Biological Molecules

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  • Created by: lizbarc
  • Created on: 19-04-16 17:00

WATER

Structure:

  • 1x oxygen atom / 2x hydrogen atoms -> shared electrons
  • shared negative electrons pulled towards oxygen atom = slight positive charge
  • unshared negative electrons = slight negative charge

Dipolar molecule  -  negative charge on one side, positive on the other

-  Very cohesive -> strong attraction between molecules (helps water flow + transport substances)

-  Good solvent -> bio reactons - ionic substances dissolve (opposite ions attract to opposite charges)

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CARBOHYDRATES

Carbohydrates = long chains of monosaccharides

  • mono + mono = disaccharide

- condensation reaction

- glycosidic bond forms - H2O released

(reverse = hydrolysis)

-> glucose + glucose = maltose  (1-4)

-> glucose + galactose = lactose  (1-4)

-> glucose + fructose = sucrose (1-2)

  • mono + mono + mono ... = polysaccharides

e.g.  amylose - lots of (a) glucose  (1-4)

+ amylopectin   + glycogen

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POLYSSACHARIDES

excess glucose stored as:

1)   STARCH   (energy storage - plants)

amylose

  • long, unbranched
  • (1-4)
  • coiled - compact - storage

amylopectin

  • long, branched
  • (1-4 / 1-6)
  • side branches - enzymes break down molecule/bonds quickly - quick energy release

- insoluble

2)   GLYCOGEN   (energy storage - animals)

  • large
  • (1-4 / 1-6)
  • LOADS of branches - animals = higher demand for energy
  • compact - storage

- insoluble

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LIPIDS

Triglycerides:

1x glycerol    3x fatty acids

  • 3x fatty acids = hydrocarbon tail -> hydrophobic  (insoluble)

Formed:

- Condensation  <--->  hydrolysis

- Ester bonds

- H atom on glycerol binds to OH group on fatty acid   -> H2O released

Saturated (animal fats)  = NO double bonds

Unsaturated (plants)  = double bonds  -> kinks, melt at lower temps  2+ double bonds = POLY

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PROTEINS

Proteins  -  long chains of amino acids    (one or more polypeptide)

  • carboxyl group (-COOH)
  • amino group (-NH2)
  • variable group (R)

- amino acid + amino acid = dipeptide

- amino + amino + amino ... = polypeptide

Condensation <-----> hydrolysis

polypeptide bonds

Primary structure - sequence of amino acids  (peptide bonds)

Secondary structure - coil -> alpha helix or B pleated sheet  (hydrogen bonds)

Tertiary structure - 1x polypeptide chain coils further  (ionic, disulfide, hydrophobic/phylic, hydrogen)

Quaternary structure - the way 2+ polypeptide chains are assembled -> 3D structyure  (all bonds)

Globular     e.g. haemoglobin

  • round, compact
  • multiple polypeptide chains coiled up - hydrophilic OUTWARDS hydrophobic INWARDS
  • soluble - easily transported

Fibrous      e.g. collagen

  • long, tightly coiled
  • insoluble
  • lots of bonds - strong  (support)
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