This document discusses the chemical composition of the human body. It begins by explaining atoms and their components, such as protons, neutrons, and electrons. It then discusses the four main elements found in living organisms: carbon, nitrogen, oxygen, and hydrogen. Various types of bonds are also explained, including covalent, ionic, and hydrogen bonds. The main classes of organic molecules that make up the body are then outlined, including lipids, carbohydrates, proteins, and nucleic acids. For each class, some of the main subgroups and characteristics are defined.

1. Chapter 2
Chemical Composition of
the Body
Human
Physiology

2. Atoms
• Smallest units of matter that can
undergo chemical change.
• Nucleus (center) contains:
▫ Protons (+ charge)
▫ Neutrons (no charge)
• Atomic mass:
▫ Sum of protons and neutrons.

3. Atoms
• Atomic Number
▫ Number of protons in an atom
• Neutral atom
▫ Number of protons = number of electrons
• Isotopes
▫ Vary in number of neutrons
▫ Same in atomic number
▫ Vary in atomic mass

4. Atoms
• Chemical element
▫ Includes all of the isotopic forms of a given atom
▫ Eg: Element Hydrogen: 3 isotopes
 Most common: one proton
 Deuterium: one proton, one neutron
 Tritium: one proton, two neutrons
 Commonly used in research
▫ 106 chemical elements

5. Elements
• Four elements important to living organisms
▫ Carbon (C)
▫ Nitrogen (N)
▫ Oxygen (O)
▫ Hydrogen (H)

6. Atoms
• Electrons (outside the nucleus):
▫ - charged
▫ Occupy orbitals surrounding nucleus.
• Valence electrons:
▫ Electrons in the outer most orbital that
participate in chemical reactions (if orbit
incomplete).
▫ Form chemical bonds.

7. Orbitals
• Also called shells or energy levels
• Electrons usually found within a given orbital
• Levels (and max number of electrons)
▫ First shell: 2 electrons
▫ Second shell: 8 electrons
▫ Third shell: usually 8 electrons

9. Chemical Bonds, Molecules, and
Ionic Compounds
• Chemical bonds:
▫ Interaction of valence electrons
between 2 or more atoms.
• # bonds determined by # electrons
needed to complete outer orbital.

10. Covalent Bonds
• Atoms share their valence
electrons.
• Nonpolar bonds:
▫ Electrons are equally distributed
between the two identical atoms.
▫ Strongest bond.
▫ H2

13. Covalent Bonds
• Polar bonds:
▫ Electrons are shared between two
different atoms.
▫ Electrons may be pulled more toward
more atom.
▫ Oxygen, nitrogen, phosphate pull
electrons towards themselves.

15. Ionic Bonds
• One or more valence electrons from
an atom are completely transferred
to a second atom.
• First atom loses electrons, +
charged (cation).
• Second atom has more electrons,
- charged (anion).

16. Ionic Bonds
• Cation and anion attract, form ionic
compound.
• Weaker than polar bonds.
• Dissociate easily when dissolved in
H20.
• NaCl Na+
and Cl-

17. Table Salt, an Ionically Bonded Molecule
Slide number: 1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
11p
12n
17p
18n+
(+)
(–)
Na Cl+ NaCl

18. Table Salt, an Ionically Bonded Molecule
Slide number: 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
Na Cl+

19. Table Salt, an Ionically Bonded Molecule
Slide number: 3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
Na Cl+

20. Table Salt, an Ionically Bonded Molecule
Slide number: 4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
Na Cl+

21. Table Salt, an Ionically Bonded Molecule
Slide number: 5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
Na Cl+

22. Table Salt, an Ionically Bonded Molecule
Slide number: 6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17p
18n
11p
12n
Na Cl+
(+) (–)

23. Table Salt, an Ionically Bonded Molecule
Slide number: 7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
NaCl
11p
12n
(+)
17p
18n
(–)

25. Interaction with water
• Hydrophilic:
▫ Formation of hydration spheres.
▫ Polar covalent bonds.
• Hydrophobic:
▫ Cannot form hydration spheres.
▫ Nonpolar covalent bonds.

26. Hydrogen Bond
• Hydrogen forms a
polar bond with
another atom,
hydrogen has a
slight + charge.
• Weak attraction
for for a second
electronegative
atom.

27. Acids, Bases, and the pH Scale
• Acid:
▫ Molecule that can release protons (H+
).
▫ Proton donor.
• Base:
▫ Negatively charged ion that can combine with
H+
.
▫ Proton acceptor.

28. pH
• pH = log _1__
[H+
]
• Normal pH blood = 7.35 - 7.45.
• Buffer:
▫ System of molecules and ions that act
to prevent changes in [H+
].

29. Organic Molecules
• Molecules that contain carbon and
hydrogen.
• Carbon has 4 electrons in outer
orbital.
• Carbon covalently bonds to fill its
outer orbital with 8 electrons.

