nutrition = how an organism obtains –energy and –a carbon source to build the organic molecules...
TRANSCRIPT
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• Nutrition = how an organism obtains– energy and
– a carbon source to build the organic molecules of cells.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Metabolism & energetics
• Metabolism – sum total of all chemical reactions occurring in living organisms.– Anabolic pathways – synthesize compounds, generally
endergonic.– Catabolic pathways – break down compounds, usually
exergonic.• Many reactions also involve conversion of energy
from one form to another. • Energy can exist as potential energy or kinetic
energy.
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There are many kinds of energy that can interconvert from one form to another.
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1. How does a cell maintain & regulate its metabolism?
2. How does a cell garner & utilize energy?
3. From where does this energy come?
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Organisms within the biosphere exchange molecules and energy
1st Law of Thermodynamics:In any process, the total energy of the universe remains constant.In any process, the total energy of the universe remains constant.
(e.g. some bacteria, animals, humanshumans)
complex carbon, glucose, amino acids
CO2, H2O
Autotrophs:Phototrophs
& chemotrophsHeterotrophs
Chemical oxidations(via iron & sulfur
bacteria)
Light (via Light (via plantsplants))
Need 9 amino acids & 15 vitamins from
outside sources
Energy of sunlight
Useful chemical bond energy
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• Ways to obtain energy:– phototrophs use light energy
– chemotrophs get energy from chemicals.
• Ways to obtain Carbon– autotrophs only need only CO2 (inorganic C)
– Heterotrophs need organic carbon sources
• How do we get energy and carbon?
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Several ways to generate energy!
All organisms
Chemotrophs (use chemical compounds as
10 energy source)
Phototrophs
(use light as 10 energy source)
Chemolithotrophs
(use inorganic chem)Chemoorganotrophs
(use organic chem)
Includes: Animals, bacteria, fungi Includes: plants,
bacteria
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Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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pp. 375
What is the main role for enzymes?MetabolismMetabolism
1) All biochemical reactions are integrated. 3) Energetics
and the reactions in the pathways are
important.2) All living organisms
have similar metabolic pathways.
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The Tokyo subway system is much like cellular metabolism.
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Food molecules: complex carbohydrates, etc.
Adapted from Molecular Biology of the Cell, 4th ed.
Building blocks for biosynthesis: sugars, amino acids, etc.
Useful forms Useful forms of energyof energy
Catabolic Catabolic pathwayspathways
Anabolic Anabolic (biosynthetic) (biosynthetic)
pathwayspathways
Molecules that form the cell: lipids, proteins, etc.
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How are catabolism and anabolism coupled?
Heterotrophic metabolism: Interconversion of material and energy
CatabolismCatabolism (breakdown):Yields energy,
precursors
AnabolismAnabolism (synthesis):
Requires energy, precursors
coupledcoupled
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pp. 381
ATPATP couples energy between catabolism and anabolism
catabolismcatabolism
anabolismanabolism
ADPATP + Pi
Energy from food (fuel molecules) or from
photosynthesis
Energy available for work & chemical synthesis (e.g.
movement, signal amplification, etc.
ATPATP is the principal carrier of chemical energy in the cell!
Major activities promoted by ATP:
-locomotion-membrane transport-signal transduction-keeping materials
in the cell-nucleotide synthesis
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ATP: the universal currency of free energy;“high energy” phosphate compound
ATP + H2O ADP Pi H+ Go’ = -7.3 kcal/mol+ +
Go’ = -7.3 kcal/molPi H+ADP H2O+ + +AMP
(G in cells = -12 kcal/mol)
ATP
ADPMolecular Biology of the Cell, 3rd ed. Fig. 2-28
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pp. 380
Why ATP? It’s not the highest energy compound… It (and other nucleotide triphosphates) are stable
& the high free energy of hydrolysis
ATP is an intermediate “high energy” compound
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Another source of energy is the coupling of Oxidation & Reduction reactions
anabolismanabolism
catabolismcatabolismReduced fuel
Reduced Products
Oxidized Fuel
Oxidized Precursors
NADH(reduced)NAD+(oxidized)
“LEO the lion goes GER.”
Losing Electrons (is) Oxidation … Gaining Electrons (is) Reduction.
NADNAD++ (and NADP (and NADP++) carry high-energy electrons and hydrogen atoms.) carry high-energy electrons and hydrogen atoms.
