energy releasing pathways atp
DESCRIPTION
Energy Releasing Pathways ATP. Aerobic Respiration. A redox process Glucose contains energy that can be converted to ATP Uses oxygen therefore aerobic. Cellular Energy Transfer. Cells transfer energy by redox reactions Remember: oxidation is the loss of electrons - PowerPoint PPT PresentationTRANSCRIPT
Energy Releasing Pathways
ATP
Aerobic Respiration
•A redox process•Glucose contains energy
that can be converted to ATP
•Uses oxygen therefore aerobic
Cellular Energy Transfer• Cells transfer energy
by redox reactions• Remember:
– oxidation is the loss of electrons
– reductions is the gain of electrons
• Oxidation involves loss of energy
• Reduction involves the gain of energy
Aerobic Respiration- Redox
• C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + Energy
• Water is both a reactant and a product
• Glucose is oxidized to form CO2
• C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + Energy
• Oxygen is reduced, forming water
• C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + Energy
• The electrons produced are used to form ATP
oxidation
reduction
Aerobic Respiration- 4 Stages
•Glycolysis•Formation of acetyl coenzyme
A•Citric Acid Cycle•Electron transport system and
chemiosmosis
Glycolysis
•Glucose is converted to 2 3-carbon molecules of pyruvate
•ATP and NADH are formed•Occurs in the cytosol
•Yellow- products•Green- reactants
Glycolysis Pyruvate Yield• Glycolysis means “sugar splitting”• One 6-carbon molecule is converted to
two 3-carbon molecules• Occurs in cytosol• Occurs in both aerobic and anaerobic
conditions• A series of reactions; each catalyzed by
a different enzyme• Glucose yields two pyruvates
Glycolysis• First phase requires ATP
investment
G3P
2 ATPs used
Glucose
2 glyceraldehyde-3-phosphate (G3P)
Fructose- 1,6-diphosphate
2 ATPs used
PHASE 1
Glycolysis• Second phase yields NADH and
ATP
G3P
Pyruvate
G3P
Pyruvate
+ 2 NADH
+ 4 ATP
PHASE 2
Pyruvate to acetyl CoA
• A carboxyl group is removed from pyruvate (carbon dioxide is produced)
• NADH is produced• acetyl group joins with coenzyme A
forming acetyl CoA• Coenzyme A is made from
pantothenic acid
Pyruvate
acetyl CoA
Coenzyme A
+ NADH
+ CO2
Glycolysis
Krebs Cycle
acetyl CoA
Acetyl Coenzyme A
• Pyruvate is converted into acetyl CoA
• NADH is produced • Carbon dioxide is a waste product• Occurs in the mitochondria
•Yellow- products•Green- reactants
2 pyruvate + 2 NAD+ + 2 CoA ----> 2 acetyl CoA + 2 NADH + 2 carbon dioxide
Citric Acid Cycle• Oxidizes acetyl CoA• Also known as Krebs cycle• Occurs in mitochondria (matrix)• Series of steps ultimately
reforming oxaloacetate• All of the energy of glucose is
carried by NADH and FADH2
Citric Acid Cycle
• Acetyl CoA combines with oxaloacetate, forming citrate
• Citrate undergoes conversions, ultimately re-forming exaloacetate
• Carbon dioxide is a waste product• ATP, NADH, and FADH2 are
produced
Acetyl CoA
oxaloacetate
+ 6 NADH
+ 2 ATP
+ 2 FADH2
One Turn of Citric Acid Cycle*
1. 2C molecule enters the cycle & joins a 4C molecule.
2. In a series of steps, the remaining H and high energy e- are removed from the 2C.
3. 3 NAD+ are converted into 3 NADH & 3H+.
4. 1 FAD is converted into 1 FADH2.5. 1 ATP is made.6. 2 CO2 are released.7. At the end of the cycle, nothing remains
of the original glucose molecule. * remember…this is x2!
