Chapter 2 The Chemical Basis of Life

1. Chapter 2The Chemical Basis of Life

2. Basic principles of chemistry • It is important for us to understand the basic principles of chemistry so we can understand how the human body is organized.

3. Elements • Matter —anything that has mass and occupies space • Element—simple form of matter, a substance that cannot be broken down into two or more different substances • There are 26 elements in the human body • There are 11 “major elements,” four of which (carbon, oxygen, hydrogen, and nitrogen) make up 96% of the human body • There are 15 “trace elements” that make up less than 2% of body weight

4. Compounds • Compound—atoms of two or more elements joined to form chemical combinations • List some compounds that are made up in your body.

5. Atoms • Atomic structure—atoms contain several different kinds of subatomic particles; the most important are the following: • Protons (+ or p)—positively charged subatomic particles found in the nucleus • Neutrons (n)—neutral subatomic particles found in the nucleus • Electrons (– or e)—negatively charged subatomic particles found in the electron cloud

6. Atomic Number • Atomic number • The number of protons in an atom’s nucleus • The atomic number is critically important; it identifies the kind of element

7. Atomic Weight • Atomic weight • The mass of a single atom • It is equal to the number of protons plus the number of neutrons in the nucleus (p + n)

8. Basic Chemistry • Energy levels • The total number of electrons in an atom equals the number of protons in the nucleus (in a stable atom) • The electrons form a “cloud” around the nucleus

9. Basic Chemistry • Isotopes • Isotopes of an element contain the same number of protons but contain different numbers of neutrons • Isotopes have the same atomic number, and therefore the same basic chemical properties, as any other atom of the same element, but they have a different atomic weight

10. Molecules and Compounds • Molecule—two or more atoms joined together • Compound—consists of molecules formed by atoms of two or more elements

11. Three types of bonds • Covalent—formed by sharing of electron pairs between atoms • Ionic—formed by transfer of electrons; strong electrostatic force that binds positively and negatively charged ions together • Hydrogen---much weaker than ionic or covalent bonds results from unequal charge distribution on molecules

12. Three chemical reaction in human physiology • There are three main chemical reactions in human physiology: • Synthesis reaction • Decomposition reaction • Exchange reaction

13. Synthesis reaction • Synthesis reaction—combining of two or more substances to form a more complex substance; formation of new chemical bonds: A + B → AB Example: Amino Acid + Amino Acid → Protein

14. Decomposition reaction • Decomposition reaction—breaking down of a substance into two or more simpler substances; breaking of chemical bonds: AB → A + B Example: ATP → ADP + P + Energy (Heat)

15. Exchange reaction • Exchange reaction—decomposition of two substances and, in exchange, synthesis of two new compounds from them: AB + CD → AD + CB Example: H*Lactate + NaHCO3 → Na*Lactate + H*HCO3

16. Metabolism • Metabolism—all of the chemical reactions that occur in body cells • There are two types of metabolism: -Catabolism -Anabolism

17. Catabolism • Chemical reactions that break down complex compounds into simpler ones and release energy; hydrolysis is a common catabolic reaction • Ultimately, the end products of catabolism are carbon dioxide, water, and other waste products • More than half the energy released is transferred to ATP, which is then used to do cellular work (Figure 2-28)

18. Metabolism • Anabolism • Chemical reactions that join simple molecules together to form more complex molecules • Chemical reaction responsible for anabolism is dehydration synthesis

19. Organic molecules is a compound that contains carbon—specifically C-C or C-H bond Inorganic compounds—few have carbon atoms and none have C–C or C–H bonds Organic vs. Inorganic Molecules

20. Inorganic Compounds • Water • The body’s most abundant and important compound • Properties of water (Table 2-2) • Polarity—allows water to act as an effective solvent; ionizes substances in solution (Figure 2-8) • The solvent allows transportation of essential materials throughout the body (Figure 2-12)

21. Properties of water • Polarity—allows water to act as an effective solvent; ionizes substances in solution • The solvent allows transportation of essential materials throughout the body • High specific heat—water can lose and gain large amounts of heat with little change in its own temperature; enables the body to maintain a relatively constant temperature • High heat of vaporization—water requires absorption of significant amounts of heat to change water from a liquid to a gas, allowing the body to dissipate excess heat

