- A cumulative function of three metabolic stages:
2. The Krebs cycle
3. The electron transport chain and oxidative phosphorylation
- Glycolysis is a catabolic pathway that:
o Occurs in the cytosol
o Partially oxidizes glucose
o (6C) in two private
o (3C) molecules
- The Krebs Cycle is a catabolic pathway that:
o Occurs in the mitochondrial matrix
o Completes glucose oxidation by breaking down pyruvate derivative (acetyl CoA) into
- Glycolysis and the Krebs cycle produce:
o A small amount of ATP by substrate-level phosphorylation
o NADH by transferring electrons from substrate to NAD+ (Krebs cycle also produces
FADH2 by transferring electrons to FAD+
- The electron transport chain stages:
o Is located at the inner membrane of the mitochondrion
o Accepts energized electrons from reduced coenzymes (NADH and FADH2) that are
harvested during glycolysis and Krebs cycle
o Couples this exergonic slide of electrons to ATP synthesis or oxidative phosphorylation.
This process produces most (90%) of the ATP.
- During glycols is each glucose molecules is broken down into two molecule of the compound
- The pryuvate crosses the double membrane of the mitochondrion to enter the matrix, where
the Krebs cycle decomposes it to carbon dioxide
- The electron transport chain converts the chemical energy to a form that can be used to drive
oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration.
- A smaller amount of ATP is formed directly during glycolysis and the Krebs cycle by substrate
level phosphorylation Substrate level phosphorylation
- Some ATP is made by direct enzymatic transfer of P group from a
substrate to ADP
- Phosphoenolpyruvate (PEP) is formed from breakdown of sugar during
- Harvest chemical energy by oxidizing glucose to private
- Glycolysis – catabolic pathway during which six-carbon glucose is split into two three-carbon
sugars, which are then oxidized and rearranged by a step-wise process that produces two
o Each reaction is catalyzed by specific enzymes dissolved in the cytosol
o No CO i2 released as glucose is oxidized to private; all carbon in glucose can be
accounted for in the two molecules of private
- Occurs whether or not oxygen is present.
The energy input and output of glycolysis Glycolysis:
- The orientation diagram at the right relates glycolysis to the
whole process of respiration
- Steps 1-5 are the energy investment phase of glycolysis
- Ten reaction, each catalyzed by a specific enzyme, make up the
process we call glycolysis
- ALL organisms have glycolysis occurring in their cytoplasm.
- At steps 1 and 3 ATP is converted to ADP, inputting energy into
the reaction as well as attaching a phosphate to the glucose.