The Chemical Level of OrganizationChapter #2

• •Element
• –A substance that can not be
• broken down into two or more substances
• –Human body is composed of 26
• elements
• •4 major elements
• –carbon, oxygen, hydrogen and nitrogen make up approximately 96% of the body’s weight
• •8 lesser elements
• •14 trace elements
• •Compound
• –Joint atoms of two or more elements

• •Atom is the smallest part of an element
• •Atom is composed of:
• -Nucleus
• •Neutron
• –The neutral particle in the atomic nucleus
• •Proton
• –The positive particle in the atomic nucleus
• –Electron
• •The negative particle found in orbital's surrounding nucleus

• •Atomic Number
• –Equal to the number of protons in each atom
• –In a stable element (electrically neutral), the number of protons equals the number of electrons.
• •1H - one proton, one electron
• •6C - six protons, six electrons

• •Mass Number
• –Protons and Neutrons have about the same mass
• –Mass number equals the number of protons and neutrons in the nucleus
• •12C – six protons, six neutrons
• •16O – eight protons, eight neutrons

•An Isotope,

• –Two or more forms of the same
• element that have the same number of protons and electrons but a different
• number of neutrons

• –Same atomic number, Different
• atomic mass

•Same number of protons

•Different number of neutrons

–Radioactive isotopes

• •Emit electromagnetic radiation as
• they decay to a more stable state

• •Used extensively in diagnostic
• imaging

• –Iodine-131 is use to
• treat the thyroid cancer and hyperthyroidism (over-active thyroid).

• •Ionic Bonds
• (electrovalent bond)

• –Formed
• when one atom loses an electron and another atom accepts that electron

• –Strong
• electrostatic force that binds positively and negatively charged ions together

• •Cations
• (positively charged ions)

• •Anions
• (negatively charged ions)

•Eg,

• Na+
• + Cl- à NaCl

• –There
• are a number of physiologically important ions that we will cover in subsequent
• sections

•Ca++, Na+, K+, OH-, HCO3-

•Covalent Bonds

• –Characterized
• by the sharing one or more pairs of electrons

• –The
• resultant combination is called a molecule

• –Non-polar
• covalent bond

• •When
• electrons are shared equally between atoms

• –Eg.
• Hydrogen bond H-H

• –Polar
• covalent bond

• •When the
• nucleus of one atom attracts the electrons more strongly than the other nucleus

• –Eg. Water
• (H20)

• •Results from unequal
• charge distribution on molecules

• •Weaker then ionic and
• covalent bonds

• •All the chemical
• reactions that occur in the body

•Catabolism

• –Breaks
• down complex molecules into simpler forms and release energy

•Anabolism

• –Simple
• molecules are joined into more complex one.

• •Usually lack carbon
• atoms

• •Dissociate in solution
• to form ions

• •Positively
• charged ions – cations

• •Negatively
• charged ions - anions

–Water

•The body’s most abundant compound

• –Oxygen
• and Carbon Dioxide

• •Oxygen
• is necessary for the release of energy in the body

• •Carbon
• dioxide-waste product; helps maintain the acid-base balance in the body

–Electrolytes

• •Includes
• acids, bases and salts

• –Substancethat releases hydrogen ions (H+)
• •Protondonor

• –Electrolytethat dissociate to yield hydroxide ions (OH)
• •Protonacceptor

Compoundsthat results from chemical interaction of acid and base

• •Describe compounds that
• contain C-C or C-H bonds

–Carbohydrates

–Proteins

–Lipids

• –Nucleic
• Acid and Related Molecules

•The best energy source for the human body

• •Composed of carbon, hydrogen, and
• oxygen in a ratio 1:2:1

•Monosaccharide's

• –Simple sugars with short carbon
• chain

–E.g. glucose or fructose

•Disaccharides and polysaccharides

–E.g. Glycogen

• •Most abundant organic
• compounds

• •Consist of carbon,
• hydrogen, oxygen and nitrogen

•Composed of amino acids

• –Essential
• amino acids

• •Cannot
• be produced by human body

• –Nonessential
• amino acids

• •Produced
• from molecules available in the human body

• –Primary-refers
• to the number, kind and sequence of amino acids that form a polypeptide chain

• –Secondary-polypeptide
• chain that is twisted and folded; structure stabilized by hydrogen bonds

• –Tertiary-
• three dimensional shape of polypeptide chain

• –Quaternary-
• cluster of more than one polypeptide chain

• –Provide a structural framework
• •Eg. Collagen, Keratin

–Enzymes

•Class of functional proteins

• •Serve as catalysts for
• biochemical reactions

• –Facilitate reactions, but are not
• changed by the reaction

• –Act to speed up the rate at which
• metabolic reactions occur.

•Water insoluble organic molecules

•Composed of carbon, hydrogen and oxygen

•Often contain nitrogen and phosphorus

•Functional Roles:

–Energy

• •Fats can be broken down for
• energy

–Structure

•Integral part of cell membranes

–Protection and insulation

–Vitamins

• •Vitamin A- necessary for night
• vision

• •Vitamin D- increases calcium
• uptake

• •Vitamin K- required for the
• synthesis of blood clothing proteins

–Most abundant lipids

• –Composed of three molecules of
• the six-carbon fatty acid attached to a glycerol molecule.

• –Vary in the number of hydrogen
• atoms

–Saturated fatty acids

• •All available bonds of its
• hydrocarbon chain are filled

–Unsaturated fatty acids

• –Important
• components of cell membranes

• –Phosphate
• containing region

•Polar

• •Hydrophilic
• (attracted to water)

• –Fatty
• acid chains

•Non-polar

• •Hydrophobic
• (repels water)

•Composed of four rings of carbon atoms

•Cholesterol

• –Important component of membrane
• that surround every cell in the body

• –High levels in body increase risk
• of heart disease

• •Other molecules are synthesized from
• cholesterol

•Reproductive hormones

• –Estrogen, progesterone and
• testosterone

• •Bile salts: increase fat
• absorption

• •Deoxyribonucleic Acid
• (DNA)

• –Exists
• in the nucleus

• –Double
• stranded molecule

• –Has four
• bases

• •Adenosine
• (A)

• •Thymine
• (T)

• •Guanine
• (G)

• •Cytosine
• (C)

• –Contains
• the hereditary information of the cell

•Ribonucleic Acid (RNA)

–Messenger molecule

• –Usually a single stranded
• molecules

• •There is no thymine in RNA,
• instead of thymine uracil is used

–Formed within the nucleus

• –Makes a perfect impression of DNA
• (transcription), leaves the nucleus (through the nuclear pores) and serves as a
• template for protein synthesis (translation).

• –Synthesis
• of mRNA (messenger RNA)

• –Double
• strands of a DNA segment separate and RNA nucleotides pair with DNA nucleotides

• –Pairing
• ensures accurate genetic coding

• –mRNA
• contains information required to determine the sequence of amino acids in a
• protein structure

• –Synthesis
• of protein at the ribosome in response to the genetic code (codons) of
• mRNA

• –Requires
• tRNA and ribosomal RNA (rRNA)

• •Produced
• in the nucleus

• –Ribosomes align codons of mRNA
• with the anticodons of tRNA and the
• join amino acids

• –As amino
• acids are jointed together a chain is formed.

• –Composed
• of adenine (a nitrogen containing molecule) bonded to a ribose sugar with three
• phosphate attached

• –High
• energy bonds are present between phosphate groups

• –Used to
• do the body’s work during catabolic reactions

• –Used as
• co-enzymes

• –Transfer
• energy containing molecules from one pathway to the other

–Intracellular signaling molecule