2009A15 Describe the formation, fate and role of lactate in energy production.

Structure

·  3 carbon molecule

·  Conjugate base of lactic acid

Homeostasis

·  Daily production 1,500mmol, ∝ rate of anaerobic metabolism

·  Normal plasma concentration 0.5-2mmol/L
(up to 16mM in well trained athletes at max effort)

·  Formed in ICF; crosses cell membranes by facilitated diffusion (MCT transporter)

Pathology

·  In excess causes high anion gap metabolic acidosis

o ↑ Strong ion difference

Facilitates glycolysis

·  Pyruvate -> lactate regenerates NAD⁺

·  Important if no mitochondria i.e. RBC

·  Important in anaerobic metabolism

Substrate for metabolism

·  Lactate -> oxidative phosphorylation as in the above pathway

·  Will occur in any nucleated cell when O₂ supply restored

·  Efficient uptake from plasma into myocardium

Substrate for Cori cycle

·  Re-generate glucose during anaerobic exercise

Substrate for glycogenesis