4 and 5 - Bioenergetics and ATP Flashcards Preview

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Flashcards in 4 and 5 - Bioenergetics and ATP Deck (28):

Enthalpy, entropy and free energy are state functions, meaning?

That they depend only on the beginning and final states, and not on the trajectory between those states


First Law of Thermodynamics

Total energy is constant. Energy can be converted from one form to another, but it cannot be created or destroyed.


Second Law of Thermodynamics

There is a tendency towards increasing disorder. The disorder is referred to as entropy


If enthalpy (ΔH) is negative

The reaction gives off heat and is exothermic


If enthalpy (ΔH) is positive

The reaction takes in heat from its surroundings and is endothermic


If ΔH = 0

No heat is exchanged, Isothermic


If ΔG is negative the reaction is ___ and ____

Reaction is exergonic and is spontaneous


If ΔG is positive the reaction is ____ and ___

Reaction is endergonic and is not spontaneous (energy is required)


If ΔG = 0 the reaction is?

Reaction is in equilibrium


What is ΔG*?

Definable standard free energy, all reactions have this. Under standard conditions.


What is ΔG'?

ΔG* but also where the pH is close to 7 and where the concentration is ~ 1 x 10^-7 M. If it is a biolical reaction, the ΔG* will often be positive and coupled with a negative ΔG'


What does catalysis do?

Reduces the activation energy needed for a reaction


What does anhydride mean?

Without water


What are the 2 main structural components of ATP (not including adenosine)

Two phosphoanhydride bonds formed between two phosphoryl groups


What are three main reasons for ATP storing energy?

Charge repulsion between negative phosphates

Hydration, ATP hydrolysis products are more easily solvated than ATP as a whole (to get greater entropy).

Resonance, competition between phosphoanhydride bonds and neighbouring phosphoryl groups for the O electrons.


Creatine Kinase does what?

catalyzes the conversion of ADP to ATP while simultaneously converting phosphocreatine to creatine (phosphate group transfered from phosphocreatine to ATP). ATP + creatine = ADP + phosphocreatine


What is substrate-level phosphorylation?

Where a high energy compound donates a phosphate group to ADP forming ATP (eg phosphocreatine giving phosphate group to ADP to form ATP and creatine)


What is enthalpy?

Total heat content of a system


What is entropy?

State of disorder of a system


What is free energy?

Energy available to do chemical work


What is a state function? List three that are important to thermodynamics

Functions that depend only on the beginning and final states, and not on the trajectory between those states, we are only interested in change.

Enthalpy, entropy and free energy are all state functions.


How is the hydrophobic effect supported by thermodynamic principles?

The aggregation of hydrophobic particles decreases the surface area of their contact with water, increasing its entropy. The free energy then is negative (ΔG = ΔH - TΔS) because ΔS is positive, meaning the reaction is spontaneous.

This spontaneous exclusion of water is important in membrane formation and protein folding


How is ΔG' correlated with phosphoryl transfer potential?

A very negative ΔG is correlated with a high phosphoryl transfer potential. That is, that when a phosphate group is transferred to something to release energy (eg. hydrolysis of ATP), this reaction is highly exergonic and also spontaneous.


Why type of energy does the hydrolysis of ATP to ADP + Pi provide?

It provides free energy that can drive coupled reactions


What types of bonds exists between ATP's phosphate groups?

Phosphoanhydride bonds


Whay types of bonds exists between the 5' carbon of adenosine and the phosphate group, in ATP?

phosphoester bonds


How can phosphocreatine replenish ATP? (answer: because...)

Because phosphocreatine hydrolysis is more exergonic under standard conditions than is ATP hydrolysis.


Where is phosphocreatine most commonly found in the body?

Where ATP is most rapidly turned over

Muscles and the nervous system