Chapter 13 Flashcards
Catabolism
breakdown of complex molecules into smaller ones
anabolism
reactions that build cells
Catabolism provides energy for
anabolism. some energy is released as heat.
Metabolism
all chemical reactions in an organism
• Balance b/w catabolism and anabolism
Entropy
measure of randomness in a system
Cells use energy to assemble
disordered molecules into ordered ones.
Gibbs free energy change (ΔG)
how much energy is available to do work. Negative ΔG – reaction is favorable
ΔG=ΔH-TΔS
ΔH = change in enthalpy
• Heat absorbed/released as reactants become products
• ΔS = change in entropy
• More ordered = lower entropy
Excess reactants over products
more negative ΔG
environ factors that change ΔS and ΔG
• Temperature, pressure, ionic strength
Standard reaction conditions
• Temperature 298K, Pressure 1 atm, concentration 1M
accounts for concentration
ΔG=
ΔG° +RT lnQ
• Q – reaction quotient
• R – gas constant
• T – temperature in K
A+B ⟷C+D
Q=?
if products=reactants
if products < reactants
Q= C D/A B
If products = reactants, Q = 1; ln(1) = 0; standard conditions
If products < reactants, Q < 1; ln(<1) = negative number
temp can change Q
Cells often break down reactions
into several steps
Cells need energy carriers to transfer energy between reactions
energy carriers are
molecules that gain/release small amounts of energy in reversible reactions
atp is made by
phosphorylating ADP. atp is a medium energy carrier.
• Energy carried in phosphate bonds
three ways of transferring energy
- Hydrolysis releasing phosphate (ATP–>ADP)
- Hydrolysis releasing pyrophosphate (PPi)
- Phosphorylation of an organic molecule
• ATP can transfer its phosphate to hydroxyl group of another molecule (e.g. glucose)
Electron acceptor
molecule that accepts electrons
Nicotinamide adenine dinucleotide (NAD)
- NADH – reduced
* NAD+ - oxidized
Flavin adenine dinucleotide
- FADH2 – reduced
- FAD – oxidized
- Weaker electron donor than NADH
Activation energy (Ea)
determines rate of reaction
input energy needed to generate the high energy transition state
catalyst
lowers Ea, isnt consumed.
Carbohydrates
sugars, polysaccharides
lipids
milk, animal fats, nuts
• Broken down to glycerol and fatty acids ->acetate (TCA)
peptides
– proteins
• Deamination to produce carboxylic acid (TCA)
aromatic compounds
lignin
• Broken down to acetate (TCA)
fermentation
all e- from organic substrates are put back onto organic products
• No terminal e- acceptor
respiration
e- removed are transferred to inorganic electron acceptor
• Oxygen, nitrate (anaerobic respiration)
photoheterotrophy
bacteria gain energy from light while using organic C substrates for catabolism
enzymes
lowers activation energy
tca/krebs
add acetyl-CoA.removes one C. (removal of co2)
