Download Cellular Respiration

Cellular
Respiration
Energy
Flow
• photosynthesis
– carried out by plants
• uses energy from
sunlight
• converts into glucose &
oxygen
• used in cellular
respiration
• oxygen is consumed
• glucose is broken
down CO2 & H2O
Respiration
• means breathing
• cellular respiration
– exchange of gases
• O2 from environment
is used & CO2 is
released & removed
by blood
Cellular Respiration
• provides ATP for cellular work
• called oxidation
• oxidizes food molecules, like
glucose, to CO2 & water
• 6C6H12O2 + 6O2   6CO2 +
6H2O + ATP
• energy is trapped in ATP
Cellular Respiration-Oxidation
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electrons are transferred from sugar to
O2 making H2O
6C6H12O2 + 6O2   6CO2 + 6H2O + ATP
do not see electron transfer in equation
see changes in H ions
glucose molecule loses hydrogen
atoms as it is converted to CO2
O2 gains hydrogen atoms to form water
O2 is an electron grabber
– pulls harder than other atoms to get
electrons
these hydrogen movements represent
electron transfers
each hydrogen atom consists of one
electron and one proton
electrons move along with hydrogens
from glucose to O2
it is as if they are falling
energy is released in the process
process is possible only because of O2
if you stop breathingno ATP would be
madeall processes stopdeath
Complete Oxidation of Glucose
• C6H12O6 + 6O2 6CO2 + 6H2O
• for one thing to be oxidized-another must
be reduced
• oxidation & reduction reactions occur
together
• redox reactions
Oxidation/Reduction Reactions
• Oxidation
– H+ atoms are removed from
compounds
• Oxidized things lose electrons
• electron lostoxidized-loses
energy
• Reduction
– H+ atoms are added to
compounds
• gain electronreduced-gains
energy
• food fuels are oxidized-lose
energy transferred to other
moleculesATP
• coenzymes act as hydrogen or
electron acceptors
– reduced each time substrate
is oxidized
CoEnzymes
• NAD+-niacin-nicotinamide adenine dinucleotide
• FAD-flavin adenine dinucleotide-riboflavin
Glucose Oxidation Steps
• Glycolysis
– occurs in cytosol
– does not require oxygen
– also called anaerobic
• Kreb’s Cycle
– occurs in mitochondria
– require O2
– aerobic
• Electron Transport Chain
– occurs in mitochondria
– require O2
– aerobic
Glycolysis
• first step in complete
oxidation of glucose
• occurs in cytosol
• begins when enzyme
phosphorylates
glucose
– adds PO4 group to
glucose Glu6PO4
• traps glucose
• reaction uses 2 ATPs
• Energy Investment
Phase
Glycolysis
• Sugar Splitting
Stage
• 6 carbon
compound2
pyruvates (3
carbon
compounds)
ATP
Glycolysis
Pyruvate
• fate depends on oxygen
availability
• not enough oxygen
– NAD+ is regenerated
by converting
pyruvatelactic acid
• anaerobic fermentation
• O2 available
• pyruvic acid enters
aerobic pathways of
Krebs cycle
• aerobic respiration
Anaerobic Fermentation
• not enough oxygen
• NAD+ regenerated by
converting pyruvatelactic
acid
• limited by buildup of lactic acid
– produces acid/base
problems
– degrades muscle
performances
• used for short bursts of high
level activity lasting several
minutes
• cannot supply ATP for long,
endurance activities
Alcohol Fermentation
• yeast without
oxygen
• provides ATP
• by productethanol
• regenerates
NAD+
Aerobic Respiration
• pyruvic acid enters
mitochondria
• once inside converted
acetyl CoA
• during conversion
• pyruvate is
decarboxylated
(carbons removed)
released as CO
• pyruvic acid + NAD + +
coenzyme A CO2 +
NADH + Acetyl CoA
Krebs Cycle
• acetyl CoA enters Krebs Cycle
– tricarboxylic acid cycle or
Citric Acid Cycle
• during cycle hydrogen atoms are
removed from organic
moleculestransferred to
coenzymes
• cycle begins & ends with same
substrate: oxaloacetate (OAA)
• acetyl CoA condenses with
oxaloacetate- 4 carbon
compoundcitrate-6 carbon
compound
• cycle continues around through 8
successive step
• during steps atoms of citric acid
are rearranged producing different
intermediates called keto acids
• eventually turns into OAA
Krebs Cycle
• Yields
– 2 CO2
– reducing equivalents-3
NADH & 1 FADH2
• further oxidized in
electron transport
chain
– 1 GTP-ATP equivalent
Since two pyruvates are
obtained from oxidation
of glucose amounts
need to be doubled for
complete oxidation
results
Electron Transport Chain
• transfers pairs of electrons
from entering substrate to
final electron acceptoroxygen
• electrons are led through
series of oxidationreduction reactions before
combining with O2 atoms
• reactions takes place on
inner mitochondrial
membrane
• only permeable to water,
oxygen & CO2
Oxidative Phosphorylation/Electron
Transport Chain System
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responsible for 90% of ATP used by
cells
basis-2H + O22 H20
releases great deal of energy all at
once
cells cannot handle so much energy
reactions occur in series of steps
Oxidation reactions
– remove H+ atoms & lose energy (H+)
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Oxidized things lose electrons
compounds that gain electrons
reduced-gain energy
enzymes cannot accept H atoms
Coenzymes needed to accept
hydrogens
when coenzyme accepts hydrogen
atoms coenzyme reduced & gains
energy
Chemiosmosis
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ETC creates conditions needed for ATP
production by creating concentration
gradient across inner mitochondrial
membrane
as energy is released-as electrons are
transferred  drives H ion pumps that
move H across membrane into space
between 2 membranes
pumps create large concentration
gradients for H
H ions cannot diffuse into matrix because
not lipid soluble
channels allow H ions to enter matrix
Chemiosmosis
– energy released during oxidation of
fuels=chemi
– pumping H ions across membranes of
mitochondria into inter membrane
space =osmo
– creates steep diffusion gradient for Hs
across membrane
when hydrogens flow across membrane,
through membrane channel proteinATP
synthase attaches PO4 to ADP ATP
ATP
synthase
Oxidative Phosphorylation
• for each pair
of electrons
removed by
NAD from
substrate 3
ATPs are
made
• FAD2 ATPs
are made
Energy Yield
• aerobic metabolism generates
more ATP per mole of glucose
oxidized than anaerobic
metabolism
• Glycolysis
– net 2 ATPs
• Krebs Cycle
– 2 ATP
– 8 NADH + H+ X 3=24 ATP
– 2 FADH2 X 2=4 ATP
• 2 moles pyruvate2 NADH + H+glycolysis 2 X 2 = 4 ATP
• Total 36 ATP