03 bio+210+fq+2014+ch+5+metabolism
TRANSCRIPT
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Metabolism: broken down into two components:
(1) Catabolism: degrading or breaking down larger molecules
to smaller components and generates energy.
(2) Anabolism (biosynthesis): building larger molecules from
smaller ones. Anabolic reactions require energy and use
energy generated by catabolic reactions.
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Enzymes
Act as biological catalysts to increase the rate of a
reaction
only act with one or a few specific substrates
enzymes are not altered by the chemical reaction
they catalyze
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Chemical reactions require energy to break/form chemical
bonds
Enzymes do not add energy, they lower the energy of activationand allow the reaction to proceed more rapidly
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Environmental factors that affect the activity ofan enzyme:
Temperature, pH, and salt concentration
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Functional protein Denatured protein
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Allosteric Regulation
Regulates production of product (controlsmetabolic activity)
Regulatory molecule binds to allosteric site ofenzyme
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Feedback inhibition
A chemical pathway is shut down by buildup of a product that acts on allosteric site of
enzyme
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Scheme of metabolism:
Key pathways
Glycolysis
Tricarboxcylic acid cycle
Fermentation
Pathways are catabolic and provide
Energy
Reducing power
Precursor metabolites
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Role of Adenosine triphosphate (ATP):
it is chemical energy used by the cell to do work
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Acetyl-CoA
Pyruvic acid
(or derivative)
Formation of
fermentation
end-products
2 Pyruvic acid
GlucoseGL
YCOL
YSIS
Respiration Fermentation
KREBS
CYCLE
Electrons
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Substrate phosphorylation
Uses chemical energy to add a phosphate ion to a moleculeof ADP
Occurs in glycolysis and Krebs cycle
Oxidative phosphorylation
Uses energy from proton motive force to add a phosphateion to ADP
Photophosphorylation
Uses radiant energy from sun to phosphorylate ADP toATP
Occurs in photosynthesis
Where ATP is generated:
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Glycolysis (Embden-Myerhoff Pathway)
oxidizes one glucose to two pyruvate
Pathway generates
Two 3-C pyruvate molecules Net gain of two ATP
Two molecules of NADH (reducing power)
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Role of electron carriers:
Three different types of electron carriers NAD
+(Nicotinamide adenine dinucleotide)
FAD (Flavin adenine dinucleotide)
NADP+
(Nicotinamide adenine dinucleotide phosphate)
These listed above are all oxidized forms
Reduced forms represent reducing power (energy in bonds)
These listed below are all reduced forms
NADH
FADH2
NADPH
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Alternatives to Glycolysis
Yield fewer molecules of ATP than glycolysis
Two pathways:
Pentose phosphate pathway generates
net gain of two molecules of NADPH one molecule of ATP
Entner-Doudoroff pathway generates
net gain of two molecules of NADPH one molecule of ATP
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Transition step:
links Glycolysis to Tricarboxylic Acid Cycle
Modifies 3-C pyruvate from glycolysis toform acetyl-CoA
NAD+is reduced to NADH
This modification occurs twice for oneglucose
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Pyruvic acid
Decarboxylation
Acetate
Coenzyme A
Acetyl-coenzyme A
(acetyl-CoA)
Respiration Fermentation
Transition step:
links Glycolysis to
Tricarboxylic Acid
Cycle
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Tricarboxylic acid cycle (TCA)
uses pyruvate formed in glycolysis and pentosephosphate pathway (remember pyruvate is modified toform Acetyl-CoA)
cycle turns twice to complete oxidation of one glucosemolecule
T i b li
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Acetyl-CoA
Oxaloacetic acid
Malic acid
Fumaric acid
Succinic acid
Succinyl-CoA
-Ketoglutaric acid
Isocitric acid
KREBS
CYCLE
Citric acid
OOH
OOH
OOH
OOH
OOH
HOO
OOH
OOH
OOH
OOH
OOH
OOH
OOH
OOH
OOH
OOH
OOH
Tricarboxylic
Acid
Cycle
Substrate
phosphorylation
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Tricarboxylic Acid Cycle (also known as Krebs Cycle):
Completes the oxidation of glucose
Uses Acetyl-CoA (generated using pyruvate formed during
glycolysis)
Releases CO2
Cycle turns once for each Acetyl-CoA
Two turns for each glucose molecule
For each glucose molecule, the cycle generates
2 ATP 6 NADH
2 FADH2
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What happens to the molecules of
NADH and FADH2?
