Cell Biology/Introduction/The elements of life

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The various elements that make up the cell are:

  • 59% Hydrogen (H)
  • 24% Oxygen (O)
  • 11% Carbon (C)
  • 4% Nitrogen (N)
  • 2% Others - Phosphorus (P), Sulphur (S), etc.

The difference between these elements is their respective atomic weights, electrons, and in general their chemical properties. A given element can only have so many other atoms attached. For instance carbon (C) has 4 electrons in its outer shell and thus can only bind to 4 atoms; Hydrogen only has 1 electron and thus can only bind to one other atom. An example would be Methane which is CH4. Oxygen only has 2 free electrons, and will sometimes form a double bond with a single atom, which is an 'ester' in organic chemistry (and is typically scented).


Methane Water Methanol (Methyl Alcohol)
  H
  |
H-C-H
  |
  H
H   H
 \ /
  O
  H
  |
H-C-O-H
  |
  H

As for the organic molecules that make up a typical cell:

  • 50% protein
  • 15% nucleic acid
  • 15% carbohydrates
  • 10% lipids
  • 10% Other

Here is a list of Elements, symbols, weights and biological roles.

Element Symbol Atomic Weight Biological Role
Bromine Br 79.9 Defense and pigmentation in certain marine organisms, esp. algae.
Calcium Ca 40.1 Bone; muscle contraction, second messenger
Carbon C 12.0 Constituent (backbone) of organic molecules
Chlorine Cl 35.5 Digestion and photosynthesis
Chromium Cr 52.0 Metabolism of sugars and lipids in humans.
Copper Cu 63.5 Part of Oxygen—carrying pigment of mollusk blood.
Fluorine F 19.0 For normal tooth enamel development
Hydrogen H 1.0 Part of water and all organic molecules
Iodine I 126.9 Part of thyroxine (a hormone)
Iron Fe 55.8 Hemoglobin, oxygen caring pigment of many animals
Magnesium Mg 24.3 Part of chlorophyll, the photosynthetic pigment; essential to some enzymes.
Manganese Mn 54.9 Essential to some enzyme actions.
Nitrogen N 14.0 Constituent of all proteins and nucleic acids.
Oxygen O 16.0 Respiration; part of water; and in nearly all organic molecules.
Phosphorus P 31.0 Constituent of DNA and RNA backbones; high energy bond in ATP.
Potassium K 39.1 Generation of nerve impulses.
Selenium Se 79.0 For the working of many enzymes.
Silicon Si 28.1 Diatom shells; grass leaves.
Sodium Na 23.0 Part of Salt; nerve conduction
Sulfur S 32.1 Constituent of most proteins. Important in protein structure: Sulfide bonds are strong.
Zinc Zn 65.4 Essential to alcohol oxidizing enzyme.