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Chemical Foundations for Cells
Chapter 2
Chemical Benefits and Costs
•Chemical pollutants damage ecosystems
•Understanding of chemistry provides fertilizers, medicines, etc.
• Fundamental forms of _________
• Can’t be broken apart by normal
means
• ___ occur naturally on Earth
Elements
Most Common Elements in Living Organisms•________•________•___________•__________ The big fo
ur
What Are Atoms?• 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 _______
= Atoms of an element with different numbers of ______(different mass numbers)
Isotopes
•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 _____ rateRadiation therapy-
using radioisotopes to destroy _________cellsnormal thyroid enlarged cancerous
Thyroid Scan
What Determines Whether Atoms Will Interact?
Answer- The _____ and ________ of their electrons
• Carry a ______ charge• Repel one another • Are attracted to _______ in the
nucleus• Move in orbitals (shells)
Electrons
1st shell- ___electrons max
2nd, 3rd and 4th shells- ___electrons max
CALCIUM20p+ , 20e-
Only _______ electrons matter!
Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their ____ shells- hence are ______
CARBON6p+ , 6e-
NITROGEN7p+ , 7e-
HYDROGEN1p+ , 1e-
•A bond is union between electron structures of atoms
Electron Vacancies make atoms reactive
What holds molecules together?
a._______b. __________c. ____________ Weak
Strong
•_________ Bonds= share electrons•________ Bonds= swipe or gain electrons•__________ Bonds= weak, opposite charge attraction
Three major 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)
• ______ # of protons• Electrons near nucleus with most protons• Water - Electrons more attracted to O nucleus
than to H nuclei
________Covalent Bonds
• __________ –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).
Fig. 2.14
These are now called ____
Na+ is a _______
Cl- is an _______
Cations and anions are attracted - form __________
• 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
• ___________ - a hydrogen atom that is already ________________ bonded to a strongly electronegative atom is attracted to another strongly electronegative atom.
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
The magic of water
• 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
• 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
Water adheres to itself- called _______
a.cohesionThe magic of water
• _____________, 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 ______.
b.Surface tensionThe magic of water
• 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 moderates temperatures on Earth
• Water resists changes in temperature – Why? ________________.– Heat must be absorbed to break __________________
and is released when hydrogen bonds form.
c.Temperature stabilizationThe magic of water
• 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.
The magic of water d. evaporative cooling
– 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.
e. Prevent lake freezing
• Water (unlike most liquids) is less dense as a solid than as a liquid.
The magic of water
• ________- A completely _______________ mixture of substances.
• ______ = dissolving agent
• _______ = agent being dissolved.– Example-water is a solvent and sugar the solute.
f. Powerful solventThe magic of water
Water dissolves almost anything polar or ionic
• 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 ___
_________________.
Hydrophobic vs. hydrophilic
• 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.
The pH Scale• Measures ___ concentration of fluid• Change of 1 on scale means ____
change in ____ concentration
Highest H+ Lowest H+
0---------------------7-------------------14______ Neutral _____
• How do we measure acidity? – Answer: In _______.
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 7.8 - 8.3
– Baking soda: pH _____
• Weak acids- Reluctant H+ donors
– __________ acid (H2CO3)
• Strong acids- Completely give up H+ when dissolved
– HCl (hydrochloric acid)
Carbonic Acid-Bicarbonate Buffer System
• When blood pH rises, carbonic acid
dissociates to form ____________ and __
H2C03 -----> HC03- + H+
• When blood pH drops, bicarbonate binds H+
to form ________ acid
HC03- + H+ -----> H2C03
• ______________ (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 _________ organismsThis has done major damage to forests in Europe and substantial damage of forests in North America