across CHRISTAE membrane 3. PHOSPHORYLATIONS of ADP –> ATP in the MATRIX H+ flow through lollipop where the enzyme ATP Synthase is active This is called the CHEMIOSMOTIC THEORY of ATP generation F. Summary: ATP Produced by Aerobic Cellular Respiration GLYCOLYSIS PREPARATORY KREB'S CYCLE Substrate Level 2 ATP 0 ATP 2 ATP 4 ATP Respiratory ETS 2 NADH → 4 ATP 2 NADH → 6 ATP 6 NADH → 18 ATP 2 FADH2 → 4 ATP 32 ATP Therefore, 36 ATP/glucose VII. The Anaerobic Pathways Two Major Pathways: 1) Lactate Fermentation 2) Alcoholic Fermentation A. SHARED START – SHARED PROBLEM Both pathways follow GLYCOLYSIS: GLUCOSE –> 2 PYRUVATE All organisms must deal with the toxicity of Pyruvate B. Quick Look at Lactate Fermentation Performed by Animals and some Bacteria Commercial Benefits from lactic acid: __________________________________________________ Lactic Acid formation in Skeletal Muscles: A quick, but low yield of ATP 16 Leads to Muscle fatigue C. Closer Look at Lactate Fermentation: 2 ATP (net) GLUCOSE 2 PYRUVATE 2 LACTATE -----------------------/ \ / \ 2 NAD+ 2 NADH ---------> 2 NADH 2 NAD+ \______________________________/ THEREFORE: Net gain of ATP is only 2 molecules NADH is used to make pyruvate less toxic (will not make more ATP) D. Quick Look at Alcoholic Fermentation Performed by Yeast Cells (Kingdom Fungi) Commercial Benefits: _______________________________________________________________ _______________________________________________________________ E. Closer Look at Alcoholic Fermentation: 2 ATP (net) 2 H2O / \ GLUCOSE 2 PYRUVATE /-----------\ /-----------\ 2 EtOH + 2 CO2 2 NAD+ 2 NADH ------> 2 NADH 2 NAD+ \________________________________/ THEREFORE: Net gain of ATP is only 2 molecules NADH used to make pyruvate less toxic (will not make more ATP) VIII. Comparison of Aerobic and Anaerobic Pathways AEROBIC GLYCOLYSIS: PREP RXN: KREB'S & ETS: ANAEROBIC 1. Site is cytoplasm 2. 2 ATP/glucose 3. Waste product is pyruvate 1. Site is cytoplasm 2. 2 ATP/glucose 3. Waste products are organism dependent 1. Site is the Mitochondrion 2. 2 Acetyl Co-A/Pyruvate 3. NADH/Pyruvate 3. CO2 is a “waste product” 1. Site is the Mitochondrion 2. Substrate ATP = 2/glucose 3. Chemiosmotic ATP = 32/glucose 4. “Waste products” of CO2, H2O, & heat ________________________________________________ TOTAL ATP = 36 TOTAL ATP = 2 Another way to look at this: 36 ATP potential yield in Aerobic Respiration vs. 2 ATP potential yield in Anaerobic Respiration Therefore; 36 ATP / 2 ATP → 18 times more ATP from Aerobic Pathway than the Anaerobic Pathway 17 CELLULAR RESPIRATION PATHWAYS ANAEROBIC AEROBIC GLYCOLYSIS * GLUCOSE (C6H12O6) occurs in cytoplasm (PROTEINS) (amino acids) KREB'S CYCLE *** | oxaloacetate C4 (LIPIDS) (fatty acids & glycerol) | citrate C6 + C4 C5 moves into mitochondrion |_________________| if O2 present PYRUVATE (C3) ACETYL CoENZYME A (C2) PREP RXN ** CO2 ATP NADH FADH2 CoA CO2 e- donors O2 not present ELECTRON TRANSPORT + FERMENTATION NAD SYSTEM **** RXNS FAD+ H+ / eAnimals/Monerans: |_ A series of embedded proteins + + H2O 2 LACTATE (C3) H are not accepted by the |_ accept and pass the e-s to Yeasts: the ETS -- pool instead in |_ the final e- acceptor – O2. NET ATP = 2 |_ The e-s and H+ combine |_ with the O2 to form H2O. |_ Fermentations are the anaerobic means H+ H+ H + H + H + H + H + H + H + H + + + + + + + + + + + O2 –> H2O of dealing with the toxic pyruvate that forms H H H H H H H H H during glycolysis. CHEMIOSMOTIC THEORY OF H+ gradient used to drive the Total Net Energy Gain: ATP GENERATION formation of ATP in the matrix. Anaerobic Path = 2 ATP/Glucose ***** Catalyzed by ATPsynthase. (Produced during glycolysis alone) Aerobic Respiration is the aerobic means of dealing with the toxic pyruvate that forms during glycolysis. Summary of Fermentations: (balanced) C6H12O6 –> 2 C2H5OH + 2 CO2 (Yeast) Total Net Energy Gain: C6H12O6 –> 2 C3H6O3 (Animal & Bacteria) Aerobic Path = 36*ATP/Glucose in skeletal muscle cells. Includes the 2 from glycolysis, the remaining 34 are made in the mitochondrion. Five Steps for Aerobic Path: Glycolysis – cytoplasmic Summary of Aerobic Respiration: (balanced, "all" cells) Preparatory Rxn – mitochondrial C6H12O6 + 6 O2 -----> 6 CO2 + 6 H2O + 36 ATP Kreb's Cycle Rxns – mitochondrial with Electron Transport – mitochondrial O2 *Note: Some cells (heart muscle, kidney, & liver) can Chemiosmotic ATP – mitochondrial make 38 ATP/Glucose. (An extra NADH made) ETHYL ALCOHOL (C2) + CO2 the outer compartment. H+ H + H + H + H + H + H + H + H + NOTE: The NADH molecules produced during glycolysis and the preparatory reaction are not shown. 18