Bio Content Block 1

Null Hypothesis

A hypothesis of “no difference.” No relationship between observations

Alternative Hypothesis

States that there is a relationship between observations

Taxonomic Levels of Organization

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

3 Domains

Archaea, Bacteria, Eukarya

Atom

Smallest unit

Charges of protons, neutrons, and electrons

Protons +

Neutrons

Electrons -

Isotopes

Differ in the # of neutrons, many elements exist in nature as a mix of different isotopes

Ions

The result of certain chemical reactions causing atoms to gain or lose electrons

Cation

An atom that has lost an electron and is positively charged

Anion

An atom that has gained an electron and is negatively charged

Atomic Mass

Protons + Neutrons

How many electrons can each shell hold?

1st shell- 2 electrons

2nd shell- 8 electrons

3rd shell- 8 electrons

energy levels increase in each subsequent shell

Rules for filling the electron shells

1. First 2 electrons go in the first shell

2. Next 4 electrons go in the 2nd shell, unpaired

3. Next 4 pair up with the first 4 in the second shell

Valence Electrons

Electrons in the outermost shell (can be paired or unpaired)

Valence Shell

The outermost shell

What are chemically inert elements?

Elements with a full valence shell

Valence Number

The number of unpaired electrons in the valence shell
Valence number determines the number and type of bond an atom can form

What creates bonds?

Atoms taking, giving up, or sharing electrons (the atoms want to fill their valence shell)

Types of chemical bonds

• ionic bonds

• covalent bonds

• hydrogen bonds

What happens to an atom after an electron transfer?

Both atoms become ions

Ionic Bonds

Atoms give up/receive electrons to/from their bonding partners

Covalent Bonds

The sharing of 2 valence electrons by 2 atoms - very strong and stable

Single bond and double bond

Single bond - sharing 1 pair of electrons

Double bond - sharing 2 pairs of electrons

Electronegativity - what does it depend on

The ability of an atom to attract electrons - depends on number of protons in each atom and the molecular structure

The ____ electronegative an atom is, the ______ it pulls covalently shared electrons towards itself

More

Stronger

In general, an atom with ____ protons is ____ electronegative than an atom with ____ protons

More

More

Fewer

Nonpolar covalent bond

both atoms in the bond have equal or almost equal electronegativity

atom share electrons equally

Polar covalent bond

one atom is more electronegative than the other

atoms do not share electrons equally

Hydrogen Bonds

Not really a true bond, bonds of molecular force

• no sharing/stealing electrons

• the attractive force b/w 2 polar molecules

Hydrogen bonds contribute to the unique properties of water:

• cohesion

• adhesion

• surface tension

• high specific heat

• evaporative cooling

• expansion when frozen

Cohesion

water molecules share hydrogen bonds with other water molecules

Surface tension

allows water to be stretched

Adhesion

water molecules share hydrogen bonds with other polar covalent molecules

Heat and temperature

Heat is the total amount of energy due to molecular motion

Temperature is a measurement of the heat

What kind of molecule is water

Polar covalent

Specific Heat

The amount of energy it takes to change the temp of a substance by 1ºC

As temperature decreases, density ___

increases

Why does ice float?

Hydrogen bonds

What is max water density at?

4ºC

What happens to water density below 4ºC?

Hydrogen molecules expand and push water molecules farther apart, then freeze in place

Why is water a great solvent?

Due to its polarity

Hydrophilic

loves water

ex: sugar, salts

Hydrophobic

fears water

ex: oils, fats, waxes

pH less than 7

acidic

pH greater than 7

basic

pH 7

neutral

What is the pH of H+= 1×10^-4

pH=4

What is the pH of OH-= 1×10^-11

pH = 11

What are the different types of hydrocarbons?

Length, double bond, ring structure, branching

What type of hydrocarbon bond is this?

Length

What type of hydrocarbon bond is this?

branching

What type of hydrocarbon bond is this?

double bond position

What type of hydrocarbon bond is this?

Ring structure

Isomers

Compounds with the same molecular formula but different structural arrangements

What are the 3 types of isomers?

• structural

• cis-trans

• enantiomers

Structural isomers

Molecules have the same molecular formula but have different covalent bond arrangements - results in different structures (structure determines function)

Cis-trans isomers

Molecules have the same molecular formula but differ in spatial arrangement around a double bond - results in different structures (structure determines function)

Enantiomers - and qualities

Molecules are mirror images of each other

• non-super imposable

• very biologically important

• most biologically active enantiomers are L isomers

What are all of the functional groups?

• Hydroxyl (-OH)

• Carbonyl ( >C=O)

• Carboxyl (-COOH)

• Amino (-NH₂, NH₃)

• Sulfhydryl (-SH)

• Phosphate (OPO₃)

• Methyl (-CH₃)

Hydroxyl

Oxygen and hydrogen bonded to a carbon

• creates polar compound due to electronegativity of oxygen

• makes molecules hydrophilic

• forms hydrogen bonds with water

• make a compound an alcohol

Carbonyl

Oxygen double bonded to carbon

• creates a polar molecule, hydrophilic

2 types of Carbonyl:

Ketone- if oxygen is in the middle of hydrocarbon

Aldehyde- if oxygen is at the end of hydrocarbon

Carboxyl

Carbon has double bond to oxygen and single bond to OH

• makes molecules polar and hydrophilic

• acts as an acid

Amino

Nitrogen bonded to 2 hydrogens and a carbon

• acts as a base

• still polar and hydrophilic

• very important in proteins

Sulfhydryl

Sulfur bonded to hydrogen and carbon

• slight polarity and hydrophilic

• 2-SH groups interact to stabilize protein structure

Phosphate

Phosphate bonded to 4 oxygens, one bond is a double bond

• one of the oxygens is bonded to carbon

• energy currency of cells - ATP

Methyl

Carbon bonded to 3 hydrogens

• bond occurs in ring structures and in macromolecules such as DNA

• affects gene expression

• affects shape and function of male and female sex hormones