Metabolism Flashcards
metabolic pathway
series of enzyme catalyzed reactions
two major purpose of metabolism
1) to obtain usable chemical energy form the environment
2) to make specific molecules that cells need to live and grow
anabolic pathways
USE energy to build larger molcules (generally reductive)
electrons in anabolic pathways
used to make new bonds
catabolic pathway
release energy (generally oxidative)
electrons in catabolic pathway
removed as bonds are broken
Amphibolic pathway
operate in both anabolic and catabolic
carbohydrate storage
glycogen
fat storage
triacylglycerols
carbons in cataboilism
more oxidized (usually)
fatty acids oxidation
fatty acids are more reduced then carbohydrates and need more steps to ozidize them
Free energy
review symbols
What do you need for a reaction to proceed forward
DeltaG^1reaction must be negative (exergonic)
Actual Free energy > 0
reaction will not occur (in fowards direction)
Actual Free energy < 0
reaction will occur (spontanous)
Actual Free energy «0
May be irreversible
Actual Free energy appox 0
reaction is reversible
free energy close to equilibrium
will be near 0
irreversible steps
usually regulated
Steady-State (metabolic pathways)
concertration of metaboilic intermediates often do not change drastically (the amount of water going in equals the amount of water going out)
Free energy in Pathways
must be less then 0. Nothing happens if it’s not exergonic
reversible steps
not usually regulated
Rate-limiting step
irreversible regulated reaction that determines the overall rate
product inhibition
An enzyme is inhibited by the product of its reaction (A being inhibited by B)
feedback inhibition
An enzyme is inhibited by a metabolite further down the pathway (downstream) (A being inhibited by E)
Upstream Activation
(feed-forward Activation)
A increase E. As A increases B,C,D would want to increase to maintain steady state.
reciprocal regulation problem
opposing pathways catalyze the reverse of another pathway (short of like to people moving boxes in separate ways, no net movement but a waste of energy)
reciprocal regulation
pathways are regulated to ensure that both do not operate simultaneously.
High-energy intermediates
compounds which contain usable chemical energy
Three major types of high energy molecules
Electron carriers, nucleoside triphosphates, thioesters
Catabolism Ox or Red
Oxidative
metabolites are oxidized (lose electrons), cofactors are reduced (oxidizing agents), usually NAD+ and FAD
Anabolism Ox or Red
reductive
metabolites are reduced (gain electrons), cofactors are oxidized (reducing agents), usually NADPH
Nucleotides role in metabolism
electron carriers. The nitrogen base portion of these dinucleotides enables them to undergo a reversible reduction reaction
FAD/FADH2 as a prostetic group
FADH2 must be reoxidized back to FAD for next enzyme cycle
why is ATP high energy
phosphoanhydide bonds
phosphoanyhdride bond
hydrolosis is -32kJ/mol, formation is +32 kJ/mol
thioesters
high energy compunds, similar to esters but have no electron delocalization
Adenosine triphosphate
energy currency, phophoanhydride bond makes it high energy. generated by catabolism
Adenosine triphosphate genrrated by catabolism
direclty as part of enzyme rxn, via reduction of NADH/FADH2
Adenosine triphosphate uses
driving unfavourable reactions (coupling), movement (muslces), primary active transport (ion pump).
Coupling of free energies
free energy changes for reactions are additive. An unfavourable rxn can occur if a favourable rxn occurs in concert, combined they must be spontaneous.
Phosphate transfer potential
free energies of hydrolysis for phosphate-containing compounds
