PLANT SCIENCE 184
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Transcript of PLANT SCIENCE 184
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint® Lecture Slides for Essential Biology, Second Edition & Essential Biology with Physiology
Neil Campbell, Jane Reece, and Eric Simon
Presentation prepared by Chris C. Romero
PLANT SCIENCE 184PLANT SCIENCE 184
Cellular Respiration: Harvesting Chemical Energy
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• Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese
• Both carbon monoxide and cyanide kill by disrupting cellular respiration
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• All the energy in all the food you eat can be traced back to sunlight
• If you exercise too hard, your muscles shut down from a lack of oxygen
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• When you exercise
BIOLOGY AND SOCIETY: FEELING THE “BURN”
– Muscles need energy in order to perform work
– Your cells use oxygen to release energy from the sugar glucose
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• Aerobic metabolism
– When enough oxygen reaches cells to support energy needs
• Anaerobic metabolism
– When the demand for oxygen outstrips the body’s ability to deliver it
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• Anaerobic metabolism
– Without enough oxygen, muscle cells break down glucose to produce lactic acid
– Lactic acid is associated with the “burn” associated with heavy exercise
– If too much lactic acid builds up, your muscles give out
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• Physical conditioning allows your body to adapt to increased activity
– The body can increase its ability to deliver oxygen to muscles
• Long-distance runners wait until the final sprint to exceed their aerobic capacity
Figure 6.1
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ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE
• Fuel molecules in food represent solar energy
– Energy stored in food can be traced back to the sun
• Animals depend on plants to convert solar energy to chemical energy
– This chemical energy is in the form of sugars and other organic molecules
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• Photosynthesis
Producers and Consumers
– Light energy from the sun powers a chemical process that makes organic molecules
– This process occurs in the leaves of terrestrial plants
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• Autotrophs
– “Self-feeders”
– Plants and other organisms that make all their own organic matter from inorganic nutrients
• Heterotrophs
– “Other-feeders”
– Humans and other animals that cannot make organic molecules from inorganic ones
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• Producers
– Biologists refer to plants and other autotrophs as the producers in an ecosystem
• Consumers
– Heterotrophs are consumers, because they eat plants or other animals
Figure 6.2
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• The ingredients for photosynthesis are carbon dioxide and water
– CO2 is obtained from the air by a plant’s leaves
– H2O is obtained from the damp soil by a plant’s roots
• Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules
– Oxygen gas is a by-product of photosynthesis
Chemical Cycling Between Photosynthesis and Cellular Respiration
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• Both plants and animals perform cellular respiration
– Cellular respiration is a chemical process that harvests energy from organic molecules
– Cellular respiration occurs in mitochondria
• The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis
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Figure 6.3
Sunlightenergy
Ecosystem
Photosynthesis(in chloroplasts)
Glucose
Oxygen
Carbon dioxide
Cellular respiration(in mitochondria)
Water
for cellular work
Heat energy
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• Cellular respiration
CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
– The main way that chemical energy is harvested from food and converted to ATP
– This is an aerobic process—it requires oxygen
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• Cellular respiration and breathing are closely related
– Cellular respiration requires a cell to exchange gases with its surroundings
– Breathing exchanges these gases between the blood and outside air
The Relationship Between Cellular Respiration and Breathing
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Figure 6.4
Breathing
Lungs
Musclecells
Cellularrespiration
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• A common fuel molecule for cellular respiration is glucose
– This is the overall equation for what happens to glucose during cellular respiration
The Overall Equation for Cellular Respiration
Unnumbered Figure 6.1
Glucose Oxygen Carbondioxide
Water Energy
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• During cellular respiration, hydrogen and its bonding electrons change partners
– Hydrogen and its electrons go from sugar to oxygen, forming water
The Role of Oxygen in Cellular Respiration
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• Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions
Redox Reactions
– Redox reactions for short
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• The loss of electrons during a redox reaction is called oxidation
• The acceptance of electrons during a redox reaction is called reduction
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Unnumbered Figure 6.2
[Oxygen gains electrons (and hydrogens)]
Oxidation[Glucose loses electrons (and hydrogens)]
Glucose Oxygen Carbondioxide
Water
Reduction
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•RS IS NECESSARY IN ALL LIVING CELLS.
•PLANTS ARE WELL KNOWN FOR PS, BUT THEY MUST ALSO REPIRE IN ORDER TO
SURVIVE.
• PS - OCCURS ONLY IN PLANT CELLS CONTAINING CHLOROPHYLL DURING THE DAYLIGHT HOURS.
•RS - OCCURS IN ALL OF A PLANT’S LIVING CELLS 24 -7.
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PLANTS NEED ENERGY TO PERFORM MANY ESSENTIAL FUNCTIONS OF LIFE:
GROWTH,
REPAIR,
NUTRIENT MOVEMENT,
REPRODUCTION, &
NUTRIENT TRANSPORT.