30. Organic Molecules
• Organic Chemistry: deals with molecules that
contain carbon
• More than 5 million organic compounds have
been identified
• The carbon atom can form bonds with a
greater number of different elements than
any other type of atom

32. Functional Groups
• Inactive “backbone” to which more reactive
atoms are attached.

33. Classes According to Functional
Groups
• Ketone and
aldehyde:
carbonyl group
• Organic acid:
carboxyl group
• Alcohol: hydroxyl
group

34. Stereoisomers
• Exactly the same atoms arranged in same
sequence.
• Differ in spatial orientation of a functional
group.
▫ D-isomers: right-handed
▫ L-isomers: left-handed
• Enzymes of all cells can combine only with
the L-amino acids and
D-sugars.

35. Four main classes of Organic
molecules
• Lipids
• Carbohydrates
• Proteins
• Nucleic Acids

36. Lipids
• GR: Lipos=Fat
• Diverse group of molecules.
• Insoluble in polar solvents (H20).
• Hydrophobic (nonpolar)
• Consist primarily of hydrocarbon
chains and rings.

37. Lipids
• Hydrocarbons
• Fatty acids
• Triglycerides
• Ketone Bodies
• Phospholipids
• Steroids
• Prostaglandins

38. Hydrocarbons
• Includes oils and
gases
• Carbons can be
single bonds
(saturated)
• Carbons can be
double bonded
(unsaturated)

39. Fatty acids
• Nonpolar hydrocarbon chain
▫ Can be saturated (are stright)
▫ Can be unsaturated (bend at the double bond)
▫ Can be poly unsaturated (multiple bends)
• Carboxyl group on one end
• Large group

41. Triglycerides
• Formed by condensation of glycerol and 3
fatty acids.
▫ Ester bond
• Fatty acid consists of hydrocarbon chain
with carboxylic acid end.
▫ May be saturated or unsaturated
▫ Saturated fats:
 Mostly animal sources
 Mostly solid at room temperature
▫ Unsaturated fats
 Mostly plant sources
 Mostly liquid at room temperature

43. Nutritional considerations of
triglycerides
• Also called fat or neutral fat
• Stored in adipose cells
• Total fat intake should be about 30% of total
energy intake
▫ Saturated fat >10%
• Saturated fats are implicated in heart disease
and stroke
▫ Data suggests they promote high blood
cholesterol

44. Phospholipids
• A number of categories
• All contain a phosphate group
• Most common
▫ Glycerol (3 carbons)
▫ Fatty Acids on carbon 1 and 2
▫ Phosphate group attached to carbon (and other
polar groups eg.: choline)

45. Lecithin

46. Phospholipid
• Are amphipathic: contain both polar and
nonpolar domains
▫ Head:
 contains polar groups
 Hydrophilic
▫ Tail:
 Contains fatty acids (nonpolar)
 Hydrophobic

47. Phospholipids
• Major component of cell membranes
▫ Hydrophylic heads orient to water
▫ Hydrophobic tails orient to each other
• Kind of phospholipid varies based on cell or
organelle

48. Micelle formation

49. Ketone Bodies
• Results from the hydrolysis of triglycerides by
adipocytes
▫ Liberates free FA into blood
▫ FA function as an acid in blood
• Most FA used as energy source by some
tissues
• If not, converted by liver into Ketone bodies

50. Ketone Bodies
4-carbon chunks

51. Ketone Bodies
• Produced in the rapid breakdown of FA
▫ Low-carbohydrate diets
▫ Uncontrolled Diabetes mellitus
• Ketosis: Elevated level of FA in blood
• Ketoacidosis: ketosis is high enough to lower
blood ph

52. Steroids
• Nonpolar and insoluble in H20.
• All have cholesterol as precursor.

53. Prostaglandins
• Prostaglandins:
▫ Fatty acid with cyclic hydrocarbon
group.
▫ Derived from arachidonic acid.

54. Prostaglandins

55. Carbohydrates
• Organic molecules that contain
carbon, hydrogen and oxygen.
• CH20
• General formula:
▫ CnH2nOn
• -ose denotes a sugar molecule

56. Carbohydrates
• Supply energy
▫ Glucose
▫ Complex carbohydrates
• Provide structural support
▫ cellulose
• Part of plasma membrane
• Monomer: monosaccarides

57. Carbohydrates
• Monosaccharide: the “simple sugars”
▫ Pentoses (5-carbons):
 Ribose: in RNA
 Deoxyribose: in DNA
▫ Hexoses (6-carbons):structural isomers
 Glucose, fructose and galactose
 Characteristics
 Soluable
 Sweet
 Alcoholic fermentation

58. Glucose
• Also called :
▫ Dextrose
▫ Transportable in the blood
 Blood glucose
▫ C6H12O6

60. Fructose
• Fruit sugar

61. Galactose
▫ C6H12O6

62. Carbohydrates
• Disaccharide:
▫ 2 monosaccharides joined covalently.
 Sucrose
 Glucose and fructose
 Maltose
 Glucose and glucose
 Lactose
 Glucose and galactose

