UNIT 4 ENERGY AND ENZYMES Flashcards
Central role of energy
Is the ability to do work.
Types of energy.
Heat, chemical, electrical, mechanical, electromagnetic radiation.
Forms of energy
Kinetic and potential
What is the first law of thermodynamics?
Energy can be transferred from one form to another but can’t be destroyed or created.
What is the second law of thermodynamics?
Every time the energy is transferred, some energy is lost and unavailable to do work. This lost energy creates entropy.
Does spontaneous reactions require the input of energy?
No
The change in free energy must be negative for the reaction to be spontaneous?
Yes
What is kinetic energy?
Energy possessed by an object in motion.
What is potential energy?
The stored energy that an object has because of it’s location or chemical structure.
The study of energy and it’s transformation is called?
Thermodynamics
What are the 3 systems studied in thermodynamics?
Isolated, open, closed
What is an isolated system?
One that doesn’t exchange matter or energy with it’s surroundings. (thermos)
What is an open system?
One that the matter and energy can move freely between the system and it’s surroundings. (living organisms)
What is a closed system?
Exchange energy but not matter with it’s surrounding.(earth)
The unusable energy that is produced during energy transformation produces what?
An increase in the disorder of the universe. (entropy)
The entropy of a system and it’s surroundings always increases?
yep
What does it take to maintain low entropy?
Energy
What do we do to maintain low entropy?
We eat food, aka we bring in energy.
Reactions tend to be spontaneous when?
The products have less potential energy than the reactants.
Enthalphy?
potential energy in a system
endothermic
reactions that absorbs energy. products have more potential energy than reactants.
exothermic
reaction that releases energy. Products have less potential energy than reactants.
Free energy
energy available to do work. Abbreviated by G.
Free energy formula?
G= H - TxS
H change in enthalpy
S change in entropy
G must be negative for a spontaneous reaction to occur?
yep
Systems that have high free energy are more or less stable?
Less stable
Can systems change into being less stable?
No, but they can change to being more stable.
What is equilibrium?
A state in which the reaction doesn’t stop and the rate of the forward reaction equals the rate of the backward reaction.
Closer to the equilibrium means?
Less free energy.
The more negative free energy = what for equilibrium?
The further the reaction will more before equilibrium is established.
When does organisms reach equilibrium?
Only when they die.
Metabolic pathway
series of reactions where the products of one reaction. is immediately used as the reactant for the next reaction in the series.
Metabolic pathway consists of ?
Exergonic and endergonic reactions
Catabolic pathway
Energy is released by the breakdown of complex molecules to simpler compounds.
Anabolic pathway
Consumes energy to build complex molecules from simpler ones.
Energy currency of cells
ATP
What is hydrolysis?
A process in which free energy is released.
How does hydrolysis works?
Each phosphate group are close together but their negative charges makes them repel each other, making the bonds unstable.The removal of one or two group Is spontaneous reaction that releases the repulsion and releases free energy.
ATP to ADP releases more energy than?
ATP to AMP
How does a living cell doesn’t loose energy as heat by hydrolysis?
By energy coupling.
How does energy coupling works?
ATP is brought close to a reactant of an endergonic reaction. When the ATP is hydrolyzed, the terminal phosphate group is transferred to the reactant molecule This makes the reactant molecule less stable
What brings the ATP and reactant close together in energy coupling?
Enzyme
Energy coupling produces an overall reaction that is?
exergonic
The energy for ATP synthesis comes from?
from an exergonic breakdown of complex molecules that contains a lot of free energy. Ex food
How can the speed of a reaction be changed?
by enzymes
What needs to be done for a reaction to happen quickly?
The bonds must be broken and to do so, they need to be less stable (input of energy).
Activation energy
to get molecules into an unstable state (to break them) it need a little input of energy.
Transition state
molecules that gain activation energy and that the bonds are now ready to break.
activation energy prevents what?
spontaneous reactions to happen quickly
How does enzymes accelerate reactions?
by reducing the activation energy
catalyst
agent that speeds up the rate of reacti0on without taking part of it itself.
