Carbohydrates

• Glucose is main respiratory substrate in mammalian cells (brain cells only respire this), other hexose sugars (fructose and galactose) modified for glycolysis, animal cells store glycogen; and plant cells make starch, both hydrolysed to make glucose
• Theoretical energy yield is 2870kJmol-1; 94 ATP per glucose molecule (hydrolysis to ADP + Pi makes 30.6kJmol-1), actual ATP yield is ~30 molecules; 32% efficiency, remaining energy lost as heat; important for enzyme activity