Define metabolism
sum of all chemical transformation that occur in living cells
metabolism = catabolism + anabolism
1st law of thermodynamics?
e=mc^2
total energy of the universe is constant. It can’t be created or destroyed but can be transformed
2nd law of thermodynamics?
the universe has a tendency to increase disorder.
more disorder = spontaneity
3rd law of thermodynamics?
as the temp approaches absolute zero (0k or -273.8deg ) atomic motion stops (but electronic motion is not affected)
What happens during catabolism?
break down of energy containing compounds.
releases energy as ATP and reduced electron carriers (NADH)
How can energy be released?
as ATP of reduced electron carriers: NACH, NACPH, FADH2
Define Gibbs free energy
the energy available in a system
What is the Gibbs free energy equation?
G = H - TS
H=enthalpy
S=entropy
T=temp in K (25 C = 298k)
What is enthalpy?
heat content reflecting the number and type of bonds
What is entropy?
extent of disorder in the system
do organized systems have high or low entropy?
low entropy (low disorder)
When energy is released, what is the sign of delta G? Is this spontaneous?
negative
yes
When energy is absorbed, what is the sign of delta G?
positive
no
What is delta G naught?
What is delta G prime naught?
standard free energy change at 25C, 1atm, 1M initial conc of solutions. Used by chemists/physicists
biochemical standard free energy change at pH 7. used by biochemists
what is the delta G in oxidation of glucose?
deltaG = -2840kJ/mol
is the oxidation of glucose spontaneous or not spontaneous?
spontaneous (because negative delta G)
what is the terminal electron acceptor?
oxygen
because it
delta G gives no information on the reaction rates. T or F?
T
At equilibrium, delta G prime naught = ?
delta G prime naught = -RTln(K’eq)
K’eq = products / reactants
what is the relationship between delta G prime naught and K’eq?
directly proportional
What does a small or big K’eq mean?
small K’eq = +delta G prime naught = not spontaneous = favours substrate
big K’eq = -delta G prime naught = spontaneous = favours product
why are reactions coupled together?
to drive unfavourable steps in a metabolic process
when you find the overall K’eq, do you multiply or add K’eq values?
multiply
what are referred to as high energy compounds?
when delta G prime naught of hydrolysis is bigger than -25kJ/mol
What are the 4 chemical basis for the high energy stored in the phosphoanhydride bonds?
- 4 negative charges (repulsion is from bond stress. hydrolysis releases electrostatic stress)
- Resonance delocalization of PO4^2-
(delocalization = more molecules = more disorder = higher delta S = higher delta G) - ADP ionizes releasing H+ (more molecules = increases delta S)
- ATP hydrolysis increases solvation of ADP and Pi
(need less h20 molecules to solvate ATP than inorganic phosphate = increases randomness = increases E)
what is solvation
formation of sphere of hydration
what is a hydride
proton with two electrons
H-
transports electrons in biological systems
what is the general formula for half cell reactions?
Ared Aox + ne-
Box + ne- Bred
overall: Ared+box Bred + Aox
what does the equilibrium point for REDOX reactions depend on?
relative affinity of Aox and Box for electrons
in the reduction of Fe3+ by Cu+, which is the oxidizing and reducing agent?
Fe3+ is the electron acceptor (oxidizing agent)
Cu+ is the e donor (reducing agent
which agent has an excess of e-?
reducing agent
which agent picks up e-?
the oxidizing agent
what are the half cell reactions of Fe3+ by Cu+?
Cu+ Fe2+
overall: Fe31+ + cu+ Fe2+ + Cu2+
What is E naught?
reduction potential tendency to gain electrons
does reducing potential decrease or increase down the ETC?
decrease
what does a large positive Eprime naught mean?
bad reducing agent. good oxidizing agent
wants to take electrons
ex: oxygen
what does a negative E prime naught mean?
good reducing agent. bad oxidizing agent
wants to give away electrons
ex: H2
Is the beginning or the end of the ETC a better reducing agent?
the agent in the beginning of the chain will be the best reducing agent. (decreases as you move down)