Human Physiology Chemistry

1. Human Physiology
Chemistry

3. • Atoms of elements link together to form
molecules
• Molecules form cells.
• 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 specialisations

4. • Tissues
– collections of cells that carry out related functions
– 4 tissue types-Epithelial, Connective, Muscle and Nervous
(see chapter 3 in text)
• Organs
– composed of different types of tissues arranged in various
proportions and patterns to perform a certain function
– Anatomical structure supports function
• Organ systems
– groups of organs with integrated functions
• Organism
– body as a whole

5. • 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
– 3 make up over 90% of the body mass-Oxygen (O), Carbon
(C), Hydrogen (H), Nitrogen (N)
– Major essential elements (4): H (63%), O (26%), C (9%), N (1%)
Ca, P, K, S, Na, Cl, Mg
– Minor essential elements (13): Fe, I, Cu, Zn, Mn, Co, Cr, Se,
Mo, F, Sn, Si, & V.
Elements

6. • 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
Atoms

7. • Nucleus = centre 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
Structure of Atom

8. 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
Atomic Number

9. • 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
Chemical Symbols ( ) and Atomic Numbers

10. 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
Minor Essential Elements (Trace Elements)
Chemical Symbols ( ) and Atomic Numbers

11. • 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
Mass Number

12. • 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
Isotopes

13. • Atomic mass (weight) is derived from taking the
average weight of all of the isotopes for a
particular atom
Atomic mass (weight)

14. • The weight of 1 mole (6.02  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
litre). This measure tells us how many molecules there are in
a given volume of solution. You will not have to do this
calculation but you will have to understand the concept.
Moles

15. The chemical properties of an atom
• The chemical properties of an atom are
determined by its electron configuration
• ie; how its electrons are arranged around the
nucleus

16. The Behaviour 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.

17. The Behaviour 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 stabilise
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.

18. The Behaviour 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

20. • 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
Molecules

21. 4 Main Types-
1. Covalent Bonds- strong
2. Ionic Bonds- strong
3. Hydrogen Bonds- weak
4. Van der Waals forces- weak
Molecular Bonds- link atoms together

22. 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

23. 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

24. Covalent Bonds

25. 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

26. Polar Molecules
• Polar Molecules- have +ve and –ve 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

27. 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 e.g.; oils

29. • 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
2. Ionic Bonds

30. 2. Ionic Bonds

31. 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).

32. 3. Hydrogen Bonds
• A weak attractive force between a hydrogen atom
and a nearby Oxygen, Nitrogen or Fluorine atom.
• Can occur between neighbouring 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.
• Impt for protein folding and shape of DNA

33. Hydrogen Bonds in DNA double helix

34. 4. 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

35. 4. Van der Waals Forces

36. • 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
Molecular Shape
• You can draw out a molecule so it shows where
the covalent bonds are and get an idea of
molecular shape e.g.; is it a ring structure or a
chain

37. Molecular Shape
• Covalent bonds between atoms will form at
various angles giving a molecule its characteristic
shape
• Weak bonds also help shape molecules e.g.;
protein folding, DNA double helix