Chapter 2- The Chemical Context of Life - Quia



Chapter 2- The Chemical Context of Life

I. Matter Anything which takes up space and has mass

A. Elements

B. Compounds

C. Elements essential to life

1. C,O,H,N = about 96% of living matter

2. P, S, Ca, K = most of remaining 4%

3. Trace elements are required in small amounts- Fe, I

D. Atoms- units of matter, smallest unit having physical and chemical properties of its elements

1. subatomic particles- neutrons, protons, electrons

2. atomic number- number of protons

3. mass number/atomic mass- number of protons and neutrons

4. isotopes- different number of neutrons, radioactive- nucleus decays releasing particles and energy, used as tracers

5. energy levels or electron shells- different states of potential energy of electrons

6. electron orbitals- 3-D space where electron is 90% of the time

7. valence electrons- outer electrons, helps determine the reactivity of the atom

II. Chemical Bonds and Molecules

A. Covalent bond- sharing of a pair of valence electrons

1. structural formula H-H

2. molecular formula H2

3. double covalent bond O = O, O2

B. Molecular shape- important because it is the basis for how most molecules of life

recognize and respond to each other

C. Electronegativity- attraction of an atom for the electrons of a covalent bond

1. nonpolar covalent bond- electrons are equally shared

2. polar covalent bond- electrons are not equally shared

D. Ionic bond- attraction between cations and anions

1. ion- charged atom or molecule

2. cation- positive charge

3. anion- negative charge

4. ionic compounds are called salts

E. Hydrogen bond- occurs when a hydrogen atom covalently bonded to one

electronegative atom is also attracted to another electronegative atom

1. in living cells the partners are often O and N

2. very weak bond

3. allows for brief meeting, interaction and separation

F. van der Waals interactions- weak, briefly hold atoms and molecules together, caused

by brief positive and negative charges

III. Molecular Shape

A. Molecular shape is critical the functioning of organisms

B. Determines how biological molecules recognize and respond to each other

IV. Chemical Reactions- making and breaking of chemical bonds, leading to changes in the

composition of matter

A. Reactants

B. Products

C. Coefficients

D. Yield sign/ double yield sign

E. Chemical equilibrium

Chapter 3- Water and the Fitness of the Environment

I. Water Facts

A. 75% of Earth

B. 65% of human body

C. Cells contain about 70-95% water

D. Only common substance to exist in natural environment in all 3 states of matter

II. Properties of Water

A. Polar molecule

B. Cohesive due to H bonding

1. contributes to transport of water against gravity in plants

2. surface tension- measure of how difficult it is to stretch or break the surface of

a liquid

C. Adhesion

III. Heat and Temperature

A. Kinetic energy

B. Heat- total quantity of kinetic energy due to molecular motion in body of matter

C. Temperature- measures intensity of heat due to average kinetic energy of molecules

D. Celsius scale

E. Calorie (ca) amount of heat it takes to raise 1g of water 1 degree C

F. Specific Heat- amount of heat that must be absorbed or lost for 1g of that substance

to change its temp. 1 degree C

IV. Water and Heat

A. Stabilizes air temperature by absorbing heat from air that is warmer and releasing

the stored heat to air that is cooler

B. High specific heat

1. due to H bonding

2. helps keep water on earth at temp. conducive to life

3. water in organisms helps prevent rapid changes in body temperature

C. High heat of vaporization- quantity of heat a liquid must absorb for 1 g of it to

be converted from liquid to gas

1. moderates climate

2. sweat evaporation

D. Water expansion- when frozen

1. H bonds keep molecules apart ↓ density

2. greatest density of 4 degrees C

3. prevents lower lake water from freezing

E. Universal solvent- dissolves most solutes

1. aqueous solution- water is solvent

2. hydrophilic (ionic, polar)

colloid – suspension of particles in liquid, like inside a cell or cotton

3. hydrophobic (nonionic, nonpolar)

V. Aqueous Solutions

A. Molarity- moles of solute per L of solution

B. Hydrogen ion – charge of +1 (H+)

C. Hydroxide ion- charge of -1 (OH-)

d. Acids- substances that increase the H+ concentration (0-6.9 on pH scale)

E. Bases- substances that reduce the H+ concentration (7.1-14 on pH scale)

F. pH scale (0-14)

1. as H+ ↑ pH ↓

2. pH = -log [H+]

G. Buffers- substances which reduce changes in the concentration of H+ and OH-

Chapter 4- Carbon and the Molecular Diversity of Life

I. History/Foundation

A. Vitalism- belief that life force is found outside of the physical and chemical laws

1. Berzelius- distinguished between inorganic and organic

2. Wohler- made urea in lab (not accepted because used extract from animal

blood)

3. Kolbe- made acetic acid from all inorganic substances

4. Miller/Urey- abiotic synthesis experiment

B. Mechanism- belief that all natural phenomena including processes of life are joined

by physical and chemical laws

II. Carbon

A. 6 electrons (4 valence) tetravalent which allows for large molecules

B. chains form the skeletons of organic molecules

C. hydrocarbons- contain only C and H

D. asymmetric Carbon- attached to 4 different atoms or groups of atoms

III. Isomers pg 62

A. compounds having the same molecular formula but different structures and

properties

B. Structural- differ in covalent arrangements of their atoms, may differ in location of

double bonds

C. Enantiomer/Sterioisomer- molecules which are the mirror images of each other

1. usually one is biologically active and the other is not

2. pharmaceuticals- important because often one isomer is not as effective or

could produce harmful effects ( thalidomide)

IV. Functional Groups- most often involved in chemical reactions (pg 64-65**)

A. Hydroxyl group- hydrogen atom is bonded to an oxygen atom, which in turn is

bonded to the carbon skeleton of the organic molecule (-OH, HO-)

1. contributes to solubility of sugars, polar molecule

2. alcohols- organic compounds containing hydroxyl groups (-ol)

B. Carbonyl group- carbon atom joined to an oxygen atom by a double bond (-CO)

1. aldehyde- term for when the carbonyl group is on the end of the carbon

skeleton

2. ketone- term for when the carbonyl group is not on the end of the carbon

chain (must be at least three carbons long)

3. ketone and aldehyde may be structural isomers of each other

C. Carboxyl group (carboxylic acids/organic acids) oxygen is double bonded to a

carbon atom that is also singe bonded to a hydroxyl group (-COOH)

1. usually gives acids a sour taste

D. Amino group- nitrogen atom bonded to two hydrogen atoms and to the carbon

skeleton (-NH2)

1. also known as amines

2. act like bases

E. Sulfhydryl group- sulfur atom bonded to an atom of hydrogen (-SH)

1. also known as thiols

2. often seen in protein structure

F. Phosphate group- phosphate ion covalently attached by one of its oxygen atoms

to the carbon skeleton (-OPO3 ) (-OPO3H2)

1. can transfer energy between organic molecules (i.e. ATP)

G. Methyl group- carbon bonded to three hydrogens (-CH3)

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