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Life: Levels of Organization
•Atoms
•Molecules
•Macromolecules
•Organelles
•Cells
•Tissues
•Organs
•Organ systems
•Organism
THE ELEMENTS OF LIFE
•
ABOUT 20–25% OF THE 92 NATURAL ELEMENTS ON EARTH ARE ESSENTIAL TO
LIFE = ESSENTIAL ELEMENTS
•
•
•
•
NEEDED TO LIVE A HEALTHY LIFE AND REPRODUCE
OF THE TOTAL AMOUNT OF NATURAL ELEMENTS ON EARTH - CARBON,
HYDROGEN, OXYGEN, AND NITROGEN MAKE UP 96%
MOST OF THE REMAINING 4% CONSISTS OF CALCIUM, PHOSPHORUS,
POTASSIUM, AND SULFUR
TRACE ELEMENTS ARE THOSE REQUIRED BY AN ORGANISM IN MINUTE
QUANTITIES
Organizational Levels
Atom = smallest unit of an element that still retains the chemical &
physical properties of that element
i.e. really, really, really tiny thing!
-composed of:
protons = one positive charge, 1 atomic mass unit (1.673x10-24g)
electrons = one negative charge, no mass (9.109x10-28g)
neutrons = no charge, 1 atomic mass unit
each atom is
comprised of a
nucleus of protons
and neutrons +
orbiting electrons
PERIODIC TABLE OF ELEMENTS
-elements are grouped on a Periodic Table of Elements
-the elements are grouped according to physical and chemical characteristics
-on the chart each element is associated with a letter, an atomic number & an
atomic mass
IA
IIA
http://oxford-labs.com/xray-fluorescence/theperiodic-table/
IIIA IVA VA VIA VIIA VIII
atomic
symbol
atomic
mass (weight)
7
3
Li
e.g. # protons (e-) = 3
# pr+3 + #No 4 = 7
atomic
number
39
19
K
e.g. # protons (e-) = 19
# pr+19 + #No 20 = 39
Atomic mass = number of protons + neutrons
Atomic number = number of protons when the element is electrically
neutral
** when neutral, the number of protons and electrons are equal
Molecule
• particle formed by the union of more than one atom
e.g. same kind of atom - O2
e.g. different types of atoms - H20, C6 H12 O6
•
•
atoms interact with one another through chemical bonds
2 kinds of chemical bonds:
• 1. covalent – sharing of electrons between two atoms
• 2. ionic bonds – interaction between a +ve and a –ve ion
-chemical bonds form through interactions between electrons
Molecule
• the true definition of a molecule: a molecule consists of two or
more atoms held together by covalent bonds
• a single covalent bond – or single bond – is the sharing of ONE pair
of electrons
• denoted with the structural formula H-H
• a double covalent bond – or double bond – is the sharing of TWO
pairs of electrons
• denoted as O=O or C=C
ORGANIC MOLECULES
1. carbohydrates
2. lipids
3. proteins
4. nucleic acids
• MUST contain carbon, oxygen and hydrogen
1. Carbohydrates:
• provide energy to cells
•
can be stored as reserve energy supply (humans = glycogen)
• supply “building materials” to build certain cell structures
•
e.g. cell wall of plants
• water soluble = hydrophilic
• characterized H - C - OH (ratio C:H 1:2)
•
e.g. glucose C6H12O6
sucrose C12H22O12
classified by size: simple sugars – saccharides
complex – polysaccharides
monosaccharides
disaccharides
A. Simple carbohydrates
• monosaccharides = known as simple sugars
• single saccharide subunit in which the # of carbon atoms is low - from 3 to
7
• e.g. 5 carbon sugar = pentose
• e.g. 6 carbon sugar = hexose
- formula: C:2H:O
• monosaccharides found in humans: glucose
galactose
fructose
Monosaccharides:
- in aqueous solutions – the monosaccharides are not linear
-they form rings
-three ways to represent the ring structure of a monosaccharide
3. Simplest form
1. Molecular
ring form
2. Abbreviated ring structure
A. Simple carbohydrates
• disaccharide = two 6-carbon monosaccharides joined through a
covalent bond (glycosidic linkage)
-forms by a dehydration synthesis reaction
-broken up by a hydrolysis reaction
e.g. glucose + glucose = maltose
e.g. glucose + fructose = sucrose
e.g. glucose + galactose = lactose
B. Complex carbohydrates:
• known as polysaccharides
• built of repeating saccharide subunits
• polymer: large molecule built of multiple, repeating monomers or “building
blocks”
• the monomer of the polysaccharide is usually glucose,
• can also include galactose or fructose
• some serve as storage materials – hydrolyzed into individual
monosaccharides – e.g. starch
• others serve as structural or building materials – e.g. cellulose
Chloroplast Starch granules
Amylopectin
Amylose
(a) Starch:
1 m
a plant polysaccharide
Mitochondria Glycogen granules
