Lecture 7 + 8 Flashcards
1
Q
deltaH = deltaE
A
- delta H is a direct measure of the energy of a process
- value of H depends on the number and kind of chemical bonds in the reactants and products
- enthalpy (H) measures the change in temp of a water jacket surrounding a reaction chamber during a chemical reaction
2
Q
Entropy (S)
A
- measure of disorder or randomness
- increases in a spontaneous reaction
- systems have a tendency to increase disorder, any process leading to S becoming great is thermodynamically favored
- ex. melting ice -> requires input of heat, happens spontaneously, ordered to less ordered state
- hydrophobic effect
3
Q
Gibbs free energy
A
deltaG = deltaH - TdeltaS
units = kJ/mol
4
Q
Protein folding and entropy
A
- unfolded protein is disordered, folded is more ordered S< 0 when protein folds
- in an unfolded protein hydrophobic regions are exposed to polar water molecules which order themselves around the hydrophobic regions to maximize hydrogen bonding, organized water is low in entropy
- S > 0 for water when protein folds
- protein folding increases order of protein but releases ordered water molecules (increases disorder of surroundings)
- net entropy S>0
- protein folding optimizes weak interaction (electrostatic, H-bonding, van der Waals) entropically favorable
5
Q
What is deltaG a measure of
A
- measure of the distance a system is from its equilibrium position
- large deltaG = further from equilibrium
- deltaG = 0 = equilibrium
6
Q
deltaG = - and deltaG= +
A
- deltaG = -, Keq is greater than 1 (more products than reactants)
- deltaG = +, Keq less than 1 (more reactants than products)
7
Q
What effect do enzymes have on biological reactions
A
- enzymes are proteins that catalyze reactions
- increase rate of reaction by lowering the activation energy
- enzymes are catalyst
- accelerate reactions by 10^5 to 10^17
8
Q
3 key aspects of enzymes
A
- enzymes bind substrates with high affinity and specificity
- substrate binding to the active site induces structural changes in the enzyme
- enzyme activity is highly regulated in cells
9
Q
Lock and Key model
A
- substrate is a perfect fit for the enzyme active site
10
Q
Induced fit model
A
- both substrate and active site must be distorted and fit conformations close to the transition site
11
Q
What are cofactors and prosthetic groups
A
- non protein compounds that are not part of the enzyme but are required for activity
- can be simple inorganic metal ions or complex organic or coenzymes
- 30% of enzymes use cofactors
- prosthetic group = coenzymes that are tightly bound to enzymes or other proteins
12
Q
General strategies for enzyme catalysis
A
- enzyme binds to two substrate molecules and orients them to encourage a reaction between them
- binding of substrate to enzyme rearranges electrons in the substrate, creating partial negative and positive charges that favor a reaction
- enzyme strains the bound substrate molecule forcing it toward a transition state to favor a reaction
