1. Topic 3: The Chemistry of Life: an Introduction
Corresponding Textbook chapters:
Chapter 2: Chemical Context of Life
Chapter 3: Water and the Fitness of the Environment

2. Chemical Context of Life (skip)
Living things are matter so they are made up of elements that combine to build biological molecules!
Element--a substance that can not be broken down to other substances by chemical reactions. In other words, an element is composed of a single type of Atom
The atom-- smallest unit of matter having the physical and chemical properties of an element.

3. Atomic Structure (skip?)
Nucleus
Protons (+ charge)
Neutrons (no charge)
Electrons (- charge)
Atomic number (# of protons);
mass number (protons + neutrons)

4. Most frequent elements in life! (3.1.1)
Top 4: HONC (Why?)
b/c they are the main elements found in organic molecules in organisms.
Some other necessary elements include:
Sulfur – found in 2 amino acids
Calcium – chemical messenger that helps regulate cell processes…
Phosphorus – ATP and DNA, RNA (as phosphate)
Iron – needed in cytochromes for electron transport chains, hemoglobin.
Sodium – water balance/homeostasis– pumped in to cells to cause water uptake (why does this work?), nerve impulses.

5. Chemical Bonds Elements bond in order to be stable
Stable = having a full valence energy level
Compound -- two or more elements combined in a fixed ratio.

6. Types of Bonds Ionic Covalent Hydrogen Single,double, triple
Nonpolar covalent
Polar covalent
Hydrogen
Note: The type of bond formed is due to the electronegativity (attraction for electrons) of the atoms involved.

7. Ionic bonding
One atom strips valence electrons away from another atom (due to high electronegativity difference)
Electron transfer creates ions (charged atoms)
Cation (positive ion); anion (negative ion)
Ex: Salts (sodium chloride)
Animations

8. Covalent Bonding Sharing pair of valence electrons
Number of electrons required to complete an atom’s valence shell determines how many bonds will form
Ex: Hydrogen & oxygen bonding in water, bonding in organic molecules
Molecule= when elements covalently bonded
Animations

9. Polar/nonpolar covalent bonds
Electronegativity attraction for electrons
Nonpolar covalent •electrons shared equally •Ex: O2 , C-H bonds
Polar covalent
•one atom more electronegative than the other (creates partial charges)
•Ex: water

10. Polar/nonpolar bonds

11. Hydrogen bond
Attraction between a partially positive hydrogen atom of one polar molecule and a partially negative atom (like oxygen or nitrogen) of another polar molecule.
Be able to draw water, showing its polarity and hydrogen bonds!

12. Properties of Water (How are its characteristics important to living things???)
Note: Water’s properties are due to its POLARITY and the resultant HYDROGEN BONDS.
Thermal Properties:
High Specific heat~ amount of heat absorbed or lost to change temperature by 1°C (water= 1cal/g/°C)
Heat= a type of energy (associated with molecular motion).
High Heat of vaporization~ quantity of heat required to convert 1g from liquid to gas states. Evaporative cooling/ sweat!
High boiling point ~ 100oC

13. Application: Thermal Properties (Water vs. Methane)
Specific Heat Capacity
4.2 J/g/oC
2.2J/g/oC
Heat of vaporization
2257 J/g
760 J/g
Melting Point
0 oC
-182 oC
Boiling Point
100oC
-160oC

14. Cohesion~ H bonds holding water molecules together
Cohesive Properties:
Cohesion~ H bonds holding water molecules together
Surface tension~ measurement of the difficulty to break or stretch the surface of a liquid
“Jesus Lizard”

15. Properties of Water (continued)
Solvent Properties:
Very good solvent. Sometimes called the “universal solvent”
What types of substances are soluble in water?
Solution= completely homogenous mixture.
Review: Solute… Solvent…

16. Application: Modes of transport in blood depend on solubility
Discuss: Which types of molecules would be easily dissolved and transported in water?
Evaluate these in terms of solubility and hypothesize how they would be transported:
Sodium Chloride
Amino Acids
Glucose
Oxygen gas
Fats
Cholesterol

17. Application: Modes of transport in blood depend on solubility
Sodium Chloride – dissolved in plasma (ions)
Amino Acids – dissolved in plasma (sufficient solubility due to charged regions)
Glucose – dissolved in plasma (polar)
Oxygen gas– carried by hemoglobin (nonpolar)
Fats – transported in lipoprotein complexes (nonpolar)
Cholesterol -- transported in lipoprotein complexes (nonpolar)

18. Other properties:
Adhesion~ H bonds holding molecules to another substance
Density…

19. Density Less dense as solid than liquid Due to hydrogen bonding
Crystalline lattice keeps molecules at a distance

20. Water’s Uses in Organisms
Journal: Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions, transport medium, and habitat (see question 4 of journals).
Do the above for each property…
8 marks

21. end

22. Chemical Reactions
Making and breaking of chemical bonds leading to the changes in the composition of matter
A chemical reaction is represented by a chemical equation
6 CO2 + 6 H2O  C6H12O6 + 6 O2
reactants  products

23. Acid/Base & pH
Acid: increases the hydrogen concentration of a solution
Base: reduces the hydrogen ion concentration of a solution
pH scale
Buffers: substances that minimize H+ and OH- concentrations (accepts or donates H+ ions)