Mol Lecture #25 Flashcards
Thermodynamics and why the interest
The study of energy and its transformations
- the energy required to perform certain chemical reactions, the energy released by certain chemical reactions and linking these 2 processes.
Energy is …
- the ability to do work (Life is an energy-driven process)
Thinking about reactions going in the following way:
A+B → C+D
←
Reactants Products (Thermodynamics tells us…)
- Thermodynamics can tell us whether a reaction requires or releases energy, but not its rate. (Important in thinking about how cells function→ living systems control the rates of reactions a lot of the time)
Laws of thermodynamics (1st Law)
- Conservation of energy: Energy can be converted from one form to another but neither created nor destroyed
Laws of thermodynamics (2nd Law)
- increasing entropy: Total disorder (entropy) of a system always increases or systems always progress to equilibrium. (ex. Going from one molecule towards a greater number of the molecules is entropy→ DNA wrapped around histones is an ordered state, when its is not wrapped around histones it’s going towards disorder)
Forms of energy
Energy exists in a few forms
→ Chemical, heat, electrical (can be thought of as the ability to do work)
Energy exists in 2 forms (Potential and Kinetic)
→ Potential Energy- Stored energy (ex. Rock sitting on top of the hill that could roll down– stored energy)
→ Kinetic Energy- Energy in motion (ex. Once the rock is rolling down the hill- in motion- it uses kinetic energy)
(ex. Energy is also stored in bonds- potential- and when the energy is used to break the bonds- kinetic energy)
- Energy can be converted between the states, but it is inefficient
Free energy (Look at slides)
- energy available in a system to do work (ex. Bound (boundaries) what we’re talking about- system)
- Free energy (G) (J. Gibbs)
Change in the whole free energy for a given reaction (delta G)
What are the 2 terms that can change?
- Entropy & Enthalpy (combination of plus and minus that gives us the ultimate product of the reaction)
- Delta G tells us whether a reaction releases energy or requires it.
Types of reactions
- Exergonic Reaction: releases energy
→ Delta G is negative - Endergonic Reaction: requires energy
→ Delta G is positive
Endothermic and Exothermic are in reference to the Delta H (Change in enthalpy)
Types of Delta G: Negative Delta G
- exergonic reaction (spontaneous- could occur without energy being put in→ not in reference to rate*)
→ Reactions tend to be exergonic if:
1) The products have less potential energy than the reactants
2) If the products are less ordered than the reactants
(They both have to add up to a negative delta G)
Types of Delta G: Positive Delta G
- endergonic reaction (non-spontaneous)
1) The products have more potential energy than the reactants
2) If the products are more ordered than the reactants
Equilibrium
- The condition of a system in which all competing forces are balanced
Equilibrium Reaction Example: Glucose 1-phosphate → Glucose 6-phosphate *
- For it to go to 6-phosphate, it will achieve a negative delta G.
- At some point, we achieve a delta G that is equivalent (neither - or +); whatever parameters driving this reaction (ΔH and ΔS) that achieved the delta G are no longer pushing this reaction. (Equilibrium does not always mean that everything is balanced in terms of number)
Metabolic Pathways: Metabolism
- the set of life-sustaining chemical transformations within cells of living organisms.
–> Ex. Use exergonic and endergonic reactions to make and break molecules
Catabolic Pathways:
Energy is released, and molecular building blocks are made available (ex. Breaking down into constituent nucleotides
→ - ΔG for whole pathway
Anabolic Pathways:
Energy is required to build more complex molecules from simple ones. (ex. Dehydration synthesis, making peptides from amino acids, etc.)
→ + ΔG for whole pathway
Coupling Reactions
- Use reactions/pathways that release energy to provide it for those that require energy
→ By using a high energy intermediate
Hydrolysis of ATP
- GTP can also function to deliver energy as well, but its much more useful with ATP (due to evolution)
- Convenient intermediate for transferring energy between reactions
-Releasing one phosphate or both to go to ADP
Energy Coupling with ATP
- Hydrolize ATP in order to release energy
Coupling ATP check slides
- Adding the phosphate onto glutamyl phosphate which is then converted to glutamine + phosphate
- Using ATP to do this reaction
ATP/ADP cycle (Cellular Respiration)
- Taking energy from some source, and through chemical reactions we allow that energy to be harnessed so we can convert ADP +P to ATP
- Constantly making ATP in order to do these reactions happen