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Nicotinamide adenine dinucleotide
(PO4) NADP+ NADPHpp. 383
H: (hydride ion)
NAD+(oxidized) NADH(reduced)
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Summary
1. Metabolism consists of many coupled & connecting reactions
• • Major source of energy = oxidation of carbon fuels• • ATP = major carrier of energy
2. Few kinds of reactions; many recurring themes3. Two major activated carrier molecules couple
catabolism/anabolism reactions:• ATP/ADP couples energy (through hydrolysis)• NAD+/NADH couples oxidation/reduction (by carrying
electrons & hydrogen atom)
pg. 373
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
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Respiration
• The 3 types of bacterial respiration– Aerobic - require oxygen for their growth and existence
– Anaerobic – do not require oxygen for any respiration
– Anaerobes - prefer growing in the presence of oxygen, but can continue to grow without it
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Catabolism - Respiration, fermentation
Respiration:
• Glycolysis
• Krebs/Tricarboxylic acid (TCA) Cycle
• Electron transport chain & oxidative phosphorylation
Fermentation:– Glycolysis followed by
NAD+ regeneration reactions.
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
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Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Cellular Metabolism
Adapted from MBOC4, fig. 2-70 & pp. 383
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Glucose catabolismcatabolismO
O
O
O
OO
glucose (a sugar)
C6H12O6 +O
O
6 CO2Carbon dioxide
OHH
6 H2Owater
3 stages involved:1) Glycolysis
2) TCA (citric acid) cycle3) Electron transport/oxidative phosphorylation
–Food = electron donor–Oxygen = terminal electron acceptor
oxidation reduction G= -686 kcal/molExergonic rxn
+ 6O2
(requires O2)
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Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Regulation of Energy Metabolism
Adapted from MBOC4, fig. 2-70 & pp. 383
glycolysis
TCA cycle
electron transport &ox. phosphorylation
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Glucose catabolismcatabolism
Go’ = -686 kcal/mol
O
O
O
O
OO
glucose (a sugar)
C6H12O6 (requires O2)+
O
O
6 CO2Carbon dioxide
OHH
6 H2Owater
3 stages involved:1) Glycolysis
2) TCA (citric acid) cycle3) Electron transport/oxidative phosphorylation
glucose lactate (muscle)ethanol (yeast)
no O2 requiredGlycolysis:Glycolysis:
What organisms use glycolysis?1. Anaerobes (grow without O2)2. Facultative organisms (grow with & without O2)3. Aerobes (grow only with O2)
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
GlycolysisGlycolysis
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Glycolysis
• Splitting of glucose: yield of 2 pyruvate molecules from one glucose molecule. (Also H2O.)
• ATP invested in early steps, energy generated in later steps. Net energy yield: 2 ATP, 2 NADH + 2 H+.
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
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Krebs Cycle• Transition step required after pyruvate enters
mitochondrion; pyruvate converted to Acetyl CoA. (NAD+ reduced to NADH during this process.)
• Krebs cycle doesn’t directly need oxygen, but won’t occur without it.
• Krebs cycle involves decarboxylation, oxidation to generate NADH, FADH2, ATP. CO2 is byproduct of these steps.
• NADH, FADH2 will relay electrons to electron transport chain.
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
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Electron transport system• Electron transport chain and oxidative
phosphorylation produce ATP from products of glycolysis, Krebs.
• Electron transport chain = protein complexes with prosthetic groups in/on inner mitochondrial membrane. (Some groups are able to move! E.g. Cyt C)
• ETC facilitates series of redox reactions, with oxygen as final electron acceptor.
• ATP formation uses proton motive force - voltage across membrane (ion gradient) that results from high [H+] in intermembrane space.
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Redox reactions• Many energy transfers involve transfer of
electrons (or hydrogen atoms).• Oxidation and reduction occur together.
– Loss of electrons from one substance = oxidation.
– Addition of electrons to a substance = reduction.
– Oxidizing agent - accepts electrons.
– Reducing agent - gives up electrons.
E.g. Na + Cl -> Na+ + Cl-
oxidation reduction
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Electron transport chain - series of redox reactions
• Cells release energy in stages.
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Electron transport system
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Development of Proton Motive Force from Chemiosmosis
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Formation of ATP from Proton Motive Force and ATP Synthase
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ATP Production during Aerobic Respiration by Oxidative Phosphorylation involving Electron
Transport System and Chemiosmosis
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Bacterial electron transport
ASM digital image collection:
http://www.asmusa.org
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Bacterial chemiosmotic ATP generation
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Cellular Metabolism
Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Adapted from MBOC4, fig. 2-70 & pp. 383
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Part 1:Breakdown of large macromolecules to
simple subunits
Part 2:Breakdown of
simple subunits to acetyl CoA
accompanied by production of
limited amounts of ATP and NADH
Part 3:Complete oxidation
of acetyl CoA to H2O and CO2
accompanied by production of large amounts of NADH
and ATP in mitochondrion
fats
fatty acids and glycerol
polysaccharides
simple sugars
proteins
amino acids
Acetyl CoA
glucose
Citric acid cycle
CoA
2 CO2
8 e- (Reducing power as NADH)
oxidative phosphorylatio
n
O2
H2O
ATPATP
glyc
olys
is
pyruvate
ATPATP
NADH
Cellular Metabolism
Adapted from MBOC4, fig. 2-70 & pp. 383
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Fermented … food?• Yogourt
– Fermented milk, fermentation carried out by lactic acid bacteria.
