M12 enzyme regulations and bioenergetics

What are metabolic pathways?

Series of enzyme-catalyzed reactions that either break down molecules (catabolic) or build complex molecules (anabolic).

How can unfavorable reactions in pathways proceed?

They are driven forward by coupling to favorable reactions.

What role do end-products play in pathway regulation?

Products can inhibit early enzymes (feedback inhibition) to prevent overproduction.

Which enzyme in a pathway is usually regulatory?

The first enzyme (E1), making the pathway more energy-efficient.

What are the two main types of enzyme regulation?

Allosteric regulation and reversible covalent modification.

What is allosteric regulation?

Regulatory molecules bind to a site other than the active site, altering enzyme activity.

What is reversible covalent modification?

The addition/removal of groups (e.g., phosphorylation by kinases, dephosphorylation by phosphatases) to modulate activity.

What is bioenergetics?

The study of energy transductions in biological systems.

What does the First Law of Thermodynamics state?

Energy cannot be created or destroyed, only transformed.

What does the Second Law of Thermodynamics state?

The entropy of the universe always increases.

What is Gibbs free energy (ΔG)?

The energy available to do work at constant temperature and pressure.

When is a reaction exergonic?

When ΔG < 0; it releases free energy (favorable).

When is a reaction endergonic?

When ΔG > 0; it requires energy input (unfavorable).

What is the relationship between ΔG and equilibrium constant (K’eq)?

ΔG°’ = –RT ln K’eq.

Do enzymes affect equilibrium?

No, they only change the reaction rate, not the equilibrium position.

Why is ATP called the "energy currency" of the cell?

Its hydrolysis releases large amounts of free energy, which can be coupled to drive endergonic reactions.

What actually drives cellular processes: ATP hydrolysis or group transfer?

Group transfer of phosphoryl, pyrophosphoryl, or adenylyl groups.

modulators change the __

AS

binding of a positive regulator ____ activity

increases

absence of a ___ regulator increases activity

negative

an enzyme can regulate the activity of a second enzyme by covalently ___ the enzyme

modifying

phosphorylation

tyr, ser, thr, his

ubiquination

lys

adenylylation

tyr

acetylation

lys, alpha-amino

myristolyation

alpha-amino

ADP-ribosylation

arg, gln, cys, diphthamide

methylation

glu

Keq=1

ΔG=0

Keq>1

ΔG<0

Keq<1

ΔG>0

ATP+H2O←> ADP + Pi

ΔG’=-30.5

ATP +H2O←> AMP +Pi

ΔG= -45.6

if you add up ΔGs of a rxn and its a negative value then the rxn..

will happen