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Respiration
1. Glycolysis
2. Citric Acid Cycle (Krebs cycle)
3. Oxidative phosphorylation: Electron transport and chemiosmosis.
4. Overall
~~~~~~~~~~~~~~~~~~ 1. Glycolysis
Occurs in cytosol.
degradation process--break
glucose into 2 pyruvate.
Some steps are redox reactions.
Dehydrogenase
enzymes carry electrons to NAD+ to form NADH.
Forms small amount of ATP
by substrate-level phosphorylation.
Consists of 2 stages: * Energy investment
phase & * Energy pay off phase.
* Energy investment
2 ATP used, 2ATP-->2ADP +
2P (P=phosphate)
2P + glucose --(1ATP)-> glucose-6-phosphate
glucose-6-phosphate-->
fructose-6-phosphate
fructose-6-phosphate --(1ATP)->
fructose-1,6-biphosphate
* Energy pay off phase
4 ADP+4P--> 4ATP
2 NAD+
+ 4e-
+ 4H+
-->2NADH + 2H+
Phosphorylated glucose
splits into 2 Pyruvate
2 H2O
formed from 2H+
+2e-
~~~~~~~~~~~~~~~~~~ 2.
Citric Acid Cycle (Krebs cycle)
Occurs in mitochondria's matrix.
Breakdown
glucose by oxidizing a derivative of pyruvate to carbon dioxide.
Some steps are
redox reactions.
Dehydrogenase enzymes carry electrons to NAD+
to form NADH.
Forms small amount of ATP by substrate-level
phosphorylation.
~~~~~~~~~~~~~~~~~~~ 3. Oxidative
phosphorylation: Electron transport and chemiosmosis.
Mitochondria's inner membrane is the site of
electron transport and chemiosmosis.
electron transport+ chemiosmosis=oxidative
phosphorylation. It yields 90% of
ATP in respiration. electron
transport chain is made of mostly proteins embedded in membrane of
mitochondria. Chemiosmosis: hydrogen
atoms moved into ATPsynthase to make ATP
~~~~~~~~~~~~~~~~~~~~~
4. Overall
Cell makes about 38 ATP per glucose degraded
to carbon dioxide and water.
(c) copyright Susanna Shiu & Queenie Liew, since September 2007