Levels of Structural Organization -Organism – made up of the organ systems -Organ system – consists of 2 or more different organs that work closely together -Organ – consists of 2 or more different types of tissues -Tissue – consists of 2 or more similar types cells -Cellular – cells are made of many different types of molecules -Organelle – machinery of the cell Macromolecular – large “super” molecules -Molecular – atoms are combined to form molecules -Atomic – atoms make up all matter

Levels of Structural Organization

Matter The “stuff” of the universe Anything that takes up space States of matter Solid has definite shape and volume Molecules have enough energy to vibrate Liquid has definite volume, changeable shape Molecules can move over around each other Gas has changeable shape and volume Molecules have enough energy to escape each other -Plasma -electrons separated from atoms

Composition of Matter The Chemical Elements Elements unique substances that cannot be broken down by ordinary chemical means Atoms -building blocks for each element -smallest part of element that still has properties of that element The Chemical Elements Organized on the Periodic table atomic symbols of elements arranged by atomic number (number of protons) Atomic number of each element number of protons in its nucleus

-Atomic Mass- - number of protons and neutrons in an atom Only 24 elements have a role in our body 98.5% of body weight consists of O, C, H, N, Ca, P

Atomic Structure (Bohr or Planetary Model) Nucleus, the center of atom which contains: protons positive charge, mass (weight) of 1 atomic mass unit (amu) determines atomic number neutrons neutral (no) charge, mass of 1 amu Electron shells that surround the nucleus and contain: Electrons -negative charge, mass of 0 amu (1/2000 of proton’s mass) valence electrons are in the outermost shell furthest from the nucleus interact with other atoms

All atoms have: an equal number of protons and electrons -therefore unreacted atoms are neutral (have no net charge) -an atomic mass = total mass of protons + neutrons -Isotope -an atom of a particular element that has a different number of neutrons -therefore a different atomic mass

Planetary Model of an Atom

Electron Shells -The electron shell closest to the nucleus can hold up to 2 electrons additional electrons are located in shells outside of the first shell -All other electron shells outside of the first shell can hold up to 8 electrons octet rule an electron shell is full when there are: 2 electrons in the first shell 8 electrons in 2nd, 3rd, 4th,… shell -an atom will undergo a reaction in order to ensure that it has a full outer shell

-If the valence shell of an atom is not completely FULL, then that atom is UNSTABLE valance electrons of unstable atoms interact with valance electrons of other unstable atoms to create chemical bonds allows both atoms to become stable - The valence shells ( and their electrons) are the parts of atoms which will encounter other atoms -Hence, reactions will occur or not as a result of the contents of the valence shell

Planetary Models of Atoms p+ represents protons, no represents neutrons

Chemical Bonds The interaction between 2 atoms may result in the formation of a chemical bond whereby 2 atoms are chemically linked to one another Atoms bond with one another to become stable an atom is stable when the valence shell is completely full (satisfying the “octet rule”) Groups of atoms that are associated with each other through bonds are called molecules i.e.chemicals that are LARGER and structurally more CoMpLeX than individual atoms

Chemically Inert (Non-reactive) Elements Inert elements have their valence shell fully occupied by electrons Incapable of bonding with other atoms

Chemically Reactive Elements Reactive elements do not have their outermost energy level fully occupied by electrons

Types of Chemical Bonds Ionic Covalent Hydrogen

Molecules Molecules two or more atoms bonded together carbon dioxide (CO2), Glucose (C6H12O6), water (H2O), sodium chloride (NaCl)… Structural formula shows arrangement of atoms in a molecule used to show how the anatomy of a molecule dictates its physiology Molecular formula itemizes each element present (and its quantity) in a molecule

- In a molecular formula, subscripts are used to show the number of atoms that are present in a molecule - a subscript immediately follows the atom it is associated with - the number 1 is never used, so subscripts start with the number 2 e.g. H2O the number 2 indicates that 2 atoms of hydrogen are present. Note that the number 1 is not used to indicate the number of Oxygens present Coefficients are used to indicate the number of molecules - coefficients are written in front of the molecular number e.g. 2H2O means that there 2 water molecules and therefore 4 hydrogens and 2 oxygens are present

Molecular and Structural Formula

Biologically Important Molecules Water most abundant molecule in the human body Monosaccharides basic (smallest) unit of carbohydrates (sugars) Amino acids basic (smallest) unit of proteins Fatty acids basic (smallest) unit of lipids (fats, oils, waxes) Nucleotides basic (smallest) unit of nucleic acids

Formation of an Ionic Bond Ionic bonds form between atoms after the transfer of one or more electrons from one atom to another atom in a process called ionization -results in the creation of 2 ions Ions atoms that have an unequal numbers of protons and electrons also known as electrolytes -therefore charged atoms

Ionization transfer of electrons from one atom to another

Anions and Cations Anion atom gained one or more electrons more electrons than protons = net negative charge Cation atom lost one or more electrons more protons than electrons = net positive charge

Anions and Cations The anion and the cation are held together by the ATTRACTION between a positively charged substance and a negatively charged substance 2 substances that have the same charge REPELL one another Atoms bound by ionic bonds form crystals (salts) NaCl (sodium chloride)

Sodium Chloride Salt Crystal Ionic bonds cannot exist in water the bond breaks (dissociates) (water pulls it apart) the components of the molecule exist in their ionic form (anion and cation) as seen in the body NaCl → Na+ and Cl-

