Enzymes III

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Enzymes- III Kinetics:

Enzymes- III Kinetics Dr. Hariharan MD, Assistant Professor,Dept of Biochem, Karpagam Faculty of medical Sciences and Research, Coimbatore. Dr. Hariharan. V, free download available in Internet

Thermodynamics :

Thermodynamics The rates of reactions are determined by their activation energy When a reaction occurs there will be a state where there will be neither free substrate or the product. That state is called transition state A + B-L  A..B..L  A-L + B To reach this transition state, a high amount of energy is required, termed activation energy Enzymes reduces this activation energy Dr. Hariharan. V, free download available in Internet

Factors affecting reaction rate:

Factors affecting reaction rate Kinetic theory states that ‘for 2 molecules to react they must approach within bond forming distance or collide’. It must also possess sufficient kinetic energy to overcome the energy barrier. Anything that increases the energy of substrates or that will increase the collision will increase the rate of the reaction Dr. Hariharan. V, free download available in Internet

1. Temperature :

1. Temperature Raising the temperature will increase the kinetic energy of the molecules Increasing the kinetic energy of the molecules also increases the motion and increases collision On increasing the temperature, the reaction rate increases. The temperature at which the rate of the reaction is maximum is called optimal temperature Above this temperature, the enzyme gets denatured  reaction rate slows down Dr. Hariharan. V, free download available in Internet Dr. Hariharan. V, free download available in Internet

Effect of pH:

Effect of pH The pH decides the charge on the aminoacids of the enzyme Optimal pH for many enzymes are around 5-9 For enzymes involved in acid base catalysis, the pH of the medium is important to decide the charge on the groups Dr. Hariharan. V, free download available in Internet

Effect of enzyme concentration:

Rate of the reaction is directly proportion to enzyme concentration when sufficient substrate is present Dr. Hariharan. V, free download available in Internet Effect of enzyme concentration Enzyme concentration Rate of the reaction [V]

Effect of product conecentration:

Effect of product conecentration As product accumulates the rate of the reaction reduces In a reversible reaction, when equilibrium is reached, products will try to turn back substrates, so reaction rate is slowed down Dr. Hariharan. V, free download available in Internet

Effect of substrate concentration:

Effect of substrate concentration When substrate concentration is increased, V increases until a maximum value is reached( V max ). Then increasing the substrate won’t increase the rate of reaction. At half maximal velocity (1/2 V max ), 50% of enzymes are attached with substrates. As more substrate is added, all the enzymes saturate and thereafter, adding substrate wont increase the V. Dr. Hariharan. V, free download available in Internet

PowerPoint Presentation:

Dr. Hariharan. V, free download available in Internet

PowerPoint Presentation:

Dr. Hariharan. V, free download available in Internet

Michealis Menten equation:

Michealis Menten equation The Michaelis-Menten equation illustrates the relationship between initial velocity of the reaction Vs substrate concentration V i = V max [S] K m + [S] The Michaelis Constant, K m is the substrate concentration at which V i is half the maximal velocity(1/2 V max ). Dr. Hariharan. V, free download available in Internet

Km:

K m K m value is the substrate concentration at half maximal velocity. K m is independent of enzyme concentration K m value is the signature of the enzyme. It is constant for an enzyme K m denotes the affinity of the enzyme towards its substrate. Higher the K m lower the affinity. Dr. Hariharan. V, free download available in Internet

Lineweaver Burke plot:

Lineweaver Burke plot Calculation of K m using the traditional curve needs impractically higher amount of substrate concentration So a linear form of the curve is used. Dr. Hariharan. V, free download available in Internet V i = V max [S] K m + [S] Invert this => 1 = K m + [S] V i V max [S] 1 = Km + [S] V i V max [S] V max [S] 1 = K m 1 + 1 V i V max [S] Vmax

PowerPoint Presentation:

Dr. Hariharan. V, free download available in Internet

Hill equation:

Hill equation The binding of substrates to some enzymes facilitates binding of other substrates. This is called cooperative binding For enzymes which undergo this kinetics, Hill equation is used Dr. Hariharan. V, free download available in Internet logV i = n log [S] - log k’ V max - v i K’ = complex constant, n= degree of cooperativity

PowerPoint Presentation:

Dr. Hariharan. V, free download available in Internet Substrate –saturation kinetics for cooperative binding Graphical representation of linear form of Hill equation

PowerPoint Presentation:

Dr. Hariharan. V, free download available in Internet Thank you References: Harper’s Biochemistry Vasudevan

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