I am having trouble with the following HW questions for my lab, It is from a pri

Question

I am having trouble with the following HW questions for my lab, It is from a principles of physiology class. The following are the questions that I am having trouble answering:

1. a. How do changes in [S] affect reaction rate?

     b. What is the significance of the Km? What does a higher or lower Km indicate?

     c. How do changes in [Enzyme] affect the reaction rate?

I attached photos of my lab report along with the data collected (shown after the photos)

BIO 361 Michaelis Menten Kinetics of Enzyme-catalyzed Reactions Effect of Concentration Learning Objectives: After completing the lab exercise and analyzing data at home, students will be able to 1. Describe how the rate of an enzyme-catalyzed reaction is affected by concentrations of substrate and/or enzyme 2. Measure the rate of a biochemical reaction accurately using a spectrophotometer 3. Calculate concentrations of a reaction mixture efficiently and accurately using a spreadsheet Introduction Various factors affect the rate of enzyme-catalyzed reactions. This exercise investigates the influence of concentration, both substrate concentration and enzyme concentration In 1913 Michaelis and Menten proposed the general theory of enzyme action and the well-known Michaelis-Menten equation is named in their honor. This equation, which has the form, v Vmax IS Km [S] describes mathematically the relationship between rate (or velocity v and substrate concentration IS] for many (not all) enzymatic reactions. V corresponds to the maximum velocity of the reaction when max substrate levels are very high. The Km (Michaelis constant) is the substrate concentration at which the rate, v, is equal to V2 of the Vmax. The Km is of interest in that it gives an indication of the affinity that the enzyme has for a substrate (i.e., the enzyme's ability to bind the substrate). A high Km corresponds to a low affinity, and vice versa In the first part of the experiment you will measure the rate using different substrate concentrations This will enable you to calculate the Km value for the enzyme In the second part of the experiment you will measure the rate when substrate concentration is held constant and different enzyme concentrations are used

Explanation / Answer

a. Ans. Increase in substrate concentration gradually increases the rate of enzymatic reaction within the limited range of substrate levels. The concept behind this is very simple, that is as the concentration of substrate increases more no. of molecule of substrate exposed to the enzyme and hence the rate of reaction increases with increase in substrate concentration provided the concentration of enzymed is constant. When all the enzyme molecule is occupied with substrate molecule (saturation point), then the rate of reaction is maximum and after that there will be no increase in rate of reaction. Your lab data also explain it, as the absorbance (propotional to concentration) increases rate of reaction increases.

b. Ans. Km (Michaelis-Menten constant) is defined as the substrate concentration to produce half-maximum velocity (Vmax/2) in an enzyme catalysed reaction. It indicates that half of the enzyme molecules are bound with the substrate molecule when the substrate concentration equals the Km value. Km value is a constant and a characteristic feature of a given enzyme which measures the strength of enzyme-substrate complex. Alow Km value indicates a strong affinity between enzyme and substrate, whereas a Km value reflects a weak affinity between them.

c. Ans. Again if the substrate concentration is constant then the rate of reaction increases with the increase in enzyme concentration and the concept is same here the the exposure of more enzyme molecule to the substrate till the saturation (all the substrate molecule is occupied by enzyme) point. After this there will be no change in rate of reaction as all the substrate molecule has been occupied. part 2 of your lab experiment explain it, as the rate of reaction is increases as the absorbance (concentration of enzyme) increases.

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