Chapter 2 The Chemistry of Life

Section 1: The Composition of Matter

The Big Idea Life Depends on chemistry Chemical reactions keep you alive

Atom Basic unit of matter Matter is anythng that has mass and volume Mass is the quantity of matter an object has

Mass vs. Weight

Subatomic particles Protons - Neutrons - Electrons - Positively charged (+) Not charged (neutral) Negatively charged (-) Bind together to form the nucleus Electrons Protons Neutrons Nucleus

If a particular atom was the size of: AT&T Park Energy Levels of Electrons

The nucleus would be the size of: a push pin Energy Levels of Electrons

The electrons would be the size of: a gnat Energy Levels of Electrons

If the push pin is in the center of the park and the gnats are flying around, it follows that an atom is mainly _________________________. Only electrons are involved in chemical reactions. Energy Levels of Electrons

Element A pure substance that consists of just one type of atom

There are about 25 elements that are known to be essential to life but 4 of these _________, __________, ____________ and ____________ make up 96% of living matter. Another 4 elements, _____________, _____________, _______________ and _____________ and a few others make up the remaining 4%. Matter

6 C Carbon Atomic number An elements atomic number = number of protons

Isotope Atoms of the same element that differ in the number of neutrons they contain

Nonradioactive carbon-12Nonradioactive carbon-13Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 8 neutrons 6 electrons 6 protons 7 neutrons

6 C Carbon Mass number The Sum of protons and neutrons in the nucleus of an atom is its mass number

The weighted average of the masses of an elements isotope is called its atomic mass

Radioactive isotopes Can be dangerous Can be used practically –Radioactive dating –Treat cancer –Kill bacteria

Compounds A substance formed by the chemical combination of two or more elements in definite proportions Ex) H 2 O, NaCl

Table Salt

Ionic Bonds Formed when one or more electrons are transferred from one atom to another

Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na + ) Chloride ion (Cl - ) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1

If an atom loses an electron it becomes positive If an atom gains an electron it becomes negative

Ions Positively and negatively charged atoms

Covalent Bonds Forms when electrons are shared between atoms

Molecule The structure that results when atoms are joined together by a covalent bond Smallest unit of most compounds

Section 2: Properties of Water

Objectives Why are water molecules polar? What are acidic solutions? What are basic solutions?

The Big Idea Much of our planet is covered in water Water is necessary for life to exist If life exists on other planets, there most likely is water present Water has many properties that make life possible

Polarity (-) (+) The oxygen atom has a stronger attraction for electrons

Hydrogen Bonds Because of waters partial charges, they can attract each other and create hydrogen bonds Not as strong as covalent or ionic bonds Waters ability to create multiple hydrogen bonds gives it many special properties

Cohesion Attraction between molecules of the same substance

Adhesion Attraction molecules of different substances

Solutions Mixture of two or more substances in which the molecules are evenly distributed Ex.) salt water Settles out over time

Solutions Cl - Water Cl - Na + Water Na +

Solute Substance that is dissolved Ex.) salt

Solvent The substance that does the dissolving Ex.) Water

The pH scale Indicated the concentration of hydrogen ions in a solution

Neutral Acid Base

Acids Any compound that forms H + (hydrogen) ions in solution

Base A compound that produces OH - (hydroxide) ions in solution

Buffers Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden pH changes

Macromolecules “giant molecules” Formed by a process called polymerization

Monomers Smaller units

Polymers Linked up monomers

Carbohydrates Compounds made up of carbon, hydrogen, and oxygen atoms usually in a ratio of 1:2:1 Main source of energy The monomers of starch are sugars

Single sugar molecules are called monosaccharides The large macromolecules formed from monosaccharides are known as polysaccharides

Starch Glucose

Lipids Made mostly from carbon and hydrogen atoms Used to store energy

Lipid Glycerol Fatty Acids

Proteins Macromolecules that contain nitrogen as well as carbon, hydrogen, and oxygen Proteins are polymers of molecules called amino acids

Amino Acids General structureAlanineSerine Carboxyl group

More than 20 different amino acids, can join to any other amino acid The instructions for arranging amino acids into many different proteins are stored in DNA Each protein has a specific role The shape of proteins can be very important

Proteins Amino Acids

Nucleic Acids Macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus Double Helix

Nucleotides Consists of 3 parts: 5-carbon sugar, phosphate group and nitrogen base Nitrogen Base 5-Carbon Sugar Phosphate group

2 kinds of nucleic acids RNA (ribonucleic acids) – contains sugar ribose DNA (deoxyribonucleic acid) – contains sugar deoxyribose

Homework

1.Name four groups of organic compounds found in living things carbohydrate, lipid, protein, nucleic acids 2. Describe at least one function of each group of organic compounds carbohydrates – energy lipids – store energy proteins – form tissue nucleic acids – transmit hereditary information

3. Compare the structures and functions of lipids and starches Lipids are made from carbon and hydrogen. Starches are made of carbon, hydrogen and oxygen. They both can be used to store energy

Section 4: Chemical Reactions and Enzymes

Objectives What happens to chemical bonds during chemical reactions? How do energy changes affect whether a chemical reaction will occur? Why are enzymes important to living things?

The Big Idea Living things are made up of chemical compounds Everything that happens to an organism is based on chemical reactions

Chemical Reactions A process that changes or transforms one set of chemicals into another

Reactants Elements or compounds that enter into a reaction

Products Elements or compounds produced by a chemical reaction

Example Reaction: Getting rid of carbon dioxide In the blood In the lungs CO 2 + H 2 0  H 2 CO 3 (carbonic acid) H 2 CO 3  CO 2 + H 2 O Released as you breathe

Energy in reactions Energy-Absorbing Reaction Energy-Releasing Reaction Products Activation energy Activation energy Reactants

Activation Energy The energy that is needed to get a reaction started

Enzymes Some chemical reactions are too slow or have activation energies that are too high to make them practical for living tissue These chemical reactions are made possible by catalysts

Catalyst Substance that speeds up the rate of chemical reactions Work by lowering a reactions activation energy

Enzyme Biological catalysts Speed up reactions in cells Very specific Named for the reaction is catylzes Enzyme names always end in - ase

Reaction pathway without enzyme Activation energy without enzyme Activation energy with enzyme Reaction pathway with enzyme Reactants Products

Substrates The reactants of enzyme catalyzed reactions The active site of the enzyme and the substrate have complementary shapes Fit like a lock and key

Enzyme Action Enzyme – substrate complex

Glucose Substrates ATP Substrates bind to enzyme Substrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Active site

Regulation of Enzyme Activity Enzymes are affected by any variable that affects chemical reactions 1.pH 2.Temperature 3.Concentration of enzyme

Homework

1.What happens to chemical bonds during chemical reactions Bonds are broken in reactants and new bonds are formed in products 2. Describe the role of energy in chemical reactions some chemical reactions release energy, and other chemical reactions absorb energy. Energy changes determine how easily a chemical reaction will occur

3. What are enzymes, and how are they important to living things? Enzymes are biological catylasts. Cells use enzymes to speed up virtually every important chemical reaction that takes place in cells

4. Describe how enzymes work, including the role of the enzyme substrate complex Substrates, the reactants of an enzyme-catylzed reaction, attach to the enzyme at an active site and form an enzyme – substrate complex. Once the complex is formed, the enzyme helps convert substrate into product

5. A change in pH can change the protein. How might a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key) A change in pH could change the shape of hexokinase. This change would diminish the ability of glucose and ATP to bind to the active site of the enzyme.