Types of Reactions
• Dehydrogenation– Hydrogens are transferred to a
coenzyme (NAD+ or FAD)• Decarboxylations
– Carboxyl groups are removed from the substrate as carbon dioxide
• Preparation reactions– molecules are rearranged in
preparation for decarboxylations or dehydrogenations
Electron Transport SystemChemiosmosis
• Electrons that originated in glucose are transferred via NADH and FADH2 to a chain of electron acceptors
• Hydrogen ions are pumped across the inner mitochondrial membrane
• ATP is produced by chemiosmosis
Electron Transport Chain• Coupled to ATP synthesis• Transports e- from NADH and
FADH2 to O2
Electrons FMN a series of cytochromes and coenzyme Q
Electron Carriers
• Most electron carriers carry hydrogen atoms
• Electron carriers transfer energy• Electrons lose energy as they are
transferred between acceptors• NAD+ is a common hydrogen acceptor
is respiratory and photosynthetic pathways– Nicotinamide adenine dinucleotide
Electron Carriers• Nicotine adenine dinucleotide
phosphate (NADP+) is involved in photosynthesis
NAD+ is a coenzyme derived from the vitamin nicotinic acid (niacin)
Electron Carriers• Flavin Adenine Dinucleotide- FAD+
is involved in cellular respiration
Electron Carriers• Cytochromes- proteins containing
iron
Electron Transport Chain
– Electrons lose energy as they pass through the chain
Electron Transport Chain– Hydrogen ions (protons) are passed
into the intermembrane space of the mitochondria
Electron Transport Chain
– Electrons are finally passed to oxygen thereby forming water
FMN
Q
cyt b
cyt cr
cyt c
cyt a
cyt a3
2H+
2H+
2H+
NADH
FADH 2
O 2 H 2O
Complex I
Complex II
Complex III
Chemiosmotic Model• 1978 Nobel Prize in
Chemistry for a 1961 paper on the chemiosmotic model
• Cornwall, UK• Glynn Research
Laboratories• Died in 1992
Peter Mitchell
Chemiosmotic model
• Explains the coupling of ATP synthesis to electron transport
• A proton gradient is formed across the inner mitochondrial membrane
Chemiosmotic Model
• Protons diffuse through the channels formed by the enzyme complex ATP synthase
• Movement of protons catalyze production of ATP
• Protons diffuse through the channels formed by the enzyme complex ATP synthase
• Movement of protons catalyze production of ATP
http://telstar.ote.cmu.edu/biology/animation/ATPSynthesis/biochem.html
Energy Yield• Efficiency is about 40%; the
rest is disseminated as heat• Maximum yield of ATPs
– from NADH- 3 ATP– from FADH2- 2 ATP
• The NADHs from glycolysis produce fewer ATPs due to the necessity of transport of NADH across the mitochondrial membrane
Energy Yield
The NADHs from glycolysis produce fewer ATPs due to the necessity of transport of NADH across the mitochondrial membrane
36 to 38 ATPs yield
GLUCOSE ATP produced
GLUCOSE
GLYCOLYSIS
2 ATPproduced directly
2 ATP
ACETYL CoA
GLUCOSE
GLYCOLYSIS
2 NADH
2 ATPproduced directly
2 ATP
6 ATPthrough electron transport
+
8 ATP
PYRUVIC ACID
2 NADH
6 ATPthrough electron transport
+
14 ATP
KREBS CYCLE
2 ATPproduced directly
+
16 ATP
6 NADH18 ATP
through electron transport
+
34 ATP
2 FADH24 ATP
through electron transport
+
38 ATP
Other Nutrients• Nutrients other that glucose
provide energy• Humans gain more energy from
oxidation of fatty acids than glucose– Lipids contain 9 kcal per gram– Lipids are broken down and glycerol
enters glycolysis; fatty acids are converted to acetyl CoA and enter the citric acid cycle
Other Nutrients
• Proteins are broken down into amino acids– Amino acids are deaminated (the
amino acids are removed)– The remaining carbon chain
centers at various points– Proteins contain about 4 kcal per
gram
Regulation of Aerobic Respiration
•ATP synthesis continues until ADP stores are depleted
•Enzyme regulation is important•An important regulation point is
phosphofructokinase
PFKPFK is the committed step in glycolysis. Once this step is done then glycolysis will carry through.
PFK is activated by ADP/AMP
PFK is inhibited by
ATP
low pH
citrate groups
Anaerobic Respiration
• Various inorganic substances serve as the final electron acceptor like sulfur
• Yield is only the two ATP molecules from glycolysis
• Seen is some bacteria
Alcoholic Fermentation
• Produces ethanol• Pyruvate is converted to ethanol
to regenerate NAD+• Ethanol is a potentially toxic
waste product • Yeast carry out alcoholic
fermentation when oxygen deprived
Lactate Fermentation
• Bacteria and some fungi carry out lactate fermentation
• Pyruvate is converted to lactate to regenerate NAD+
• Strenuous exercise in mammals results in lactate fermentation as well
http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html