What is a biological system?
Anything of interest (biochemical reactions, cells, organisms, ecosystems, etc…) that interacts with its surroundings and the rest of the universe.
Describe the 3 types of systems?
- Isolated system: does not exchange matter or energy with its surroundings.
- Closed system: exchanges energy with its surroundings.
- Open system: Exchanges both energy and matter with its surroundings.
What is energy?
The ability to cause change.
What is work?
The change that requires energy.
What is the first law of thermodynamics?
- Energy cannot be created or destroyed.
But it can:
- change location (outside a cell to inside).
- change into different forms (potential to kinetic).
- all energy that enters a system must come from the surroundings.
What is potential and kinetic energy?
Potential energy: stored energy due to position (energy at rest).
Kinetic energy: energy of motion/change (energy doing work)
What has more potential energy (Ep), an electron closer to a nucleus or further away? Why?
An electron close to a nucleus has smaller Ep, an electron far from a nucleus has larger Ep.
This is because when an electron moves to a higher energy level, it has the potential to fall back down to a lower energy level again. But when its at a low energy level, it can’t move lower so it has little Ep.
What type of chemical bond (non-polar covalent, polar covalent or ionic) has more Ep? Why? Give a full explanation.
The amount of potential energy within a molecule depends on the arrangement of electrons in its chemical bonds.
- Molecules with non-polar covalent bonds have more Ep.
- This is because the non-polar covalent bond holds the electrons in the middle of the bond and it can fall further towards either electron.
What is an electrochemical gradient? Is the potential energy higher or lower when one side has a higher concentration than the other?
- An electrochemical gradient is a difference in ion or solute concentration across a membrane.
- It is higher, since the ions or solutes have not yet traveled across the membrane.
What is enthalpy?
The sum of Ek (kenetic energy) and Ep (potential energy)
What happens when work occurs? What does Delta H represent?
- Something changes (a chemical reaction changes reactants to products).
- New system has a different enthalpy.
- Delta H represents the change before a reaction to after a reaction
- Measured as the amount of heat released or absorbed to the surroundings
- If heat is released, delta H is negative, if heat is absorbed, delta H is positive
What does exothermic mean?
The products have less enthalpy than the reactants. ( - (number) Kj/mol^-1)
What does endothermic mean?
The products have more enthalpy than the reactants. ( + (number) Kj/mol^-1)
Define spontaneous vs nonspontaneous. Are spontaneous reactions instantaneous?
Spontaneous: A reaction that can occur under corrent conditions. (just bcause they can happen, does not mean they are NOT instantaneous)!!!!
Nonspontaneous: A reaction that can not occur under current conditions.
What are some important “current conditions” to be aware of? Which ones are usually manipulated in biology?
Not typically manipulated in biology:
- Temperature
- pH
- Atmospheric Pressure
Manipulated:
- Concentration of reactants or [reactants]
- concentration of products or [products]
Does enthalpy (Delta H) determine if a reaction is spontaneous?
NO it does not!!!!
What is entropy? What happens when work occurs?
entropy is a measure of how dispersed the energy in the surrounding system is.
When work occurs, the new system/surroundings have different entropy (the dispersion of energy in the universe changes)
What does ‘Delta S’ represent? What does a positive or negative delta S represent?
- The change in energy before a reaction to after a reaction. Measured as the degree to which energy dispersal has changed.
- Positive delta S: energy has become more dispersed
- Negative delta S: energy has become less dispersed
What is the second law of thermodynamics?
Energy in the universe must always increase. Every transfer or transformation of energy must increase total entropy.
Does entropy determine if a reaction is spontaneous?
Yes it does.
What is the equation to calculate Delta S Total? Why does it work?
- The equation to calculate delta S total = Delta S (system) + Delta S (surroundings).
- This is because entropy considers the system and surroundings. This means that the entropy of the system can decrease if the entropy of the surrounding increases to a greater degree.
What is free energy and how is it Represented?
Free energy is represented by (G) and is a measure of the energy in a system that is free to do work.
When does work occur? What is this changed represented by? (all in refrence to G)
- Work occurs when the reactants have more free energy than the products.
- The change in free energy before a reaction to after a reaction is measured as the amount of energy that was used to make the change. This is Delta G
What does a positive or negative delta G represent?
Negative delta G: energy is available.
Positive Delta G: energy is not available.
