Chapter 2.1: Chemical Reactions Flashcards
(19 cards)
Chemical reaction
Occurs when chemical bonds are formed, broken, rearranged, or when electrons are transferred between two or more atoms.
Chemical notation
A series of symbols & abbreviations that demonstrates what occurs in a reaction.
Chemical equation
A basic form of chemical notation.
Co2 + H2o —> H2Co3
<—
Reactants: On left side
Plus sign: “reacts with”
Arrows: Both ways indicate the reaction is reversible
Products: Right side
Energy
The capacity to do work.
Kinetic & Potential are interconvertible.
Chemical energy: 2 types
1.) The energy inherent in chemical bonds.
2.) Kinetic energy that is present in the e- that are always in motion.
(Protons attract e-, providing the work to transfer & share e- )
How is Electrical energy generated?
Electrical energy is generated by the movement of charged particles.
In the body, electrical energy is seen in the flow of ions (observable in neuron communication, heart & skeletal muscle contractions)
Mechanical energy
Application of force.
Energy that has been transferred from one object to another (ex. sliding filaments, to myofibril, to fasicle, to whole muscle, to body part movement)
Endergonic reactions
Reactions that require chemical, electrical, or mechanical energy from another source to proceed.
The products of an endergonic reaction contain more energy than the reactants b/c energy was invested in the reaction.
Exergonic reactions
Occur when the reactants have more energy than the products.
In this case, the excess energy stored in the reactants is released during the reaction.
A reactant that stores a great deal of energy is known as unstable, when it releases this energy in an exergonic reaction, it becomes a more stable product. (Ex. Elemental Na + Cl)
Catabolic reaction
Larger substances are broken down into smaller ones.
AB —> A + B
Generally are EXERGONIC b/c chemical bonds are broken.
Exchange Reaction
One or more atoms from the reactants are exchanged for another.
Bonds are BROKEN & FORMED.
AB + CD —-> AD + BC
Ex.
Hydrochloric acid reacting with Sodium hydroxide to form an exchange reaction of Water and Sodium chloride
HCl + NaOH —-> H2o + NaCl
Oxidation-Reduction reaction
(redox reaction)
Electrons are exchanged instead of atoms.
The reactant that loses e- is said to be oxidized.
The reactant that gains e- is said to be reduced.
Oxidation-Reduction reactions are generally Exergonic and can release large amounts of energy.
Anabolic reactions
(Synthesis reactions)
Reactions that create new chemical bonds.
A + B —-> AB
Anabolic reactions are ENDERGONIC and are fueled by chemical energy.
Activation energy
All chemical reactions require the input of some energy to overcome the repulsion of the atoms’ electrons and to allow strong collisions to take place.
All reactions, even Exergonic must overcome this barrier to proceed.
Transition state
The peak of activation energy, aka the top of the hill.
The state of potential energy, where the stored energy can roll back down the hill or forward downhill using its own kinetic energy.
Factors influencing Rate of Reaction
Concentration:
When the reactant concentration increases, more reactant particles are present, which increases the chances for collisions b/t the particles.
Temperature:
Raising the temp of reactants increases the kinetic energy of their atoms, resulting in more forceful & effective collisions.
Properties of Reactants:
The size of the particles and their phases (solid/ liquid/ gas) influence reaction rates. Smaller particles move faster and have more energy than large particles. Gasses have higher kinetic energy than solids or liquids.
Presence or absence of a Catalyst:
Catalysts are substances that lower the activation energy needed, and thus increase reaction rates.
Catalysts
(aka Enzymes in biology)
Substances that LOWER the activation energy needed for a reaction to occur.
Catalysts are neither consumed or altered in the reaction
Enzymes are involved in all catabolic/ anabolic & exchange reactions.
They don’t “break anything down”, rather, they increase the rate of reaction.
Enzyme characteristics
1.) Highly specific for individual substrates and reactions.
2.) Do not alter chemical reactions
3.) Not permanently altered in the reaction, merely changes shape and then changes back & can be reused.
Enzyme mechanism of action
1.) Substrates approach the enzyme and bind to the enzyme’s active site.
2.) When the substrates bind the enzyme, both the substrate & enzyme change shape.
3.) The substrates enter the transition state and are converted into products.
4.) The product and enzyme dissociate and the enzyme returns to its original shape.
*Because biological compounds have low kinetic energy, the activation energy for biological reactions are high. Without enzymes, the chemical reactions in metabolism would occur far too slowly for us to remain alive.
