What is Biology?

Study of life & characteristics of life

Expectations/learning outcomes:– Understand, explain, describe, & integrate the

natural world of living things– Focusing on:

• How life works… rather than the “meaning of life”

Characteristics of Life?

In other words… what are the essential properties/functions of “living” systems?

• DNA• Cells• Acquire & use energy• Highly complex & organized• Growth & development• Metabolize chemicals• Reproduce• Evolve by natural selection

Levels of organization• Biosphere• Ecosystem• Community• Population• Organism• Organ system• Organ• Tissue• Cell -------functional units of life• Organelle• Molecule• Atom• Subatomic particle

How can we study: all these characteristics, diversity, complexity… and, try to make sense of it?

• Scientific Method– What?

– Why?

– How?

Inductive approach: from specific observations to the general

Deductive approach: use general principles in predicting specific outcomes

Scientific Method

Complexity builds from the atomic level up (Ch. 2)

• Atoms– Chemical unit – Made up of subatomic particles

• Nucleus of an atom– Protons positive charge– Neutrons neutral charge

• Electrons– negative charge– Orbit around nucleus in energy shells (2,8,8…)– Determine chemical nature, reactivity, and interactions with other

elements …incomplete shells create potential for interactions.

Lets make an atom of Carbon…• Symbol for Carbon element• Atomic number

6 protons

• Nucleus w/ 6 protons & 6 neutrons• 1st shell with 2 electrons• Second shell with only 4 electrons

…has space for 4 more e-

• Atomic mass?6 protons6 neutrons6 electrons= 12.011 (electrons negligible mass)

6

C12.011

1

H1

Relationships between atoms & molecules or, Bonds

• Interactions of outer shells or valence electrons

• Form molecules of multiple atoms• Form compounds of multiple molecules

• Covalent bonds– Atoms share

electrons (e-) between pairs to satisfy each of their valence shells

Example

• Ionic bonds– Unequally charged ions…

e- transferred from one ion to another (gain/loss of e-)

1

H1

17

Cl35.4

11

Na22

1

H1

+

+

Although the strongest bonds are Covalent, it is the weak Hydrogen bonds that are perhaps

the most significant to cell functions.

• Polar molecules– Covalent bonds of unequal

sharing (H20)

– O is more electronegative than H

• Hydrogen bonds include H• Opposites (+ & -) attract

creating H-bonds between water molecules

What else do we know about water?• Naturally occurs in 3 forms with varying levels of energy

and density.– Solid, liquid, gas

• Which is the most dense?

• Molecules in constant motion– Breaking & making H-bonds

• Varies with temperature, density, and dissolved particulates

Water is a common solvent that dissolves substances (solutes) to form an aqueous solution

• Additional water molecules dissociate leaving some hydrogen ions (H+) and some hydroxide ions (OH-)

• These ions are very reactive

• [H+] in solution = acidic Therefore a lower pH

• [OH-] in solution = basic Therefore a higher pH

The importance of Organic chemicals… (Ch. 3)

• contain at least one C atom– 4 electrons in outer shell

– in need of 4 more

– covalent bonds with H, O, N, or other C

• Molecules of only C and H are called hydrocarbons

• Bonding determines shape• Functional groups

– determine properties & functions of organic compounds

– Are usually polar, thus soluble in water, thus more reactive than carbon backbone by itself

Common Functional Groups

Most of a cells molecules are variations and extensions of a small set of small molecules.

Making Macromolecules• Many repeating smaller

molecules• Polymers of monomers• Built by dehydration

synthesis reaction (rxn)

Hydrolysis – breaking polymers

Classes of Macromolecules

• Carbohydrates– Simple & complex sugars– Monosaccharides & Polysaccharides

• Lipids– Fats, oils, waxes, etc.

• Proteins– Made of 20 Amino acids

• Nucleic Acids– DNA made of only 4 monomers (nucleotides)

Carbohydrates

• E.g. glucose, fructose, lactose, sucrose, starch, glycogen, cellulose…

• Fuel to do work• Raw material for bigger

molecules• 2 sugars linked =

disaccharide via dehydration synthesis

• More sugars = polysaccharides

Note: Animals can’t hydrolyze cellulose very well, therefore use bacteria to do it for us -- Byproduct is methane gas

Lipids• Fats, oils, waxes, steroids

• Polymers of fatty acids and glycerol

• Energy storage molecules

• Hydrophilic heads (w / polar functional group(s); interacts easier with water)

• & hydrophobic tails (nonpolar; insoluble)

• Saturated fats– Very few double bonds– Lots of H’s– Solid at room temperature (butter, lard, and

most animal fats)

• Unsaturated fats– Kinked due to double bonds, less H’s, take up

more space– Liquid at room temperature– E.g. oils, margarine, and most plants fats– Hydrogenating unsaturated fats make them

solid (margarine); trans fats

Steroids

• Lipids with backbones bent into rings

• Cholesterol– functions in digestion of fats– Important component in cell

membranes (see ch 5)– Starting material of other

steroids like sex hormones

Note: Anabolic steroids (synthetics) mimic testosterone (see ch 12)

Proteins – have many roles

Made from 20 different amino acids monomers• Structural – hair, cell, cytoskeleton• Contractile – muscles, motile cells• Storage – sources of amino acids (egg whites)• Defense – antibodies, membrane proteins• Transport – hemoglobin, membrane proteins• Signaling – hormones, membrane proteins• Catalyst – free enzymes, membrane proteins

Protein properties…

• Amino group• Carboxyl group• Variable R group

– Could be a single H– Or, C’s with functional

groups– Determines specific

properties and protein diversity

• Nonpolar & hydrophobic

• Polar & hydrophilic are easier to dissolve in a cells aqueous solution

• Linked to form polymer proteins by peptide bonds– Specific covalent bond between amino acids– Two aminos bonded = dipeptide– More aminos = polypeptides

Protein’s shape determines function

• 1o structure: unique sequence of amino acids

• 2o structure: coils or folds via H-bonding

• 3o structure: 3-D globular or fibrous subunit via bonds of R-groups

• 4o structure: multiple subunits

Nucleic Acids

• Polymers of 4 specific monomers = nucleotides– Via dehydration synthesis

between sugars

• Builds chain w/sugar-phosphate backbone

• Single stranded RNA

• Double stranded DNA