1. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Chapter 2 Chemistry of Life

2. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Levels of Chemical Organization Atoms –Nucleus—central core of atom Proton—positively charged particle in nucleus Neutron—non-charged particle in nucleus Atomic mass—number of protons in the nucleus; determines the type of atom

3. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Levels of Chemical Organization Atoms –Energy levels—regions surrounding atomic nucleus that contain electrons Electron—negatively charged particle May contain up to 8 electrons in each level Energy increases with distance from nucleus

4. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Levels of Chemical Organization Elements, molecules, and compounds –Element—a pure substance; made up of only one kind of atom –Molecule—a group of atoms bound together in a group –Compound—substances whose molecules have more than one kind of atom

5. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Chemical Bonding Chemical bonds form to make atoms more stable –Outermost energy level of each atom is full –Atoms may share electrons, or donate or borrow them to become stable

6. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Chemical Bonding Ionic bonds –Ions form when an atom gains or loses electrons in its outer energy level to become stable Positive ion—has lost electrons; indicated by superscript positive sign(s), as in Na + or Ca ++ Negative ion—has gained electrons; indicated by superscript negative sign(s), as in Cl –

7. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Chemical Bonding Ionic bonds –Ionic bonds form when positive and negative ions attract each other because of electrical attraction –Electrolyte—molecule that dissociates (breaks apart) in water to form individual ions; an ionic compound

8. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Chemical Bonding Covalent bonds –Covalent bonds form when atoms shared their outer energy to fill up and thus become stable –Covalent bonds do not ordinarily easily dissociate in water

9. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry Organic molecules contain carbon-carbon covalent bonds and/or carbon-hydrogen covalent bonds; inorganic molecules do not Examples of inorganic molecules: water and some acids, bases, and salts

10. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry Water –Water is a solvent (liquid into which solutes are dissolved), forming aqueous solutions in the body

11. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry –Water is involved in chemical reactions Dehydration synthesis—chemical reaction in which water is removed from small molecules so they can be strung together to form a larger molecule Hydrolysis—chemical reaction in which water is added to the subunits of a large molecule to break it apart into smaller molecules Chemical reactions always involve energy transfers, as when energy is used to build ATP molecules Chemical equations show how reactants interact to form products; arrows separate the reactants from the products

12. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry Acids, bases, and salts –Water molecules dissociate to form equal amounts of H + (hydrogen ion) and OH – (hydroxide ion) –Acid—substance that shifts the H + /OH – balance in favor of H + ; opposite of base –Base—substance that shifts the H + /OH – balance against H + ; also known as an alkaline; opposite of acid

13. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry Acids, bases, and salts –Ph—mathematical expression of relative H+ concentration in an aqueous solution 7 is neutral (neither acid nor base) Ph values above 7 are basic; ph values below 7 are acidic

14. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Inorganic Chemistry Acids, bases, and salts –Neutralization occurs when acids and bases mix and form salts –Buffers are chemical systems that absorb excess acids or bases and thus maintain a relatively stable ph

15. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Carbohydrates—sugars and complex carbohydrates) –Contain carbon (C), hydrogen (H), oxygen (O) –Made up of six-carbon subunits called monosaccharides or single sugars (e.g., glucose) –Disaccharide—double sugar made up of two monosaccharide units (e.g., sucrose, lactose)

16. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Carbohydrates—sugars and complex carbohydrates) –Polysaccharide—complex carbohydrate made up of many monosaccharide units (e.g., glycogen made up of many glucose units) –Function of carbohydrates is to store energy for later use

17. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Lipids—fats and oils –Triglycerides Made up of one glycerol unit and three fatty acids Store energy for later use

18. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Lipids—fats and oils – Phospholipids Similar to triglyceride structure, except with only two fatty acids, and with a phosphorus-containing group attached to glycerol The head attracts water and the double tail does not, thus forming stable double layers (bilayers) in water Form membranes of cells

19. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Lipids—fats and oils – Cholesterol Molecules have a steroid structure made up of multiple rings Cholesterol stabilizes the phospholipid tails in cellular membranes and is also converted into steroid hormones by the body

20. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Proteins –Very large molecules made up of amino acids held together in long, folded chains by peptide bonds –Structural proteins Form structures of the body Collagen is a fibrous protein that holds many tissues together Keratin forms tough, waterproof fibers in the outer layer of the skin

21. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Proteins –Functional proteins Participate in chemical processes Examples: hormones, cell membrane channels and receptors, enzymes Enzymes –Catalysts—help chemical reactions occur –Lock-and-key model—each enzyme fits a particular molecule that it acts on as a key fits into a lock

22. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Proteins –Proteins can combine with other organic molecules to form glycoproteins or lipoproteins

23. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Nucleic acids –Made up of nucleotide units Sugar (ribose or deoxyribose) Phosphate Nitrogen base (adenine, thymine or uracil, guanine, cytosine)

24. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Nucleic acids –DNA (deoxyribonucleic acid) Used as the cell’s “master code” for assembling proteins. Uses deoxyribose as the sugar and A, T (not U), C, and G as bases Forms a double helix shape

25. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Nucleic acids –RNA (ribonucleic acid) Used as a temporary “working copy” of a gene (portion of the DNA code) Uses ribose as the sugar and A, U (not T), C, and G as bases

26. Copyright © 2005, 2002, 1997, 1992 by Mosby, Inc. All rights reserved. Organic Chemistry Nucleic acids –By directing the formation of structural and functional proteins, nucleic acids ultimately direct overall body structure and function