Biochemical ReactionsChemistry 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

http://www.docbrown.info/page03/3_51energy.htm

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

http://www.simpert.com/technologies.html

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?