Biochemical Reactions that Make and Break Molecules

Macromolecules Macromolecules are large organic molecules. The four main types of macromolecules are 1.Carbohydrates – sugars and starches 2.Lipids – fats and hormones 3.Proteins – enzymes and structures 4.Nucleic acids – DNA and RNA Macromolecules are also called polymers.

Monomers and Polymers “mono” means “one” “mer” means “unit” So a single unit of a large molecule is a monomer “poly” means “many” So a polymer is a large molecule made of many monomers For example: sugar + sugar  starch amino acid + amino acid  protein

Five Major Biochemical Reactions Making and breaking bonds is important to forming polymers from monomers. 1.Condensation or dehydration synthesis 2.Hydrolysis or decomposition with water 3.Neutralization of acids and bases 4.Redox or electron trading 5.Phosphorylation or adding a phosphate group

1. Condensation Reactions A condensation reaction joins monomers to form polymers. When a bond is formed between two monomers a water molecule is also produced. This reaction is also called dehydration synthesis. + + H 2 0 Example: glucose + fructose  sucrose + H 2 0

2. Hydrolysis Reactions A hydrolysis reaction breaks a polymer into monomers. Water is added to a molecule which causes a bond to break. The H+ is added to one monomer and the OH- to the other monomer. Example: sucrose + H 2 0  glucose + fructose

3. Neutralization Reactions Acids have a -COOH or H + group. Bases have a –OH or –NH 2 group. A neutralization reaction occurs when acids and bases react to produce a salt and water. Buffers are molecules that react to minimize pH changes in a cell. Buffers absorb excess H+ (acids) or OH- (bases)

4. Redox Reactions Redox stands for reduction – oxidation reactions “LEO goes GER” Loss of Electrons is Oxidation Gain of Electrons is Reduction Common in metabolic reactions like photosynthesis and cellular respiration. The electrons are carrying energy.

5a. Substrate-level Phosphorylation ATP, adenosine triphosphate, is the energy molecule of all cells. The bond formed by adding a 3 rd phosphate group to adenosine diphosphate (ADP) is an important energy storage location. Substrate-level phosphorylation uses the energy released from breaking a phosphate group off another molecule to attach the phosphate to ADP to form ATP.

5b. Oxidative phosphorylation Oxidative phosphorylation is a metabolic reaction that uses energy released by the oxidation of glucose to produce ATP in cellular respiration.

5c. Photophosphorylation Photophosphorylation is the production of ATP using the energy of sunlight during photosynthesis.