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Biomolecules - Coggle Diagram
Biomolecules
Lipids
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Triglycerides: 3 fatty acid molecules with 3 ester bonds; insoluble in water, soluble in ethanol
Roles: energy stores, insulation, metabolic source of water
Phospholipids
One of 3 fatty acids replaced by a phosphate group, which is polar, so one end dissolves in water. Tails are hydrophobic, so insoluble
Carbohydrates
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Polysaccharides
Starch
Amylose
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Long unbranching chain of 1,4 linked glucose molecules
Curved chains, coil up into helical structures (compactness)
Amylopectin
1,4 linked alpha-glucose molecules
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Also contain 1,6 linkages, which start branches out to the sides of the chain
Glycogen
Like amylopectin: 1,4 chains with 1,6 linkages as branch points
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Cellulose
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Successive glucose molecules are linked 180° to each other, so that OH groups are aligned
60-70 cellulose molecules become tightly cross-linked by hydrogen bonding, to form microfibrils. These are in turn held together to form fibres
Proteins
Structure
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Secondary: The structure of a protein molecule resulting from the regualr coiling or folding of the chain of amino acids (an alpha-helix or beta-pleated sheet)
Tertiary: the compact structure of a protein molecule resulting from the 3D coiling of the chain of amino acids
Quaternary: the 3D arrangement of two or more polypeptides, or of a polypeptide and non-protein component suh as haem, in a protein molecule
Globular proteins
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Non-polar, hydrophobic R groups point into the center of molecule
Usually soluble, since water molecules cluster around their outward-pointing hydrophilic R groups
Eg: Haemoglobin
4 polypeptide chains of a protein called globin. Two of these chains are a-globin, and the other 2 are beta-globin. Each of these four chains contains a haem group (prosthetic group). Each haem group contains an iron atom, which can bind to 2 oxygen atoms (1 O2 molecule).
Fibrous proteins
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Eg: Collagen
3 polypeptide chains, each in the shape of a helix (NOT alpha-helix). These 3 chains are wound around each other, forming a triple helix. The 3 chains are held together by H bonds and covalent bonds, Every third amino acid in each chain is glycine. It allows the 3 chains to lie close together. Each 3-chained collagen molecule reacts with other collagen molecules running parallel to it. Covalent bonds between the R-groups of amino acids lying next to each other form cross-links, which forms fibrils. The cross links being out-of-step with each other strengthens the collagen molecule. Fibrils lie along each other, forming fibres.