Tutorial - Week 8 (thermodynamics) Flashcards
Energy is transformed using…? List 5 points
biochemical reactions (chemical transformation)
- Energy is spent to do work
- Some energy is returned to the surroundings as heat
- Some molecules are end-products, which are simpler, less organised, than the original
source of energy (increased randomness of the universe) - Some energy is used to produce complex macromolecules (decreased randomness).
Energy is spent to do…?
Work
Some energy is returned to the surroundings as…?
Heat
T/F: Some molecules are end-products, which are simpler, less organised, than the original
source of energy (increased randomness of the universe)
True
Some energy is used to produce…? Increased or decreased randomness?
complex macromolecules (decreased randomness)
What is energy and work? The three types of work?
Energy is the ability to do work (do something, change something in a system)
Work in living organisms:
1. Mechanical work: moves cells, organisms against gravitational force or frictional force
2. Gradient work: creates concentration gradients or electrical gradients across membranes
3. Synthetic work: making or breaking of bonds and production of molecules
Mechanical work: Define
moves cells, organisms against gravitational force or frictional force
Define Gradient work:
creates concentration gradients or electrical gradients across membranes
Define Synthetic work:
making or breaking of bonds and production of molecules
What is the main type of energy used?
Potential energy: is stored energy, and the energy attributed to the position or “condition” of an object
* Chemical bond energy: energy stored in chemical bonds, condition or position of the atoms &
electrons within molecule.
* Concentration gradient energy, nuclear energy
In biological systems, biomolecules can be converted into energy via biochemical reactions
Chemicals store energy in their ____________
In biological systems, biomolecules can be converted into energy via _________
chemical bonds
biochemical reactions
Chemical compounds can store energy in their…?
Chemical bonds
What is an example of a compound that stores energy in its chemical bonds?
Petrol
How is energy stored in chemicals?
- Food obtained from diet is converted into energy
- Covalent bonds store energy
Sugars
Fats - To obtain energy from biomolecules, they are rearranged into other
molecules following several biochemical reactions
Covalent bonds like in proteins, carbohydrates, and sugars
ATP!
Describe ATP in terms of energy currency
ATP: Is the principal molecule for storing and transferring energy in cells
AKA energy currency
Describe ATP in terms of energy currency
ATP: Is the principal molecule for storing and transferring energy in cells
AKA energy currency
How are biochemical reactions controlled?
What is the first law of thermal dynamics?
the total amount of energy in the universe remains constant, although the form of energy may change
- Energy is converted from one type to another, but it cannot be destroyed
- E.g. Potential energy from chemical bonds is converted into kinetic energy (heat & mobility)
What is this an example of?
Chemical energy being utilised as the atoms and bonds are changed and energy is released
How are biochemical reactions controlled?
- Living organisms together with their surroundings constitute the universe
- Living organisms are open systems constantly exchanging material and energy
What is the second law of thermal dynamics? Explain
Cells require sources of ‘free energy’ known as ________?
Gibbs free energy
Cells can obtain energy from ________?
Nutrients (or sunlight)
Cells transform free energy into…? Following which law of thermodynamics?
ATP, or other energy-rich compounds (1st Law of thermodynamics)
Cells are ___________ systems (i.e. temperature is constant)
isothermal
The Gibbs free energy function predicts…?
the direction of chemical reactions
What does the Gibbs free energy function also predict?
Cells produce _______ when they grow, by using free energy from the environment (e.g. sunlight, food)
but create _________ in their surroundings
order
disorder
T/F: the entropy of individual reactions might not increase, but the overall entropy of the universe increases
True
When considering the overall system (the universe), cells release to their environment…?
Equal amount of energy as heat and entropy
In terms of Gibbs free energy:
Reactions are thermodynamically favourable (∆G ___ 0 ) if:
* they release energy in the form __________ and/or,
* they increase the ___________
<
of heat (∆H < 0)
disorder of the system (∆S >0)
In terms of Gibbs free energy:
Reactions are thermodynamically favourable (∆G ___ 0 ) if:
* they release energy in the form __________ and/or,
* they increase the ___________
<
of heat (∆H < 0)
disorder of the system (∆S >0)
∆G is the…?
driving force in a biochemical reaction, which represents the effect of ∆H and ∆S and at a fixed temperature
∆S, Entropy change:…?
describes the variation
of entropy in the system
T = ?
