1. Chemical Foundations for Cells
Chapter 2
Chemical Foundations for Cells
Chemical Benefits and Costs
Chemical pollutants damage ecosystems
Understanding of chemistry provides fertilizers, medicines, etc.

2. Elements
Fundamental forms of _________
Can’t be broken apart by normal means
___ occur naturally on Earth
Most Common Elements in Living Organisms
________
___________
__________
The big four

3. What Are Atoms? Atomic Number = Number of ___________
Smallest particles that retain properties of an element
Made up of subatomic particles:
______ (+)
__________(-)
_________ (no charge)
HELIUM
electron
proton
neutron
Atomic Number
= Number of ___________
Carbon= 6 protons
Mass Number
= # of _______ + # of _______

4. Isotopes Radioisotopes Thyroid Scan
= Atoms of an element with different numbers of ______(different mass numbers)
Carbon 12 has 6 protons, 6 neutrons
Carbon 14 has 6 _____, 8 ________
Radioisotopes
Have an _____ nucleus that emits energy and particles
Decay occurs at a _____ rate
Radiation therapy-
using radioisotopes to destroy _________cells
normal thyroid
enlarged
cancerous
Thyroid Scan

5. What Determines Whether Atoms Will Interact?
Answer- The _____ and ________ of their electrons
Electrons
Carry a ______ charge
Repel one another
Are attracted to _______ in the nucleus
Move in orbitals (shells)
CALCIUM
20p+ , 20e-
1st shell- ___electrons max
2nd, 3rd and 4th shells- ___electrons max
Only _______ electrons matter!

6. Electron Vacancies make atoms reactive
Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their ____ shells- hence are ______
HYDROGEN
1p+ , 1e-
NITROGEN
7p+ , 7e-
CARBON
6p+ , 6e-
A bond is union between electron structures of atoms

7. What holds molecules together?
Three major bonds
_________ Bonds= share electrons
________ Bonds= swipe or gain electrons
__________ Bonds= weak, opposite charge attraction
Strong
a._______
b. __________
Weak
c. ____________

8. _________ Covalent Bonds
_____________ Atoms share a pair or pairs of electrons to fill outermost shell
Single covalent bond
Double covalent bond
Triple covalent bond
_________ Covalent Bonds
Atoms share electrons _______
Nuclei of atoms have same number of ______
Example: Hydrogen gas (H-H)
________Covalent Bonds
______ # of protons
Electrons near nucleus with most protons
Water - Electrons more attracted to O nucleus than to H nuclei

9. __________ –between two atoms are so unequal in their attraction for valence electrons that one atom strips an electron completely from the other.
Example- sodium (one valence electron) in its third shell transfers this electron to chlorine with 7 valence electrons in its third shell.
Now, sodium has a full valence shell (the second) and chlorine has a full valence shell (the third).
These are now called ____
Na+ is a _______
Cl- is an _______
Fig. 2.14
Cations and anions are attracted - form __________

10. Hydrogen atoms - partial ______ charges
___________ - a hydrogen atom that is already ________________ bonded to a strongly electronegative atom is attracted to another strongly electronegative atom.
Example- ammonia molecules and water molecules link together with weak hydrogen bonds.
Hydrogen atoms - partial ______ charges
Nitrogen atom - partial ________ charge.
Thus- ammonia forms hydrogen bonds with water
Fig. 2.16

11. The polarity of water molecules results from _____________ bonding
The magic of water
The polarity of water molecules results from _____________ bonding
Water molecule- two hydrogen atoms form ______ _______ bonds with an oxygen atom.
Partial negative charge
Partial positive charge
_______- because each share one electron
_____- because O is more electronegative than H
_______- because they each share electrons

12. Water has unusual properties because of attractions between _____ molecules.
The slightly negative regions interact with slightly positive regions of nearby molecules, forming a hydrogen bond.
Each water molecule can form hydrogen bonds with up to ____ neighbors.
Fig. 3.1

13. Water adheres to itself- called _______
The magic of water
a.cohesion
Water adheres to itself- called _______
How? By _______ bonds
Water cohesion is key role in the ____ ________in plants.
Water that evaporates from a leaf is replaced by water from vessels in the leaf.
________, clinging of one substance to another, contributes too

14. The magic of water b.Surface tension
_____________, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion.
Water has h igh _______________
Why? __________ bonds resist breaking the surface.
Water behaves as if covered by an invisible ______.

