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Cell Biology > Thermodynamics > Flashcards

Thermodynamics Flashcards

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1
Q

What are the 3 stores of internal energy (U)

A

Chemical bond storage

Between molecules (H bonds)

Kinetic energy = motion store

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2
Q

What is temperature identical to in thermodynamics

A

Kinetic energy of a particle

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3
Q

What does exothermic reaction mean in terms of internal energy of reactants and products

A

Reactants have more Internal energy = -ve U change

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4
Q

What reaction shows a +internal energy change (products have more Internal energy)

A

Endothermic reaction

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5
Q

What is the 1st law of thermodynamics

A

The energy released by a chemical reaction either is used to transfer heat or to do work on surroundings

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6
Q

How would you measure internal energy change?

A

Measuring heat released (due to the chemical reactions internal energy)

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7
Q

What is enthalpy

A

It is the heat released = enthalpy of a reaction

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8
Q

How do you work out enthalpy change of a reaction? And the sign

A

Triangle H = enthalpy change

Energy released - work done = enthalpy change

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9
Q

Why is enthalpy change (H)used more than internal energy (U) change

A

1- easier to measure than internal energy

2- enthalpy is used to measure Gibbs free energy

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10
Q

What would positive or negative enthalpy (H) change mean?

A

The heat is absorbed (endothermic) = +

-= heat is released (exothermic)

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11
Q

Which reaction is often favoured?

A

Exothermic reactions (release heat)

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12
Q

What concept explains why sometimes endothermic reactions are favoured?

A

Entropy

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13
Q

What is entropy and entropy change sign

A

Entropy (S) = the disorder of a substance

Entropy change triangle (S)

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14
Q

What is the 2nd law of thermodynamics

A

Entropy S of a system either increases or remains the same (in terms of disorder you can’t go back to being ordered)

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15
Q

How is solid to gas an example of entropy change

A

In a solid = ordered

Gas = disordered = most entropic

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16
Q

Why is solid to gas enthalpically unflavoured but entropically favoured

A

Enthalpically unfavoured because it is endothermic (absorbs heat)

Entropically favoured because more disordered

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17
Q

Do number of micro states increase when entropy /disorder increases?

A

Yes, in a gas there are multiple micro states (positions available)

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18
Q

How does temperature relate to entropy

A

Kinetic energy if it drops, there are less micro states available (particles not in motion = no entropy)

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19
Q

What is the 3rd law of thermodynamics

A

Entropy at 0 temperature = 0 itself

20
Q

How do you work out Gibbs free energy change?

A

Triangle G= enthalpy (H) change - (temp x entropy (S) change)

21
Q

If Gibbs free energy is negative a reaction takes place, why is this

A

Because if Gibbs free energy is negative , entropy is increased = entropically favoured (disorder)

22
Q

How do cells sometimes carry out unfavoured reactions?

A

They couple with favoured

Eg atp synthesis helped by H+ ion transport = favoured

23
Q

What determines the rate of reaction (collisions and reaction)

A

The kinetic energy available to overcome an activation energy barrier

24
Q

How is speed distributed to particles (kinetic energy)

A

Where they are put in a closed space and collide with eachother transferring energy to particles

25
Q

What 2 things affect the kinetic energy (speed of a particle)

A

1- temperature

2- mass (bigger = slower)

26
Q

How does temperature increase cause increase in rate of reaction

A

High temp = high kinetic energy

Enough Ke can cause them to go over the barrier

27
Q

What is the first order reaction

A

A single molecule which dissociates into 2

28
Q

What is the second order reaction

A

Where 2 molecules will collide together to transfer kinetic energy

29
Q

What is the 3rd order reaction

A

3 molecules colliding together

30
Q

How would increasing concentration of molecules in first second and 3rd order increase rate of reaction

A

More likely collisions / dissociation

31
Q

How do you work out the equilibrium constant (Keq)

A

Conc of products (forward) / conc of reactants (backward)

32
Q

What does a positive Keq mean

A

More product than reactants in a beaker

33
Q

What does a negative Keq mean

A

More reactants than product in beaker

34
Q

At what point in a reaction is the change in Gibbs energy the lowest

A

At equilibrium

35
Q

What would adding reactant or product do to equilibrium

A

It would push Gibbs energy change from minimum

The reaction counteracts it by either producing more reactant or product = equilibrium

36
Q

What is le chateliers principle

A

If something is pushed out of equilibrium eg by adding more reactant , it’s overcome by producing more product

37
Q

What is free energy

A

The useful energy left over when wasted work is lost

38
Q

What is chemical potential of solutes

A

The free energy of a solute at 1M

And accounting for entropy when mixing

39
Q

When is chemical potential of solutes the same?

A

At equilibrium

40
Q

What is the equilibrium potential

A

When the concentration gradient and an electrical gradient set up due to movement of ions are the same

41
Q

How does the Nernst equation find electrical gradient needed to for an equilibrium potential eg of K+

A

The Nernst potential is the voltage needed to oppose the conc gradient = reach potential equilibrium

42
Q

What actually allows for an electrical gradient

A

Movement of ions which causes negative or positive voltage within the cell and this attracts the ions back eg K+

43
Q

What would it be called if all of the ions involved were at their Nernst potential (potential equilibrium)

A

Donnan equilibrium

44
Q

Why is it unrealistic that all ions would be in equilibrium potential (ie no more net movement, conc equal in and out)

A

The cell would be hypertonic due to other macromolecules in it aswell as ions,

The cell lives in a chemical disequilibrium due to the Na+ k+ pump = prevents cell bursting

45
Q

What 2 ways is free energy stored due to the increased H conc in the intermembrane of a mitochondria

A

1- chemical contributions (concentration gradient)

2- electrochemical gradient (the -160mv inside)

46
Q

What is the effect of the electrochemical gradient and the concentration gradient for free energy called in mitochondria which drives protons into ATPase

A

Proton motive force

Cell Biology (21 decks)

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