BIO 120 - Lecture 1/8/25

What is science?

A way of explaining the natural world.

A hypothesis must be:

Testable, falsifiable, and can never prove true.

A hypothesis is __________, ___________ are broad.

Narrow, theories

What is biology?

The study of life.

The Scientific Method

Exploration (observations, questions, literature) --> Investigation (hypothesis, predictions, experiments, data) --> Communication (discuss, share results, publish papers, inform policy)

Characteristics of Life

Reproduction, Growth (cell division), Homeostasis (responding to environment), Energy processing (metabolism/photosynthesis/cell respiration), Cell(s), Evolution, Carbon, Order (molecules, cells, tissue, organ)

Element

A substance that cannot be broken down into simpler substances

Molecule

Two or more atoms held together by covalent bonds

Compound

A substance consisting of two or more elements

Four elements of life, why?

Carbon (!!), hydrogen, oxygen, nitrogen. H, O, and N are found because they like to bond with carbon

Carbon can make up to ________ bonds.

Four

Valence electrons

Electrons on the outermost energy level of an atom

First shell requires _______ electrons to be stable and has __________ potential energy.

Two, lowest

The 2nd and 3rd shell require __________ electrons to be stable. Energy potential _____________ the further the shell is from the nucleus.

Eight, increases

Three types of bonds

Ionic, covalent, hydrogen

Ionic bond

A chemical bond resulting from the attraction between oppositely charged ions. No electrons are shared.

Nonpolar Covalent Bond

A type of covalent bond in which electrons are shared equally between two atoms. Can have single or double bonds. Equal attractive force. Bond is linear

Polar Covalent Bond

A covalent bond in which electrons are not shared equally. The atom with stronger electronegativity pulls electrons closer to nucleus creating negative region & partial negative charge. Less electronegativity creates positive region & partial positive charge. Bond is non-linear

What is the charge of a water molecule?

Neutral/no charge - but there is polarity.

Hydrogen bond

Attraction between a slightly positive hydrogen atom and a slightly negative atom. Forms between two polar molecules. No sharing of electrons. Positive charge pulls towards negative charge. Takes place between molecule, not within.

Can two water molecules form a hydrogen bond?

Yes!

Solvent (in biology)

Water

Solute

Dissolved particles in solvent

Solution

Homogeneous mixture of solute(s) and solvent.

What drives the characteristics of water?

Polarity

Cohesion

H2O sticks to other H2O molecules through hydrogen bonds.

Adhesion

H2O sticks to non-water molecules through hydrogen bonds.

Property of water that causes extensive hydrogen bonding on the surface of liquid water.

High surface tension

Property of water that causes extensive hydrogen bonding of liquid water.

High specific heat (how much heat can be gained or lost per gram of substance). Why water takes so long to boil.