Question

BIOL-211 ICA - Metabolism, Cellular Respiration and Photosynthesis 1. You are doing an experiment looking at how octopus cells change color for camouflage. The enzyme responsible for catalyzing this metabolic change has a delta G of -100kcal/mol. A) Is this a spontaneous, or non-spontaneous reaction? B) Is ATP hydrolysis necessary for this reaction to occur? Yes or No. C) If you were to add more enzyme, would the delta G be affected? Explain your answer. 2. You are performing an experiment on a drug X that can affect the function of the ATP synthase pump. The graph below shows the pH level in the intermembrane mitochondrial space over time within an active cardiac cell. At the time marked by the arrow, you add your drug. If the added drug serves to activate the function of the ATP synthase pump, would pH levels in the intermembrane space be INCREASED or DECREASED?. Please indicate if the pH levels would be increased or decreased, followed by explanation. intermembrane pH in space time 3. Would you classify photophosphorylation as most like substrate level phosphorylation OR oxidative phosphorylation in cellular respiration? Please explain in 1-3 sentences.

Answer 1

Answer 1:

Background information:

A chemical reaction can be represented as :

E+S= ES + E + P

Where, E is the enzyme, S is the substrate and P is the product.

Gibbs free energy for the reaction is given as :

AG = Ep - Es

Where, Ep is the energy of product and Es is the energy of substrate.

The role of enzyme is to reduce the activation energy required for the reaction, but it doesn't change the final energy states of substrate and product. Thus, enzyme doesn't change the deltaG of reaction.

Spontaneous reactions are those which can occur on its own and do not need external energy. For such reactions, energy of substrate is higher than that if product , thus ∆G is negative.

On the other hand, if energy of product is greater than energy of substrate, then ∆G becomes positive in value. Such a reaction requires external supply of energy to occur and are called non-spontaneous reactions.

(a) The reaction has a Delta G of -100kcal/mol. Since ∆G is negative, thus the reaction will be spontaneous.

(b) The reaction is spontaneous and thus supply of external energy is not required. Thus, ATP hydrolysis will not take place.

(c) Adding more enzymes will not change delta G. This is because enzymes do not change the final energy states of substrate and product. Enzymes act to reduce only the activation energy required for reaching transition state.

∆G = Ep-Es