Biochemical Reactions

First… a Summary Macromolecules  Monomers + functional groups Four types of macromolecules of interest to us:  Carbohydrates  Proteins  Lipids  Nucleic Acids

Carbohydrates Monomer: simple sugar  Ex. Glucose Functional group(s):  Carboxyl  Hydroxyl Polymer: complex CHO  Starch, glycogen

Proteins Monomer: amino acids  20 total, 8 or 9 essential Functional group(s):  Carboxyl  Amino Polymer  Polypeptide  Protein

Lipids Monomer: Fatty acid Functional group(s):  Carboxyl Polymers: many – depending on the type of lipid  Phospholipid, triglyceride

Nucleic Acids Monomer: nucleotide  A, T (or U), C, G Functional group(s):  Phosphate  Amino  Hydroxyl Polymer:  DNA and RNA

Biochemical Reactions Chemical reactions associated with biological processes Often involve a combination of more than one type of reaction Four main types of reactions:  Neutralization  Oxidation-Reduction  Condensation  Hydrolysis

Acid-Base Reactions Acid: produces H + ions in water  pH value less than 7 Base: produces OH - ions in water or accepts H + ions  pH value more than 7 Neutralization Reaction: interaction of an acid and a base to form a salt (an ionic compound) and water Neutralization Reaction

Necessary to maintain a constant pH state within the body Buffers: resist changes in pH  Release H + ions when fluid is too basic  Take up H + ions when fluid is too acidic

Oxidation-Reduction Reactions Involves the transfer of electrons  Oxidation: loss of electrons  Reduction: gain of electrons Electrons are highly reactive and don’t exist on their own in cells  If oxidation occurs to one molecule in the cell, reduction must immediately to another molecule The entire reaction is often called a redox reactionredox reaction

Condensation Reactions Involved in the assembly of all four types of macromolecules  An H atom is removed from a functional group on one molecule, and an OH group is removed from another molecule  Result: a larger molecule + water (water out, monomer in)  Also known as dehydration synthesis dehydration synthesis

Hydrolysis Reactions Involved in the breakdown of macromolecules into their monomers  Water is added to break the bonds between monomers (water in, monomer out)  H from the water is added to one molecule, and the OH group is added to the adjacent monomer  Covalent bond between monomers breaks to form two smaller molecules

Role of Enzymes An enzyme is a biological catalyst  Speeds up a biochemical reaction, but is not used up in the reaction Enzymes are proteins  Have a specific shapeshape  Each enzyme fits specifically with a substrate (the reactant for the reaction) to form an enzyme-substrate complex Like a lock and key!

Enzyme-Catalyzed Reactions Enzymes prepare substrates for reaction by changing the substrate, its environment, or both, in some way  Causing bonds to stretch or bend (making them more fragile)  Bring two substrates together  Transfer electrons to or from the substrate (i.e. reduce or oxidize it), making it less stable  Add or remove H + ions to or from the substrate (i.e. act like an acid or base), destabilizing it

Enzyme Denaturation Proteins are called denatured when they have lost their shape.  Caused by changes in temperature, pH, environmental factors, etc.  Because shape is so important to protein function, denatured proteins are no longer able to carry out their proper function

Liver Functions

Importance of Catalase H 2 O 2 (hydrogen peroxide) is a harmful byproduct of many of the metabolic processes that take place in the liver  Must be removed quickly  This is the responsibility of the enzyme catalasecatalase

Factors Affecting the Action of Catalase What might our liver be exposed to that