Cell metabolism Flashcards
The oxidation of Acetyl CoA provides
Large amounts of ATP
What is the purpose of enzymes
Increase reaction rate without being consumed
Describe enzymes
Not consumed, highly selective, bind specific substrate for 1 reaction. Usually named by substrate and -ase
What is the Michaelis constant?
The concentration of a substrate that results in half-max reaction velocity. A high kM indicates a low affinity and a low kM indicates a high substrate-enzyme affinity
What is a regulatory mechanism for enzymatic pathways?
Substrates are usually present in concentrations near their kM, so small changes in substrate concentration result in tight control of the pathway
What is the main role of enzymes?
Decrease energy of activation for reaction
What does the regulatory enzyme do?
Rate limiting step, committed step in reaction
Are rate limiting enzymes always committed steps?
Yes, but committed steps are not always rate limiting
What factors can affect enzyme activity?
pH and Temperature (positive relationship)
Describe the enzyme activation pathway
Pronezymes (zygomens, not active) are activated to active enzymes. The activation of this enzyme may activate other enzymes from proenzymes (amplification pathway)
Name enzyme regulatory roles
Controlling rate limiting steps, controlling committed steps, negative feedback on enzyme by excess subtrate
Describe allosteric control of enzymes
A substrate will bind to a ligand at a place other than the active site on an enzyme and either up-regulate or down-regulate enzyme activity by changing enzynme’s affinity for the substrate
Describe positive and negative feedback
An excess of product [B] will down regulate the enzyme, an excess of substrate [A] will upregulate the enzyme
Name types of enzyme control
pH, temperature, Gentic control (slowest, via transcription), covalent modification (phosphorylation), allosteric (non-covalent ligand) control
Name types of enzymes and function
Kinase (phosphorylation), Dehydrogenase (removal of hydrogen), Mutase (transfers functional group), Isomerase (converts ketose to aldose), Enolase ( dehydration)
