Transcript Ch. 9 Cellular Respiration

Ch. 9 Cellular Respiration
Harvesting chemical energy
 Living is lots of work
 Polymerization, Growth, highly organized,
and movement all require energy
 Energy enters Earth’s ecosystems as sunlight
 Harvesting of energy requires a series of
metabolic steps
 AEROBIC CELLULAR RESPIRATION
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Glycolysis
Kreb’s cycle
Electron transport chain
Organic compounds
 Energy stored in chemical bonds (position)
 Enzymes help regulate this metabolism
 Organic macromolecules are rich in potential
energy and are broken down to simpler
compounds with less energy.
 Breaking of bonds allows work to be done.
 Organic + oxygen  carbon + water + energy
compounds
dioxide
Exergonic reaction
 Organic + oxygen  carbon + water + energy
compounds
dioxide
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy
(ATP + heat)
DG
=
- 686 kcal
Possible pathways
 Complete, aerobic cellular respiration
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Complete oxidation of carbohydrates using
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Glycolysis
Kreb’s cycle and
Electron transport chain REQUIRES OXYGEN
Incomplete/ partial oxidation
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Gylcolysis only
Glycolysis + Lactic acid fermentation
Glycolysis + Alcoholic fermentation
Redox reactions
 Movement of e- is what is used to store and
release energy in bonds of organic cpds.
 Redox reactions – “oxidation-reduction
reactions” transfer an e- from one reactant to
another
 Reduction
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Addition/receipt of e-, more negative
 Oxidation
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Loss of e- (often to O), more positive
Falling electrons
 The step wise fall of electrons from organic
compounds rich in bonds, to simpler
compounds increases the entropy of the
system.
 Electrons are shuttled through a series of
carriers (membrane proteins) that allows for
release of energy to be in small (usable)
increments.
 Electron transport chains
Aerobic cellular respiration
 Requires oxygen ( for e- acceptor at end of ETC)
 3 parts
 Glycolysis ( splitting of sugar molecules )
 Some substrate level phosphorylation of ATP
 Kreb’s cycle ( transfer of e- to NADH, FADH)
 Some substrate level phosphorylation of ATP
 ETC ( generates ATP using ETC)
 Much oxidative phosphorylation of ATP
 Occurs in eukaryotic cells – need mitochondrion (for
Krebs and ETC) and oxygen supply for (ETC)
Glycolysis
 Glyco = sugar, glucose
 Lysis = to split or break
 “sugar splitting”
 Cytoplasm
 ALL CELLS !
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Doesn’t require mitochondrion or O2
1 glucose = 2 ATP and 2 NADH
2 ATP are net ( 4 generated – 2 invested )
Know steps on pgs. 168-169….green boxes
Note color coding used in chapter – green =
glycolysis, salmon = Kreb’s and purple = ETC
Summary of Steps
1. Spend 1 ATP
Add P to glucose
2. Glucose converted to
isomer (fructose) by
an enzyme
3. Spend 2nd ATP
add 2nd P to fructose
now in debt ( 2ATP)
Molecule very
unstable (primed)
Summary of Steps
4. 6 C sugar
“cleaved” into 2 –
3C sugars
They are isomers
PGAL
5. An enzyme
called ‘isomerase’
converts both
isomers into
glyceraldehyde
(PGAL)
From now on all
steps are X2
Summary of Steps
6. Enzyme adds an inorganic phosphate, sugar give
e- and H+ to NAD making NADH…remember x2
7. MAKE ATP (X2) now out of debt, organic acid
8. Relocate P ( on both molecules)
Summary of Steps
9. Generates water and creates double bond…. P bond now
unstable
10. P leaves – adds to ADP generates more ATP (2more) now
have 2 net ATP. Glucose is now split into 2 – 3 C molecules
PYRUVATE
2 NADH can go to ETC and make ATP using oxidative phosphorylation
Krebs Cycle – aka Tricarboxylic Acid
Cycle (TCA) and Citric Acid Cycle
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Sir Hans Krebs: 1900-1981, 1953 Nobel Prize, 1958 knighted
3 C pyruvate at end of glycolysis
Not soluble in mitochondrial membrane
Loses C (CO2) becomes acetyl
Creates a NADH ( stores some energy )
Bonds to coenzyme for transport –
now Acetyl CoA
Crosses mitochondrial membrane
Bonds to 4C oxaloacetate to make
6C citrate or citric acid
Series of steps to lose C ( makes CO2 ) and
Store energy as NADH and FADH and ATP
Regenerates the oxaloacetic acid…. “cycle”
Electron Transport Chain
 Collection of molecules embedded in the inner mitochondrial
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membrane
Folding increases surface area ( # of reactions)
Most compounds are proteins (some pigments) cytochrome c
used to trace DNA lineage
Function as enzymes directing the flow of reactions that move e(alternate between oxidized and reduced state)
NADH and FADH2 are from Krebs and glycolysis
NADH and FADH2 release H to these reactions
H is split into H+ and eThe e- move through the carriers to the biggest e- acceptor
(moving down hill – releasing potential energy and increasing
entropy)
The H+ accumulate in space btwn membranes
ETC continued
 As the e- get to the last acceptor they have released
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all the energy they were carrying from C-C bonds in
glycolysis and Krebs
The H+ can not accumulate indefinitely btwn
membranes (high acidity)
H+ flows through protein pump called ATP synthase
toward e- and their acceptor (OXYGEN)
This creates water and also
Is used to generated energy to add P to ADP
ATP is generated using oxidative phosphorylation