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Chapter 8 and 9 (Cellular Respiration and Fermentation (Catabolic pathways…
Chapter 8 and 9
Cellular Respiration and Fermentation
Catabolic pathways yield energy by oxidizing organic fuels
catabolic pathways and production of ATP
compounds participating in exergonic reactions act as fuels
cellular respiration
uses both aerobic and anaerobic respiration
anaerobic respiration
the most efficient catabolic pathway
is where oxygen is consumed as a reactant along with organic fuel
aerobic respiration
oxygen is not present along with organic fuel
an example of this is
fermentation
which is the partial degradation of sugars that occur without oxygen
similar to combustion of gasoline in an engine after oxygen is fixed with fuel
the stages of cellular respiration
cumulative of three metabolic stages
pyruvate oxidation and citric acid cycle
pyruvate enters the mitochondria and oxidizes into acetyl CoA
which enters the citric cycle
the critic acid cycle
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oxidative phosphorylation: electron transport and chemiosmosis
where the electron transport chain accepts electrons from NADH or FADH2
and passes these electrons down the chain
the energy is released at each step of the chain is stored in a form the mitochondria can use to make ATP from ADP
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inner membrane of mitochondria is the site of electron transport and another process called chemiosmosis
produces oxidative phosphorylation
glycolysis
produces the starting material for the citric acid cycle
begins with degradation process by breaking glucose into two molecules of a compound
which is called pyruvate
redox reactions
the principle of redox
oxidation-reduction reactions, or redox reactions
the transfer of one or more electrons from one reaction to another
redox reactions
reduction
the addition of electrons
oxidation
the loss of electrons
oxidizing agent
accepts electron
reducing agent
electron donor
oxidation of organic fuel molecules during cellular respiration
combustion of gasoline and methane
fuel (glucose) is oxidized
and oxygen is reduced
electrons lose potential energy
and energy is released
stepwise energy harvest via NAD and the electron transport chain
if energy is released all at once
it cannot be harnessed efficiently for constructive work
then the cellular respiration cannot oxidize glucose in a single step
instead its broken in a series of steps
catalyze by an enzyme
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electron transport chain
consist of a number of molecules
built into the inner membrane of the mitochondria of eukaryotic cells
higher energy
are when electrons are removed from glucose shuttled by NAH
lower energy
O2 captures these electrons along with hydrogen nuclei (H+) forming water
glycolysis harvest chemical energy by oxidizing glucose to pyruvate
glycolysis means sugar-splitting
which is broken down into three-carbon sugars
those smaller sugars are oxidized
and rearranged to form two pyruvate
can be divide into two parts
energy investment
the cell spends ATP
then is repaid with interest during energy payoff phase
energy pay-off
ATP produced by substrate-level phosphorylation
and NAD+ is reduced by NADH
citric acid cycle
oxidative phophorylation
Metabolism
is the totality of chemical reactions within an organism
it transform matter and energy
metabolic pathways
is how a cell's metabolism is organized
it begins with a specific molecule
then is altered in a series of defined steps
which results in a certain product
each pathway is catalyzed by a specific enzyme
types of pathways
catabolic
is a degradative pathway
where energy is released by complex molecules breaking down to simpler compounds
example
would be cellular respiration
which breaks down glucose in the presence of oxygen
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anabolic
also known as biosynthetic pathways
consumes energy to build complicated molecules
for example
synthesis of amino acids from simpler molecules
then the synthesis of protein from amino acids
catabolic and anabolic
starts with catabolic pathways
by releasing energy from downhill reactions
which is stored
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bioenergetics
the study of how energy flows within organisms
energy
is the capacity to cause change
by rearranging a collection of matter
exists in various forms
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sub-branches of the study of energy
laws of energy transformation
study of energy transformations in a collection of matter
is thermodynamics
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Enzymes speed up metabolic reactions
ATP powers cellular work by coupling exergonic and endergonic reactions
ATP
contains sugar ribosome with nitrogenous base adenine and a chain of three phosphate groups
makes RNA
plays a role in energy coupling
energy coupling
use of exergonic process to drive an endergonic one
hydrolysis
is where phosphate groups of ATP is broken with the presence of H2O
occurs under cellular conditions
it releases energy
which comes from
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performs work
the released free energy heats its surroundings
generation of heat could be beneficial
it alone could be inefficient as a valuable energy resource
instead the free energy
is harnessed by the cell's proteins to perform cellular work
transport and mechanical
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chemical
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regeneration of ATP
ATP is used continuously by an organism
which is a renewable resource
that can be regeneration with the addition of ADP
the shuttling of inorganic phosphate and energy is the ATP cycle
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free energy charge of a reaction
free-energy change ΔG
Gibbs free energy of a system
without consideration of surroundings
free energy
the portion of a system's energy that can perform work
when temperature and pressure are uniform throughout the system
a measure of a system's instability
can be calculated
ΔG = ΔH – T ΔS
ΔH is change in system's enthalpy (total energy)
ΔS is change in system's entropy
T is temperature in Kelvins
positive ΔG
are non-spontaneous
negative ΔG
are spontaneous
ΔH needs to be negative (system gives up enthalpy and H decrease)
or T ΔS is positive
where system gives up order and S increases
also represents difference between final free energy and initial free energy
ΔG = G(final state) – G(initial state)
ΔG
stable
when there's less energy (lower G)
which ΔG is only negative
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unstable
higher G
standard for spontaneity
free energy and metabolism
exergonic and endergonic reactions in metabolism
endergonic reactions
energy inward
absorbs free energy from surrounding energy
stores free energy in molecules (G increases) / ΔG is positive
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exergonic reactions
energy outward
proceeds with a net release of free energy
chemical mixture loses free energy (G decreases)
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magnitude for ΔG
represents the maximum amount of work the reaction can perform
the greater the decrease in free energy
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equilibrium and metabolism
chemical reactions of metabolism are reversible
and reached equilibrium when occurring in isolation
and cannot do any work
metabolism as a whole cannot be at equilibrium
Regulation of enzyme activity