63. Disaccharides
• Characteristics
▫ Sweet
▫ Soluable
▫ Can be fermented
• Formation: called condensation
▫ Requires an enzyme
▫ Removal of molecule of water
▫ Also called dehydration synthesis
▫ Formation of a covalent bond

64. Formation of Disaccharides

65. Hydrolysis
• Reverse of dehydration synthesis.
• Digestion reaction.
• H20 molecule split.

66. Carbohydrates
• Polysaccharides:
▫ Many monosaccharides joined covalently.
▫ General formula: (C6H10O5)n
▫ Characteristics:
 Devoid of taste
 Do not form solutions
 Iodine test
 Iodine +starch+blue

67. Polysaccarides• Kinds:
▫ Starch
 Glucose subunits
 branched
▫ Dextrins
▫ Glycogen (animal starch)
 Glucose subunits
 Branched
▫ Cellulose
 Glucose subunits
 Long, unbranched chains

68. Proteins
• General Information:
▫ GR: proteios=first rank
▫ ~50% of the organic material of the
body
▫ Functions
 Structural:
 Cell structures, CTs
 Functional:
 Enzymes, hormones, Hb, etc!

69. Proteins• Protein Structure
▫ Large molecules (polymers) composed
of amino acid sub-units (monomers).
▫ Amino Acid structure
 amino group (NH2)
 carboxylic acid group (COOH)
 Radical group (R): functional group
 H

71. Proteins
• 20 different standard amino acids.
▫ Based on the properties of the
functional group
▫ E.g.:

72. Proteins
• Dehydration synthesis:
▫ Amino end of one amino acid
combines with hydroxyl group of
carboxylic end of another amino acid.
• Peptide bond:
▫ Bond between two adjacent amino
acids.

73. Peptide bond

74. Proteins• Dipeptide: 2 amino acids
• Tripeptide: 3 amino acids
• Polypeptide: many amino acids
▫ Number of amino acids varies
▫ Up to 100 aa
• Protein
▫ Over 100aa
▫ Great variety!

75. Protein structure
• Four structural levels
▫ Primary structure
 Based on amino acid sequence
 Amino acid sequence determined by DNA
▫ Secondary structure
 Based on hydrogen bonding between close aa
▫ Tertiery structure
 3-D shape
▫ Quaternary structure
 Only in proteins with 2 or more polypeptide
chains

77. Secondary structure (2o
)
• Based on the primary structure
• Weak hydrogen bonds form between
hydrogen and oxygen of a different amino
acid.
• Two main kinds of secondary structure:
▫ Alpha helix: Bond cause chain to twist in a helix.
▫ Beta pleated sheet: interactions between lengths of
the polypeptide chain

78. Secondary structures

79. Tertitary structure
• Polypeptide chains bend and fold.
▫ Based on interactions with aa in different parts of
the polypeptide chain
 disulfide bonds: covalent
 Hydrogen bonds: weak
• Produce 3 -dimensional shapes.
• Chemical interaction of each protein produces
own characteristic tertiary structure
• Denaturing protein
▫ Irreversible disruption of tertiary structure

80. Bonds responsible for 3o
structure

81. Tertiary structure

82. Quaternary Structure
• Number of
polypeptide
chains covalently
linked together.
• Insulin,
hemoglobin

83. Conjugated proteins
• Protein combined with another type of
molecule
• Glycoproteins: carbohydrate with protein
▫ Membranes, hormone
• Lipoproteins: Lipid and protein
▫ Membranes, blood plasma
• Hemoproteins: iron and protein
▫ Hemoglobin, cytochromes

84. Nucleic Acids
• Include the macromolecules:
▫ DNA: deoxyribonucleic acid
▫ RNA: ribonucleic acid
• Involved in heredity and genetic regulation
• Are polymers:
▫ Monomeric subunit:nucleotides
▫ Bonded together in a dehydration synthesis
reaction

85. Nucleic Acids

86. Nucleotides• Structure of a nucleotide: 3 subunits
▫ Pentose sugar
▫ Phosphate group
▫ Nitrogenous base
 Purines: two rings
 Guanine
 Adenine
 Pyrimidines: one ring
 Cytosine
 Thymine
 Uricil

87. Nucleotide Structure

88. Nitrogenous Bases

89. DNA
• Huge molecules with simple structure
• Big time data storage!
• Structure
▫ Nucleotides
 Pentose sugar: Deoxyribose
 Bases:
 Purines: G and A
 Pyrimidines: C and T
▫ Form double-stranded helix

90. DNA
• Nucleotide strands: 2
▫ Sugar-phosphate backbone
▫ Bases stick out
▫ Bases bond to each other
• Base pairing:
▫ A – T
▫ G – C
▫ Called law of complementary base pairing

91. Nitrogenous Bases

92. DNA

93. RNA
• Means by which DNA directs cellular
activities
• Structure
▫ Pentose sugar: ribose
▫ Bases: uracil (not thymine)
▫ Single stranded
• Three main types
▫ Messenger RNA (mRNA)
▫ Transfer RNA (tRNA)
▫ Ribosomal RNA (rRNA)

94. DNA vs RNA