Upload
wil7ver
View
180
Download
4
Embed Size (px)
Citation preview
Ch 9: Cellular Respiration and Fermentation Overview: Life is Work Key Concepts C 9.1: Catabolic pathways yield energy by oxidizing organic fuels Redox Reactions: Oxidation and Reduction
Livening cells require energy from outside sources Animals…
-by eating plants (herbivore, primary consumers) and break down for energy -by eating animals that eat plants (carnivores, secondary consumers) for energy
Plants - absorb solar energy and make carbohydrates that provide energy
9.1: Catabolic pathways yield energy by oxidizing organic fuels 9.2: Glycolysis is harvest chemical energy by oxidizing glucose 9.3: after pyruvate is oxidized, the citric acid cycle completes the energy-yielding
oxidation of organic molecules 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP
synthesis 9.5: Fermentation and aerobic respiration enable cells to produce ATP without use of O2 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways Energy enters ecosystem as sunlight and leaves as heat Photosynthesis generate O2 and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to regenerate ATP, which powers
work Several processes are central to cellular respiration and related pathways. Catabolic pathways and production of ATP: Breakdown of organic molecules is exorgonic Fermentation is a partial degradation of sugars that occur without O2
Aerobic respiration consumes organic molecules and oxygen and yields ATP Anaerobic respiration is similar to aerobic respiration, but uses compounds other than O2 Cellular respiration includes both aerobic and anaerobic respiration but often referred as
aerobic respiration Although cells use carbs,fats,and proteins as fuel, its helpful to see it with sugar (glucose)
C6H12O6 + 6O2 -> 6CO2 + 6 H2O + Energy (ATP + heat) Transfer of electrons during chem. reaction releases energy stored in organic molecules This released energy is used to synthesize ATP Principle of Redox
- chem. rxn that transfer electrons between reactants are called oxidative-reduction rxn, or redox reaction -in oxidation, a substance loses electrons, or is oxidized -in reduction, a substance gains electron, or is reduced (positive charge is reduced)
Electron donor is the reducing agent Electron receptor is the oxidizing agent An electron loses potential energy when shifts from less electronegative atom to a more
electronegative atom Redox reaction moves electron closer to O2,
therefore releases chem. energy for work Some redox rxn don’t transfer electrons but
change electron sharing in covalent bond Example is reaction b/w methane and O2
Oxidation of Organic fuel molecules during cellular respiration Stepwise Energy Harvest via NAD+ and the electron transport chain Stages of Cellular Respiration: C 9.2: Glycolysis harvest chem. energy by oxidizing glucose to pyruvate C 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy- yielding oxidation
During cellular respiration, the fuel (like glucose) is oxidized and O2 is reduced In cellular respiration, glucose and other organic molecules are broken down in a series of
steps Electrons from organic compound are fist transferred to NAD+, a coenzyme As electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration Each NADH (reduced form of NAD+) represents stored energy that is tapped to
synthesize ATP NADH passes electron to electron transport chain Unlike an uncontrolled reaction, electron transports chain passes electrons is series of
steps instead of one explosive reaction
O2 pulls electron down the chain in the energy yielding tumble Energy yielded is use to regenerate ATP Harvesting energy from glucose has three stages
1) Glycolysis (breaks down glucose into two molecules of pyruvate)
2) Citric acid cycle (completes the breakdown of glucose to CO2)
3) Oxidative phosphorylation (accounts for most of the ATP synthesis)
Most ATP is formed by oxidative phosphorylation and little bit by substrate level phosphorylation
Each glucose degrade by CO2 and water by respirations, cell makes 32 molecule of ATP Glycolysis (“splitting of sugar””) breaks glucose down to two molecules of pyruvate Glycolysis occurs in cytoplasm and has two major phases - energy investment phase - energy payoff phase glycolysis occurs whether of not O2 is present In presence of O2 pyruvate enters the mitochondria
(eukaryote) where oxidation of glucose is complete
before citric cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA) which links glycolysis to citric acid cycle
citric acid cycle takes place within mitochondrial matrix cycle oxidizes organic fuel derive from pyruvate, generating 1 ATP, 3 NADH, and 1
FADH2 per turn