15. Water moderates temperatures on Earth
The magic of water
c.Temperature stabilization
Water moderates temperatures on Earth
Water _______ air temperatures by ___________ heat from warmer air and releasing heat to cooler air.
Water can absorb or release relatively _________ of heat with only a slight change in its own temperature.
Water resists changes in temperature
Why? ________________.
Heat must be absorbed to break __________________ and is released when hydrogen bonds form.

16. The magic of water d. evaporative cooling
As a liquid evaporates, the surface of the liquid that remains behind cools - ___________________.
The most energetic molecules evaporate, leaving the lower kinetic energy molecules behind.
Evaporative cooling moderates ___________________ in lakes and ponds and prevents terrestrial organisms from overheating.
Evaporation of water from the leaves of plants or the skin of humans removes excess heat.

17. e. Prevent lake freezing
The magic of water
e. Prevent lake freezing
Water (unlike most liquids) is less dense as a solid than as a liquid.
At 0oC-water becomes a ______________________ with each molecule bonded to the maximum of ______ partners.
Ice is about ___________ dense than water at 4oC, thus ice _____.
If ice sank, eventually all ponds, lakes, and even the ocean would freeze solid.

18. Water dissolves almost anything polar or ionic
The magic of water
f. Powerful solvent
Water dissolves almost anything polar or ionic
________- A completely _______________ mixture of substances.
______ = dissolving agent
_______ = agent being dissolved.
Example-water is a solvent and sugar the solute.

19. Affinity for water = _________.
Hydrophobic vs. hydrophilic
Affinity for water = _________.
Substances with _______________ bonds.
no affinity for water = _______________.
substances with ___________________ covalent bonds.
Example-Oils, such as vegetable oil, are non-polar
Hydrophobic molecules are major ingredients of ___ _________________.

20. How do we measure acidity?
Answer: In ____________.
A water molecule dissociates into a hydrogen ion and a hydroxide ion:
H2O <=> H+ + OH-
At equilibrium the concentration of H+ or OH- is 10-7M (25°C) .
Hydrogen and hydroxide ions are very reactive, and thus drastically affect the proteins and other molecules of a cell.

21. 0---------------------7-------------------14
How do we measure acidity?
Answer: In _______.
The pH Scale
Measures ___ concentration of fluid
Change of 1 on scale means ____ change in ____ concentration
Highest H Lowest H+
______ Neutral _____

22. Examples of pH Pure water is neutral with pH of ____
Acidic- pH= < 7.0
Stomach acid: pH ____________
Lemon juice: pH ____
Basic- pH= > 7.0
Seawater: pH
Baking soda: pH _____
Weak acids- Reluctant H+ donors
__________ acid (H2CO3)
Strong acids- Completely give up H+ when dissolved
HCl (hydrochloric acid)

23. Carbonic Acid-Bicarbonate Buffer System
When blood pH rises, carbonic acid dissociates to form ____________ and __
H2C > HC03- + H+
When blood pH drops, bicarbonate binds H+ to form ________ acid
HC H > H2C03

24. ______________ (a product of the formation of carbonic acid from carbon dioxide and water) occurs when rain, snow, or fog has a pH that is more acidic than 5.6.
caused primarily by _____________ and ______ ______ from burning of fossil fuels
Rain in the Adirondack Mountains of upstate New York averages a pH of ____
Great impact on eggs and early developmental stages of _________ organisms
This has done major damage to forests in Europe and substantial damage of forests in North America

25. How many valence electrons?
Isotope?
Radioactive isotope
Reactivity of an atom?
What is a valence shell?
Is this reactive?
How many valence electrons?