Occupational Therapy Chemical Composition of the Human Body

1. Occupational Therapy
Chemical composition of the Human Body

4. Atoms of elements link together to form molecules
- Atoms are the basic building blocks of ordinary matter.
Atoms can join together to form molecules, which in
turn form most of the objects around you. Atoms are
composed of particles called protons, electrons and
neutrons.
Molecules form cells.
- A molecule is the smallest particle in a chemical
element or compound that has the chemical properties
of that element or compound. Molecules are made up
of atoms that are held together by chemical bonds.
These bonds form as a result of the sharing or
exchange of electrons among atoms.

5. Cell is smallest unit capable of carrying out all life
processes.
- Is a collection of molecules separated from the external
environment by a physical barrier= plasma membrane
- Simple organisms have 1 cell but complex organisms
have many cells with different structural and
functional specializations

6. Tissues
- Collections of cells that carry out related functions
- 4 tissue types-Epithelial, Connective, Muscle and
Nervous

7. Organs
- Composed of different types of tissues arranged in
various proportions and patterns to perform a certain
function
- Anatomical structure supports function

8. Organ systems
- Groups of organs with integrated functions

9. Organism
- Body as a whole

10. Elements
- A simple substance that cannot be decomposed by
ordinary chemical means. It is the basic “stuff” which
all matter is composed.
- There are at least 105 elements known.
- There are 24 essential elements found in human body

15. Atoms
- Elements are composed of atoms
- Atom is the smallest particle of an element that has all
properties of the element.
Atom consists of 3 types of particles:
- Protons (p+)- has positive charge neutrons (n)
- Neutral charge electrons (e-)- has negative charge
- Atoms contain equal numbers of protons and electrons
hence have an overall charge of zero

16. Structure of an Atom
Nucleus = center of atom
- contains the protons and neutrons, is dense- contains
most of the mass of the atom
Space around the nucleus contains electrons
- Electrons are rapidly moving, lightweight, move in
orbits
- Are held in orbit by electrical attraction to nucleus due
to positively charged protons
Remember
- Like charges repel and opposite charges attract

17. Structure of an Atom

18. Atomic Number
- Atomic Number = the amount of protons in the nucleus
of an atom (= amount of electrons)
- The atomic number determines which element the atom
is.
- Periodic Table of Elements lists over 100 different
elements
- Each element has a name and a symbol and an atomic
number

19. Atomic Number
- Oxygen (O) 8
- Hydrogen (H) 1
- Carbon(C) 6
- Nitrogen (N) 7
- Phosphorus (P) 15
- Sodium (Na) 11
- Potassium (K) 19
- Calcium (Ca) 20
- Magnesium (Mg) 12
- Sulfur (S) 16
- Chlorine (Cl) 17

20. Minor Essential Elements (Trace Elements)
- Iron (Fe) 26
- Iodine (I) 53
- Copper (Cu) 29
- Zinc (Zn) 30
- Manganese (Mn) 25
- Cobalt (Co) 27
- Chromium (Cr) 24
- Selenium (Se) 34
- Molybdenum (Mo) 42
- Flourine (F) 9
- Tin (Sn) 50
- Silicon (Si) 14
- Vanadium (V) 23

21. Mass Number
- Proton has a mass of 1 dalton(Da) = 1 Atomic Mass
Unit (amu)
- Neutron has a mass of 1 Da = 1 amu
- Electron has zero mass (negligible)
- Mass Number = sum of protons + neutrons in an atom
- Mass Number – Atomic Number = number of neutrons
in the atom

22. Isotopes
- An element will always have the same number of
protons but they have varying numbers of neutrons
- Isotopes = atoms of an element that have different
numbers of neutrons
- All Isotopes of an element have the same chemical
properties because the chemical properties are
determined by the electron configuration not the
number of neutrons

23. Atomic mass
- Atomic mass (weight) is derived from taking the
average weight of all of the isotopes for a particular
atom
Atomic number = 12
Symbol = Mg
Name = Magnesium
Atomic weight = 24.30

24. Moles
The weight of 1 mole (6.02 x 1023) atoms equals the
atomic mass in grams.
602,000,000,000,000,000,000,000 atoms = ? Grams
= Avogadro’s Number
This information is used to calculate the concentration of
atoms or molecules in a solution in Molarity (= moles per
liter). This measure tells us how many molecules there are
in a given volume of solution.

26. Chemical properties
- The chemical properties of an atom are determined by
its electron configuration
- How its electrons are arranged around the nucleus

27. Behavior of Electrons
- Electrons move around nucleus at different levels.
Their orbits are termed electron shells (or energy
levels).
- Each shell contains a fixed maximal number of
electrons (2n2) where n = the level of the shell.
However, the maximal number in the outer shell is
always 8 (except the first shell which has 2). E.g. 2) 8)
18) 32) 8)
- For the main elements, the number of electrons in the
outer shell determines the chemical property of the
atom.

