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2
The Chemical Level
of Organization
Matter: Atoms and Molecules
Atoms
• Smallest unit of
an element
• Subatomic
particles
• Protons: (+)
charge
• Neutrons:
neutral
• Electrons: (-)
charge
Figure 2-1
Matter: Atoms and Molecules
Structure of atom
• Electrons surround nucleus
• Electrons organized in shells
• The outer shell determines
chemical properties
Matter: Atoms and Molecules
Key Note
All matter is composed of atoms
in various combinations. Their
interactions establish the
foundations of physiology at the
cellular level.
Matter: Atoms and Molecules
Ionic Bonds
• Atoms gain or lose electrons
• Charged atoms are ions
• Ions bear (+) or (-) charge
• Cations have (+) charge
• Anions have (-) charge
• Cations and anions attract
• Ions form bonds
Matter: Atoms and Molecules
Table 2-2
Chemical Reactions
Metabolism
All the chemical reactions in
the body
• Consumes reactants
• Produces products
• Breaks or makes chemical
bonds between atoms
Chemical Reactions
Basic Energy Concepts
• Potential energy—stored energy
• E.g., glycogen stored in muscle cells
• Kinetic energy—energy of movement
• E.g., leopard pounces on prey
Inorganic Compounds
Nutrients
Essential elements and molecules
obtained from the diet
Metabolites
Molecules synthesized or broken
down by chemical reactions inside
the body
Inorganic Compounds
Inorganic
Smaller molecules such as water,
oxygen and ions that lack carbon
and hydrogen
Organic
Larger molecules such as sugars,
proteins, and fats composed largely
of carbon, hydrogen and oxygen
Human Body Composition
Element
Percent by mass
Oxygen
65
Carbon
18
Hydrogen
10
Nitrogen
3
Calcium
1.5
Phosphorus
1.2
Potassium
0.2
Sulfur
0.2
Chlorine
0.2
Sodium
0.1
Magnesium
0.05
Iron, Cobalt, Copper, Zinc, Iodine
<0.05 each
Selenium, Fluorine
<0.01 each
Organic Compounds
Carbohydrates
• Most important energy source for
metabolism
• Three major types
• Monosaccharides (E.g., glucose)
• Disaccharides (E.g., sucrose)
• Polysaccharides (E.g., glycogen)
Organic Compounds
Glucose
Figure 2-10
Organic Compounds
Formation of Glycogen
Figure 2-11(c)
Organic Compounds
Lipids
• Water-insoluble
• Four important classes
• Fatty acids
• Fats
• Steroids
• Phospholipids
Organic Compounds
Fatty Acids
Figure 2-12
Organic Compounds
Cholesterol
• Building block for steroid hormones
• Component of cell membranes
Figure 2-14
Organic Compounds
Proteins
• Most abundant organic
component in human body
• About 100,000 different proteins
• Contain carbon, nitrogen,
oxygen, hydrogen, and a bit of
sulfur
Organic Compounds
Proteins play vital roles
•
•
•
•
•
•
Support
Movement
Transport
Buffering
Regulation
Defense
Organic Compounds
Proteins are
built from
amino acids
Figure 2-16(a)
Protein Structure
Figure 2-17
Organic Compounds
Enzyme Function
• Substrates (reactants) bind to
active site on enzyme surface
• Binding lowers activation
energy needed for reaction
• Substrates react to form
product
• Product is released from
enzyme surface
Enzyme function made simple
Figure 2-18
Organic Compounds
Nucleic Acids
• Large molecules
• Built from atoms of C, H, O, N, and P
• Store and process molecular
information
• Two classes of nucleic acid
• DNA (deoxyribonucleic acid)
• RNA (ribonucleic acid)
The Structure of Nucleic Acids
Figure 2-19ab
The Structure of Nucleic Acids
Organic Compounds
Structure of Nucleic Acids
• Nucleotides contain a sugar,
a phosphate, and a base
• Sugar-phosphate bonds link
nucleotides in long strands
• Hydrogen bonds hold two
DNA strands in a double helix
Summary of Body Chemistry
Organic Chemical Building Blocks
Figure 2-22