Molecular Biology & Urea

Molecular Biology explains living processes in terms of the chemical substances involved


Nitrogen containing compound and is a compenent of urine

Naturally produced to help and excrete excess amino acids (proteins) from the body

Artificially it is used as a nitrogen fertilizer for growing crops

Metabolism: The sum of all the chemical reactions in the cells. Most occur in the cytoplasm catalysed by enzymes

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Carbon Atoms

We are Carbon based life forms

Carbon atoms contain four electrons in their outer shell - this allows for four covalent bonds with other types of atoms to be formed (Methane is CH4)

Covalent bonds: Strongest types of bonds between atoms therefore stable molecules can be formed

From these properties of carbon,  there is an infinite number of possible molecules involving carbon 

Life is based on Carbon compounds such as:

  • Carbohydrates
  • Lipids (Fats)
  • Proteins
  • Nucleic Acids (DNA)
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Contain: Carbon Hydrogen and Oxygen

Carbohydrates: Organic compounds consisting of one or more simple sugars

Monomers are commonly ring shaped molecules (sugars that consist of single sub-unit) 

Isomers of Glucose: Compounds with the same chemical formula but different arrangement of atoms

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Disaccharides: Pairs of monomers linked together by condensation to form dissacharrides

Polysaccharides: All composed of Glucose

The basic linkage between the glucose subunits is a glycosidic bond

  • Glycosidic bonds from Carbon 1 to Carbon 4 (linear sturcture)
  • Glycosidic bonds from Carbon 1 to Carbon 6 (branced structure)

Cellulose: Found in plant walls made up of 1,4 glycosidic links (beta glucose)

Starch: Type 1 Amylose only 1,4 linkages Type 2 Amylopectin has some 1,6 linkages

Glycogen: Store glucose in liver and muscles more 1,6 glycosidic linkages than Amylopectin (alpha glucose)


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Contains Carbon Hydrogen Oxygen

Insoluble in Water but soluble in non polar organic solvents

Common Lipids are:

  • Triglycerides (fats and oils)
  • Phospholipids (plasma membrane)
  • Steriods (membrane structure)

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Contains Carbon Hydrogen Oxygen and Nitrogen

Proteins: Large organic compounds made of amino acids arranged into one or more linear chains that then fold more complex 3D structures



Uses of Proteins:

  • Hormones - Insulin                 Antibodies - Immunoglobin
  • Enzyme - Lactase                  Transport - Haemoglobin
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Nucleic Acids

Contains Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

Sub-units are called Nucleotides

Nucleotides consist of:

  • Base
  • Sugar
  • Phosphate

All of which are covalently bonded

If the sugar is Ribose RNA is formed

If the sugar is Deoxyribose then DNA is formed

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Anabolism & Catabolism

Anabolism: The synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions

Condensation makes bonds and releases water (reaction). Anabolism is the process.

Condensation builds molecules an example is Protein Synthesis

Catabolism: The breakdown of complex molecules into simpler molecules including the hydrolysis of maromolocules into monomers

Hydrolysis breaks bonds and water is used up (reaction). Catabolism is the process.

Hydrolysis breaks down molecules an example is Digestion

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