28. Behavior of Electrons
- Electrons move around nucleus at different levels.
Their orbits are termed electron shells (or energy
levels).
- Each shell contains a fixed maximal number of
electrons (2n2) where n = the level of the shell.
However, the maximal number in the outer shell is
always 8 (except the first shell which has 2). E.g. 2) 8)
18) 32) 8)
- For the main elements, the number of electrons in the
outer shell determines the chemical property of the
atom.

29. Behavior of Electrons
Each level can hold 2n2 electrons (where n = the level of
the shell (1,2,3 etc.)
The outermost level can only hold a maximum of 8
electrons

30. Behavior of Electrons
- Atoms with incompletely filled outer shell (<8
electrons) tend to combine with other atoms in a
chemical reaction.
- Atoms can donate, accept, or share electrons to stabilize
their outer energy levels.
- E.g. Calcium has 20 protons and electrons 2) 8) 8) 2)
so calcium has 2 electrons in its outer shell.
- It is these 2 electrons that will participate in chemical
reactions.

31. Behavior of Electrons
- Shells fill with electrons in sequence from inner to
outer shell. It is the arrangement of electrons in the
outer shell of an atom that determines its ability to bind
with other atoms.
- Periodic Table- all elements in a ‘Group’ will have the
same number of electrons in their outer shell, and
hence, will behave similarly in a chemical reaction

33. Molecules
- When atoms combine with other atoms, or break apart
from other atoms, the process is called a chemical
reaction.
- When two or more atoms combine in a chemical
reaction, the resulting combination is called a
molecule. E.g. O2, H2
- A molecule that contains two or more different kinds of
atoms is called a compound. E.g. CO2, H2CO3

35. Molecular Bonds
4 Main Types
1. Covalent Bonds- strong
2. Ionic Bonds- strong
3. Hydrogen Bonds- weak
4. Van der Waals forces- weak

36. Covalent Bonds
- Covalent Bonds- form when 2 atoms share a pair of
electrons- 1 from each atom.
- Most molecules are formed via covalent bonds.
- Energy is required to break the bonds apart.
- An atom is most stable when all its electrons are paired
so it will share its unpaired electrons with another atom
that has unpaired electrons

38. Covalent Bonds
- You can predict the number of covalent bonds an atom
will form by counting the number of unpaired electrons
in the outer shell.
- E.g; Carbon -Atomic Number 6 Outer shell has 4
electrons so will form 4 covalent bonds
- Double Bond = adjacent atoms share 2 pairs of
electrons rather than just 1 e.g; C : : C

39. Covalent Bonds

40. Covalent Bonds

41. Polar and Non-Polar Molecules
- Electron pairs in covalent molecules are not always
evenly shared between the linked atoms.
- The atom with the stronger attraction for the electrons
will gain a slight negative charge and the atom with the
lesser pull will gain a slight positive charge
- Overall charge on the molecule is neutral

42. Water Polar Molecule

43. Polar Molecules
- Polar Molecules- have positive and negative poles.
- O and N in particular have strong attraction for
electrons and often are found in polar molecules
- Polar Molecules will dissolve in water = Hydrophilic-
water loving e.g.; sugar

45. Non-Polar molecules
- Non-polar molecule= shared electrons are distributed
evenly so there are no regions of partial positive or
negative charge
- Molecules composed mostly of C and H tend to be non-
polar as C doesn’t tend to attract electrons as strongly
as O does
- Non-polar molecules do not dissolve well in water=
hydrophobic= water hating eg; oils

46. Non-Polar molecules

47. Polar vs Non-Polar molecules

50. Ionic Bonds
Form when an atom has such a strong attraction for
electrons that it completely pulls one or more electrons
away from another atom so one atom gains electrons and
the other atom loses electrons

51. Ionic Bonds

52. Ionic Bonds

54. Ions are non-covalent
- Bonds are formed by sharing electrons, but the atoms
are easily separated and become cations or anions.
- Cations (+): ions that are positively charged (donated
electrons).
- Anions (-): ions that are negatively charged (accepted
electrons).

55. Hydrogen Bonds
- A weak attractive force between a hydrogen atom and a
nearby Oxygen, Nitrogen or Fluorine atom.
- Can occur between neighboring atoms or molecules or
between portions of the same molecule
- E.g.; water molecules are attracted to each other and
line up in an ordered fashion creating surface tension.
- Important for protein folding and shape of DNA

56. Hydrogen bonds between water molecules

57. Hydrogen Bonds in DNA double helix

58. Van der Waals Forces
- Weak non-specific attractions of nucleus of any atom
and the electrons of nearby atoms.
- These forces allow atoms to pack closely together and
take up minimum space.
- A single Van der Waals attraction is very weak but
multiple ones supplement Hydrogen bonds that hold
proteins in their 3-D shapes

59. Molecular Structure

60. Molecular Shape
- Molecular shape is closely related to its function
- Molecular bonds play a critical role in determining
molecular shape
- Molecular formula doesn’t tell you anything about
shape just tells you the number and type of atoms NOT
what is joined to what
- Covalent bonds between atoms will form at various
angles giving a molecule its characteristic shape

61. Molecular Shape
- Weak bonds also help shape molecules e.g.; protein
folding, DNA double helix