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CELLULAR RESPIRATION
The process by which mitochondria break down food
molecules to produce ATP
There are three stages.
1.Glycolysis2.Citric acid cycle3.E-transport chain
GLYCOLYSIS
• Overview: series of chemical reactions in the cytoplasm of cells that break down GLUCOSE(C6H12O6) into two-three carbon molecules called pyruvic acid.
• 2 ATP are required to start glycolysis• Glycolysis is inefficient because it only
produces 4 ATP and has to use two to get going. Leaving a net ATP of 2 for each molecule of glucose broken down.
Two Kinds of Glycolysis
• Anaerobic (W/O O2)– Prokaryotic– Typically bacteria– Fermentation- which
produces ethyl alcohol and then breaks down into lactic acid
• Aerobic ( with O2)– Eukaryotic– Glycolysis-4 ATP– Kreb’s Cycle-2 ATP– E- transport – 32 ATP
– Cellular Respiration: Max Produced 38 ATP/molecule of glucose. Usable is 36
Step 1
• 2 phosphate groups are attached to glucose(6 carbon sugar)
• 2 ATP’s are broken down to supply phosphates
• P-C-C-C-C-C-C-P
Step 2
• 6 Carbon molecule is split into (2)3 Carbon molecules
• C-C-C-P
• C-C-C-P
STEP 3
• C-C-C-P(1st PGAL) Oxidized• C-C-C-P(2nd PGAL) Oxidized• 2NAD+(nicotinamide adenine dinucleotide) are
reduced (accepts e-),carries it becoming 2NADH + (2H+)
NAD is a coenzyme that accepts e- and p+
2 Phosphates are added to becomeP-C-C-C-P and P-C-C-C-P
Step 4
• Phosphates added in Step I and 3 are removed
• Leaving 2 molecules of pyruvic Acid
C-C-C and C-C-C
The 4 phosphates are combined with molecules of ADP to form 4 ATP’S
ATP TOTAL SO FAR
• 4 ATP are produced at the end of glycolysis.
• 4 ATP – 2 ATP= net of 2 ATP going into the citric acid cycle
The Citric Acid Cycle or Kreb’s Cycle
• Where: Mitochondria
• Who: All living things
• When: Always going on
• Why: Produce ATP
Electron and Proton Carriers
• FAD(flavin adenine diphosphate)
• NAD(nicotinamide diphosphate)
• A total of 3 NADPH molecules are formed and 1 FADH2 molecule is formed
• These e-carriers transport energized e- from the citric acid cycle to the electron transport chain in the inner membrane of the mitochondrion
STEP 1
• Pyruvic acid: (Product of glycolysis) (2C2H3OCOOH) reacts with coenzyme A
to form
• Acetyl Coenzyme A or
Acetyl CoA
• C-C-CoA
STEP 2
• C-C-CoA combines with oxaloacetic acid
(C4H4O5) and forms Citric Acid
A 6 carbon compound
CO2 is released and a H+ is released
H+ joins with NAD(an enzyme that accepts e- and H+) to form NADH+
The 6 Carbon compound is now a 5 carbon compound called ketoglutaric acid
STEP 3
• The Ketoglutaric acid loses a CO2 and a H+ ion and becomes a 4 carbon compound. C-C-C-C (Succinic Acid)
• The H+ joins with a NAD and forms NADH
• One ATP forms here
STEP 4
• Succinic Acid Loses a H+ and breaks down into Fumaric acid, another 4 carbon compound
• This H+ hooks up with FAD(flavin adenine dinucleotide) another enzyme to create FADH
Another H+ attaches to FADH and becomes FADH2+
Step 5
• Fumaric Acid breaks into another 4 carbon compound called Malic acid
• NADH and FADH are used to regenerate Oxaloacetic acid and the cycle begins again
Part 3 : The Electron Transport Chain
• Where: inner mitochondrion membrane• NADH and FADH2 Pass energized e- from
protein to protein within the membrane.• Releasing energy along the way• Some of that energy is used to create ATP
and some is used to pump H+ ions into the center of the mitochondrion
• Inside the membrane is + charged and outside is - charged
Electron Transport Continued
• The inner membrane forms ATP from this electrochemical gradient across the mitochondrial membrane.
• The final electron acceptor is Oxygen Which reacts with 4 H+ to form 2 H2O’s
• The e- transport chain produces 32 ATP’s• 32 ATP + 2 ATP in Kreb’s + 2 from
glycolysis = 36 total ATP’s produced in cellular respiration
Comparison of photosynthesis and Cellular Respiration
• Photosynthesis– Food accumulated– Energy from sun stored in
glucose– Carbon dioxide taken in– Oxygen given off– Produces glucose from
PGAL– Goes only in light– Occurs in the presence of
chlorophyll
• Cellular Respiration– Food broken down– Energy of glucose is
released– CO2 given off– Oxygen taken in– Produces CO2 and H2O– Goes on all day and night– Occurs in living cells