Intro to metabolism Flashcards
what is catabolism?
the breaking of bonds
-releases energy
what is anabolism?
formation of new bonds
-uses energy
how are FA activated?
linkage to an Acetyl-coA
what organ can carry out all major pathways in fuel metabolism?
the liver
True or FALSE: metabolic pathways are irreversible and highly endergonic
False; they are highly irreversible and EXERGONIC
what makes metabolic pathways irreversible?
a rate limiting step
-confers directionality
True or False: all metabolic pathways are regulated
TRUE
what is reciprocal regulation?
the regulation of opposing pathways so that only one is on at a time
if an enzyme functions near equilibrium how does this affect the direction of the rxn?
the rxn is reversible and depends on [substrates]
if an enzyme functions far from equilibrium how does this affect the direction of the rxn?
the rxn that is being catalyzed is irreversible and their activity is regulated in response to cell signaling
what is synchronous regulation?
one pathway of concern with enzymes that regulate the rxn based on [ ]
what factors control enzyme level?
-transcriptional regulation
-mRNA degradation
-Translational regulation
- protein degradation
what factors control enzyme activity?
-allostery
-covalent modification
-substrate availability
-interaction with regulatory protein
-sequestration
what is product inhibition?
when the product of an enzymatic rxn inhibits the enzyme that produced it
what is feedback inhibition?
when the end product of a metabolic pathway inhibits an enzyme involved earlier in the pathway, reducing or halting the production of that product
does activation shift a graph left or right?
left
what is substrate cycling?
simultaneous activity of both forward and reverse reactions catalyzed by different enzymes that have the same substrate and product
why is substrate cycling needed?
it allows for steady-state metabolism and quick changes in metabolic activity
how does substrate cycling differ from reciprocal regulation?
Substrate Cycling: simultaneous activity of both forward and reverse pathways, which can be energetically inefficient but allows for rapid changes in metabolic flux
Reciprocal Regulation: ensures that only one pathway is active at a given time, avoiding energy waste by turning off one pathway while turning on its opposite, depending on cellular conditions.
what are general characteristics of second messengers?
-low amounts at resting
-regulated synthesis and destruction
-small and highly mobile
-non-protein but act through a protein
what kind of receptors regulate glucagon and epinephrine?
GPGRs
what steps are involved in G proteins?
1) ligand (first messenger) binding to GPCR causing conformational change
2) inactive G protein is bound to GDP which is exchanged for GTP upon activation
3) alpha subunit dissociates from beta/gamma units and the alpha-GTP subunit interacts w adenyl cyclase to convert ATP into cAMP
4) cAMP can then activate protein kinase A which will phosphorylate target enzymes
what bonds are broken and made when converting ATP TO cAMP?
phosphodiester bond made and phosphoanhydride bond broken
How many cAMP molecules bind to PKA in order to activate it?
4
-2 binding sites per unit
explain the steps in G protein deactivation?
intrinsic GTPase activity of the alpha subunit causes GTP to convert back to GDP and the alpha-beta-gamma subunit reforms
what enzyme breaks down cAMP to AMP ?
phosphodiesterase
what effect does caffeine have on cAMP?
Caffeine affects cAMP levels by inhibiting an enzyme called phosphodiesterase
