The induced dipole ( d,e ) and the dispersion forces (f) depend on the distortion of the electron distribution in a nonpolar atom or molecule. The symbols q-, q+ denote a fraction of an electron or proton charge (a partial charge δ ). Types of non-covalent interactions.
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The induced dipole (d,e) and the dispersion forces (f) depend on the distortion of the electron distribution in a nonpolar atom or molecule. The symbols q-, q+ denote a fraction of an electron or proton charge (a partial charge δ)
Biochemistry, Mathews, Van Holde, Ahern
In large animals, collagen may make up a third of the total protein mass.
Collagen fibers form the matrix material in bone, on which the mineral bind; it makes up a major portion of tendons and is an important component in skin.
Example of helical fibrous protein
Stacked β sheets
This arrangement of alternating Gly and Ala or Ser makes this fibrous protein VERY strong and inextensible, but flexible – perfect for building.
Dissolvable films of silk fibroin for ultrathin conformal bio-integrated electronics. Nature Materials 2010.
Most of the synthesizing, transporting, and metabolizing that goes on in the cell is carried out by these proteins.
Aside from the difference in shape (elongated vs. spheroidal) and solubility (insoluble vs. soluble), fibrous proteins generally have only primary and secondary structure whereas globular proteins have tertiary and sometimes quaternary structure in addition to primary and secondary structure.
2nd Law of Thermodynamics:
The entropy (disorder) of an isolated system will tend to increase to a maximum value.
In an isolated system, disorder is the ruler!!
BUT….we never deal with isolated systems in biology!!!!
EVERY biological system is open to exchange with matter and energy in its environment.
G = H – TS
∆G = ∆H – T∆S
MAKES ∆G NEGATIVE!!!
When ∆G is negative, is the process
endergonic or exergonic??
A catalyst may increase the rate for some reactions but the favored direction is always determined by ∆G.
You’ve got to pay the piper for organization – there is a price for life!
Exergonic:(Releases Energy) Cell Respiration Catabolism
(Requires Energy) Active transport Cell Movements Anabolism
ADP + Pi
Synthesis of ATP from ADP and Pi requires energy
Hydrolysis of ATP to ADP and Pi releases energy
The energy ATP releases is greater than the energy most other molecules could deliver
An enzyme works by forcing the substrate(s) into a position or orientation that allows for collisions between molecules to occur or for atoms with a molecule to stretch and bend.
This is the induced fit model
Originally biochemists adopted the “Lock and Key” model of enzyme catalysis, but the Induced Fit is more accurate – BOTH the enzyme and the substrate change their conformation in order for catalysis to occur.
The binding of glucose to hexokinase induces a major conformational change in the enzyme. The enzyme is a single polypeptide chain, but its two major domains are shaded differently to distinguish them. Notice how the cleft between the domains closes around the glucose molecule!
The zinc atom serves as a metal ion catalyst to promote hydrolysis.
It does so by stabilizing the negative charge on the oxygen in the transition state.
The bond cleaved is indicated by the red wedge.
Prevents Cellular Respiration by blocking cytochromeoxidase in the mitochondria
Was used in WWI as a chemical warfare agent – causes severe burns, blindness
Good ol’ Penicillin – antibiotic inhibits transpeptidase and enzyme that helps build the cell wall