Metabolic Regulation Flashcards
Why catabolic pathways only run when we need energy?
Too expensive to run catabolic pathways; prevent waste,flux
Why flux is controlled at irreversible steps?
1.flux through irreversible steps does not depend on substrate and product []; 2. they are characterized by a large negative delta G for the reaction, which makes climbing the hill back to S too difficult.
____ reactions have delta G are close to zero. The flux of the reaction only depends on ____ and ____ ____. These ____ can be hard to control.
Reversible
substrate
product []
[]
How are these steps regulated?
The ____ catalyzing the ____ steps are sensitive to ____ ____ and ____.
enzymes
irreversible allosteric activators
inhibitors
What are allosteric activators and inhibitors?
Allosteric activators and inhibitors are compounds that bind to an Allosteric site. Allosteric site is NOT the active site.
Allosteric inhibitors ____ ___ enzymes, ____ them from catalyzing their chemical reactions. ____ signal to the cell that we ____ ____ of energy. Many of these inhibitors are known as ____ ____.
TURN OFF preventing Inhibitors HAVE PLENTY
Feedback inhibitors.
____ enzymes, the binding of ____, ____ and ____ ____ to one subunit affect the ____ of other subunits.
Oligomeric
substrate, inhibitor and product molecules
activity
In the ____ of inhibitors, subunits are ____ and ____ to substrate.
In the ____ of inhibitors, subunits are ____ and not ____ to substrate. However, that the enzyme can be ____ to bind to substrate at ____ __ (____ than physiological []). Binding of __ is communicated to other subunits. km is ____.
absence relaxed receptive presence "tense" receptive "force" higher [S] higher S higher
Allosteric activators ____ __ enzymes, ____ them to catalyze their chemical reactions. ____ ____ signal to the cell that we are ____ ____ of energy. Many activators are known as ____ ____.
TURN ON allowing Activator molecules RUNNING OUT
Feedforward activators
A ____ ____ is usually a ____ ____ early in a pathway, and it ____ an enzyme that catalyzes a ____ further down in the pathway.
feedforward activator
metabolite produced
activates reaction
Allosteric activators that affect the function of ____ ____. The enzyme can adopt one of ___ states depending on whether the ____ is present: 1. ____: ____ state observed when A is present; 2. ____: ____ state observed when A is absent.
oligomeric enzymes
two activator
R-state (relaxed) active
T-state (tense) inactive
In the ____ of activator, subunits are ____ and ____ to substrate.
In the ____ of activator, subunits are ____ and not ____ to substrate. However, that the enzyme can be ____ to bind to substrate at ____ __ (____ than physiological []). Binding of __ is communicated to other subunits. km is ____.
presence "relaxed" receptive absence "tense" receptive "forced" higher [S] higher S higher
Why is low pH listed for PFK?
low pH protonates allosteric site for ATP; makes ATP a better inhibitor.
ATP is negative charge, makes it binds to positive better..
Glycolysis and gluconeogenesis do not occur at the same time to avoid ____ ____. To prevent (or minimize) this, there is tight ____ ____ of enzymes in both pathways. _____ acts as activator for ____ reaction, and inhibitor for ____ reaction.
futile cycles
coordinate regulation
F-2,6-bPi forward backward
How do low-carbohydrate diets work? They induce a state of fat burning called ____ or ____. This occurs when ____ are consumed at less than ____ g/day, and ____ stores become depleted. The decrease in ____ ____ is compensated by increase in fat breakdown, which leads to the production of ____. It can be used by cells for ____, while other are expelled via ____, ____ and ____.
ketosis ketogenesis carbohydrates 65-180 glycogen glucose oxidation ketones energy breath, skin and urine
