Biological Molecules

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Water

  • Water is a solvent - substances can dissolve in it 
  • Water transports substances

Structure of water related to transportation

  • Shared electrons pulled closer to the oxygen atom than hydrogen atoms
  • (this makes it) dipolar
  • Good solvent for other polar molecules
  • Substances can be transported more easily when dissolved into water
  • Water is cohesive (due to dipolar nature) - helps water to flow
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Carbohydrates

Monosaccharides ---> Disaccharide ---> Polysaccharide

Made from long chains of monosaccharides. Joined by Glycosidic bonds in condensation reaction (H2O removed)

Monosaccharides;

  • e.g. glucose, fructose, galactose

Disaccharide

  • e.g. sucrose, lactose, maltose
  • Made of two monosaccharides

Polysaccharide

  • e.g. amylose, amylopectin, glycogen
  • Made of more than two monosaccharides
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Starch

  • Energy store in plants - get energy from glucose
  • Store excess glucose as starch - breaks starch down to release glucose
  • Mixture of two polysaccharides of alpha - glucose:
  • Insoluble

Amylose

  • 1-4 glycosidic bond
  • Long, coiled, unbranched 
  • Compact - good for storage

Amylopectin

  • 1-4 + 1-6 glycosidic bonds
  • Long, branched
  • Side brances allow enzymes to break bonds easily to release glucose
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Glycogen

  • Energy store in animals
  • Store excess glucose as glycogen
  • 1-4 + 1-6 glycosidic bonds
  • Side branches - release energy quicker
  • Compact - good for storage
  • Insoluble - cells don't swell by osmosis
  • Large molecule - store more energy
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Lipids

  • Triglycerides - one glycerol + three fatty acids - joined by ester bonds
  • Fatty acids have long tails made of hydrocarbons
  • Tails are hydrophobic - make lipids insoluble

Saturated

  • Animal fats (e.g. butter)
  • NO double bonds between carbon atoms

Unsaturated

  • Plants (e.g. olive oil)
  • Has double bonds between carbon atoms
  • Melt at lower temperatures
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Proteins

  • Made from long chains of amino acids (monomers)
  • Dipeptide - two amino acids
  • Polypeptide - two or more amino acids
  • Joined by peptide bonds

Structure of Amino Acids

  • Carboxyl group (-COOH)
  • Amino group (-NH2)
  • Carbon atom (C)
  • Variable group (R)
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Enzymes

Biological Catalysts - speeds up chemical reactions

e.g. digestion, respiration

Globular proteins

Have active site - specific shape for substrate molecules to bind to

Specific - catalyse one reaction

Lowers activation energy - speeds reaction up

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Enzymes 2

Lock & Key Method

Substrate fits enzyme

Induced Fit Method

Substrate has to be right shape 

Makes active site change shape

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