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Biological molecules (Monomers, Polymers e.g. carbohydrates (Monomer:…
Biological molecules
Monomers, Polymers e.g. carbohydrates
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Monosaccharides, amino acids and nucleotides are examples of monomers
A condensation reaction joins 2 molecules together with the formation of a chemical bond and involves the elimination of a water molecule
A hydrolysis reaction breaks a chemical bond between 2 molecules and involves the use of a water molecule
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Glucose, Galactose and fructose are monosaccarides
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Alpha glucose, both hydroxide groups are on the same side of the molecule and Beta glucose, the hydroxide groups are on opposite sides of the molecule
Lipids
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A saturated fatty acid contains only single bonds between the carbons in the hydrocarbon chain but still contain the double bond between the Carbon and Oxygen at the end of the chain
An unstaturated fatty acid do have double bonds between the carbon chains as well as the double bond between the carbon and oxygen at the end of the chain
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The phospholipid bilayer is arranged in the way it is because the heads of the phospholipids are polar (negative charge) and the tails are non polar this means the tails repel water and the heads attract it (hydrophilic and hydrophobic)
Phospholipids
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Properties: Will form a phospholipid bilayer with hydrophobic fatty acid tails pointing in away from the water and hydrophilic phosphate heads pointing out towards the water
Why is it useful: Forms cell membranes. The hydrophobic fatty acid centre means that water soluable molecules cannot easily pass across the membrane.
Lipids have many uses as well as storage and for membranes, including as certain hormones such as testosterone and as respiratory substratesa ( molecules used in respiration to release energy).
Tests for Lipids
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Procedure: Add 2cm3 of ethanol and shake, this dissolves the lipids. Then add water drop wise and shake
Result: If lipid is present, a white emulsion will be visible (this is fat droplets)
Nucleic Acids
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DNA contains Deoxyribose and contains the bases cytosine, thymine, adenine, guanine
DNA is also double stranded and allows for accurate replication. It also protects the bases from some damage with strong hydrogen bonding so protein coding can be as accurate as possible
RNA contains ribose. and contains the bases uracil, adenine, cytosine, guanine
RNA is single stranded, short and is copied from DNA for protein sythesis.
Polynucleotide strands are formed when many nucleotides link to form a long chain. They are joined togehter using a condensation reaction to form phosphodiester bonds.
Water, ATP and inorganic Ions
ATP is made of Adenine, a ribose sugar and 3 phosphate groups.
A nucleotide derivative is a molecule that is related to a DNA nucleotide displaying similar characteristics to DNA nucleotides
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Proteins and enzymes
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Protein structure
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Secondary structure: This is the folding of the polypeptide into an alpha helix or beta- pleated sheet. This structure is maintained by hydrogen bonds between the amine group of one amino acid and the carboxyl group of another
Tertiary structure: This is further folding off the secondary structure into a specific complex 3D shape. This structure is maintained by 3 different types of bonding, Hydrogen bonds the weakest, Ionic bonds also weak which form between oppositely charged R groups, disulphides bridges, covalent bonds, which form between sulphur containing R groups. The tertiary structure of the protein is essential for its function. The shape of the protein determines how it reacts with other molecules
Quaternary structure: Some proteins consist of 2 or more polypeptide chains joined together. A common example is Haemoglobin which has 4 polypeptide chains
A high increase in temperature will cause the protein to denature which changes the 3D tertiary structure of the protein which means it will no longer be specific to its substrate
