The Cori cycle is a metabolic pathway where lactic acid produced during anaerobic glycolysis in muscles is transported to the liver and converted back to glucose, which returns to the muscles. During intense exercise, muscles produce lactic acid when oxygen demand exceeds supply. The lactic acid travels to the liver where it is converted to pyruvate and then glucose through gluconeogenesis. The glucose returns to the muscles and is broken down again to lactic acid, completing the cycle. The Cori cycle plays an important role in preventing lactic acidosis in muscles during exercise and provides energy when muscle activity stops to repay oxygen debt.

1. Cori cycle
Done by :
‫السالم‬ ‫عبد‬ ‫سمية‬‫رمضان‬‫الفيتوري‬
Misruta / Libya

2. The Cori cycle (also known as the
Lactic acid cycle)
metabolic pathway in which lactat produced by
anaerobic glycolysis in the muscles moves to
the liver and is converted to glucose, which
then returns to the muscles and is
metabolized back to lactate .

3. Mechanism of cycle

4. Skeletal muscle
• Its cells, and particularly fast-twitch fibers
contracting under low oxygen conditions, such
as during intense exercise, produce much
lactate

5. During intense
exercise
require moderate amount of glucose uses oxygen faster than it can be supplied by
the blood stream
Muscle that is vigorously
exercising will enter anaerobiosis
and show a decreasing NAD/NADH
ratio, which favors reduction of
pyruvate to lactate.

6. • typically during intense muscular activity,
energy must be released through anaerobic
metabolism , the rate of ATP production by
anaerobic glycolysis is greater than that
produced by the complete oxidation of
glucose .
• But this could lead to an intracellular
accumulation of lactate, and a consequent
reduction in intracellular pH .

7. Anaerobic glycolysis

8. This lactic acid from muscle diffuses
into the blood.
The plasma membrane is freely
permeable to lactate

9. In liver
• In the liver, glucogenesis occurs .
• The lactate thus produced can be transported
to the liver, where it is reoxidized by liver
lactate dehydrogenase to yield pyruvate,
which is converted eventually to glucose.
in this way, the liver shares in
the metabolic stress created
by vigorous exercise

10. From a biochemical point of view
,
withgluconeogenesislinksCori cyclethe
glycolysisanaerobic

11. Energy cost of the Cori cycle
• The Cori cycle results in a net consumption of
4 ATP.
• The gluconeogenic leg of the cycle consumes 2
GTP and 4 ATP per molecule of glucose
synthesized, that is, 6 ATP.
• the glycolysis part of the cycle produces 2 ATP
molecules
As a result, the cycle cannot be sustained indefinitely

12. Importance of cori cycle:
• Red blood cells
These cells, lacking a nucleus, ribosomes, and
mitochondria, are smaller than most other
cells.
anaerobic glycolysis

13. In skeletal muscle
• Prevent lactic acidosis in the muscle under
anaerobic conditions and producing ATP, an
energy source during muscle activity
BUT
Cori cycle functions ,more sufficiently when the
muscle activity has ceased thus allowing the oxygen
debt to be repaid.

14. Fasting
The contribution of Cori cycle lactate to overall glucose
production increases with fasting duration Specifically,
after 12, 20, and 40 hours of fasting by human
volunteers, the contribution of Cori cycle lactate to
gluconeogenesis is 41%, 71%, and 92%,
respectively.
A similar condition seems to occur also in cancer patients
with progressive weight loss.

15. Metformin
The drug metformin can precipitate lactic
acidosis in patients with renal failure because
metformin inhibits cori cycle. Normally the
excess lactate would be cleared by kidney but
in patients with kidney failure the kidney
cannot handle the excess lactic acid.

16. Thankyou for your attention

17. Referrences
•cycle/-http://www.medbiochemistry.com/cori
•https://en.wikipedia.org/wiki/Cori_cycle