Question 2 a (800 words)

i) When yeast metabolises glucose under anaerobic conditions, itproduces ethanol and CO2 as end products of glycolysis but underaerobic conditions, pyruvate is the end-product of the glycolyticpathway. What is the physiological rationale for producing ethanoland CO2 under anaerobic conditions? Fully explain your answer.

ii) The standard free energy change for the oxidation of glucoseto CO2 is shown below: Glucose + 6 O2 → 6 H2O + 6 CO2 ∆G’o = - 2840kJ mol-1 If the free energy change (∆G’o) for the hydrolysis of ATP(ATP + H2O → ADP + Pi) is - 30.5 kJ mol-1, what is the overallpercentage efficiency of glycolysis in terms of the free energy“captured” in the form of ATP? Make sure you fully explain yourcalculations and take care to include units and give your answer tothree significant figures.

iii) Clearly explain in your own words the differences betweensubstratelevel phosphorylation and oxidative phosphorylation. iv) What is the physiological rationale for the inhibitoryeffect of ATP on Phosphofructokinase?

Question 2b

In 800 words, Describe the process of receptor activation inCell Signalling pathways. Illustrate your answer with a CellSignalling system of your choice making sure to include thepathway(s) of receptor activation, the second messenger(s) involvedand the downstream cellular response(s).