Chemical Basis of Life
Ionic Bonding
http://www.es.ucsc.edu/~es10/classnotes/lectures/ionic.bond.jpg
Covalent Bonding
http://www.gcsescience.com/Methane-Molecule.gif
http://media-2.web.britannica.com/eb-media/04/96904-004-C880B85D.gif
Hydrogen Bonding
http://upload.wikimedia.org/wikipedia/commons/f/f9/3D_model_hydrogen_bonds_in_water.jpg
http://schools-wikipedia.org/images/646/64609.png
Properties of Water
1. Strong Polarity:
• Polar water molecules attract other polar compounds
causing them to dissociate
– Water is a great solvent
• Many molecules can dissolve in cells (mostly water)
– Allows for chemical reactions and transportation
Properties of Water
2. High Specific Heat
•
Hydrogen bonds absorb heat when broken and release
heat when formed
–
–
This minimizes temperature changes in the body
Body temp remain relatively constant
3. High Heat of Vaporization
•
•
Energy needed to break H+ bonds
Body can dissipate excess heat & maintain a normal
body temperature by evaporation
Properties of Water
4. Cohesion
•
Water molecules provide lubrication or cushioning
to protect against damage from friction or trauma
Electrolytes
Substances that dissociate (break up) in
solution to form charged particles or
ions.
– Examples: Acids, bases, salts
– Cations: positive charged ions
– Anions: negative charged ions
Acids & Bases
Acid – any substance that releases H+
when in solution
– “proton donor”
– Ex: HCl (stomach acid)
Base – any substance that increases the
OH- concentration when dissociated in
solution
– “proton acceptor”
– “Ex: NaOH
pH Scale
Represents the H+ ion concentration in a
solution
7 = neutral
0-6 = acidic
8-14 = basic/alkaline
Buffers
Any molecule that moderates changes in
pH.
– Key role in the body’s ability to maintain a
normal pH (homeostasis)
Many buffers are anions that have a
strong affinity for H+
– bicarbonate ion (HCO3-) is an important
buffer in the human body
Carbohydrates
Building Block – Monosacchride
Disaccharides – 2 monosacchrides
covalently bonded
Polysaccharides – complex carbohydrates
Carbohydrates
• Structure:
– Contains the elements C, H, O
• H and O always in 2:1 ratio
– Monosaccharides form short carbon chain
• Ex: Glucose (C6H12O6)
• Function:
– Provide energy for cellular activities
– Structural support in DNA (deoxyribose)
and RNA (ribose)
Lipids
Includes: fats, phospholipids, steroids and
prostaglandins
–
Water insoluble
1. Fats/Triglycerides:
–
–
Structure: glycerol & 3 fatty acid tails
Function: concentrated energy source
http://www.future-of-technology.com/web_images/triglyceride.jpg
Lipids cont….
2. Phospholipids
–
Structure: glycerol, 2 fatty acid tails & a
phosphate group
•
•
–
Head: water soluble (“hydrophilic”)
Tails: fat soluble (“hydrophobic”)
Function: main component of cell
membrane
http://www.fz-juelich.de/isb/isb-1/datapool/page/28/Figure1-500.jpg
Lipids cont….
3. Steroids
–
–
Cholesterol: Provides stabilization
function in cell membrane
Other examples: estrogen & testosterone
4. Prostaglandins
Proteins
• Wide range of functions:
–
–
–
–
–
Defense system (antibodies)
Serve as receptors or binding sites
Structural (skin, tendons, nails)
Catalyze chemical reactions (enzymes)
Communication (insulin – protein hormone)
Amino Acids
Building blocks of proteins
– 20 amino acids
– 8 are essential (must be obtained through
diet)
– Structure:
• Amine group
• Carboxyl group
• Side chain (determines
unique properties of
amino acid)
http://www.aloeveraibs.com/wp-content/uploads/2008/08/aminoacidstruc.jpg
Enzymes
• Largest group of proteins in the body.
• Chemical catalyst
– Assist in chemical reactions but are not
products nor reactants
– Not changed by the reaction
– Usually end in -ase
Nucleic Acids
• Form genes and take
part in protein synthesis
• Building block –
nucleotide
– Phosphate
– Nitrogen Base (Adenine,
Guanine, Cytosine,
Thymine)
– 5-carbon sugar
(deoxyribose in DNA)
• Ex: DNA, RNA
http://bbruner.org/bitn/bitn_fig/dna.gif
Metabolism
All the chemical reactions that take place in
our body’s cells.
– Catabolism: Chemical reaction that breaks
down large molecules into smaller units. This
type of reaction releases energy. Also called a
hydrolysis reaction because a water molecule
is added for the reaction to occur.
– Anabolism: Chemical reaction that combines
smaller molecules to form larger molecules.
This type of reaction requires energy, usually
ATP. Also called a dehydration synthesis
reaction because a water molecule is removed
during the reaction.
– Fig 2-25, p. 61