C 9.4: During oxidative phosphorilation, chemiosmosis couples electron transport to ATP synthesis Chemiosmosis: the energy coupling mechanism Accounting of ATP by cellular respiration C 9.5: Fermenation and anaerobic respiration enable cells to produce ATP without oxygen Types of fermentation
also called Krebs Cycle or the Tricarboxcylic Acid (TCA) cycle
following glycolysis and the citric acid cycle, NADH and FADH2 account for most of energy extracted from food
these two electron carries donate electron to electron transport chain, which powers ATP synthesis via oxidative phosphorilation
electron transport chain is in the cristae of the mitochondrion most of chain's proteins, which exist in multiproteins complexes carries alternate reduced and oxidized states as they accept and donate electrons electrons drop in free energy as they go down the chain and are finally passed to O2
forming H2O electron transport chain generates no ATP electron transfer in electron transport chain causes proteins to pump H+ from
mitochondrial matrix to intermembrane space H+ moves back across membrane, passing through the proton, ATP synthase ATP synthase uses exergonic flow of H+ to drive phosphorylation of ATP Example of cehmiosmosie, use of energy in H+ gradient to drive cellular work During respiration, energy flows like this: Glucose -> NADH -> electron transport chain -> ptotn-motive force -> ATP 34% of energy in glucose molecule is trnasfoerred to ATP durein cellular respiration,
making ~32 ATP Most cellular respiration requires O2 for ATP, when none glycolysis couples with
fermentation or anaerobic respiration to make ATP Anaerobic respiration- uses electron transport chain with final electron acceptor other
than O2 Fermentation- uses substrate-level phosphorylation instead of an electron transport chain
to make ATP Fermentation of glycolysis plus rcn that generate NAD+, which reused by glycolysis Two common types are:
- alcohol fementation, pyruvate is converted to ethanol in 2 steps, with the first releasing CO2 (yeasiti n brewing, winemaking, and baking) - lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of O2 (fungi and bacteria is use to make cheese and yogurt,
Comparing fermentation with anaerobic and aerobic respiration Evolutionary significance of glycolysis C 9.6: The versatility of catabolism Biosynthesis (anabolic pathways) Regulation of cellular respiration via feedback mechanisms You should now be able to:
cheese and yogurt, muscle dells use lactic fermentation to generate ATP when O2 scarce)
All glycolysis (net ATP = 2) to oxidize glucose and harvest chem. energy of food
In all three, NAD+ is oxidizing agent that accepts electrons during glycolysis
Process have diff final electron acceptors -O2 in cell respiration -an organic molecule (such as pyruvate or acetaldehdyde) in fermentation -cellular respiration produce 32 ATP per glucoses; fermentation produces 2 ATP per
Obligate anaerobes carry out fermentation or anaerobi respiration and cant survive in presence of O2
Facultative anaerobes (yeast and nay bacteria) can survive using either fermentation of cellular respiration
In facultative anaerobes, pyruvate is a fork in metabolic rode that leads to 2 alt. routes Ancient prokaryotes is thought to believed that only use glycolysis back
when little O2 existed Glycolysis is a very ancient process Catabolic pathways funnel electrons from many kinds of
organic mol into cellular resp. Glycolysis accepts with range of carbohydrates Proteins must be digested to amino acids; amino groups can feed
glycolysis or citric acid cycle Fats digested to glycerol (used in glycolysis) and fatty acids (used
to create acetyl CoA) Fatty acids broken down by beta oxidation and yield acetyl
CoA Oxidative gram of fat produces more than twice as much ATP as
oxidized gram or carbohydrate Body uses small molecules to build other substances Them small molecules may come directly from food, from
glycolysis, of from citric acid cycle Feedback inhibition is most common mechanism for control If ATP concentration drops, respiration speeds up; when plenty of ATP respiration slows Control of catabolism is based mainly on regulating activity of enzymes at points along
catabolic pathways 1.Explain in general terms how redox reactions are involved in energy exchanges 2.Name the three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result 3.In general terms, explain the role of the electron transport chain in cellular respiration 4.Explain where and how the respiratory electron transport chain creates a proton gradient 5.Distinguish between fermentation and anaerobic respiration 6.Distinguish between obligate and facultative anaerobes