Week 7-8 Flashcards
1
Q
METABOLISM
- Metabolism
- Catabolism
- Anabolism
A
Metabolism: break down
- Metabolic reactions involve energy changes
- Energy is the capacity to do work/ capacity for change
- Energy changes are usually associated with changes in chemical composition
- Chemical energy is stored in bonds
Catabolism: break down
- Involves the breakdown of complex macromolecules
- Causes release of energy stored in chemical bonds
- Occurs via oxidative pathways
- Released energy can be recaptured in new chemical bonds or used as kinetic energy
Anabolism: build up
- Uses precursors (small molecules) to synthesize complex macromolecules
- Requires energy input
- Energy is captured in the chemical bonds and stored as potential energy
- Large molecules broken down in CATABOLIC reactions and are oxidised to produce electrons
- Eventually broken down into precursors (CO2, H2O, NH3)
- These precursors are used to synthesize larger molecules in ANABOLIC reactions, where electrons are used as energy
- Hence the reactants are reduced (reductive synthesis)
- Cycle repeats
2
Q
METABOLISM
- Laws of Thermodynamics
- Entropy
A
1st Law of Thermodynamics:
Energy is neither created or destroyed
2nd Law of Thermodynamics:
When energy is converted from one form to another, some energy is lost due to disorder (entropy)
Entropy:
- Entropy is the disorder in system
- It takes energy to impose order on a system
- Unless energy is applied to a system, it will be randomly arranged/disordered
3
Q
METABOLISM
- Energy conversions
A
- In a cell, you have both exogenic and endogenic reactions
- Exogenic provide the necessary energy for endogenic reactions to occur
ΔG = ΔH - TΔS
where ΔG = free energy/usable energy
(exogenic -ve, endogenic +ve)
(G = 0, system = equilibrium)
ΔH = total energy (enthalpy)
T = absolute temperature
ΔS = usable energy (entropy)
4
Q
METABOLISM
- ATP
A
- In all metabolism, the final objective is to gain ATP
- ATP = adenosine triphosphate
- Consists of 3 phosphate groups, a sugar, and an adenosine nucleotide
- It is a high energy molecule
- ATP has 4 -ve charges in proximity, hence there is a strong electron repulsion
- When hydrolysised for the first time, the first phosphate group will break off, forming adenosine diphosphate
(less for 2nd time, forming adenosine monophosphate)
(adenosine is made up of sugar+adenosine nucleotide) - Energy released is directly proportional to the charge repulsion felt by the molecule
- This is the energy used to power ENDOGENIC reactions
5
Q
METABOLISM
- 5 principles that govern metabolic pathways
A
- Complex chemical reactions occur as a series of separate pathways
- Each reaction is catalysed by a specific enzyme
- Many metabolic pathways are similar in all organisms
- Key enzymes can be inhibited or activated to alter the rate of the pathway
- In eukaryotes, metabolic pathways are compartmentalised n specific organelles
