1. Chapter 2 Chemical Basis of Life

2. 2.1: The Importance of Chemistry in Anatomy and Physiology
Why study chemistry in Anatomy & Physiology?
Chemistry is concerned with composition of substances and how they change in chemical reactions
Human body, food, and medications are all composed of chemicals
All anatomical structures are chemicals, and all physiological processes are based on chemical reactions
Biochemistry helps explain physiological and disease processes

3. Structure of Matter
Matter: Anything that takes up space and has mass. Matter is composed of elements. Solids, liquids, and gases are matter.
Elements: Simplest types of matter with certain chemical properties. 98 naturally occurring elements.
Atoms: Smallest particles of an element that have properties of that element

4. Structure of Matter
Different elements are required by the body in different amounts:
Bulk elements: required by the body in large amounts (C, O, H)
Trace elements: required by the body in small amounts (Fe, I)
Ultratrace elements: required by the body in very
minute amounts (As)

5. Structure of Matter Table of major and trace elements in the
human body

6. Atomic Structure Atoms: Composed of subatomic particles:
Proton: Carries a single
positive charge
Neutron: Carries no electrical
charge
Electron: Carries a single
negative charge
Nucleus:
Central part of atom
Composed of protons and
neutrons
Electrons move around the
nucleus

7. Atomic Structure

8. Atomic Number & Atomic Weight
Number of protons in the nucleus of an atom of a
specific element
Each element has a unique atomic number
Number of protons is equal to the number of
electrons in the atom; atoms are electrically neutral
Atomic Weight:
The number of protons plus the number of neutrons
in one atom
Electrons do not contribute to the weight of the atom

9. Isotopes
Isotopes:
All atoms of a certain element have same atomic number
Isotopes are atoms with the same atomic numbers but with different atomic weights
Isotopes contain different numbers of neutrons, but same number of protons & electrons
Oxygen often forms isotopes (O16, O17, and O18, with numbers representing atomic weights)
Radioactive isotopes are unstable, releasing energy or
atomic fragments (atomic radiation) until they gain
stability; some are used to detect and treat disease.
For any element, the atomic weight is often considered the average of the atomic weights of all of its isotopes.

10. From Science to Technology
Radioactive Isotopes Reveal Physiology
Radioactive iodine-131 can be used to destroy cancerous thyroid gland tissue. This is very effective, because the thyroid gland is the only part of the body that actively transports and metabolizes iodine.
Radioactive isotopes have many medical uses: detecting coronary blood vessel disorders, evaluating kidney function, measuring hormone concentrations in body fluids, and assessing changes in bone density.

11. From Science to Technology
Ionizing Radiation
Radiation (alpha, beta, and gamma) is called ionizing radiation, because its energy can remove electrons from atoms, resulting in the formation of ions. The free electrons can damage nearby atoms.
Ionizing radiation sources include X rays, naturally occurring radioactive elements in the crust of the earth, and nuclear weapons.

12. Molecules and Compounds
Molecule: particle formed when two or more atoms chemically combine
Compound: particle formed when two or more atoms of different elements chemically combine
Molecular formulas: depict the elements present and the number of each atom present in the molecule
H2 = a molecule of hydrogen
C6H12O6 = a molecule of glucose
H2O = a molecule of water

13. Molecules and Compounds
Molecules of hydrogen or
oxygen form when 2 identical
atoms combine chemically.
When 2 atoms of hydrogen
combine with 1 atom of oxygen,
the compound water is formed.

14. Bonding of Atoms
Chemical bonds form when atoms combine with other atoms. They result from interactions between the electrons of the atoms.
Electrons of an atom occupy regions of space called electron shells (energy shells), which circle the nucleus
For atoms with atomic numbers of 18 or less, the following rules apply:
The first shell can hold up to 2 electrons
The second shell can hold up to 8 electrons
The third shell can hold up to 8 electrons
Lower energy shells / inner orbits are filled first, and are stable with a certain number of electrons in the outermost shell (2, 8 or 18—in larger atoms)

15. Bonding of Atoms

16. Bonding of Atoms: Ions Ion:
An atom that gains or loses electrons to become stable
An electrically charged atom
Cation:
A positively charged
ion
Formed when an
atom loses electrons
Anion:
A negatively charged
Formed when an atom gains electrons

17. Bonding of Atoms: Ionic Bonds
Formed when electrons are transferred from one atom to
another atom
The attraction between a cation and an anion forms a very strong bond between the ions, called an ionic bond.

18. Bonding of Atoms: Covalent Bonds
Covalent Bonds: Strong chemical bonds, formed between atoms that share electrons Two atoms of hydrogen (H) have combined to form a hydrogen molecule (H2). Both atoms in the molecule become stable.

