Thermodynamics Flashcards
Thermodynamics
A branch of science with energy and how it changes during chemical and physical transformations
The system
The object that is being studied, can be anything
The surroundings
Everything outside the system
3 types of systems
open, closed, isolated
Isolated system
Does not exchange energy or matter. The universe is the only true example
Closed system
Exchanges energy but not matter with its surroundings. Ex a sauce pan with a lid or the earth
Open system
Energy and matter can move freely between system and surroundings. Ex the ocean
First law of thermodynamics
Energy can be transformed but not created or destroyed.
1st law example
Niagara falls. High potential energy at the top of the fall is transformed to kinetic energy and then heat sound and mechanical energy as it hits the rocks
Second law of thermodynamics
The entropy of a system and the systems will increase- energy will always become more spread out
Entropy
The natural tendency of energy to move from being localized to spread out
Why is nothing 100% effective
Because of energies desire to spread out. Cars and laptops get hot because of Ek becoming heat
Cells and effectiveness
Only half of cellular respiration’s energy is transformed into usable glucose
Free energy
Determines if a reaction needs energy, or will go on its own
Spontaneous processes
A process that can occur without the input of energy. Does not mean it is fast
Enthalpy (Delta H)
The total potential energy of a system
Endothermic
Transformations that absorb energy, more potential energy than at the start, enthalpy is positive
Endothermic example
Ice melting
Exothermic
A process that releases energy. Less potential energy than at the start, enthalpy is negative
Exothermic example
Burning of wood
2 things that predict reactions spontaneity
Reactions tend to be spontaneous if they are exothermic and when the entropy of the products is greater than the entropy of the reactants
Why exothermic reactions are spontaneous
Electrons are held tighter by the products than the reactants which leads to lower potential energy
How to determine a change in entropy
The is a bigger number of molecules in the products than reactants, or the state changed from solid to liquid, or liquid to gas
Josiah Gibbs
Determined how enthalpy and entropy effect a reaction. Made a formula
Gibb’s formula
Delta G=Delta H- TDeltaS (T= temperature in kelvin)
Spontaneous reaction in terms of free energy
Free energy of the products is less than free energy of the reactants. -delta G
Exergonic process
A spontaneous reaction
Endogenic process
A nonspontaneous reaction
Diffusion across a membrane
No change in enthalpy but entropy increases creating energy used by the cell
Equilibrium rather than completion
Occurs as it requires the least amount of energy
Chemical equilibrium
The reaction is continuing to go at an equal rate, appearing to be not reacting
Moving towards chemical equilibrium
Free energy decreases and is at its lowest at equilibrium to there is no energy to do work, so no G
Very negative delta g
A reaction will come close to completion
Kind of negative delta g
A reaction will not be as close to completion
Barely negative delta g
Readily reversible by adjusting the product to reactant concentration
Thermodynamics and life
All living things harness and use energy
How do cells follow the second law?
They are open systems that use the energy they bring in. The second law states that the entropy of the system and the surroundings must increase. The surroundings entropy increases
How does the surroundings of the cell enthalpy increase
Cells give off heat, H2O and CO2
Why do systems always need energy
Because we are growing and need more cells. They because it is energies tendency to spread out it leaves cellular components broken or breaking down
Metabolism
All the reactions in breaking food down and making it into energy. Can never stop because cells never reach chemical equilibrium
Foods that provide energy
Mostly goes to maintaining low entropy, high organized state of the cell
Energy and the biosphere
The sun gives us heat allowing light. Light comes in photons
Energy entering the world
It enters as photons and becomes chemical energy through photosynthesis.
Two types of metabolism
Needs energy to build stuff, release energy by breaking molecules down
Main energy transformation reactions
Photosynthesis and cellular resperation
Pathways
Individual reactions that make up metabolism are put into groups
Testosterone
Product of a 5-step pathway starting with cholesterol
Catabolic pathway
A series of reactions that lead to the breakdown of large molecules. Energy is released because free energy decreases
Example of catabolic pathways
Cellular respiration
Anabolic pathway (biosynthetic pathway)
A series of reactions resulting in larger, more complex molecules. Needs energy because free energy increases
Exmples of anabolic pathways
Photosynthesis , biosynthesis of carbohydrates, proteins, and nucleic acid
ATP
A form of chemical energy that links the 2 pathways. Chemical currency-a widely accepted form of energy that can convert chemical energy to mechanical and electrical
ATP structure
5 carbon sugar, ribose, nitrogen base (adenine), a chain of 3 phosphate groups
Hydrolysis of ATP
Free energy is released as Pi is removed. ATP+H2)—ADP+Pi.
Delta G of hydrolysis of ATP
-7.3 Kcal/mol
Why is ATP—ADP exergonic
The decrease in potential energy and increase in entropy
Why is there a decrease in potential energy in ADP
Decrease in electrical repulsion between the negative charged of oxygen and the phosphate
ATP’s energy
Released from being hydrolyzed, not from the bond breaking
ATP and common ansestors
All living things use ATP. Other phosphate groups that can do the same things, but don’t. Suggests we all started from one thing
ATP reaction rate
Relatively slow. Good because all the energy is used and the cell does not overheat
How does ATP provide energy example
Glutamic acid+NH3— glutamine and H2O. G=3.4
Energy coupling
An endergonic reaction occurs by being coupled with an exogenic reaction
Coupled reactions
Reactions that occur because of energy coupling. The G value is the sum of their G values
How energy coupling works
An enzyme bonds with a substrate and ATP, it takes that newly released phosphate to the substrate. This increase in free energy allows the reaction to occur spontaneously
Completion of ATP hydrolysis
When Pi is released in the second reaction.
Where does ATP come from
Some from a biosynthetic pathway that combines the molecule. Mostly, ADP and Pi recombine
The recombination of ADP and Pi
is endergonic
Free energy for ATP synthesis
Comes from catabolism of molecules. For plants this is sunlight, for animals this is fats, carbs, and protiens
ATP cycle
The breakdown and recombination of ATP
