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Chapter 2:The Chemistry of

Life

Remember metabolism?

Those reactions involve chemicals and chemistry! Chemistry: the science of matter

What it’s made of What it does- reactions

Democritus’ question…

Atoms- the basic unit of matter

VERY small- 100 million = 1 centimeter! Subatomic particles

Protons (+) Neutrons (0) Electrons (-)*

Atomic number: # of protons Mass number: # of protons + # of neutrons

Element

A pure substance consisting of just one type of atom

Over 100 known- only about 24 commonly found in nature

Isotopes

Atoms of the same element that differ in the number of neutrons So they have a different what?

Same number of electrons means same chemical properties Radioactive isotopes

Used to date fossils and rocks Cure cancers/kill bacteria Tracers- “label” a substance and follow it thru the body

Chemical Compounds

A substance formed by the chemical combination of two or more elements in definite proportions

Formulas- ex: H20 and NaCl Chemical/physical properties of compounds are

very different than their individual elements

Chemical Bonds

Chemistry- what matter “does”- depends on the forming/breaking of bonds

Involve valence electrons 2 Main types of bonds

Ionic: transfer e- (ex: NaCl: Na+ and Cl- ions) Covalent: share e- (ex: H2O)

Molecule- the smallest unit of most compounds

Van der Waals forces

1. covalent bond “sharing” isn’t always “equal” 2. electrons are always in motion …therefore there are always + and – regions of a

molecule

Van der waals forces = intermolecular forces between + and – regions of molecules that attracts them together

http://www.youtube.com/watch?v=OoYeIsSkafI

2-3 Carbon Compounds

Organic chemistry: the study of all compounds with bonds between C atoms

4 macromolecules Carbohydrates Lipids Nucleic acids Proteins

Why is C so important?

4 valence electrons How many bonds can it make?

4!

Can bond with other carbon atoms Long chains Rings Can form a variety of structures

Macromolecules

What does “macromolecule” mean? “giant” molecule

Monomers: small individual molecules Polymer: a bunch of smaller monomers together This process called: polymerization

Carbohydrates

C, H & O Living things use it for energy and structural

purposes (plants) Monomer: monosaccharides Polymer: polysaccharides

Carb Examples:

Animals: Starch and glucose- store excess sugar Fiber (from plants) helps with digestion

Plants: Cellulose- rigidity and strength (ex: paper!) Plant starch- store excess sugar

Carb N. Ergy!

Lipids

C and H Fats, oils, waxes Store energy in living things Makes up waterproof membranes (ex: in cells) Steroids

Lipids are NOT polymers

Structure: A glycerol molecule 3 fatty acid chains

Saturated fatty acids: single bonds btwn Cs maximum # H atoms possible

Unsaturated fatty acids: at least one double bond btwn Cs

Polyunsaturated: two or more double bonds btwn Cs

Lipids Examples

Saturated (mostly solids): butter, waxes Unsaturated (mostly liquids): olive oil Polyunsaturated (mostly liquids): cooking oils like

canola oil

Nucleic Acids

H, O, N, C and P Store and transmit genetic material

DNA and RNA Monomer: nucleotides

Made up of: 5C sugar, phosphate group, N base Polymer: nucleic acid Covalent bonds

Proteins

N, C, H and O Regulates cell processes/ rates of reaction

Transport substances in/out of cells Growth and repair of muscles and bone Fight diseases

Proteins (continued)

Monomers: amino acids (aa) Amino group Carboxyl group R group side chain (unique)

20+ found in nature

Protein Structure

4 Levels of organization: Primary- sequence of aa form a chain Secondary- aa form either a twist or folds within the chain Tertiary-the chain itself twists/folds Quaternary-how chain interacts with other chains

Attractive forces at work: Van der waals forces H- bonds Peptide bonds

Water!

75% of earth is water! 60% of the human body is water! 70% of your brain is water! You will die in a few days without water!

2-2 Properties of Water

Density Polarity Cohesion Adhesion High specific heat

Density

Mass per unit volume Water expands when frozen Ice is less dense than water

What does this mean? Why is this important in nature?

Density Rainbow Test

At your lab tables, work with your group to make your hypothesis…

Place the following substances in order from MOST dense to LEAST dense. Corn syrup Water Vegetable oil Dish soap Alcohol Honey

Check your hypothesis…were you correct?

Polar

Uneven distribution of electrons between O and H atoms

O has 8 protons H has only 1 proton Covalent bonds

Hydrogen bonds

attraction between H and an electronegative atom (like O!)

Cohesion

The ability of water molecules to “stick together” Surface tension

*Jesus Christ lizard!

Adhesion

The ability of water molecules to “stick” to other surfaces

Ex: capillary action in plants

High Specific Heat

Water takes a long time to heat up and cool down Have you ever gone surfing in Oct? Swimming in

April?

Mixtures

Mixture- 2 or more elements physically but not chemically combined What does this mean? Ex: salt and pepper Ex: gases in the atmosphere

Solutions and Suspensions

2 types of mixtures: Solutions: when the molecules of a mixture are

evenly distributed Solute: substance being dissolved Solvent: usually water

Suspensions: a mixture of water and nondissolved material These materials are “suspended” in the mixture

Acids, Bases and pH

A water molecule can react to form ions H2O H+ + OH-

(Water H ion + hydroxide ion) # of H+ ions = # of OH- ions (water is” neutral”)

pH: concentration of H+ ions in a solution

pH Scale

Scale from 1 to 14 Water is neutral: pH of 7 Acids: any compound that forms H+ ions in a solution

1-6 on the scale Bases: any compound that forms OH- ions in a solution

8-14 on the scale aka: alkaline solutions

pH Buffers

Fluids in human body must be between 6.5 and 7.5

Sharp increases or decreases will effect chemical reactions

So we must maintain internal conditions… Hmm, what is THAT called?

Buffers: weak acids/bases that can react with strong acids/strong acids/bases to prevent sharp changes in pH

2-4 Chemical Reactions and Enzymes

Chemistry: what things are made of WHAT THEY DO!

This depends on chemical reactions!

Chemical reaction: a process that changes one set of chemicals into another Mass and energy are conserved

Chemical Reactions

Involve a change in the bonds Quick or slow Reactants (in) products (out) Ex: carbon dioxide as a waste product

CO2 + H2O H2CO3 (carbonic acid) H2CO3 H2O + CO2 (as we exhale)

Energy in Reactions

All reactions release/absorb energy Release energy- occur spontaneously Absorb energy- require energy Living things must have a source of energy

Plants- store energy from sun Animals- digested good (metabolism!)

Activation Energy

Activation energy: the energy needed to get a reaction started

Ex: cellulose will react with oxygen and burn So why don’t our books burst into flames?

Enzymes

Specific type of proteins Some vital reactions take a long time to start Catalyst: a substance that speeds up a chemical reaction

Lowers the activation energy Enzymes are biological catalysts!

Speed up chemical reactions in cells Specific!

Why is this important?

Carbonic acid example Too much CO2 in blood will kill you Enzyme (carbonic anhydrase) speeds up reaction

so it happens right away

How enzymes work…

Must form an enzyme-substrate complex Substrate = reactants Substrate meet at active site

“lock and key” = very specific Lowers activation energy needed for reaction to occur

Enzyme Action

5. enzyme available for use again

1. reactants/substrates 2. enzyme-substrate complex

4. products produced

3. *activation energy lowered *chemical reaction occurs

active site

Regulation of Enzyme Activity

Affected by changes in temp., pH, etc. Proteins can turn enzyme on/off Roles:

Regulate chemical pathways Make materials Release energy Transfer information