Glycogen
(b) Glycogen:
0.5 m
an animal polysaccharide
LIPIDS
• MANY TYPES
• 1. TRIGLYCERIDES = FATS AND OILS
• 2. PHOSPHOLIPIDS
• 3. STEROIDS
• CHOLESTEROL – ANIMAL CELL MEMBRANES, BASIS FOR STEROID
HORMONES
• BILE SALTS - DIGESTION
• VITAMIN D – CALCIUM REGULATION
• ADRENOCORTICOSTEROID HORMONES
• SEX HORMONES
A. Triglycerides (Fats)
• longest lasting, most plentiful energy supply of the human body
• “building blocks” = 3 fatty acid chains (hydrocarbons usually from 16 to 24
carbons) PLUS 1 glycerol molecule
• the 3 fatty acids are linked onto the glycerol backbone by dehydration
synthesis reactions
• fatty acids -differ in chain length with each fat
-also differ in the location and number of double bonds
within the hydrocarbon chains
1. single C bonds - saturated
2. double C bonds - unsaturated
monounsaturated:
1 double bond
polyunsaturated:
2 or more double bonds
• Saturated fatty acids
have the maximum
number of hydrogen
atoms possible and no
double bonds
• Unsaturated fatty acids
have one or more double
bonds
B. Phospholipids
• similar to fat molecules - glycerol + 2 fatty acids
• modified through the replacement of one fatty acid with a phosphate group (slight
negative electrical charge)
• phosphate gp  hydrophilic “head”
• fatty acid gps  hydrophobic “tails”
• when added to water – self-assemble and form a form a phospholipid bilayer –
major component of the plasma membrane
C. Steroids
• backbone is called cholesterol = 4 fused carbon rings
• synthesized in the liver
• diversity through attached functional groups
e.g. testosterone, estrogen, aldosterone, cortisol
3. Proteins
• nearly every dynamic function of a living organism depends on
proteins
•Greek – proteios = “first place”
•more than 50% of the dry mass of most cells
•numerous roles:
• structural – support of cells and tissues
• storage - energy source
• transport across cell membranes
• hormones and their receptors – signaling
• chemical messengers - signaling
• antibodies - defense
• metabolic role - enzymes
3. Proteins
•building blocks = amino acids
Side chain (R group)
 carbon
Amino
group
amino acid:
1. carbon atom called an alpha carbon
2. amino group at 1 end of the alphacarbon
3. carboxyl at the other end
4. a hydrogen attached to the alpha carbon
5. an R group attached to the alpha carbon
Carboxyl
group
• the R group give the amino acid a unique physical and chemical character
• 22 amino acids available for human protein synthesis
– 20 of them are coded for by our DNA
• amino acids joined together by a dehydration synthesis reaction
forming a peptide bond = between the NH2 of 1 a.a. and the COOH
of the next amino acid
2 a.a.  dipeptide
3 a.a.  tripeptide
4 or more a.a.  polypeptide
• the three dimensional
shape of the polypeptide is
CRITICAL to its function
• the 3D polypeptide is the
protein
4. Nucleic acids
• known as DNA, RNA
• C,H,O,N,P
• building blocks = nucleotides
• nucleotide:
 5 carbon sugar (pentose)
phosphate group (negative
charge) located at the 5’ carbon
organic base located at the 1’
carbon
bases: 5 types: adenine (A)
cytosine (C)
guanine (G)
thymine (T)
uracil (U)
 There are two families of
nitrogenous bases
Nitrogenous bases
Pyrimidines
1. Pyrimidines (cytosine,
thymine, and uracil) have a
single six-membered ring
Cytosine
(C)
Thymine
(T, in DNA)
Uracil
(U, in RNA)
2. Purines (adenine and
guanine) have a sixmembered ring fused to a
five-membered ring
Sugars
Purines
Adenine (A)
Guanine (G)
(c) Nucleoside components
Deoxyribose
(in DNA)
Ribose
(in RNA)
Sugar-phosphate backbone
5 end
5C
3C
• a nucleic acid is a polynucleotide
chain
• formed by dehydration synthesis
•creates a phosphodiester bond
between the phosphate group of 1
nucleotide and the sugar of the next
one
5C
3C
3 end
(a) Polynucleotide, or nucleic acid
phosphodiester
bond
• two major types of nucleic acids:
1. RNA
2. DNA
A. DNA




double chain = double helix
bases: A, C, G and T
2 chains held by hydrogen bonds between the bases
bases pair up in a complementary fashion
A=T
C G
B. RNA
 single chain
 bases: A, C, G and uracil
(U) in place of T
 3 major types: mRNA
tRNA
rRNA
HOCH2
O
OH
H
H
OH
OH
ribose
HOCH2 O
OH
H
H
OH
H
deoxyribose
c. ATP
individual nucleotides can have metabolic functions
ATP is the major source of potential energy for cells
ATP = adenosine triphosphate (adenosine = adenine + ribose sugar)