Lecture 2: Atoms, Chemical Bonds, and Water

Cell

smallest unit of life that can perform all activities required for life

- carry out metabolic processes, create energy, make copies of genome

Eukaryotic Cell

contains membrane enclosed organelles

- has nucleus

- animals, plants, fungi

Prokaryotic Cell

no nucleus and lacks membrane bound organelles

- generally smaller

- bacteria

Characteristics Shared by Cells

cell membrane, DNA genome, cytoplasm, ribosomes

Ribosomes

small structure that generate protein for the cell

Genes

inherited units made of DNA

- can code for protein

DNA Molecule

holds thousands of genes

- each are a stretch of DNA along the chromosome

- directs cell development

Central Dogma

process of going from DNA > RNA >Protein

- proteins carry out functions

Gene Expression

converting information from a gene to its cellular product

Germ Theory of Disease

microbes arose without cause; they did not know bacteria was responsible for disease

- spontaneous generation

Hypothesis

looking at observations and how we can test them

- explanation that can be tested by experiments

Theory

broader than hypothesis

Matter

anything that takes up space and has mass

- made of elements

Element

pure substance made up of one type of atom

- cannot be broken down

Compound

two or more elements in a fixed ratio

- different atoms

- take on different properties and characteristics when together

Essential Elements

carbon, oxygen, hydrogen, nitrogen

Atom

smallest unit of matter that retains properties of an element

Neutrons: no charge

Protons: positive

Electrons: negative

Atomic Number

number of protons in nucleus

Mass Number

sum of protons and neutrons

Atomic Mass

atom’s total mass

Energy

capacity to cause change

Potential Energy

energy that matter contains

Valence Shell

outermost shell

- behavior depends on number of electrons

- completed shells are unreactive

Chemical Bonda

interactions between the valence electrons between other atoms

Covalent Bond

sharing of electrons

nonpolar: equal sharing

polar: unequal sharing

Bonding Capacity

number of bonds an atom can form

- valence

Nonpolar Covalent Bonds

equal sharing

- hydrophobic

- C-C, C-H

Polar Covalent Bond

unequal sharing; causes partial charge for each atom

- hydrophilic

- N-H, OH, C-O

Electronegativity

atom’s attraction for electron’s of a covalent bond

- more electronegative = stronger pull towards itself

< 0.4: nonpolar

05.-2: polar

> 2: ionic

Ionic Bond

transfer of electrons

- attraction between anion and cation

Cation

positively charged

Anion

negatively charged

Hydrogen Bonds

forms when hydrogen is covalently bonded to one electronegative atom and is attracted to another electronegative atom nearby

- polar interactions

- critically important for life; more stable at lower temps

- partners usually are oxygen or nitrogen

Chemical Reactions

making and breaking of chemical bonds

reactant: starting molecule

product: final molecules

Chemical Equilibrium

when the forward and reverse reaction rates are equal

Cohesion

contributes to transport of water and nutrients against gravity in plants

- closely packed together

Adhesion

clinging of one substance to another

Surface Tension

measure of how hard it is to break the surface of a liquid

- related to cohesion

Van Der Waals Interactions

nonpolar molecule comes into contact with something polar

- only when they are very close together