22. Inorganic Compounds • Oxygen and carbon dioxide—closely related to cellular respiration • Oxygen—required to complete decomposition reactions necessary for the release of energy in the body • Carbon dioxide—produced as a waste product, also helps maintain the appropriate acid-base balance in the body

23. Inorganic Compounds • Electrolytes • Large group of inorganic compounds, which includes acids, bases, and salts • Substances that dissociate in solution to form ions • Positively charged ions are cations; negatively charged ions are anions

24. Inorganic Compounds • Acids and bases—common and important chemical substances that are chemical opposites • Acids • Any substance that releases a hydrogen ion (H+) when in solution; “proton donor” • Level of “acidity” depends on the number of hydrogen ions a particular acid will release • Bases • Electrolytes that dissociate to yield hydroxide ions (OH–) or other electrolytes that combine with hydrogen ions (H+) • Described as “proton acceptors”

25. Organic Compounds • There are 4 major organic compounds that are important to humans: Macromolecules: • Carbohydrates • Proteins • Lipids • Nucleic Acids

26. Carbohydrates • There are three main carbohydrates: • Monosaccharides (simple sugars) • Disaccharides (double sugars) • Polysaccharides (complex sugars)

27. Carbohydrates • Carbohydrates—organic compounds containing carbon, hydrogen, and oxygen; commonly called sugars and starches • Monosaccharides—simple sugars with short carbon chains; those with six carbons are hexoses (e.g., glucose), whereas those with five are pentoses (e.g., ribose, deoxyribose) • Disaccharides and polysaccharides—two (di-) or more (poly-) simple sugars that are bonded together through a synthesis reaction

28. Proteins • Most abundant organic compounds • Chainlike polymers • Amino acids—building blocks of proteins • Essential amino acids—eight amino acids that cannot be produced by the human body • Nonessential amino acids—12 amino acids can be produced from molecules available in the human body • Amino acids consist of a carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a side chain

29. Organic Molecules • Lipids • Water-insoluble organic molecules that are critically important biological compounds • Major roles: • Energy source • Structural role • Integral parts of cell membranes

30. Lipids Triglycerides, or fats • Most abundant lipids and most concentrated source of energy • The building blocks of triglycerides are glycerol (the same for each fat molecule) and fatty acids (different for each fat, they determine its chemical nature) • Types of fatty acids—saturated fatty acid (all available bonds are filled) and unsaturated fatty acid (has one or more double bonds) • Triglycerides are formed by a dehydration synthesis

31. Lipids • Phospholipids • Fat compounds similar to triglyceride • One end of the phospholipid is water-soluble (hydrophilic); the other end is fat-soluble (hydrophobic) • Phospholipids can join two different chemical environments • Phospholipids may form double layers called bilayers that make up cell membranes

32. Lipids • Steroids • Main component is steroid nucleus • Involved in many structural and functional roles

33. Nucleic acids • There are two types of nucleic acids: • 1) DNA • 2) RNA

34. Nucleic Acids • DNA (deoxyribonucleic acid) • Composed of deoxyribonucleotides; that is, structural units composed of the pentose sugar (deoxyribose), phosphate group, and nitrogenous base (cytosine, thymine, guanine, or adenine) • DNA molecule consists of two long chains of deoxyribonucleotides coiled into double-helix shape • Alternating deoxyribose and phosphate units form backbone of the chains

35. Nucleic Acids • Base pairs hold the two chains of DNA molecule together • DNA functions as the molecule of heredity

36. Nucleic Acids • RNA (ribonucleic acid) (Figure 2-29, Table 2-7) • Composed of the pentose sugar (ribose), phosphate group, and a nitrogenous base • Nitrogenous bases for RNA are adenine, uracil, guanine, or cytosine (uracil replaces thymine) • Some RNA molecules are temporary copies of segments (genes) of the DNA code and are involved in synthesizing proteins • Some RNA molecules are regulatory, acting as enzymes (ribozymes) or silencing gene expression (RNA interference)

37. Have similar nucleotides: Adenine (A) Guanine (G) Cytosine (C) Differences: -Double helix vs. single helix -Ribose sugar vs. deoxyribose sugar -RNA has a nucleotide of Uracil and DNA has a nucleotide of thymine Similarities and Difference of DNA and RNA

38. Energy • Adenosine triphosphate (ATP)- transfers energy from one chemical pathway to another. It is composed of one adenine molecule and three phosphate molecules.