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.

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

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 _______

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

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!

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

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. ____________

_________ 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

__________ –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 __________

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

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

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

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

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 ______.

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.

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.

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.

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.

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 ___ _________________.

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.

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+ 0---------------------7-------------------14 ______ Neutral _____

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 _________ organisms This has done major damage to forests in Europe and substantial damage of forests in North America

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