Absolute temperature (in Kelvin, K)
∆H, Enthalpy change:
variation of the Heat content of the reacting system
It depends on the number and kind of molecular bonds formed/broken (bonds with lower energy are more stable)
Explain each part
Complete
Complete
The direction of the reaction depends on the variation of free energy content between reactant and products, ∆G:
- Concentration of each of the molecules in the reaction
- Experimental conditions (e.g. temperature)
- ∆G’0 of the reaction (this is constant to each reaction)
∆G < 0 = ?
the reaction proceeds to the right
∆G = 0 = ?
the reaction is in equilibrium
∆G > 0 = ?
the reverse reaction is favoured
What happens in each reaction? Give example
Reaction on the right is called spontaneous because it can occur without the addition of energy
T/F: Most reactions are irreversible
False - most are reversible
The direction of the reaction depends on…? Give 3 points
∆G
- Concentration of each of the molecules in the reaction
- Experimental conditions (e.g. temperature)
- ∆G’0 of the reaction
The reaction tends to occur until the _________ is reached. At equilibrium, the rates of the forward and reverse reactions are ______
equilibrium
equal
∆G = 0, the reaction is in _________
equilibrium
Nomenclature:
- ∆G is the measured …? It depends on __________ conditions
- ∆G’0 = ?
- standard conditions (T = 298K, P = 1 atm or 101.3kPa, pH 7.0
(Add three points)
free energy in the reaction
experimental
standard free energy change:
- Initial concentration is 1 mol/L for reactants and products
- unit in Joules/mol (J/mol)
- It is a fixed value for a given reaction
The direction of the reaction depends on ∆G:
Keq is a constant, characteristic for each reaction?
Is this reaction thermodynamically favourable?
Yes - ∆G’0 is negative, the forward reaction proceeds with release of free energy
Is the reaction thermodynamically favourable?
Yes it is thermodynamically favourable
Is this reaction in equilibrium?
Delta G is less than 0 at -4.4kJ/mol therefore it is thermodynamically favourable and delta G is not equal to 0 therefore it is NOT in equilibrium
What does the direction of the reaction depends on? And what other aspects does it depend on?
What is this? Define
Label reactants and products
If the reactants and the products are in equilibrium then we can replace part of the equation with what?
Both equations on the right cancel out their equivalents in the main equation leaving only Delta G being equal to zero, therefore Delta G = 0 and reaction is in equilibrium
Explain this equation
What happens in biological systems? Describe bioenergetics and oxidation of glucose
Label the reactions as thermodynamically favourable and unfavourable
What is the strategy to overcome unfavourable reactions? Draw graph example of thermodynamically favourable and thermodynamically unfavourable reactions
List the high energy compounds we learned about
The usual source of free energy in coupled biological reactions is the energy released by breakage of
___________, such as those in…?
phosphoanhydride bonds
ATP and guanosine triphosphate (GTP)
Calculate the ∆G ’0 of these ATP-coupled reactions
Answer in image and Phosphocreatine is a molecule that serves as a rapidly mobilisable reserve of high energy
The sum of the reactions is thermodynamically favourable
Calculate the ∆G ’0 of these ATP-coupled reactions
The phosphorilation of the fructose is not thermodynamically favourable so we can pair it with a thermodynamically favourable reaction to make the sum thermodynamically favourable
Calculate the ∆G using physiological conditions and concentrations:
When temp is 37 celcius its the same as adding 273 to reach 310 K (kelvin)
Reaction is thermodynamically favourable in these conditions
List is releases or uses energy and if thermodynamically favourable or unfavourable
What is this showing with the purple line?
How can we speed up biochemical reactions in cells?
Biological Oxidation-Reduction reactions (5 MAIN POINTS)
Universal electron carriers: A few types of coenzymes and proteins serve as universal electron carriers: What are they?
Define NAD and NADP, describe the structures, and draw. Where is the energy contained?
Label the results after oxidised
What are two more universal electron carriers? List 4 main points
Oxidation & reduction reactions (REDOX reactions), involve?
Are these reactions always coupled?
- The loss of electrons by one chemical species (it becomes Oxidised)
- The gain of electrons by another molecule (it becomes Reduced)
Yes
Give the headings for these two columns
Describe what happens to the lactate and the NAD+
- Lactacte and NADH are reducing agents (they are oxidized in the process; they donate electrons)
- Pyruvate and NAD+ are oxidising agents (they are reduced in the process; they accept electrons)
Complete
Label which part is oxidation and which is reduction
Each reduction reaction has a _____________, E’ 0 (defined at pH 7, and 250 C),
which is always defined from the _________
Give example?
standard reduction potential
reduction
Example see image
Change in reduction potential of a redox reaction, (∆E’0 ), is calculated as?
Give example
E’ 0 from the electron acceptor minus the E’0 of the electron donor
Example in image
What is the ∆G’ 0 for the conversion of lactate in pyruvate?
Is the reaction thermodynamically favourable in standard conditions?
No the reaction is NOT thermodynamically favourable in this direction because Delta G is above 0
However, in the opposite direction the reaction is thermodynamically favourable because it would be the opposite and below zero
Is the reaction thermodynamically favourable in standard conditions?
Yes because Delta G is below zero and therefore is thermodynamically favourable
What is this diagram representing?
