Ch 2: Chemistry of Life pt. 2
4. Chemical Reactions
Bonds break and form during chemical reactions
- Chemical reactions: reactions that change substances into substances by breaking and forming chemical bonds.
Reactants, Products, and Bond Energy
- Reactants: The substances that changed during a chemical reaction.
- Products: The substances made by a chemical reaction.
- Chemical equations show what happens during a reaction. The left has the reactants and the right has the products. The arrow shows the direction of the equation.
- Bond energy: the amount of energy that will break a bond between two atoms. * Bonds between different atoms have different bond energies.
- The energy released when a bond forms is the amount of energy that will break the bond.
Chemical Equilibrium
- Chemical equilibrium: When a reaction takes place at an equal rate in both directions. (reversible chemical reactions). * Equilibrium is reached when both the reactants and products are made at the same rate.
Chemical reactions release or absorb energy.
- All chemical reactions have changes in energy. * If energy is added to reactants, chemical bonds are broken. * Energy is released when new bonds form in the products.
- Activation energy: the amount of energy that needs to be absorbed for a chemical reaction to start. * Activation energy is absorbed by reactants.
- Exothermic chemical reaction: Reaction that releases more energy than it absorbs. * Energy that is released is given off as heat or light. * Think exo → out
- Endothermic chemical reaction: Reaction that absorbs more energy than it releases. * Energy that is absorbed can come from energy sources like the sun. * Think endo → in
5. Enzymes
A catalyst lowers activation energy
- Catalyst: a substance that decreases the activation energy needed to start a chemical reaction. * A catalyst will increase the speed of a chemical reaction as it gives it a “push”.
Enzymes allow chemical reactions to occur under tightly controlled conditions.
- Chemical reactions in organisms usually need catalysts.
- Enzymes: catalysts for chemical reactions in living things * Lower the activation energy and speed up chemical reaction. * Needed in most processes of organisms.
- Most enzymes are proteins. * Changes in temperature or pH can change an enzyme’s structure and affect how an enzyme functions.
- Substrates: The only reactants that a certain enzyme will act on. * Enzymes will bring the substrates together and act as a catalyst so the product can be formed easier.
\