MCB Lecture 2 Building Blocks Flashcards
What are some general functions of protein?
Structure Enzymes Hormones (signalling molecules) Membrane receptors Channels Molecular machines
What proportion of the dry weight of cells does protein make up?
Half of the dry weight of a cell
What is GFP and what is its significance?
Green fluorescent protein
Illustrates the variety of properties that proteins have.
This protein fluoresces all by itself : no chromophore bound
E amino acid sequence produces colour, and guides protein folding
Single point mutations give other colours
What is molarity?
Concentration of solutes in solvents
What are the weak non covalent bonds?
Hydrogen bonds
Van Der Waals interactions
Hydrophobic force
What is free energy?
Energy available in a cell that is accessible for chemical reactions
What is delta G?
Change in Gibbs’ free energy
What is an exogenous reaction, and what is delta-G for exogenous reactions?
Release of energy
Negative delta G
What is an endergonic reaction, and what is delta-G for endergonic reactions?
Absorption of energy
Positive delta G
How is delta-G related to delta-H and delta-S?
Delta-G = delta-H - T x delta-S
In terms of entropy and heat, what are the requirements for an exogonic reaction?
Big release of heat or big increase in entropy
What does positive delta-H represent?
Absorption of energy
What does negative delta-H represent?
Release of heat
What does negative delta-S represent?
Decrease in entropy
What does positive delta-S represent?
Increase in entropy
Why is delta-G (change in Gibbs’ free energy) a useful thing for biochemistry?
- Predict spontaneous reactions
- Position of equilibrium
- Tightness of binding
What is delta-G nought primed?
This is the stand free energy change for a reaction
How does delta-G nought primed relate to K (equilibrium constant)?
Delta-G nought primed = - R T lnKd
What is the relationship between equilibrium and dissociation constants? (K and Kd)
They are reciprocals
What does [L] = Kd mean?
Half of the substrate is bound to the enzyme
What is the difference between delta-G and delta-G nought primed?
Stand lab conditions vs. standard biochemical conditions
What are the conditions for delta-G nought primed?
pH 7
[h2o] = 55.5 M
What are some of the ways that unfavourable reactions can be made to go?
- Couple with highly favourable reaction
- Remove product
- Have high concentration of reactant
How does Kd relate to tightness of binding?
What indicates weak, intermediate and strong binding?
Smaller the Kd, the tighter the substrate-enzyme binding
Weak: mM
Intermediate: microM
Tight: nM