Covalent Bonds -Formed by sharing valence electrons between 2 atoms Types of covalent bonds include: polar and nonpolar covalent bonds single covalent bond double covalent bond

Single Covalent Bond Each atom shares one electron with another atom Hence pair of shared electrons

Single Covalent Bond

Double Covalent Bond Each atom shares two electron with another atom stronger than a single covalent bond 2 pairs of electron being shared

Polar Covalent Bonds Polar bonds occur between an electronegative atom (O or N) and an atom that is neither O nor N - electronegative means that it pulls electrons towards itself the nucleus of an electronegative atom has a stronger “pull” on the shared electrons, pulling the shared electron(s) closer to it this causes the electronegative atom to become partially negative while the other atom in the covalent bond becomes partially positive similar to a battery Therefore most electrons are around the electronegative atom

Nonpolar Covalent Bonds Nonpolar bonds occur between two atoms neither of which are O or N (therefore between atoms that are not electronegative) the shared electrons are pulled equally between the nuclei of the 2 atoms both atoms remain neutral the nonpolar covalent bond is neutral

Nonpolar vs. Polar Covalent Bonds electrons shared equally electrons shared unequally

Nonpolar and Polar Covalent Molecules Polar molecules are ones that contain moderate amounts of O and/or N charged molecules Nonpolar molecules are ones that contain very little or no O and/or N uncharged (neutral) molecules

Functional Groups of Organic Molecules Small parts of larger molecules groups of covalently bonded atoms arranged in a very specific manner determine the chemical properties of molecules

Hydrogen Bonds Electrical attraction between a polar covalently bound H (has a partial positive charge) and a covalently bound electronegative atom (O/N) (has a partial negative charge) -Too weak to bind atoms together serve as intramolecular (within molecule) bonds aids in the stabilization of very large molecules observed in proteins and nucleic acids -serve as intermolecular (between molecules) bonds holds 2 or more molecules in close proximity to one another observed in between water molecules

Hydrogen Bonds in Water (intermolecular)

Water The most abundant molecule of the human body 70% of body mass (weight) is attributed to water The ONLY type of molecules that exist in the human body are molecules held together by covalent bonds Polar molecules Nonpolar molecules salts dissociate in water (therefore ionic compounds are not considered to be molecules)

Polarity and Water -All biochemical reactions that take place in the body occur in a water-based environment All substances within the body are either nonpolar (uncharged/neutral) or polar (charged) Nonpolar molecules include those containing a high number of nonpolar covalent bonds lipids (fats, oils, and waxes) Polar chemicals include every other substance: molecules containing polar covalent bonds ions (cations and anions)

Polarity and Water Polar substances mix easily with other polar substances, but do not mix with nonpolar substances (REMEMBER THIS) Nonpolar substances mix easily with other nonpolar substances, but do not mix with polar substances (REMEMBER THIS) “like dissolves like” -The majority of the chemicals found in the body are polar, however lipids are molecules essential for proper functioning of the body -the body must have ways to associate these nonpolar molecules in a polar dominated environment

Polarity (Water vs Lipids) All polar chemicals mix with water and are considered to be hydrophilic (water loving) polar chemicals that mix with water will not mix with lipids and are considered to be lipophobic (lipid fearing) All nonpolar chemicals mix with lipids and are considered to be lipophilic (lipid loving) Nonpolar chemicals that associate with lipids will not mix with water and are considered to be hydrophobic (water fearing) Polar = hydrophilic = lipophobic Non-polar = hydrophobic = lipophilic

Properties of Water Solvency ability to dissolve matter because water is the most abundant compound in the body it is the universal solvent provides an environment for all metabolic reactions provides a means for the transport of substances from one location in the body to another - most substances dissolve in water

Water as a Solvent water molecules form hydration spheres around polar substances note orientation of water molecules: negative side faces Na+, positive side faces Cl-

Properties of Water Adhesion attraction between two different substances -molecules of water “stick” to other types of molecules Cohesion attraction between one substance and itself molecules of water stick to themselves due to hydrogen bonds High heat capacity(means that it takes a long time to heat up and/or cool down) prevents rapid increases or decreases in body temperature (water takes along time to heat-up or cool down)

Acid/Base Concentration (pH) pH is the measurement on a scale ranging from 0 to 14 of H+ concentration in a solution H+ is the ionized form of a hydrogen atom the only electron has been removed, leaving a single proton H+ = hydrogen ion = proton pH = -log[H+] [H+] = molar concentration of H+ in a solution the greater the [H+] the lower the pH, the lower the [H+] the higher the pH

Acidic solutions have higher [H+] a lower pH Alkaline (basic) solutions have lower [H+] a higher pH

pH Scale Acidic: pH 0 – 6.99 Basic: pH 7.01 – 14 Neutral: pH 7.00

- called proton acceptors Acids and Bases Acids are molecules that are capable of increasing the number of H+ in a solution called proton donors decrease the pH of a solution Bases are molecules that are capable of decreasing the number of H+ in a solution are - called proton acceptors increase the pH of a solution

Buffers Substances that are capable of resisting large changes in the pH of a solution -allow pH to remain relatively constant buffers in the body allow the body pH to remain at 7.4 (slightly basic)