Metabolism in General Flashcards
(18 cards)
Metabolism is divided into two parts. State them
Catabolism and anabolism
Explain catabolism
- Also known as degradation, in which nutrients and cell constituents are broken down to salvage their components and/or to generate energy
- reaction carry out the exergonic (spontaneous reactions) oxidation of nutrient molecules to release free energy
Explain anabolism
- or biosynthesis, in which biomolecules are synthesized from simpler components
- free energy released by catabolic reaction is used to derive anabolic reaction which is usually endergonic (non-spontaneous reaction)
Define metabolic pathway
A series of connected enzymatic reactions that produce specific products; many pathways are branched and interconnected
What happens in a catabolic pathway?
Complex metabolites are exergonically broken down into simpler products, in many cases, into acetyl-CoA
-The free energy released is conserved by the synthesis of ATP from ADP+Pi or by the reduction of the coenzyme NADP+ to NADPH
What are the major free energy sources for anabolic reactions?
- ATP
- NADPH
What are the roles of ATP and NADPH in metabolism?
ATP and NADPH generated through the degradation of complex metabolites are the sources of free energy for biosynthesis and other reaction
Explain what happens during metabolism
1) complex metabolites are first degraded to their monomeric units and then into a common intermediate such as acetyl-CoA
2) Acetyl-CoA will then oxidize into CO2 via citric acid cycle (CAC) with simultaneous reduction of NAD+ & FAD into NADH & FADH
3) NADH & FADH will deoxidize by O2 during oxidative phosphorylation and yields H2O & ATP
Define flux
Rate of flow of metabolite through a metabolic pathway
Flux is controlled by regulating the activities of the enzymes that catalyze its rate-determining steps by:
1) Allosteric control
2) Covalent modification or enzyme interconversion
3) Substrate cycles
4) Genetic control
Describe the ‘High Energy’ compounds
- Compounds that will breakdown and produce an exergonic process that can drive any endergonic processes.
- Refers to compounds with the standard free energy of hydrolysis of more than -25kJ/mol
- We can determine the free energy by comparing it to the free energy of hydrolysis of the phosphoryl donor and acceptor
Define the standard free energy of phosphate hydrolysis
The measure of the tendency of phosphorylated compounds to transfer their phosphoryl group to H2O
List examples of ‘High Energy’ compounds
- ATP
- Phosphoryl groups
- Thioester compounds
ATP
- Free energy is produced through the cleavage of one/both of its phosphoanhydride bonds
- It is high energy because the phosphoanhydride groups are more destabilizing than the hydrolysis product
Phosphorylated compunds
- At standard condition:
“High energy” phosphate group can spontaneously transfer a phosphoryl group to ADP to form ATP - ATP then, can spontaneously transfer a phosphoryl group to the others to create a “low energy” phosphate group
Thioester compounds
It is “High energy” due to the presence of its thioester bond with an acetyl group.
- It’s ∆Go= -31.5 kJ/mol which is more exergonic than ATP and other esters
- Function: carrier of acetyl and acyl groups (for acetylation)
Explain the oxidation-reduction reactions in metabolic pathways
Aerobic metabolism
- Metabolites are oxidized to CO2 to produce free energy in the form of ATP (e is transferred through molecular carries into oxygen molecules)
Anaerobic metabolism
- Production of ATP (lower yield) through the intramolecular redox reaction of metabolites without the presence of O2 as the oxidizing agent
Give examples of the electron carriers in metabolic pathways
NAD+, FAD
