Unit 2.1.1: Biological Molecules

A condensation reaction is a chemical reaction that links biological monomers together.

In condensation reactions:

• A water molecule is released. 
• A new covalent bond is formed. 
• A larger molecule is formed by the bonding of small molecules. 

Hydrolysis splits larger molecules to monomers: 

• A water molecule is used.
• A covalent bond is broken.
• Smaller molecules are formed by the splitting of larger molecules.

Amino Acids are monomers that make up proteins. The consist of: 

A condensation reaction between an acid group and an amino group forms a covalent peptide bond as well as producing a water molecule.

Primary

• The primary structure is the specific sequence of amino acids that make up the protein. 
• They are bonded by Peptid bonds.

Secondary 

• DNA determines the sequence in which amino acids are bonded. 
  
• As the chain becomes longer, parts of the chain are stabilised by being coiled up/pleated. 
• The coils and pleats are held in place by hydrogen bonds. 
• The amount of coiling/pleating depends on the priamry structure.
• It is formed when the chain of amino acid coils/folds form an alpha helix or a beta pleated sheet.

Tertiary 

• Once the final polypeptide is formed, the coil and pleats come together in a specific way to form an overall 3D shape
• This is the tertiary structure and its specific shape is vital.
  
• Tertiary structure in proteins is stabilised by a number of bonds:
  • Disulphide bonds: when two amino acids containing sulphure are found close to each other, a covalent bond can from.
  • Ionic bonds: R-groups sometimes carry a chage, either +ve or -ve. Where oppositely charged amino acids are found close to each other, an ionic bond forms.
  • Hydrogen bonds: in the secondary structure.
  • Hydrophic - Hydrophilic interactions: in a water based environment, htdrophobic amino acids will be most stable if they're held together with water excluded. Hydrophilic amino acids tend to be found on the outside in globular proteins, with hydrophobic amino acids in the centre. These interactions keep chemical groups positioned close to each other. 

Collagen is a fibrous protein:

Collagen provides mechanical strength in:

Carbohydrates contain:

-It can act as a quick source of energy, energy storage or for structural purposes.

• Monosaccharides are the monomers of carbohydrates. 
• They contain between 3-6 carbon atoms. 
• Triose sugar - 3 Carbons.
• Pentose sugar - 5 Carbons.
• Hexose sugar - 6 Carbons.

How does the structure of glucose relate to it's functions in living organisms?

• A triglyceride consists of one glycerol molecules bonded to three fatty acid molecules.
• A condensation reaction between the acid group of a fatty acid and one of the hydroxyl groups forms a covalent bond, called and Ester Bond.

Phospholipids: consist of a glycerol molecule, two fatty acids and a phosphate group.

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