Metabolic Processes What does that mean?? The cell is a highly organized assembly of atoms and molecules programmed by genetic instructions to carry out chemical reactions that define “life”. Living organisms are characterized by a balance of anabolism and catabolism. Together, they are called metabolism.

Metabolic Processes: Chemistry of Life Monday, March 1 st Miss Tee

Chemical Fundamentals

The Atom Mass number: # protons, neutrons Atomic number: # of protons Isotope: atom of an element with same atomic number but different mass number

Isotopes Nucleus of some isotopes spontaneously decays We call these radioisotopes and they are radioactive Radioactivity results in: 1.Formation of new element 2.Release of subatomic particles 3.Radiation

Isotopes

Half-life Every radioisotope has a characteristic property: half-life What is a half-life? The time it takes for ½ atoms in a sample to decay What application does this have for us today? Radioisotopes emit radiation as they decay  can be detected Radioactive tracers are used to follow chemicals through reactions as they occur in the body BIG medical research industry

Chemical Bonding Orbital Volume of space where electrons are most likely to be found Can accommodate no more than 2 electrons When 2 electrons pair up and occupy an orbital = more stable Ion Cation, anion (loss, gain of e-) Ionic bond Force of attraction between anion and cation NaCl

Ionic Bonding

Covalent Bonding Atoms share electrons in outer shell, creating full shells for both Diamond is a good example

Molecular Shape Overall shape contributes to molecule behaviour When atoms react to form covalent bonds, their valence electrons undergo “hybridization” Change in orientation of the valence electrons Since electrons are all –vely charged, the pairs will repel each other and will move as far apart as possible Molecular shapes include: Tetrahedral Pyramidal Angular Linear

Water H 2 O’s polar covalent bonds and asymmetrical shape create a highly polar molecule Allows it to form chemical bonds with other molecules and ions Bonds BETWEEN molecules are called “intermolecular bonds” Intermolecular bonds weaker than intramolecular bonds 3 types: 1.London Forces 2.Dipole-dipole forces 3.Hydrogen bonds

London Forces Weakest, exist between all atoms and molecules Formed by temporary unequal distribution of electrons as they move randomly about the nucleus Transient “electron cloud” will attract positive nucleus of neighbour atom

London Forces

Dipole-dipole Forces Hold polar molecules together Partially positive side of a molecule attracts the partially negative side of another molecule

Hydrogen Bonds Especially strong dipole-dipole forces Form only between electropositive H of one molecule and an electronegative N, O, or F atom of neighbour polar molecule

Hydrogen Bonds

Van der Waals forces London forces, dipole-dipole forces and hydrogen bonds are collectively referred to as “Van der Waals forces” Electrostatic charges between adjacent atoms

Water as a Solvent Small non-polar molecules (O 2, CO 2 ) cannot form hydrogen bonds with water  only slightly soluble That is why we need hemoglobin Large non-polar molecules (fats, oils) also do not form hydrogen bonds “hydrophobic” (opposite is…?)

Unique Properties of Water Water clings Cohesion Adhesion Water absorbs a lot of heat High specific heat capacity High specific heat of vaporization Solid water is less dense than liquid water

Unique Properties of Water 1.Homework: Make a table listing the 5 unique properties of water with: A definition for each property The effect of that property An example of that property in everyday human or animal life 2.Prepare your unit glossary

Acids, Bases and Buffers At 25°C, 2 H 2 O molecules/ 550 million react with each other 1 H 2 O donates an H + to the other H 2 O molecule  OH -, H3O + This is called “autoionization”

Acids, Bases and Buffers What is an acid? Base? An acid is a proton donor; a base is a proton accepter What do you know about pH and the human body? Internal environment of multicellular organisms is very sensitive to pH levels Most cellular processes operate best at pH Living cells use “buffers” (proton accepting/donating system) to resist significant changes in pH

Acids, Bases and Buffers The most important buffer to the human body is carbonic acid (H 2 CO 3 ) and bicarbonate (HCO 3 - ) buffer system

Buffers Acidosis and alkalosis can be serious medical conditions, potentially fatal Internal buffers can donate H + ions when they are required (if a patient is alkalotic) and can remove H + ions when there are too many in a solution (if a patient is acidotic). They are reversible reactions.