19. Bonding of Atoms: Covalent Bonds
Hydrogen molecules (H2) often combine with oxygen (O2) molecules to form water molecules (H2O).

20. Bonding of Atoms: Structural Formulas
Structural formulas show how atoms bond and are arranged in various molecules. One line between atoms means that 1 pair of electrons are being shared (forming single bonds), while two lines indicate that 2 pairs are being shared (forming double bonds).

21. Bonding of Atoms: Polar Molecules
Molecules with a slightly negative end & a slightly positive end
Results from unequal sharing of electrons in covalent bonds
Water is an important polar molecule
In this water molecule, the
O nucleus pulls the
electrons more strongly
than the H nuclei, since
it contains more positively
charged protons.

22. Bonding of Atoms: Hydrogen Bonds
A weak attraction between the slightly positive (H) end of one polar molecule and the slightly negative (N or O) end of another polar molecule
Formed between adjacent water molecules
Important for protein and nucleic acid structure

23. Chemical Reactions
Chemical reactions occur when chemical bonds form or break between atoms, ions, or molecules.
Reactants are the starting materials of a chemical reaction: the atoms, ions, or molecules.
Products are substances formed at the end of the chemical reaction.
NaCl Na+ + Cl-
(Reactant) (Products)
The above reaction involves the dissociation of NaCl in water to form Na+ and Cl- ions.

24. Types of Chemical Reactions
Synthesis Reaction: more complex chemical structure is formed
A + B AB
Decomposition Reaction: chemical bonds are broken to form a simpler chemical structure
AB A + B
Exchange Reaction: chemical bonds are broken and new bonds are formed
AB + CD AD + CB
Reversible Reaction: the products can change back to the reactants
A + B AB
Synthesis Reaction: more complex chemical structure is formed
A + B AB
Decomposition Reaction: chemical bonds are broken to form a simpler chemical structure
AB A + B
Exchange Reaction: chemical bonds are broken and new bonds are formed
AB + CD AD + CB
Reversible Reaction: the products can change back to the reactants
A + B AB

25. Acids, Bases, and Salts NaOH  Na+ + OH-
Electrolytes: Substances that release ions in water. The solution can conduct an electric current, so it is called an electrolyte.
NaCl  Na+ + Cl-
Acids: Electrolytes that dissociate to release hydrogen ions in water
HCl  H+ + Cl-
Bases: Substances that release ions that can combine with hydrogen ions
NaOH  Na+ + OH-
Salts: Electrolytes formed by the reaction between an acid and a base
HCl + NaOH  H2O + NaCl

26. Acids, Bases, and Salts
When an ionically bonded substance is put into water, the charged ions are attracted to the slightly charged ends of the polar water molecules. This dissociates the substance, and the ions become surrounded by water molecules. The substance is now called an electrolyte, since it can now carry an electric current.

27. Acid and Base Concentrations
Concentrations of acids and bases affect chemical reactions in living organisms.
H+ ion concentration is measured in g/L of body fluid
pH scale is used as shorthand for H+ ion concentration; it is based on the number of decimal places in the concentration
If H+ ion concentration = 0.01 g/L, the pH = 2
If H+ ion concentration = g/L, the pH =9
pH scale runs from 0 – 14; each number represents a tenfold difference in H+ ion concentration
Acids have a pH <7, and bases have a pH >7
A pH of 7 is neutral

28. Acid and Base Concentrations
The higher the H+
concentration, the
lower the pH, and
the higher the
acidity.
The lower the H+
higher the pH, and
the lower the acidity
(which corresponds
to higher alkalinity).

29. Acid and Base Concentrations
pH Scale: Indicates the concentration of hydrogen ions in a solution
Neutral: A pH of 7 indicates equal concentrations of H+ and OH-. This is the pH of water.
Acidic: A pH of <7 indicates a greater concentration of H+ than OH-
Basic (alkaline): A pH >7 indicates a higher concentration of OH- than H+

30. Acid and Base Concentrations
Normal range of blood pH is 7.35 – 7.45
Acidosis occurs when blood pH drops to 7.0 – 7.3
Makes a person feel disoriented, fatigued
Caused by vomiting of alkaline intestinal contents, diabetes, lung disease with impaired CO2 exhalation
Alkalosis occurs when blood pH rises to 7.5 – 7.8
Makes a person feel dizzy and agitated
Caused by high altitude breathing, vomiting of acidic stomach contents, high fever, taking excess antacids
Homeostatic mechanisms help regulate pH
Buffers are chemical systems which act to resist pH
changes; bind and release H+ ions to regulate pH

31. Chemical Constituents of Cells Organic vs. Inorganic Molecules
Contain C and H
Dissolve in water and organic liquids
Water-soluble organic compounds do not release ions,
and are non-electrolytes
Carbohydrates, proteins, lipids, and nucleic acids
Inorganic molecules:
Generally do not contain C and H
Usually dissolve in water and dissociate, forming
ions, and are electrolytes
Water, oxygen, carbon dioxide, and inorganic salts

