Download Reactions

Reactions
Chemical Reactions
• Chemical reaction – a process in which bonds of compounds are broken and reformed into different compounds
• Molecules are rearranged during reactions, but composition stays the same
• There are the same number of atoms in the products as there are in the reactants
• Reactant – the starting material in a chemical reaction
• Product – the compounds that result from a chemical reaction
• Coefficient – the number in front of each molecule in a
chemical equation that tells how many of each molecule is present
Dehydration Synthesis
• Dehydration synthesis – a chemical reaction in which two molecules are bonded together
and a molecule of water is removed
• Hydrogen from one reacts with hydroxyl (-OH) of another
• Water molecule is removed
• Creates polymers present in macromolecules
• Monosaccharides à Polysaccharides
• Amino Acids à Proteins
• Fatty Acids à Lipids
• Hydrolysis – a chemical reaction in which the bonds between two
molecules are broken by adding a molecule of water
Biology 2.3 – Reactions
Reactions
Enzymes
• Reactions can occur at varying rates
• Catalyst – a substance that affects the rate of a chemical reaction
• Enzyme – a specialized protein that catalyzes biological reactions
• Usually end with the suffix “-ase” and its name comes from
the substrate
• Have optimal temperatures and pH to maintain normal
functioning
• Enzymes lower the activation energy of the reaction
• Activation energy – the minimum amount of energy needed
to cause a chemical reaction to occur
• Without enzymes, reactions would proceed too slowly
Enzyme Models
• Substrate – the reactant in an enzyme-catalyzed reaction
• Active site – the area of the enzyme where the substrate binds
• Two ideas on how enzymes attach to substrates:
• Lock-and-key
• Induced fit – the slight change of shape of an enzyme after the
substrate binds to it
• Substrates enter
• Induced fit around the substrate
• Lowers activation energy
• Products are released/enzyme returns to normal shape
• Enzyme can be reused
Biology 2.3 – Reactions