Metabolism Flashcards
Overall theme of metabolism
Simplicity: limited number of enzymes to perform many different functions
Phototrophs
Organisms that derive energy from light
Chemotrophs
Organisms that derive energy from breaking down chemicals
Anabolism
Building complex molecules from simpler ones
Useful energy + simple precursors -> complex molecules
Catabolism
Breaking down complex molecules to harness energy
Fuel (carbs, fats, proteins) -> CO2 + H2O + useful energy
Coupling of reactions
Using a favorable reaction to power an unfavorable one
Only works if reactions take place near each other (in the same cellular compartment)
Currency of metabolism
ATP (adenosine triphosphate)
Contains energy-rich phosphoanhydride bonds (not stable: many negative charges right next to each other)
Favorable hydrolysis of phosphates: get rid of some of negative charge
Standard delta G value of hydrolysis of ATP to ADP
-30.5 kJ/mol
Electron carriers that are derivatives of ATP
NAD+ and FAD
A in both carriers refers to adenine
Reasons why hydrolysis of ATP is favorable
- Phosphate liberated from ATP can be stabilized through resonance
- Electron repulsion of 4 negative charges on ATP is relieved when hydrolyzed
- More water can bind ADP and the free phosphate than ATP (more bonds, more stability)
What phosphoenolpyruvate (PEP) is used for
Doesn’t make good carrier: too big and too hard to regenerate
Has higher energy than ATP, so it can be used to phosphorylate ADP to ATP
Why body performs anaerobic metabolism before aerobic metabolism
There are more steps to complete in aerobic than anaerobic metabolism, so body does simplest things first
Calculating change in equilibrium constant of reaction coupled to ATP hydrolysis
1. Calculate Keq (Keq= 10^(-delta G/2.303RT) R=8.314*10^-3 kJ/(mol*K), T=temp in K 2. Subtract 30.5 kJ/mol from delta G 3. Recalculate Keq with new delta G 4. Subtract old value from new value
Way that energy to derive ATP is generated
Energy is generated from oxidizing molecules, which is then used to create a phosphoryl-transfer compound or an ionic gradient
Why CO2 acts as body’s waste
CO2 is completely oxidized- no more energy can be harnessed from it
Do sugars or fatty acids generate more energy?
Fatty acids generate more energy than sugars: they are less oxidized, so they have greater oxidizing potential
Oxidative phosphorylation
Process of using ion gradients to form ATP
90% of ATP is made through this process
Common pathway for making ATP out of nutrients
Fats, polysaccharides, and proteins follow same breakdown pathway to form ATP
Electron carriers
Molecules that are used to fuel oxidation or biosynthesis
Necessary when reactants can’t be reduced or oxidized directly
2 most common: NAD and FAD
Nicotinamide adenine dinucleotide (NAD)
Mobile electron carrier
Receives one proton and two electrons from the substrate (H-)
Flavin adenine dinucleotide (FAD)
More immobile electron carrier- often part of complex
Unlike NAD+, can take on both protons and electrons
Acetyl-CoA
Activated carrier of 2 carbon groups
Transfers acetyl group: moves carbons
Why enzymes are needed in the reactions of high energy carriers
The reactions of the high energy carriers are slow, so enzymes are needed to speed them up
Oxidation-reduction
Reaction that involves electron transfer
Ligation requiring ATP cleavage
Reaction that involves formation of covalent bonds coupled to hydrolysis of ATP
Isomerization
Reaction that involves rearrangement of atoms to form isomers
Group transfer
Reaction that involves the transfer of a functional group from one molecule to another
Hydrolysis
Reaction that involves cleavage of bonds by the addition of water
Addition or removal of functional groups
Reaction that involves addition of functional groups to double bonds or their removal to form double bonds
