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Transcript of …transferring a phosphate group to another molecule = phosphorylation -- use a little ATP to net a...
…transferring a phosphate group to another molecule = phosphorylation
-- use a little ATP to net a larger amount of kinetic E (work)
…have to make $ to spend $
How do cells do work?• ATP is involved• What organelles are
responsible for energy conversion?
• Converting E from sugar in the presence of O2 = cellular respiration
• …the cell captures E released as ATP
Respiration vs. Breathing
• Exchange of gases… O2 in & CO2 out
• Aerobic energy harvesting = cellular respiration
…more work
requires more O2
Energy extraction by cells…
• Glucose = = C6H12O6 = potential E
• electrons (energy) transfer as carbon - hydrogen bonds break
…hydrogen-oxygen bonds form as water• Transfer of electrons from reactants to products side of
reaction = oxidation-reduction reaction (redox reaction)
3 main stages of cellular respiration
• Glycolysis– Breaking glucose into – a 3-carbon, pyruvate
• Citric acid cycle– Modifies pyruvate
• Oxidative phosphorylation– Uses the E from electron transport chain to
phosphorylate ADP
• Electrons are shuttled by NAD+ – an enzyme, nicotinamide adenine
dinucleotide, that gets reduced (gain of H) to NADH
6.8 Pyruvate is chemically groomed for the citric acid cycle
• The pyruvate formed in glycolysis is transported to the mitochondria, where it is prepared for entry into the citric acid cycle– The first step is removal of a carboxyl group that
forms CO2
– The second is oxidization of the two-carbon compound remaining
– Finally, coenzyme A binds to the two-carbon fragment forming acetyl coenzyme A
Copyright © 2009 Pearson Education, Inc.
Coenzyme A
Pyruvate Acetyl coenzyme A
CoA
NAD+ NADH H+
CO2
13
2
6.10 Most ATP production occurs by oxidative phosphorylation
• Oxidative phosphorylation involves electron transport and chemiosmosis and requires an adequate supply of oxygen– NADH and FADH2 and the inner membrane of
the mitochondria are also involved– A H+ ion gradient formed from all of the redox
reactions of glycolysis and the citric acid cycle provide energy for the synthesis of ATP
Copyright © 2009 Pearson Education, Inc.
ATP
H+
Intermembranespace
O2
H2O
12
Innermitochondrialmembrane
H+NAD+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
Mitochondrialmatrix
Electronflow
Electroncarrier
Proteincomplexof electroncarriers
NADH
FADH2FAD
ATPsynthase
PADP +
Chemiosmosis
+ 2
OXIDATIVE PHOSPHORYLATION
Electron Transport Chain
Electron transport chain
• NADH delivers electrons (e-) to a cascade of reactions
…like a slinky moving down a staircase…keeps momentum resulting in a net release of greater E
6.9 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and
FADH2 molecules
• With the help of CoA, the acetyl (two-carbon) compound enters the citric acid cycle– At this point, the acetyl group associates with a four-
carbon molecule forming a six-carbon molecule– The six-carbon molecule then passes through a
series of redox reactions that regenerate the four-carbon molecule (thus the “cycle” designation)
Copyright © 2009 Pearson Education, Inc.
CITRIC ACID CYCLE
NAD+
NADH
3 H+
CO2
3
3
2
CoA
CoA
Acetyl CoA
PADP +ATP
FADH2
FAD
CITRIC ACID CYCLE
CoA
2 carbons enter cycle
Acetyl CoACoA
1Oxaloacetate
1Step
Acetyl CoA stokes the furnace.
CITRIC ACID CYCLE
CoA
2 carbons enter cycle
Acetyl CoACoA
1Oxaloacetate
1Step
Acetyl CoA stokes the furnace.
2
3
NAD+
NADH
CO2
Citrate
ADP +
+ H+
P
Alpha-ketoglutarate
leaves cycle
ATP
NAD+NADH
CO2
+ H+
leaves cycle
Steps –
NADH, ATP, and CO2 are generated
during redox reactions.
2 3
CITRIC ACID CYCLE
CoA
2 carbons enter cycle
Acetyl CoACoA
1Oxaloacetate
1Step
Acetyl CoA stokes the furnace.
2
3
NADH
CO2
Citrate
ADP P
Alpha-ketoglutarate
leaves cycle
ATP
NADH
CO2leaves cycle
Steps –
NADH, ATP, and CO2 are generated
during redox reactions.
2 3
5NAD+
NADH
Malate
+ H+
4FADH2
FAD
Succinate
Steps –
Redox reactions generate FADH2
and NADH.
4 5
NAD+
+ H+
NAD++ H+
How much energy or ATP is produced for each glucose molecule?
Is this system efficient?
• 38 ATPs = 40% of the potential E in glucose
• 60% escapes as heat
• Auto engine converts 25% E from fuel
• Muscle use 10,000,000 ATP per second
Fermentation (animal cells)• Oxidize organic fuel & produce ATP without
oxygen– Anaerobic alternative– Relies on glycolysis (1st step of respiration)
• Only 2 ATPs– Then…converts pyruvate to lactate
– muscle burn– Lactate is recycled by liver
Fermentation (yeast)• Oxidize organic fuel & produce ATP without
oxygen– Anaerobic alternative– Relies on glycolysis (1st step of respiration)
• Only 2 ATPs
– Then…converts pyruvate to ethanol and CO2– Gas bubbles in beer & champhagne, dough to rise– Alcohol is produced as yeast waste…eventually killing ‘em