Biochemical Reactions

First… a Summary

MacromoleculesMonomers + functional groups

Four types of macromolecules of interest to us:CarbohydratesProteinsLipidsNucleic 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 waterpH value less than 7

Base: produces OH- ions in water or accepts H+ ionspH 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

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

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 proteinsHave a specific shapeEach 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

H2O2 (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 catalase

Factors Affecting the Action of Catalase

What might our liver be exposed to that