Biochemical Reactions Chemistry in Biology Chapter 6

Review What is the smallest unit of matter? How are atoms and elements related? Are living organisms comprised of these same elements? How is chemistry related to the growth and survival of living organisms?

Atoms: building blocks of matter Protons: positively charged particles Electrons: negatively charged particles Neutrons: particles with no charge Elements: pure substance that cannot be broken down into other substances by physical or chemical means Compounds: pure substance formed when two or more different elements combine Atoms, Elements, Compounds

Chemical Bonds Covalent Bonds: bond formed when electrons are shared Ionic Bonds: electrical attraction between two oppositely charged atoms or groups of atoms (called ions)

Chemical Reactions The process by which atoms or groups of atoms in substances are reorganized into different substances. Reactants: starting substance (left side) Products: substance formed during reaction (right side)

Energy of Reactions Most compounds in living things cannot undergo chemical reactions without energy. Activation Energy: minimum amount of energy needed for reactants to form products in a chemical reaction Sometimes a chemical reaction must absorb energy for the reaction to start, usually in the form of heat (endothermic).

Energy of Reactions

Enzymes Catalyst: substance that lowers the activation energy needed to start a chemical reaction Enzymes: special proteins that are biological catalysts, speed up the rate of reactions

Enzymes Enzymes are very specific, each particular enzyme can only catalyze one reaction. The reactants that bind to an enzyme are called substrates. The specific location where a substrate binds is called the active site. Temperature and pH can alter enzyme structure.

Enzymes

Acids and Bases Acids: substances that release hydrogen ions (H + ) when dissolved in water Bases: substances that release hydroxide ions (OH - ) when dissolved in water

pH The amount of hydrogen ions or hydroxide ions in a solution determines the strength of an acid or a base. pH: measure of concentration of H + Majority of biological processes carried out by cells occur between pH 6.5 and 7.5.

Buffers Mixtures that can react with acids or bases to keep the pH within a particular range. In cells, buffers keep the pH between 6.5 and 7.5.

Biochemical Reactions Allow organisms to grow, develop, reproduce, and adapt

Questions What are the factors that affect the rate of biochemical reactions? Construct a cause and effect model showing how temperature, pH, and enzymes are used to control chemical reactions in living organisms. ex) If _____ happens then _____ will happen as a result. Describe the importance of enzymes to living organisms?