• Bread– Simple fermentation of sugar to alchohol and CO2 by
bread yeast Saccharomyces cerevisiae. CO2 makes bread rise.
• Kimchee– Cabbage and other veggies fermented by lactic acid
bacteria.
• Even some meat & fish products!– E.g. Country-cured ham, Katsuobushi (tuna)
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Unusual catabolism• Badger Ammunitions Plant - 1942-1976 -
provided weapons for the military and handled large quantities of explosive nitroglycerin (NG).
CONTAMINATION!!!!!
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How can we clean the NG up?
• Organisms capable of degrading NG?– Microorganisms: e.g. Pseudomonas
fluorescens, Pseudomonas putida
Pseudomonads only convert NG to mononitroglycerin (MNG). Other microbes in soil degrade MNG to glycerol. Glycerol can be converted to glyceraldehyde-3-phosphate and further metabolized.
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Amazing enzyme• P. fluorescens & P.
putida use single enzyme: xenobiotic reductase.
• Nonspecific enzyme, recognizes many molecules carrying nitro group (like trinitrotoluene: TNT).
Many bacteria important in bioremediation!
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Two nutritional modes are unique to prokaryotes
• Chemoautotrophs– use CO2 as a carbon source, but they obtain energy by
oxidizing inorganic substances,
– Inorganic energy sources = hydrogen sulfide (H2S), ammonia (NH3), and ferrous ions (Fe2+).
– E.g. Nitrobacter - key in N-cycle converts ammonia (NH4) to nitrate (NO3)
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• Photoheterotrophs – use light to generate ATP but obtain their carbon in organic
form.
– This mode is restricted to prokaryotes.
– E.g. purple bacteria - make salt flats purple & red
– E.g. green bacteria
– Where does “red herring” come from?• dead herring have salt coating: halophiles grow on salt (red color;
smelly); dragged around by animal rights activists to stop fox hunts
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Carbon cycle
• The majority of known prokaryotes are chemoheterotrophs.– parasites, which absorb nutrients from the body fluids
of living hosts.
– saprobes, decomposers that absorb nutrients from dead organisms,
• Almost any organic molecule is food for one of the many chemoheterotrophic bacteria (like oil)
• If it can’t be broken down by bacteria its called nonbiodegradable.
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Nitrogen Cycle
– Eukaryotes can only use organic nitrogen, NO3 or NH4.
– Diverse prokaryotes can metabolize most nitrogenous compounds.
• Prokaryotes are essential to converting N into usable forms for eukaryotes
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• Prokaryotes are responsible for the key steps in the cycling of nitrogen through ecosystems.– Some chemoautotrophic bacteria convert ammonium
(NH4+) to nitrite (NO2
-).
– Others “denitrify” nitrite or nitrate (NO3-) to N2, returning
N2 gas to the atmosphere.
– A diverse group of prokaryotes, including cyanobacteria, can use atmospheric N2 directly.
– During nitrogen fixation, they convert N2 to NH4+, making
atmospheric nitrogen available to other organisms for incorporation into organic molecules.
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• Cyanobacteria fix N and C (photosynthesis) – = most self-sufficient of all organisms.
– Only need: light, CO2, N2, water and some minerals to grow.
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Fig. 27.11
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• Cyanobacteria thought to put 02 in atmosphere.– = Massive change in the world
• Great for aerobes (who require O2)
• Deadly for anerobes (who are poisoned by o2)– Forced to live in remaining anerobic environments
– Prokaryotes can be facultative or obligate aerobes or anerobes• Eukaryotes are all aerobic
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• First prokaryotes were probably heterotrophs– Ate the primordial soup of early earth
• But photosynthesis (harnessing the sun) shows up early in the fossil record)
2. Photosynthesis evolved early in prokaryotic life
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• Similarity in complex machinery suggests photosynthesis evolved once.– = most parsimonious hypothesis,
– Thus:heterotrophic groups represent a loss of photosynthetic ability during evolution.
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