Download ELEMENTS An element is a substance which cannot be broken

ELEMENTS
An element is a substance which cannot be broken down into simpler substances by
any known chemical reactions.
Elements of the Earth’s Crust
% Composition (by mass)
Oxygen
50 %
Silicon
25 %
Aluminum
8%
Iron
5%
Calcium
3%
Sodium
3%
Potassium
2%
Magnesium
2%
98 %
Remaining 82
2%
Total
100 %
Elements of Living Systems
% Composition (by mass)
Oxygen
65 %
Carbon
18 %
Hydrogen
8%
Nitrogen
5%
Calcium
2%
Phosphorus
3%
99 %
Approx. 20
1%
Total
100 %
H2O content
Tooth Pulp Gray Matter Heart Small Intestine E. coli White Matter Liver Bone Teeth Hair -
Water
Protein
Lipid
Carbohydrate
NA + ash
e. coli
70
15
2
2
11
sea urchin
78.3
15.2
4.8
1.4
0.3
89%
84%
78%
71%
70%
70%
70-85%
44%
9%
4%
rat liver
73.4
16
5
3
2.6
Mammalian cell
70
18
5
2
5
human
66
16
12.4
0.6
5.0
1. Cells and organisms differ in elemental composition from their environment. This is the
result of anabolic and catabolic metabolism AND the presence of a barrier.
2. Cells of all types (whether prokaryotic or eukaryotic) have a similar composition
insofar as their elemental composition, H2O content, and organic molecular content is
concerned.
3. Cells and organisms generally have a 70% water content.
4. Organic molecules fall into four general classes and constitute approx. 25% of the w/wt
of a cell.
5. The protein content of cells is relatively constant and is approximately 15-16%.
Lipids - glycerol + fatty acids - triglycerides
Carbohydrates - polymers of sugars (monosaccharides) - starch & glycogen
Nucleic Acids - polymers of nucleotides which in themselves include some carbohydrates
Proteins - polymers of amino acids
CARBOHYDRATES
BIOLOGICAL ROLES:
1. Energy transductive compounds - participate in glycolysis, respiration, photosynthesis
2. Storage of energy (polysaccharides - starch & glycogen - polymers of hexoses)
3. Structural (cellulose and chitin - polymers of hexoses)
4. Building blocks of nucleotides (pentose sugars ribose and deoxyribose)
5. Membrane components (glycoaminoglycans - particularly in the cell membrane)
COMPOSITION
SIZE
C,
H2, O,
MW ~150-106 daltons
LIPIDS
BIOLOGICAL ROLES
1. Structural - membranes - phospholipids & glycolipids
2. Source of energy and energy reserve - fatty acids and triglycerides
3. Vitamins - vitamin D
4. Hormones - chemical messengers
5. Insulators - thermal, mechanical, and electrical
COMPOSITION
C,
H,
(O), P
SIZE
MW ~150-750 daltons
NUCLEIC ACIDS
BIOLOGICAL ROLES:
1. Information storage - DNA & RNA
2. Gene expression - transcription and translation (protein synthesis)
3. Energy transfer and activation of proteins (role of nucleotide triphosphates)
4. Second messengers - activation of biochemical systems (cAMP)
5. Coenzymes
6. Catalysts - ribozyme
COMPOSITION
C,
H,
O,
N,
P
6
SIZE
MW ~500->>>10 daltons
PROTEINS
BIOLOGICAL ROLES:
1. Enzymatic - catalysis
2. Structural - collagen, keratin, etc.
3. Motility - actin, myosin, tubulin, etc.
4. Transport - solute, osmotic, electron
5. Hormones - insulin, growth hormone, etc. - peptides
6. Nutrient storage - casein, ferritin, etc.
7. Signal transduction & gene regulation
8. Immune response - antibodies
COMPOSITION
C,
H,
O,
N,
S
SIZE - MW ~100->106 daltons
1. Of the 30% dry weight of a cell, approximately 25% is represented by macromolecules and
less than 5% represents building blocks such as monosaccharides, amino acids, fatty
acids, and nucleotides.
2. CHONPS are represented in both building blocks and in lipids, carbohydrates, nucleic acids
and proteins.
3. Proteins have structure at different levels of organization. Structure that is stabilized by
covalent peptide bonds at the primary level, hydrogen bonds at the secondary level,
hydrophobic/hydrophilic bonds, etc. at the tertiary level, and similar interactions
between primary structures at the quaternary level.
4. The specificity of antibody proteins makes them ideal molecular probes.