Chemical Foundations for Cells

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

4. Isotopes • Carbon 12 has 6 protons, 6 neutrons • Carbon 14 has 6 _____, 8 ________ = Atoms of an element with different numbers of ______(different mass numbers) 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? Electrons • Carry a ______ charge • Repel one another • Are attracted to _______ in the nucleus • Move in orbitals (shells) Answer- The _____ and ________ of their electrons 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. _____________ 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. ___________ - 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 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. The magic of water a.cohesion Water adheres to itself- called _______ • 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 • How? By _______ bonds

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. 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. 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. 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. 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. 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 _____

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 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)

23. 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

24. caused primarily by _____________ and ______ ______ from burning of fossil fuels • ______________ (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. • 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. Isotope? Radioactive isotope Reactivity of an atom? What is a valence shell? Is this reactive? How many valence electrons?