Metabolism Review Flashcards
All chemical reactions of a cell/organism
Metabolism
Series of biochemical reactions that convert >1 substrate into a final product
Metabolic Pathway
Pathway requiring energy to synthesize larger molecules
Anabolic
Pathway requiring energy to synthesize larger molecules
Anabolic
Pathway that releases energy and breaks down large molecules into small ones
Catabolic
Ability to do work
Energy
Total amount of energy in the universe is constant; energy cannot be created/destroyed
First Law of Thermodynamics
Within each chem. reaction, some energy is lost in a form that is unusable. This results in increased entropy
Second Law of Thermodynamics
Amount of energy available to do work (usable energy)
Gibb’s Free Energy
Energy is released in a chem. reaction (delta G < 0); products of these reactions have less free energy than substrates
Exergonic Reaction
Chem. reaction requires input of energy (delta G > 0); products have more free energy than substrates
Endergonic Reaction
What is the main source for activation energy in a cell?
Heat energy
Is ATP hydrolysis reversible?
Yes
What energy does the sodium potassium pump use?
Energy from exergonic ATP hydrolysis
How many sodium ions exit the cell in the NaK+ pump?
3
How many potassium ions enter the cell in the NaK+ pump?
2
Catalyst
Increases the rate of a reaction without being consumed
Why do cellular reactions need catalysts?
Activation energies are too high for heat energy from the surroundings to overcome
Protein catalysts that bind with reactant molecules to promote chemical processes; very specific and can only catalyse a single reaction
Enzyme
What is an example of a non-protein enzyme?
Ribosomes
Chemical reactants to which an enzyme binds
Substrate
Place on an enzyme where substrate binds
Active Site
What determines enzyme-substrate specificity?
3D shape of enzyme and reactants
Mild shift in shape of enzyme/substrate that optimizes reactions; expansion of “lock and key” model
Induced Fit
What determines the 3D shape of a protein?
Amino Acid Sequence
How can an enzyme help the substrate reach its transition state?
- Position two substrates so they align perfectly
- Provide an optimal environment within active site
- Contort/stress substrate so it’s more likely to react
- Temporarily react with substrate
How can enzymes be regulated?
- Modifications to temp. or pH
- Production of molecules that inhibit/promote enzyme function
- Availability of coenzymes or cofactors
Have a similar shape to substrate that competes with it for the active site; slow reactions without affecting maximal rate
Competitive Inhibitors
Bind to the enzyme at a different location than the active site, causing a slower reaction rate; slow reaction rates and reduce maximal rates
Noncompetitive Inhibitors
Modify active site of an enzyme so substrate binding is reduced/prevented
Allosteric Inhibitors
Modify active site of an enzyme so affinity for substrate increases
Allosteric Activators
Inorganic helper ions (iron or magnesium)
Cofactors
Organic helper molecules (vitamin C)
Coenzymes
Enzymes required for certain cellular processes are housed separately inside structures with their substrates
Compartmentalization
End product of a pathway inhibits an upstream step; important regulatory mechanism in cells
Feedback inhibition
