Glycolysis ad gluconeogenesis counter each other. They regulate each other. The enzymes are not active
simultaneously, to prevent wasting energy.
Conditions that favor glycolysis inhibit gluconeogenesis and vice versa. Citrate promote
gluconeogenesis, through F1,6Pase.. High AMP levels would promote glycolysis by promoting F6P into
F1,6P by using PFK.
How are glycolysis and gluconeogenesis separated during exercise?
During exercise, pyruvate is made faster than it could be oxidized. Lactate is then produced from
fermentation and enters the blood towards the liver. The liver then convert lactate into glucose through
gluconeogenesis, the Cori cycle. Glycogen can be converted to G6P as well. Skeletal muscle is not rich in
mitochondria, but cardiac muscle is. Some of the lactate from the blood is taken by the cardiac muscle.
The lactate from the blood is then processed by the cardiac muscle into pyruvate.
Glycogen: stored form of glucose. Synthesized from a glucose derivative called UDP-glucose (Uracil
diphosphate). Transfer glucose from UDP-glucose to a pre-existing chain of glucose, creating a chain and
a free UDP. A free Pi could be added to a glycogen chain to get a G1P out. G1P into G6P through
phosphoglucomutase. Then used for glycolysis.
Blood sugar levels must be regulated. Insulin and glucagon control blood sugar. Insulin decreases blood
sugar, and glucagon release sugar into blood. Both are peptide hormones. Muscle activity would cause
Fasting: blood sugar is low, glucagon is then secreted by the pancreas. Receptors on the surface of the