Most common catalyst?
enzyme
enzymes do what?
reduce the activation energy required for a reaction to occur.
enzymes only work on?
exergonic reactions as they cant supply free energy
does enzymes change the free energy of a reaction?
nope
enzyme specificity
only catalyzes reactions for a single type of protein
substrate
reactant the enzyme acts with.
what is the active site of the enzyme?
th4 small region where the subtrate interacts
induced-fit hypothesis
Just before substrate binding, the enzyme changes its shape so that the active site becomes even more precise in its ability to bind the substrate.
enzyme cycle
because the enzyme is unchanged after a reaction, it can binds again to a substrate, catalyzing the reaction again.
cofactor
non-protein group that binds to an enzyme. often metals
coenzyme
organic cofactors such as vitamins
enzymes reduces the activation energy by inducing the transition state by
- bringing reactants together
- exposing reactants to charged environment
- changing the substrate shape, which mimics the conformation of the transition state.
more enzymes =
more reactions
more substrate =
faster reactions
less substrate=
slower reactions
what does it mean when an enzyme is saturated with substrates?
When the substate increases, the rate of reaction also increases until the enzymes are cycling as quickly as possible.
enzyme inhibitor
molecule that binds to an enzyme and decrease it’s activity.
two names of the enzyme inhibitors
competitive inhibition and non competitive inhibition
What is competitive inhibition?
The molecule binds to the active site. it has a shape that ressembles the normal substrate and it blocks its access.
What is non-competitive inhibition?
The molecule binds to the critical site, elsewhere on the enzyme, it causes the enzyme to change shape so it doesn’t fit with the substrate anymore.
Reversible inhibition?
When the binding of inhibitors to the enzyme is weak, it is easily reversible and the enzyme activity returns to normal after the release of the inhibitor.
Non-reversible inhibition?
When inhibitors bind to the enzyme with covalent bon ds which completely disable it.
Irreversible inhibition is ?
Highly toxic to living cells.
What is a futile cycle?
When two metabolic process run at the same time in the opposite direction and only has the effect of loosing energy.
How do cells prevent futile cycle?
The cells control the enzyme activity with natural inhibitors, so that not all enzymes are active at the same time.
Allosteric regulation
When the enzyme activity is controlled by the reversible binding of a regulatory molecule to the allosteric site. This may increase or decrease the enzyme activity.
Where is the allosteric site?
Location on the enzyme, outside of the active site
Are allosteric inhibitors competitive or non-competitve>
Non-competitive because they bind to sites different to the active site.
Enzymes controlled by allosteric regulation have two conformations controlled by the allosteric site, what are they?
- High affinity state
- low affinity state
What is the high affinity state?
When the enzyme is active because it can bind to it’s substrate. (allosteric inhibition)
What is the low affinity state?
When the enzyme is inactive because it cant bind to it’s substate (allosteric inhibition).
What does allosteric inhibitors do?
They bind to allosteric enzymes and change their state from high to low.
What does binding an allosteric enzyme to an allosteric activator does what?
Change the state of the enzyme from low to high.
Allosteric inhibitors comes from what?
is a product of metabolic pathway that they regulate.
What do allosteric inhibitors regulates?
If a product is in excess, it will slow or stop the enzymatic reaction producing it. If a product is needed, the inhibition is reduced and the production increases.
Regulation when a product of a reaction acts as a regulator of the reaction is called?
Feedback inhibition
What does feedback inhibition does?
Prevents cellular ressources from being wasted in the synthesis of molecules made in intermediate steps.
What are some factors affecting enzyme activity?
Ph, temperature.
If Ph is not optimal =
The rate of catalyzed reactions decreases.
If temperature rises=
The rate of reaction increases and potentially denatures the enzyme.
Equilibrium can only happen in what system?
Closed system
spontaneous reaction
reactions that occur without the input of energy.
energy coupling
use of exergonic process to drive a endergonic process
