Chapter 6.2

Chemical Reaction

Chemical Reactions

• Process by which atoms or groups of atoms in substances reorganize into different substances

• Chemical bonds are broken or formed

• For example – 4 Fe + 3 O2 2 Fe2O3

Reactants and ProductsChemical Equation:

C6H12O6 + O2 CO2 + H20(Glucose and oxygen react to form carbon dioxide and water)

Reactants (starting substances):C6H12O6 + O2

Products (substances formed):CO2 + H20

Balanced Equation• According to the principle of conservation of

mass, matter cannot be created or destroyed• The number of atoms of each element on the

reactant side must equal the number of atoms of the same element on the product side

For example:

2 H2O2 2 H20 + O2

C6H12O6 + 6 O2 6 CO2+ 6 H20

Energy of Reactions

• Activation Energy – minimum amount of energy needed to start a chemical reaction; energy needed for reactants to form products

Energy of ReactionsEnergy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants

Reactants

Enzymes

• Most chemical reactions proceed slowly since the activation energy is high

• A catalyst is a substance that lowers the activation energy needed to start a chemical reaction

• Enzymes are biological catalysts; enzymes are proteins

Enzymes

How Enzymes Work

1. Reactants, called substrates, bind to specific enzymes; the site where enzymes bind is called the active site

2. Once the substrate binds to the active site, it changes shape and forms the enzyme-substrate complex

3. The substrates react to form new products; the enzyme-substrate complex helps to break and form bonds

Example of Enzyme Reaction

http://blog.poolcenter.com/print.asp?articleid=6072

Another View of Enzymes

EnzymesMany factors can affect enzyme activity such as:

– pH– Temperature– Concentration of substrates

Chapter 6.3

Water and Solution

Water’s Polarity• Water molecules are formed by

covalent bonds between 2 hydrogens and 1 oxygen atom

• Since the electrons are more strongly attracted to the oxygen, the electrons spend more time near the oxygen nucleus

• The unequal distribution of electrons gives oxygen a slight negative charge

• Molecules with an unequal distribution of charges are polar molecules – they have oppositely charged regions

Slight Negative Charge

Slight Positive Charge

Water’s Polarity and Hydrogen Bonds• The two water molecules are

brought together, their polar ends attract each other

• This attraction between water molecules is called hydrogen bonding

• It is a weak bond between the hydrogen of one atom and the oxygen of another

• A water molecule can hydrogen bond with three other water molecules

Hydrogen Bonding in Water

http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.jpg

Properties of WaterWater is the UNIVERSAL SOLVENT

• Because water is polar, it can dissolve many substances

• For example, NaCl

Properties of WaterWater Expands When It Freezes

• Because of hydrogen bonding, water molecules separate when freezing and water becomes less dense

• Extremely important for marine organisms

http://expertvoices.nsdl.org/polar/2009/02/03/teaching-about-snowflakes-a-flurry-of-ideas-for-science-and-math-integration/http://cc.oulu.fi/~nmrwww/comp_res4.html

Liquid WaterSolid Water (Ice)

Properties of WaterWater is COHESIVE and ADHESIVE

Because of hydrogen bonding, – Water is attracted to other water molecules – this

is called COHESION– Water is attracted to other surfaces – this is called

ADHESION

Cohesion

Cohesion Causes Surface Tension

Adhesion

Adhesion (Capillary Action)

http://discovermagazine.com/2003/mar/featscienceofhttp://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p033.shtml

Mixtures

• two or more substances which are combined so that each substance keeps its own chemical identity.– Water combines to form many types of mixtures

Mixtures• Mixtures can be classified as

– Homogeneous – a combination of substances that is uniform throughout

or – Heterogeneous – a combination of substances that are

physically distinct from one another

Homogenous Mixtures

• Same uniform appearance

• Same composition throughout

• Examples– Sugar water– Salt water– Water and vinegar– Air in the atmosphere

Homogeneous Mixture• Solutions are a

homogeneous mixture• There are two components

of solution:– Solvent – a substance in

which another substance is dissolved

– Solute – the substance that is dissolved

Heterogeneous Mixture

• Visibly different substances

• Components remain distinct

• Examples – – Vinegar and oil– Salad (lettuce,

vegetables, croutons, etc.)

– Sand and water

Acids and Bases

WATERH2O

ACIDS BASES

Substances that release H+ ions when dissolved

in water

Substances that release OH- ions when dissolved

in water

pH ScaleH2O H+ + OH-

•pH scale – measurement system used to indicate the concentration of H+ ions in a solution•pH scale ranges from 0-14

• pH 7 is neutral and the concentration of H+ ions and OH- ions is equal• Acids – any compound that forms H+ ions in solution; contain pH values less

than 7 (the lower the pH values, the higher the acidity)• Bases – a compound that produces hydroxide ions (OH-) in solution; contain

lower concentrations of H+ ions than water and have pH value greater than 7

•Buffers • weak acids or bases that can react with strong acid or bases to prevent sudden

changes in pH• For example, to buffer a strong acid, you would add a weak base

Chapter 6.4

The Building Blocks of Life

Organic Chemistry

• Organic compounds are those containing CARBON

• Life forms are carbon-based and therefore considered organic

Macromolecules

• Macromolecules – large molecules that form from joining smaller molecules together– The smaller molecules are called monomer– The larger molecules are called polymers

• Four biologically important macromolecules:– Carbohydrates– Lipids– Proteins– Nucleic acids

Macromolecules

Monomer – smaller molecule

Polymer – larger molecule formed by joining together smaller molecules

Biological MacromoleculesGroup Function

Carbohydrates - Store Energy

Lipids - Store energy- Provide cellular barriers

Proteins - Transport substances- Speed up reactions-Provide structural support-Make hormones

Nucleic Acids Store and communicate genetic information

CarbohydratesChemical Composition•Made of Carbon, Hydrogen , and Oxygen

•Ratio of 1:2:1 (# of C atoms: # of H atoms: # of O atoms)Or (CH2O)2

Functions in Living Things

•ENERGY!• Structural support (cellulose in plant cell walls or chitin in animal shells)

Structure• Monomers may be small carbohydrates like glucose or sucrose. These monomers are called monosaccharide

• The monomers join to form large polymer called polysaccharides

Examples

Sucrose – table sugar

Cellulose – support of plant cell walls

Chitin – rigid support for animal shells (ex. lobster)

LipidsChemical Composition

• Made of Carbon, Hydrogen, and Oxygen

• Higher ratio of Hydrogen to Carbon

Functions in Living Things

ENERGY storage

Provide barriers for cell (cell membranes)

Protective layersStructure

Composed of several fatty acids attached to glycerol

Examples

Fats

Waxes – protective coating on leaves

Oils

Biological steriods

ProteinsChemical Composition

Composed of Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur

Functions in Living Things

Transport substances

Speed up chemical reactions

Hormones

Structural supportStructure

•Monomers of proteins are amino acids

• The monomers, amino acids, join to form long chains of proteins

Examples

Enzymes – speed up chemical reactions

Nucleic AcidsChemical Composition

Composed of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus

Functions in Living Things

Store genetic information

Structure

• Smaller monomers, called nucleotides, join together to form long polymers, DNA and RNA

Examples

DNA – stores genetic information

RNA – copies and transmit genetic information; help to make proteins