1. Chemicals of Life

2. Chemistry chemicals give cells properties of life
must know principles of chemistry to understand biology
organisms-bags of chemicals
structure determines function
Hierarchy
chemicalsorganellescellstissuesorgansorganisms

3. Matter living things are made of matter
anything that occupies space & has mass
composed of elements

4. Elements
substances which cannot be decomposed into simpler substances by chemical means
92 naturally occurring ones
25 found in living things
96%-H, O, C & N
4%-Ca, P, K & S
trace elements-Fe, Mg, Mn (manganese) & I
called essential
cannot live without them

5. Periodic Table

6. Atoms elements are composed of atoms
only one kind of atom for each element
smallest units of matter that retain the properties of an element

7. Sub-atomic Particles Protons Electrons Neutrons
different elements have different numbers of sub-atomic particles
chemical & physical differences of elements are due to these differences

8. Sub-Atomic Particles Protons Neutrons Electrons one positive charge
found in nucleus of atom
Neutrons
no charge
Electrons
one negative charge
orbit nucleus

9. Periodic Table
atom’s structure determines how element it comprises forms compounds & molecules
key to this can be found by knowing number of sub-atomic particles an element possess
found in Periodic Table of the Elements

10. atomic number-number in upper left corner
atomic weight or mass number-number located on bottom
The mass of any atom is approximately equal to the total number of its protons and neutrons multiplied by the atomic mass unit, u = gram.

11. Atomic Number gives number of protons in an atom Helium
has 2 protons

12. Mass Number found by adding number of neutrons & number of protons
He = 4
some atoms of an element may have different mass numbers
these are isotopes
same number of protons & electrons but different number of neutrons

13. Number of Electrons net charge of an atom is zero
each proton has one positive charge
each electron has one negative charge
neutrons have no charge
to be neural atom must have the same number of electrons and protons
atom of helium with 2 protons
has 2 electrons

14. Atomic Number How many protons does Sulfur have? How many electrons?
Why?

16. Chemical Properties
arrangement of electrons determines chemical properties of an atom
electrons orbit around nucleus
found at different energy levels-shells
each shell accommodates a specific number of electrons

17. Electron Shells innermost shell-2 2nd & 3rd-8
number of electrons in outermost shell determines chemical properties of atom
those with shells that are not full will interact with other atoms & participate in chemical reactions
those with full shells do not interact-inert

18. Electron Shells H-only one electron in outer most shell C, N, & O
very reactive
C, N, & O
also highly reactive since outer shells are incomplete
He-inert or nonreactive because outer shell is full

19. Reactivity of Chlorine
Is Chlorine reactive or not reactive?
How can you tell?

20. Atom Interactions-Chemical Bonds
when an atom with an incomplete outer shell reacts with another atom with an incomplete outer shell they can interact or form a bond
Share
Donate
Receive electrons
in this way both atoms can have a completed outer shell

21. Types of Chemical Bonds
Covalent Bonds
share electrons
Ionic
give or receive electrons

22. Sodium & Chloride

23. Ionic Bonding

25. Covalent Bonds 2 atoms with incomplete shells
each share a couple electrons
so at any one time one atom has a completed outer shell
forms molecules

27. In Class Exercise Pretend you are an atom
Take the number of your birth month as your atomic number
Determine the configuration of electrons in your valence shell
Find another atom that you might interact with to form ions or new molecules
Demonstrate-draw on the board

28. Chemical Reactions elements combine to make molecules & compounds
2 H2 + O2  2H2O
2 molecules of H react with one molecule of O (reactants) to form 2 molecules of water (product)
arrow indicates direction of reaction
two sides of equation on either side of arrow must balance

29. Water single most important constituent of body
life on Earth depends on unusual structure & nature of water
Organisms consist mostly of water-2/3rds total body weight of humans.

30. Importance of Water Organisms consist mostly of water
2/3rds total body weight of humans
Biochemistry is a wet chemistry
biological molecules do not react chemically unless in solution
Water is an important reactant
nearly all chemical reactions in the body occur in water
Foods are digested to their building blocks by decomposition reactions called hydrolysis
involves addition of water
When large molecules form from smaller ones, water is removed in dehydration synthesis or condensation reactions

31. Water Structure 2 H atoms attached covalently to one O2 molecule
sharing of electrons is not equal
oxygen pulls more on electrons than does hydrogen
electrons spend more time near oxygen than hydrogen
unequal sharing produces- polar bond
Nonpolar bond
bonds in which two atoms involved have an equal pull on electrons

32. Water Structure
O2 attracts electrons more strongly than H-giving water an asymmetrical distribution of charge
result-V-shape
H end has positive charge
Oxygen end has negative charge
water has 2 poles-polar
polarity results in weak electrical attractions between neighboring water molecules

33. Polarity of Water
Polarity results in weak electrical attraction between neighboring water molecules
slightly positive Hs in one water molecule attract slightly negatively charged O2 in another water molecule
opposite electrical charges attract
water molecules attract each othermaking water kind of sticky
these weak attractions-hydrogen bonds
much weaker than covalent or ionic bonds