32. Inorganic Substances Water: Most abundant compound in living material
Two-thirds of the weight of an adult human
Major component of all body fluids
Medium for most metabolic reactions
Important role in transporting chemicals in the body
Absorbs and transports heat
Water balance exists when gains equal losses
Oxygen (O2):
Used by organelles to release energy from nutrients
in order to drive cell’s metabolic activities
Necessary for survival

33. Inorganic Substances Carbon dioxide (CO2):
Waste product released during metabolic reactions
Must be removed from the body through exhaling
Inorganic salts:
Abundant in body fluids
Sources of necessary ions (Na+, Cl-, K+, Ca+2, etc.)
Play important roles in metabolism
Help control H2O concentration, pH, blood clotting,
nerve and muscle processes
Electrolyte balance exists when gains equal losses

34. Organic Substances: Carbohydrates
Main source of cellular energy
Supply materials to build cell structures
Water-soluble
Contain C, H, and O
Ratio of H to O close to 2:1 (C6H12O6 = glucose)
Size classification of carbohydrates:
Monosaccharides (single sugars): glucose, fructose
Disaccharides (double sugars): sucrose, lactose
Polysaccharides (complex carbohydrates: starch, glycogen, cellulose)

35. Organic Substances: Carbohydrates

36. Organic Substances: Carbohydrates

37. Organic Substances: Lipids
Insoluble in water, but soluble in organic solvents
Include triglycerides (fats), phospholipids, steroids
Important component of cell membranes, and have several functions in cells
Most abundant lipids are triglycerides (fats):
a. Used for cellular energy
b. Contain more energy per gram than carbohydrates
c. Contain C, H, and O, but less O than carbohydrates
d. Consist of 1 molecule of glycerol and 3 fatty acids

38. Organic Substances: Lipids
Saturated fatty acids have only single carbon-carbon bonds. Most are solid at room temperature, and of animal origin.
Unsaturated fatty acids have one or more carbon-carbon double bond. Most are liquid at room temperature, and are of plant origin.

39. Organic Substances: Lipids
A triglyceride is composed of 1 glycerol molecule and 3 fatty acids.

40. Organic Substances: Lipids
Phospholipids:
Consist of 1 glycerol, 2 fatty acids, and 1 phosphate
Have hydrophilic and hydrophobic ends
Major component of cell membranes

41. Organic Substances: Lipids
Steroids:
4 connected rings of carbon
Widely distributed in the body, various functions
Component of cell membranes
Used to synthesize adrenal and sex hormones
Cholesterol is the main steroid in the body

42. Organic Substances: Proteins
Proteins are used as structural materials, energy source, hormones, receptors, enzymes, antibodies
Consist of building blocks called amino acids
An amino acid contains an amino (-NH2) group, a carboxyl (COOH) group, and a unique R (side chain) group

43. Organic Substances: Proteins
Amino acids are bound to each other by peptide bonds: Peptide bonds form between the amino group of one amino acid, and the carboxyl group of the adjacent amino acid.

44. Organic Substances: Proteins
4 Levels of Protein Structure:
Primary: Amino acid sequence
Secondary: Pleated or twisted
structure formed by hydrogen
bonding between nonadjacent
amino acids
Tertiary: Unique 3-dimensional
folded shape of the protein
Quaternary: Structure formed by
some proteins, when 2 or more
polypeptide chains are connected
to become 1 protein.

45. Organic Substances: Nucleic Acids
Carry genetic code (DNA) or aid in protein synthesis (RNA)
Encode amino acid sequences of proteins
Building blocks are called nucleotides, which consist of a
sugar (S), a phosphate group (P), and an organic base (B).
DNA (Deoxyribonucleic acid): a double chain of nucleotides
RNA (Ribonucleic acid): a single chain of nucleotides

46. Organic Substances: Nucleic Acids

47. Organic Substances: Nucleic Acids
Two major types of nucleic acids: DNA and RNA
DNA:
Stores the genetic code
Contains the sugar deoxyribose
Structure—double helix
Composed of nucleotides
RNA:
Interacts with DNA to conduct protein synthesis
Contains the sugar ribose
Structure—single strand

48. From Science to Technology
CT Scanning and PET Imaging
Computerized Tomography (CT) imaging:
Used to visualize internal anatomy
Uses X-ray emitting device to create 3-dimensional image of soft tissues
Differentiates tissues with slightly different densities, tumors
Positron Emission Tomography (PET) imaging:
Uses radioactive isotopes that emit positrons (unusual positively charge electrons) to detect biochemical activity
Used to detect various brain disorders, blood flow, normal brain physiology