The chemical reactions associated with biological processes

Learning Focus To identify and describe the 4 main types of biochemical reactions: neutralization, oxidation-reduction, condensation, and hydrolysis reactions

What is a biological Rx? Any ideas? Generally 3 broad categories… a) metabolic rx – any reaction in a living system. b) Anabolic rx – reactions that produce larger molecules. c) Catabolic rx – reactions that breakdown larger molecules.

1. Acid-Base (neutralization rx) Neutralization Rx is a chemical reaction that occurs between an acid and a base (reactants), that results in water and a salt (products) Result – the acidic and basic properties of the aqueous solution where the reaction took place are nullified (i.e. cancelled out)

pH scale review: Review – what is the pH scale? Take a second to define and describe it. It’s a numerical scale ranging from 0 – 14 that is used to classify aqueous solutions as acidic, basic, or neutral.

What is considered to be normal? The normal pH range of blood is 7.35 – 7.45 Given this is blood considered to be acidic or basic (alkaline)? What do you think the consequence is of blood pH falling below 7.0 or above 7.8? Acidosis (7.3 or lower) versus alkalosis (7.5 or higher) (you tube: precision nutrition kitchen tip)you tube: precision nutrition kitchen tip

Acid-base reactions in living organisms What do living cells use to resist changes in pH? (i.e. how do organisms neutralize acidic or basic environments?) Buffers! A substance that minimizes changes in pH by donating or accepting hydrogen ions as needed

Acid-base reactions in living organisms Buffers can donate H ions when they are required and can remove H ions when they are too many in solution Buffers usually consist of conjugate acid-base pairs in equilibrium Carbonic acid – bicarbonate buffer is important in human extracellular fluid

reactions involving electron transfer 2. Oxidation-reduction (Redox) Rx

Oxidation = chemical reaction where an atom loses electrons Reduction = chemical reaction where an atom gains elections Therefore a REDOX reaction = a chemical reaction that involves the transfer of electrons from on substance to another Redox Reactions

How to remember what happens? Use mnemonic: LEO GER LossGain ElectronElectron OxidationReduction Redox Reactions LEO the lion says GER

Redox Reactions Reducing Agent – substance that LOSES electrons; it causes the other substance to be reduced Oxidizing Agent – substances that GAIN electrons; it causes the other substance to be oxidized e.g. C 3 H 8 + 5O 2  3CO 2 + 4H 2 O + energy Combustion of propane

Redox in the Cell Many metabolic processes consist of chains of redox reactions. A-A- A B-B- B C-C- C D D-D- e.g. C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy

Involved in the assembly of all four types of biological macromolecules (as are Hydrolysis Rx) = a chemical rx that results in the formation of a covalent bond between two molecules with the production of a water molecule 3. Condensation Rx

Condensation Rx

Because the reaction involves a release of water, condensation rx are also called dehydration reactions Always involves the removal of a H atom from the functional group of one monomer (or subunit) and an – OH from the other monomers (or subunits) functional group This type of reaction always absorbs energy Also considered to be an anabolic reaction = synthesis of molecules 3. Condensation Rx

Anabolic Rx in Nucleic Acids bond that forms from the dehydration reaction between 2 (or more) nucleotides is called a phosphodiester linkage; occurs between the –OH group of one nucleotide, and the phosphate group of the next + H2O

Anabolic rx in carbs glucosefructosesucrose bond that forms from the dehydration reaction is a glycosidic bond; occurs between an –OH group on each molecule involved in the reaction

Anabolic rx in fats glycerol + 3 fatty acid  fat (triglyceride)

Anabolic rx in fats bond that forms from the dehydration reaction in the creation of a fatty acid is an ester linkage; occur between the –OH group on a glycerol molecule and the –COOH group on a fatty acid

Anabolic Rx in Proteins bond that forms from the dehydration reaction between 2 (or more) Amino acids is called a peptide linkage or bond; occurs between the carboxyl of one AA and the amino group of another

Involved in the breakdown of macromolecules into their monomers (smaller subunits) = a chemical rx that results in the cleavage of a covalent bond with the addition of a water molecule This type of reaction always releases energy Also considered to be an catabolic reaction = breaking down 4. Hydrolysis Rx