They are used in respiration through their
donation of electrons to the electrontransport chain for the generation of ATP
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Respiration in prokaryotes
Respiration is either aerobic or anaerobic
Oxygen acts as acceptor in aerobic respiration
Alternate acceptors used in anaerobic respiration
Uses NADH and FADH2to generate ATP through theprocess of oxidative phosphorylation:
uses electron transport chain
Generates proton motive force
uses ATP synthase with proton motive force to synthesize ATP
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FMN
NADH
from glycolysis,
Krebs cycle,
pentose phosphate
pathway, and
Entner-Doudoroff
pathway
FADH2
fromKrebs cycle
Ubiquinone
Cyt c2
Cyt b
Cyt c
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Cyt cCyt aCyt a3
ATP synthase
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ATP synthase:
Harvest energy from proton motive force to
phosphorylate ADP to ATP
One NADH produces 3 molecules ATP
One FADH2produces 2 molecules of ATP
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ATP from oxidative phosphorylation: (starting with 1 glucose
molecule)
Maximum theoretical yield = 34 ATP
From glycolysis
2 NADH 6 ATP
From conversion of pyruvate to acetyl coA (transition step)
2 NADH 6 ATP
From Krebs Cycle
6 NADH 18 ATP
2 FADH2 4 ATP
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ATP from cellular respiration: (starting with 1 glucose molecule)
Maximum theoretical yield = 38 ATP
From glycolysis
2 NADH 6 ATP
and 2 ATP (subs. phosphory.) From conversion of pyruvate to acetyl coA (transition step)
2 NADH 6 ATP
From Krebs Cycle
6 NADH 18 ATP
2 FADH2 4 ATP
and 2 ATP (sub. phosphory.)
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Respiration
Anaerobic respiration is less efficient
Oxygen does not act as terminal electron
acceptor
Alternate acceptors are used: e.g. nitrate, sulfate,carbonate
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Fermentation
Used by organisms that cannot respire
is a partial oxidation of glucose
ATP generated only in glycolysis
Recycles NADH (the NAD+
from fermentation feeds
back into glycolysis to form more NADH)
Fermentation pathways use pyruvate or derivative as
terminal electron acceptor
F t ti
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Pyruvic acid
Lactic acid Acetaldehyde
Ethanol
What are the terminal
electron acceptors used in:
-Lactic acid fermentation?
-Ethanol fermentation ?
Fermentation
Glucose
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Glucose
Pyruvic acid
Swiss cheeseCheddar cheese,
yogurt, soy sauce Wine, beer
Nail polish
remover,
rubbingalcohol
Propionibacter ium
Aspergi l lus
Lactobaci l lus
Streptococcus
Saccharomyces
Clostr id ium
Fermentation
examples
Ph t th i
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Photosynthesis
Use sunlight energy to power synthesis of
organic compounds from CO2
Photosynthesis has two distinct stages
Light dependent reactions
Converts light energy to chemical energy
Light independent reactions Uses energy from light reactions to
produce organic compounds
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Photosynthetic organisms have light capturing pigments
Chlorophyll plants, algae and cyanobacteria
Bacteriochlorophylls
purple and green photosynthetic bacteria
Accessory pigments:carotenoids and phycobilins carotenoids found in eukaryotes and prokaryotes
phycobilins found only in cyanobacteria
Photosynthesis
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Phototrophs: organisms that harvest the energy of
sunlight to power synthesis of organic compounds.
Chemoorganotrophs: organisms that obtain energy by
degrading organic compounds.
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Chemolithotrophs
Chemolithotrophs: organisms that use reducedinorganicchemicals as source of energy
Organisms fall into four groups
Hydrogen bacteria
Oxidize hydrogen gas
Sulfur bacteria
Oxidize hydrogen sulfide
Iron bacteria
Oxidize reduced iron
Nitrifying bacteria
Two groups
One oxidizes ammonia to nitrite
One oxidizes nitrite to nitrate