Lecture #1 ~ Date__________

Chapter 1: Themes in the Study of Life                                       

Chapter 2: Chemical Context of Life

Chapter 3: Water and the Fitness of the Environment

Unifying Themes in Biology

Evolution ~ biology’s core theme; differential reproductive success

Emergent Properties ~ hierarchy of life

The Cell ~ all organism’s basic structure

Heritable Information ~ DNA

Structure & Function ~ form and function

Environmental Interaction ~ organisms are open systems

Regulation ~ feedback mechanisms

Unity & Diversity ~ universal genetic code

Scientific Inquiry ~ observation; testing; repeatability

Science, Technology & Society ~ functions of our world

Chemical Context of Life

Matter (space & mass)

Element; compound

The atom

Atomic number (# of protons); mass number (protons + neutrons)

Isotopes (different # of neutrons); radioactive isotopes (nuclear decay)

Energy (ability to do work); energy levels (electron states of potential energy)

Chemical Bonding

Covalent

Double covalent

Nonpolar covalent

Polar covalent

Ionic

Hydrogen

van der Waals

Covalent Bonding

Sharing pair of valence electrons

Number of electrons required to complete an atom’s valence shell determines how many bonds will form

Ex: Hydrogen & oxygen bonding in water; methane

Covalent bonding

Polar/nonpolar covalent bonds

Electronegativity attraction for electrons

Nonpolar covalent •electrons shared equally •Ex: diatomic H and O

Polar covalent •one atom more electronegative than the other (charged) •Ex: water

Polar/nonpolar bonds

Ionic bonding

High electronegativity difference strips valence electrons away from another atom

Electron transfer creates ions (charged atoms)

Cation (positive ion); anion (negative ion)

Ex: Salts (sodium chloride)

Ionic bonds

Hydrogen bonds

Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)

van der Waals interactions

Weak interactions between molecules or parts of molecules that are brought about by localized change fluctuations

Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

Water

Polar~ opposite ends, opposite charges

Cohesion ~ H+ bonds holding molecules together

Adhesion ~ H+ bonds holding molecules to another substance

Surface tension ~ measurement of the difficulty to break or stretch the surface of a liquid

Specific heat ~ amount of heat absorbed or lost to change temperature by 1oC

Heat of vaporization ~ quantity of heat required to convert 1g from liquid to gas states

Density ……….

Density

Less dense as solid than liquid

Due to hydrogen bonding

Crystalline lattice keeps molecules at a distance

Acid/Base & pH

Dissociation of water into a hydrogen ion and a hydroxide ion

Acid: increases the hydrogen concentration of a solution

Base: reduces the hydrogen ion concentration of a solution

pH: “power of hydrogen”

Buffers: substances that minimize H+ and OH- concentrations (accepts or donates H+ ions)