CHAPTER 2 – CHEMISTRY IN BIOLOGY CONT’D

Chemical Reactions Definition: Process by which atoms or groups of atoms in a substance are reorganized into different substances During this process chemical bonds are broken and formed Example: Iron + Oxygen  Rust Fe + O2  Fe2O3

Chemical Reactions Not all changes in a substance is because of a chemical reaction some changes result from physical reactions Example: Water

Chemical Equations A chemical equation shows the: Example: Table Salt Starting Products ( Reactants) Ending Products (Products) Direction of the Reaction (Arrow) Example: Table Salt

Balanced Equations Law of Conservation of Mass: In chemical reactions matter cannot be created or destroyed. All equations must show this balance of mass # of atoms of each element on the reactant side = # of atoms of each element on the product side Coefficients are used to make the number of atoms on each side of the arrow equal:

Balanced Equations Example: Glucose

Energy of Reactions Much of the energy organisms need is provided by sugar (food) Chemical reactions breakdown food to provide energy But we also need energy to start a chemical reactions.

Activation Energy Activation Energy: The minimum amount of energy needed for reactants to form products in a chemical reaction. Example: Flame provides the activation energy for the reaction of the wax with oxygen. After that no further input of energy is needed

Activation Energy Activation Energy: Amount of energy needed to start a reaction. Example: Flame provides the activation energy for the reaction of the wax with oxygen. After that no further input of energy is needed

Activation Energy Energy Diagram: Is a representation of the energetic path that reaction must take from reactants to products. Some reactions have very high activation energy

Exothermic Reaction: The net release of free energy Eg. Breakdown of Sugar in the body

Endothermic Reaction: Reactions that involve a net absorption of free energy. E.g. Photosynthesis

Increase how much product is made Get used up in a chemical reaction Catalysts Catalysts: A Substance that lowers the activation energy needed to start a chemical reaction. (i.e it speeds up a chemical reaction) A Catalyst does not: Increase how much product is made Get used up in a chemical reaction

Enzyme: Is a special protein that acts as a biological catalyst Catalysts - Enzymes Enzyme: Is a special protein that acts as a biological catalyst They speed up the rate pf chemical reactions in biological processes Most enzymes are specific to one reaction Amylase  Carbohydrates Lipase  Fats

Enzyme Function Substrates: Reactants or Substance that bind to the enzyme. This is what the enzyme is breaking down Active Site: Specific location where a substrate binds to an enzyme The active sight and the enzyme have complimentary shapes that enable them to act in a precise manner Think about pieces of a puzzle Lock & Key

Enzyme Structure Enzyme Substrate Complex: Forms when the substrate binds to the active site It helps chemical bonds in the reactants to be broken and new bonds to be formed. One the reaction is complete the enzyme releases the product The Enzymes are still reusable and go on to catalyze other reactions

Enzyme Structure Examples of Enzymatic Reaction Snake Bite the enzymes in the snakes venom breaks down the membrane of the Red Blood Cell (RBC) When fruits ripen When we breakdown food in cellular respiration

Factors that affect Enzymes Temperature Human cells operate at ~37oC Bacteria: Very high or Very low temperatures Acidity Inhibitors: A substance that blocks the enzyme from working properly Enzyme Concentration Substrate Concentration

Water & Solutions

Mixture A mixture is a combination of two or more substances in which each substance retains its individual characteristics Examples: Water & Oil Fruit and nut mix Fruit basket

Mixture Two types of mixtures: Homogenous Mixture Heterogeneous mixture Also called a solution Substances are uniformly distributed in another substance Example: Stainless Steel (Iron, chromium and nickel) Salt water solution

Mixture Homogenous Mixture A homogenous mixture has two components: Solvent: Substance in which another solution is dissolved Solute: Substance which is dissolved in the solvent Example: Salt & Water solution Water is the solvent Salt is the solute

Mixture Heterogeneous Mixtures Components remain distinct that is you can tell that there are different things that make up the solution A suspension is  a type of heterogeneous mixture where solid particles do not dissolve in a liquid solution. These particles settle out of the solution Example: Salad dressing Sand and water

Mixture Heterogeneous Mixture A colloid is  a type of heterogeneous where the particles do not settle out of the mixture because the particles are suspended in the mixture Example: Fog Butter Mayonnaise Blood Paint

Acids & Bases Acid: Any substance that release Hydrogen ions (H+) in water Base: Any substance that releases hydroxide ions (OH-) in water pH: Is a measure of how much H+ ions or OH- is in a solution The more H+ in a solution the more more acidic the solution will be The more OH- in a solution the more basic the solution will be

Acids & Bases Acids: pH values between 0 and 7 Bases: pH values between 7 and 14 Neutral: pH of 7 Most processes carried out by our cells occurs between a pH of 6.5 to 7.5

Buffers Example: Antacids  Heartburn Buffers: Are mixtures than can react with either an acid or a base to keep the pH within a certain range Example: Antacids  Heartburn