Lecture 1b

Basic ChemistryBiological MoleculesIntroduction to Cells

Basic Chemistry• Atomic theory

• All matter is made of atoms

• Molecules are atoms bonded together

• Not all atoms can bind; depends on their nature

• Types of bonds

• Ionic - electrons ‘donated’, creating charge

• Covalent - electrons shared

• H bonds

Basic Chemistry

• Bonds can be strong or weak

• Chemicals form different shapes and the shape influences the activity of the chemical

• Chemical reactions are the basis for most life processes

Chemical bonds

Ionic bond

Covalent Bond

WATER

• Water has polarity

• Leads to H bonds

Water

• Water is a solvent

• Dissolves ionic substances and other polar nonionic substances

Water

• Cohesion

• Water clings to itself

• Surface tension

• Adhesion

• Water clings to other stuff too

• How it gets in everywhere

Water

• High heat capacity

• T of water rises and falls slowly

• How organisms are able to live in a changing environment

• High heat of vaporization

• Has to be really hot to break H bonds and turn to steam

Water

• Ice is less dense than liquid water

• Allows aquatic organisms to live underneath ice because it is on the surface

Carbon• Because C forms 4 bonds, it is very

versatile

• C chains are the basis of organic molecules (molecules containing C and H)

• Organic molecules are divided into 4 groups: Carbohydrates, Lipids, Proteins, Nucleic Acids

• Most are made up of polymers of different types of monomers

Carbohydrates• Polymers of saccharides (sugars)

• Energy use

• Glucose

• Energy storage

• Starch in plants; glycogen in animals

• Structure

• Cellulose in plants; chitin

Lipids• NOT soluble in water

• Fatty acid tails (usually 3) keep from dissolving

• Fats and oils; primary energy storage

• Fatty acid tails come in three varieties:

• Unsaturated, saturated, and trans

Lipids• Not all lipids are bad!

• Phospholipids

• Have polar heads (water soluble); but non-polar tails (not soluble)

• This makes them arrange themselves in a bilayer

• These create the membranes of cells

Proteins• Important to structure and function

of cells

• Support

• Metabolism

• Transport

• Defense

• Regulation

• Motion

Proteins• Amino acids are the building

blocks of proteins

• There are 20 amino acids- combine in different ways to form thousands of different proteins

• The ‘chain’ of amino acids determines its shape, and therefore its function

Proteins• Function of protein is determined by

its shape

• There are 4 levels of structure:

• Primary: the sequence of aa

• Secondary: alpha helix, pleated sheet- formed by H bonds between aa

• Tertiary: the globular shape

• Quaternary: more than one

Nucleic Acids

• DNA and RNA are the nucleic acids in cells

• Nucleotides are the monomers

• DNA stores genetic info

• RNA takes genetic info to site of protein synthesis

DNA• Each nucleotide in DNA contains one of

4 different bases: adenine, guanine, cytosine, thymine

• G always bonds to C; A always bonds to T in double helix structure

• Very important to replication

• Every 3 bases stands for one amino acid

• So, if you know sequence of gene, you know sequence of protein

RNA

• RNA is single stranded

• The complementary pairs allow information to be passed to RNA from DNA; protein synthesis actually occurs from RNA

Nucleic Acids to Proteins

• Very small changes in a gene can potentially result in very large changes in protein

• Ex. Sickle cell: one aa difference

Cells!

• Why are cells small?

• Surface to volume ratio- gives adequate surface area for exchange of chemicals

• All cells have an outer plasma membrane, which encloses the cytoplasm

Cells

• Two main types of cells: prokaryotic and eukaryotic

• Prokaryotes do not have a membrane bound nucleus, eukaryotes do

• Bacteria are prokaryotes

• Extremely successful, widespread and necessary

Prokaryotic structure

• The membrane is surrounded by cell wall and sometimes capsule

• DNA of bacterium is in a region called the nucleoid

• Ribosomes produce proteins

• Appendages include flagella, fimbriae, and conjugation pilli

Bacteria

• Fun fact: bacteria can smell!