Cori cycle

The Cori cycle (also known as the Lactic acid cycle) between skeletal muscle (during intense exercise ) and liver

1. Cori cycle
Done by :
ملاسلا دبع ةيمس ناضمريروتيفلا
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
,
with gluconeogenesislinks Cori cycle the
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. Thank you for your attention

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