WHY IS RS NECESSARY?
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• Cellular respiration is an example of a metabolic pathway
– A series of chemical reactions in cells –building or degradation process
• All of the reactions involved in cellular respiration can be grouped into three main stages
– Glycolysis
– The Krebs cycle
– Electron transport
– * WHAT IS METABOLISM?
The *Metabolic Pathway of Cellular Respiration
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A Road Map for Cellular Respiration
Cytosol
Mitochondrion
High-energyelectronscarriedby NADH
High-energyelectrons carriedmainly byNADH
Glycolysis
Glucose2
Pyruvicacid
KrebsCycle
ElectronTransport
Figure 6.7
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Glycolysis
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• Glycolysis breaks a six-carbon glucose into two three-carbon molecules
– These molecules then donate high energy electrons to NAD+, forming NADH
• A molecule of glucose is split into two molecules of pyruvic acid
Stage 1: Glycolysis
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Figure 6.8
Glucose
2 Pyruvic acid
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Krebs Cycle
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Stage 2: The Krebs Cycle
• The Krebs cycle completes the breakdown of sugar
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• In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA
Figure 6.10
CoA
1
2
3Pyruvic
acid
Aceticacid
Coenzyme A
Acetyl-CoA(acetyl-coenzyme A)
CO2
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• The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2
– The cycle uses some of this energy to make ATP
– The cycle also forms NADH and FADH2
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Figure 6.11
Input
Acetic acid
ADP
3 NAD
FAD
KrebsCycle
Output
2 CO2
1 2
3
4
5
6
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Electron Transport
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Stage 3: Electron Transport
• Electron transport releases the energy your cells need to make the most of their ATP
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• The molecules of electron transport chains are built into the inner membranes of mitochondria
– The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane
– These ions store potential energy
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Figure 6.12
Proteincomplex
Electroncarrier
Innermitochondrialmembrane
Electronflow
Electron transport chain ATP synthase
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The Versatility of Cellular Respiration
• Cellular respiration can “burn” other kinds of molecules besides glucose
– Diverse types of carbohydrates
– Fats
– Proteins
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Figure 6.13
Food
Polysaccharides Fats Proteins
Sugars Glycerol Fatty acids Amino acids
Amino groups
Glycolysis Acetyl-CoA
KrebsCycle Electron
Transport
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Adding Up the ATP from Cellular Respiration
Figure 6.14
Cytosol
Mitochondrion
Glycolysis
Glucose2
Pyruvicacid
2Acetyl-
CoA
KrebsCycle Electron
Transport
bydirectsynthesis
by directsynthesis
byATPsynthase
Maximumper
glucose:
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FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
• Some of your cells can actually work for short periods without oxygen
– For example, muscle cells can produce ATP under anaerobic conditions
• Fermentation
– The anaerobic harvest of food energy
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• Human muscle cells can make ATP with and without oxygen
– They have enough ATP to support activities such as quick sprinting for about 5 seconds
– A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds
– To keep running, your muscles must generate ATP by the anaerobic process of fermentation
Fermentation in Human Muscle Cells
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• Glycolysis is the metabolic pathway that provides ATP during fermentation
– Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going
– In human muscle cells, lactic acid is a by-product
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Figure 6.15a
2 ADP+ 2
Glycolysis
Glucose
2 NAD
2 Pyruvicacid
+ 2 H
2 NAD
2 Lacticacid
(a) Lactic acid fermentation
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• Various types of microorganisms perform fermentation
– Yeast cells carry out a slightly different type of fermentation pathway
– This pathway produces CO2 and ethyl alcohol
Fermentation in Microorganisms
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Figure 6.15b
2 ADP+ 2
2 ATPGlycolysis
Glucose
2 NAD
2 Pyruvicacid
2 CO2 released
+ 2 H
2 NAD
2 Ethylalcohol
(b) Alcoholic fermentation
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• The food industry uses yeast to produce various food products
Figure 6.16
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• Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere
EVOLUTION CONNECTION:LIFE ON AN ANAEROBIC EARTH
– Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy
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SUMMARY OF KEY CONCEPTS
• Chemical Cycling Between Photosynthesis and Cellular Respiration
Visual Summary 6.1
Sunlight
Heat
PhotosynthesisCellular
respiration
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• The Overall Equation for Cellular Respiration
Visual Summary 6.2
Oxidation:Glucose loses electrons(and hydrogens)
Glucose Carbon dioxide
Electrons(and hydrogens) Energy
Oxygen
Reduction:Oxygen gainselectrons (andhydrogens)
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• The Metabolic Pathway of Cellular Respiration
Visual Summary 6.3
Glucose Oxygen Water Energy