Download ANPS 019 Beneyto-Santonja 08-29

ANPS 019 08/29/12 Beneyto
Anatomy and Physiology 019  Structure and Function of the Human Body
Lecture Block 1: Cells, Tissues, and the Skeleton
Chemistry: Remembering the building blocks of the body
 Atoms are the smallest stable units of matter
 Electrons of one atom may interact with electrons of another atom to form bigger
chemical structures (molecules, compounds)
 Only a few elements will be important to us in this course
o Oxygen: A component of water and other compounds, gaseous form is essential
for respiration
o Carbon: Found in all organic molecules
o Hydrogen: A component of water and most other compounds in the body
o Nitrogen: Found in proteins, nucleic acids, and other organic compounds
o Calcium: Found in bones and teeth; important for membrane function, nerve
impulses, muscle contraction, and blood clotting
o Phosphorus: Found in bones and teeth, nucleic acids, and high-energy
compounds
o Potassium: Important for proper membrane function, nerve impulses, and muscle
contraction
o Sodium: Important for blood volume, membrane function, nerve impulses, and
muscle contraction
o Chlorine: Important for blood volume, membrane function, and water absorption
Chemistry of the Human Body
 Ions; Organic molecules; Inorganic compounds
 Bonds tie one atom to another to create bigger chemical structure in the body
 Most types of bonds are made and broken by enzymes
The role of enzymes
 Reactants (substrates) interact to yield a product by binding to the active site of the
enzyme
 Enzymes serve as catalysts that promote chemical reactions by lowering the activation
energy needed for the reaction, thus making it more likely the reaction will occur
 The enzyme is not used up in the reaction, and is able to catalyze the same reaction again
and again
Ions  Atoms that have gained or lost electrons and become charged
 Cations are positively charged ions
 Anions are negatively charged ions
 Biologically Important ions: K+; Ca++, H+
 Ionic Bonds – attraction positive cations and negative anions
Covalent Bonds – atoms share electrons to form a molecule
 If atoms share electrons equally  nonpolar covalent bond
 If atoms share electrons unequally  polar covalent bond
Hydrogen Bonds
 Hydrogen frequently forms covalent bonds with other elements; because of hydrogen’s
status as the smallest atom, it usually has unequal sharing of electrons in those bonds,
creating a polar molecule
 The weakly positive hydrogen atom of a polar molecule may be attracted to negatively
charged atoms of other molecules
 Hydrogen bonds create weak forces that affect the shape and properties compounds
The structure of Water is based on hydrogen bonding
 Individual water molecules are attracted to one another by hydrogen bonds between the
oxygen atom (slight negative charge) of one molecule and the hydrogen atom (slight
positive charge) of another water molecule
 Each water molecule is held together by polar covalent bonds
 One water molecule is attracted to another by hydrogen bonds
Water molecules and solutions
 The polar water molecule is attracted to any solute with charged atoms: ions, proteins,
carbohydrates, etc.
 Substances that interact readily with water are hydrophilic  most substances
 Substances that do not interact with water hydrophobic  lipid molecules
Organic Compounds
 Usually large, complex molecules containing carbon (and usually hydrogen and oxygen)
 Four major classes of organic compounds
o Carbohydrates
o Lipids
o Proteins
o Nucleic Acids
 Why Carbon?
o The structure of the carbon atom gives it unique bonding properties
o Can share 4 electrons in different ways; may form single bonds, double bonds,
triple bond
o Bonding pattern influences the shape of the molecule
o Carbon based molecules can have wide range of sizes and shapes
Carbohydrates
 Key example: Glucose – C6H12O6 “hydrated carbon”
 Sugars, starches, glucose and glycogen (storage form of glucose)
 Hydrophilic molecules
 Important energy source for metabolism
 Occur as monosaccharides, disaccharides, and polysaccharides
o Di- and polysaccharides formed from monosaccharides by dehydration synthesis
(removal of water molecule)
 The formation & Breakdown of Complex Sugars
o During dehydration synthesis, two molecules are joined by the removal of a
water molecule
o Hydrolysis reverses the steps of dehydration synthesis; a complex molecules is
broken down by the addition of a water molecule
 Polysaccharides are very large carbohydrates
o Hydrophilic
o Large size makes them ideal molecules to ‘hold’ water in the body
Lipids  include fats, oils, and waxes
 Hydrophobic
 Five Classes:
o Phospholipids and glycolipids  Cell Membranes
o Fatty Acids  building blocks, energy
o Glycerides  fatty acids + glycerol = body fat
o Steroids  cholesterol, some hormones
o Eicosanoids  prostaglandins, etc. – cell messages

Triglycerides = three fatty acids attached by dehydration synthesis to one molecule of
glycerol
 Steroids
o Cholesterol is a critical molecule, vital in cell membranes and used as building
block for important biologically active substances, including the sex hormones
(“sex steroids”) and hormones regulating metabolism (“corticosteroids”)
Proteins  Perform vital functions in the body
 Structural proteins
 Contractile proteins
 Transport proteins
 Enzyme
 Buffering protein
 Antibodies
 Amino acids are the building blocks of proteins
o 20 different amino acids in body but all share common structure
o Every amino acid contains:
 A central carbon atom
 An amino group
 A carboxylic group
 A radical group – differs between amino acids
o Amino acids join with peptide bonds to form linear strands of molecules
o Hydrophilic
 The formation of a peptide bond involves the removal of a water molecule between two
adjacent amino acid molecules
 The 20 amino acids
o Variable groups give different properties to the amino acids
o Some are hydrophilic; some are hydrophobic; some are positively charged; some
are negatively charged
o When a long chain of amino acids is formed, the side chains interact with those
of neighboring amino acids and the environment around the protein
 Interactions between molecules on the chain cause the chain to bend, spiral, or fold into a
unique shape
 Long chains of amino acids (1000-100,000)
o Short chains are usually 70 amino acids or less – call peptides
 Chains form complex shapes as amino acids in chain react with one another: Final shape
of protein chain determines its function
 These interactions are critically sensitive to pH and temperature. Proteins pushed outside
their optimal temperature and pH range become temporarily or permanently denatured
and will cease to function
o Shape changes make proteins nonfunctional
Nucleic acids
 Store and process information at the molecular level, are the building blocks of DNA and
RNA
 Large organic compounds made of building blocks called nucleotides
 Each nucleotide contains:
o A phosphate group (PO4)
o A sugar group (ribose or deoxyribose)
o A nitrogen containing base
 2 types:
 Purines are double ringed molecules (Adenine, Gaunine)


 Pyrimidines have a single ring (Cytosine, Thymine, Uracil)
RNA and DNA are built by first linking nucleotides together into strands
o A strand is formed by linking the sugar group of one nucleotide to the phosphate
group of another nucleotide
o RNA: ribonucleic acid
o RNA nucleotides contain
 A ribose sugar
 A phosphate group
 And one of these bases: Adenine, Guanine, Cytosine, Uracil
DNA: deoxyribonucleic acid
o Each nucleotide contains a deoxyribose sugar, a phosphate group, and one of
these bases: Adenine, Guanine, Cytosine, Thymine
o The DNA molecule is formed by linking one DNA strand with another by
hydrogen bonds between complementary bases
o Complementary base pairing:
 Adenine binds to Thymine (A-T)
 Cytosine binds to Guanine (C-G)