Lecture 14 - Kinetics

What does delta G dell us?

delta G tells us how favorable a reaction is, about thermodynamic potentiality

What does kinetics tell us?

Kinetics tells us how fast a favorable reaction will occur

Why are enzymes important

enzymes are important to kinetics because they accelerate reaction rates —→ 10²¹ times normal rate

Enzyme are mostly (but not always)

enzymes are most, but not always, proteins that bind substrate through weak interaction at their active site

In the active site, what does the protonation of key amino acids influence?

In the active site, the protonation of key amino acids influences enzyme mechanism

What are the three characteristics of enzymes?

1. Enzymes catalyze thermodynamically favorable reactions causing them to proceed at extraordinarily rapid rates

   • 10²¹ times over uncatalyzed rates

   • normally 10⁹-10²⁰

2. Enzymes bind specific substrates and catalyze specific reactions with high (>95%) yields

3. Enzymes are regulated and as are the agents of metabolism

what does specificity come from? - characteristics of enzymes

specificity comes from structural determinants at the active site

What is an example of an enzyme catalyst?

Urease

Enzyme Classification

What does the classification of enzymes follow?

Classification of enzymes allows the International Commission on enzymes official classification

• EC number

• class - 6

• sub-class

• sub sub-class

• protein

What are the 6 enzyme classes?

1. oxidoreductases

2. transferases

3. hydrolases

4. lyases (synthases)

5. isomerases

6. ligases (syhtetases)

What is an apoenzyme?

Protein part of the enzyme

What is a holoenzyme?

protein part of enzyme plus cofactors

What is a cofactor

non protein part that is essential fo catalytic function - ex: metal ions

What is a coenzyme?

non-protein organic molecule - B vitamin

What is a substrate?

the compounds whose reaction an enzyme catalyzes

What is the active site?

the specific portion of the enzyme to which a substrate binds during a reaction

Are all enzymes proteins?

no

What are ribozymes?

segments of RNA that displays enzyme activity in the absence of protein - pet idyl transferase

What is velocity?

Amount of product created or consumed per time

What is the velocity formula - no enzyme

what is K

what does one exponent in rate law mean

v = k[A]

• k is the rate constant (time)

• one exponent in rate law means first-order reaction

What is equilibrium

when the rate of the forward reaction equal the rate of the reverse reaction

What is the rate law for enzymes?

what does two exponents in rate law mean?

k[E][S]

k is rate constant (concentration)^-1 (time)^-1

^{two exponents in rate law means second order reaction}