Metabolic Regulation Strategies Flashcards
What are the five benefits of metabolic regulation
1 - Integration of Pathways (allowing things to move to other end-products)
2 - Regulation of Process (reactions only occurring when and where you want them)
3 - Direction of Flux (surges directed to needy processes or stored for future use)
4 - Efficiency (getting the most out of every carbon)
5 - Commitment of Resources (ensuring that resources are used for the desired end product)
Why are multi-step reactions important
They allow integration of reaction pathways, meaning that (until the committed step) intermediates can use branch points to meet the body’s immediate needs. Much more efficient than single-step reactions.
What distinguishes a linear reaction
One substrate goes in, and is synthesised to a different product.
Reaction rates are often linked to cofactor use or production (e.g. limited by ATP supply)
Early committed step, to drive the reaction quickly.
What distinguishes a cyclical reaction
They start and end with the same compound
Reaction rate is set by reactant concentration, which enters early.
Can re-direct metabolites to many different areas.
Would be ‘futile cycles’ if they did not provide a net benefit to the body.
What are Partitioned Domains
Areas on a membrane surface containing all the enzymes needed for a particular reaction - It can release them at a desired time, allowing the end-product to be synthesised at great speed.
Do reactions proceed in isolation?
No - pathways are often clustered. The body is very complex and products, cofactors, and intermediates all influence each other and can be used by something else.
Why is ATP important?
ATP bonds easily, and ATP hydrolysis is a very favourable reaction. As a result, the addition of ATP to a molecule can allow an unfavourable reaction to proceed favourably.
What are the correct terms for the process of ATP production?
Substrate-level phosphorylation (outside of TCA cycle) Oxidative phosphorylation (in TCA cycle)
What are the three primary methods of metabolic regulation?
Reciprocal Regulation - a particular signal leads to a specific response.
Control of substate availability - through compartmentalisation or otherwise controlling the flux.
Control of cofactor availability
How does short-term metabolic regulation work?
By controlling the activity of an enzyme through metabolic demand. Most commonly through the relative levels of ADP/ATP, but also through hormonal influence on a signal pathway, that can alter phosphorylation and so affect the speed of reaction.
How does long-term metabolic regulation work?
Through a persistent signal, most commonly through the levels of hormones that can either alter the behaviour of enzymes, or make new ones (which is particularly slow/long-term).
What is feedforward (in metabolism)?
A process used to speed up a regulation, wherein high levels of a substrate or intermediate can stimulate a rate-limiting step (commonly the first or last enzyme in the pathway) to create supply or demand, thus stimulating the reaction.
What is feedback (in metabolism)?
A process in which high levels of an intermediate or end product can inhibit or shut down the activity of an enzyme, or supply of a substrate, earlier in the reaction, slowing or stopping the entire pathway.
What is a committed step?
A step on a reaction pathway after which there are no more branchpoints, and a substrate or intermediate is destined to continue down that pathway to the end product. A very valuable tool for metabolic regulation. To speed production of a product, stimulate the committed step enzyme. To slow or stop it, inhibit the committed step enzyme.
Why is compartmentalisation a valuable tool in regulation
It prevents the release of key substrates and enzymes in a biological ‘locked room’. Regardless of how favourable the reaction is, it cannot proceed without a transporter.
Also very useful for controlling fluxes - storing things at a particular stage until they are ready to use.