34. Polarity, H Bonding & Water’s Properties
cohesive nature
ability to moderate temperature
ice floating
universal solvent properties
Cohesive Nature-water molecules attract eachclump together -cling or stick together to form films-surface tension. Water beads up into spheres when on hard surface. Important in living world-tress depend on this to help transport water from roots to leaves. Moderation of Temperature-High Heat Capacity-heat absorption-ability to absorb and retain heat. H bonding allows water to resist temperature changes. Temperature and heat-related-but different. Heat-amount of energy associated with movement of atoms and molecules in body of matter. Temperature-measure of intensity of heat-average speed of molecules rather than total amount of heat energy in body of matter. Example-swimmer in large body of water-may have higher temperature than water; water has more heat because of its immense volume. Heatwaterheat energy first disrupts H bonds-makes molecules move faster. Because heat first used to break bonds and not raise temperaturewater absorbs large amount of heat while only warming few degrees. Water has high specific heat index-can absorb lot of heat before begins to get hot. Why water is valuable to industries and in car radiators as coolant. High Heat of Vaporization-temperatures must be quite high before individual molecules have enough energy to break free and become water vapor-gaseous. Carries heat away with it as transforms from liquid to gas-cooling effect of perspiration-evaporative cooling. When substance evaporates-surface of liquid-what is remaining behind cools. Occurs because molecules with greatest energy-hottest ones-vaporize first. Globally-surface evaporation cools tropical oceans. Individually-prevents over heating. When water coolsremains liquid over wide range of temperatures-H bonds formreleases heat-water releases large amount of heat to surroundings while water temperature only drops few degrees. Freezing and boiling points far apart-freezes-32o F and boils-212o F. Unusually large amount of heat energy needed to change temperature of 1 gram of water by 1oC-once amount of water has reached particular temperature-changes temperatures only very slowly-thermal inertia-helps stabilize body temperatures. Large body of water can store huge amount of heat from sun. In coldheat given off from gradually cooling water can warm air-stabilizes ocean temperatures. Ice Floating-when most liquids cool molecules get closer and closerif cold enoughsolid. When water molecules coolmove apartice. Ice has fewer molecules than equal volume of liquid water less densefloats. Due to H bonding. H bonding lasts longer in ice; with each molecule bound to 4 neighbors. Ice is spacious crystal. Promotes life because if water behaved as other liquidsall water would freeze solid. When warming only upper few inches would thaw. When deep body of water coolsfloating ice insulates liquid water beneathlife persists. Universal Solvent-if substance dissolves in water-soluble-forms solution-uniform mixture of 2 or more substances. Solvent-medium in which other atoms, molecules or ions are dispersed. Dispersed substances-solutes. Water-powerful solvent-universal-dissolves more substances than any other liquid. Solution formed-aqueous solution. Fluids of lifeaqueous. Being soluble in water means that wherever water goes, through ground or through body-takes along with it chemicals, minerals, and nutrients. Useful as transport mechanism. Because of polar nature-water molecules orient themselves with slightly negative ends towards positive side of solutes and vice versa-first attracting and then surrounding them. Compounds formed by ionic bonds-ionize or dissociate-in water-broken as individual ions interact with either positive or negative end of water. Producing cations (+) and anions (-) surrounded by water molecules forming hydration sphere. Aqueous solution with anions and cations conducts electrical currents. Cations move to negative side having + change and anions move to positive side having– charge. Electrical forces across cells affects functioning of cells-muscle contraction and nerve function. Soluble inorganic molecules whose ions will conduct an electrical current in solution- electrolytes. NaCl-electrolyte. NaCl + H2ONa+ + Cl-. Changes in body fluid concentrations of electrolytes disturbs almost all vital functions. Decrease in K+ muscle paralysis; increaseweak, irregular heartbeats. Organic molecules have polar covalent bonds-attract water. Hydration shells form around large charged molecules-proteins-shielding them from effects of other charged substances and preventing them from settling out of solution. Hydration spheres carry them into solution. These mixtures are colloids-solutions of dispersed proteins or other large molecules which do not come out of solution-Jello. Particles remain in solution indefinitely. Suspension-contains even larger molecules that will if undisturbed settle out of solution due to gravity. Stirring sand in watersuspension lasts until sand settles bottom. Molecules that dissolve in water are hydrophilic-water loving-those that do not readily react with water-hydrophobic-have few if any polar, covalent bonds. These are non polar-when exposed to water-hydration spheres do not formmolecules do not dissolve. Body fat-large, insoluble droplets of hydrophobic molecules trapped in watery interior of cells.

35. Dissociation
compounds formed by ionic bonds will ionize or dissociate in water
dissociation produces cations (+) & anions (-)
aqueous solution containing anions & cations will conduct electrical currents
cations move to negative side having a + change & anions move to positive side having a – charge
soluble inorganic molecules whose ions will conduct an electrical current in solution are called electrolytes
NaCl is an electrolyte
NaCl + H2ONa+ + Cl-

36. Acids H+ & OH- are in solutions at all times
H2O < > H+ + OH- -reversible reaction
some compounds add more hydrogen ions
others remove them
compound that donates hydrogen ion-acid
HClH+ + Cl-
acidic solution is one that has more H+ than OH-

37. Bases compound that accepts or removes hydrogen ions is a base
NaOHNa+ +OH-
basic solution- has more OH- than H+

38. pH scale pH = potential hydrogen
scale developed in 1909 by Dane Soren Sorensen
beer brewer looking for a way to check acidity of beer
describes how acidic or basic a solution is
scale ranges from 0-14
0 = most acidic
14 = most basic
7=neutral

39. pH at neutral pH H+ = OH- pH < 7 is acidic
pH > than 7 is more basic or alkaline

40. Buffers pH of blood ranges between 7.35-7.45
value must be maintained in narrow range
even small change can lead to severe metabolic consequences
biological fluids contain buffers
substances that resist changes in pH by accepting H+ when in excess & donating H+ when depleted