Bioenergetics & Kinetics Flashcards
Define entropy
The degree of disorder in a system; ΔS = + in a favorable reaction
Define enthalpy
Pertains to the total heat content of the system (i.e. internal energy); ΔH = - in a favorable reaction (exothermic; heat is released)
Define free energy
Gibb’s free energy measures the favorability/usefulness of a reaction. ΔG = ΔH – TΔS. –ΔG = a favorable reaction that occurs spontaneously.
Define high-energy compounds
High-energy compounds generally contain thioester bonds or high-energy phosphate bonds. Energy is released by hydrolysis of high-energy bonds.
Define oxidation-reduction reactions
Involves an exchange of electrons. To be reduced is to gain electrons. Measured by reduction potential E, a measure of readiness of molecule to accept electrons. +E = readily accepts (favorable reactions have +E). –E = readily donates. ΔG = -nFΔE.
Define First Law of Thermodynamics
Energy can neither be created nor destroyed; it just changes form.
Define Second Law of Thermodynamics
The entropy of the universe is always increasing.
What are different forms of energy?
Kinetic (thermal, radiant, mechanical, electric) & Potential (stored in chemical bonds, concentration gradients, electric fields, and redox pairs)
What are ‘standard conditions?’
1atm, 298K, 1mmol Mg, aqueous environment, pH 7
What is the sign of standard free energy in a favorable reaction under standard conditions?
Negative
What are the major high-energy compounds used in biological systems?
ATP, acetyl CoA, phosphocreatine, phosphoenolpyruvate
What is the difference between coenzymes and cofactors?
Coenzymes are used up in an enzymatic reaction, while cofactors are not.
A coenzyme or cofactor tightly bound to an enzyme is called a ____________. The resulting complex is called a ____________. The protein in isolation is called a _____________.
Prosthetic group. Holoenzyme. Apoenzyme.
Are enzymes optimized to bind the substrate, transition state, or product?
Transition state
In the Michaelis-Menten equation, what is Km?
The substrate concentration at which enzyme velocity is half the maximal
In the Michaelis-Menten equation, what is Kcat?
The number of substrate molecules turned over into product per enzyme per second (aka how quickly the enzyme works)
What does the value of kcat/km indicate about the efficiency of an enzyme?
The higher the value, the more efficient the enzyme
What kind of enzyme usually recognizes palindromic DNA sequences?
Restriction enzyme
Gel electrophoresis separates DNA on the basis of what characteristic?
Size
SDS-PAGE separates proteins on which basis?
Size
