CELL COMPONENTS
Use chemistry to connect structure with function ! Lipids (membranes)
! Carbohydrates (cell wall)
! Proteins (membranes, enzymes, chromatin,
microtubules, microfilaments)
! Nucleic acid (chromatin, ribosomes) Note "functional groups" of biochemicals (Sadava et al. [8th edn], Fig. 3.1)
LIPIDS (FATS, OILS)
Carbon chain
C has 4 outer shell electrons, makes 4 covalent
bonds (shared e- pairs)
If the 4 bonds are to four different atoms(saturated), they are equally spaced around atom(“tetrahedral”)
Tetrahedral arrangement means that C-C chain iszig-zag
Cs bond to Cs, Hs (one bond per H)
C C C C C C
\ / \ / \ / \ / \ / \
C C C C C C
Fatty acid: hydrocarbon chain + carboxylicacid
Hydrocarbon (H,C) chain
Carbon backbone
Saturated: every Clinked to 4 differentatoms
Unsaturated: somedouble C=C bonds
Fatty acid: hydrocarbon chain + carboxylicacid
Carboxylic acid group
! Acid: H+ dissociates to leave carboxylate group (note - charge)
Triglyceride
Glycerol (glycerin)
Condensation reaction
This reaction is energetically infeasible, so it needs an input of energy to push it
Phospholipid (membrane lipid)
Diglyceride: glycerol + 2 fatty acids Phosphate group ! P: 5 covalent bonds to 4 Os
! Complex of P and Os loses 1-2 H+ at pH 7, thus ! 1-2 negative charges ! Phosphate attaches to glycerol through
condensation reaction
Combine (condense):
! diglyceride,! phosphate,! other organic molecule (usually charged)
How lipid works to make membranes
Solubility
All compounds divide into 2 groups:polar and non-polar
Polar: electrically charged, or with +or - regions (e.g. water, carboxylicacid group, salts)
Non-polar: electrically neutral, andwith no + or - regions; thus, withevenly spaced electrons (e.g.hydrocarbons)
How lipid works to make membranes
Solubility
Polar molecules dissolve in polar solvents (calledhydrophilic, because water is the prototype polarsolvent)
Non-polar molecules dissolve in non-polarsolvents (gasoline), but not in water (hydrophobic)
Phospholipids have both
polar and non-polar ends
Phospholipid bilayer
Phospholipids on thesurface of water
Micelle
Vesicle
Summary
Carbon combines with hydrogen, oxygen, andphosphorus (also nitrogen and sulfur) throughcovalent bonds to form complex molecules, the basisof life.
Functional groups allow you to predict the commontypes of molecular structures.
Phospholipids have both hydrophobic andhydrophilic regions.
Phospholipid structure allows the formation ofmembranes in aqueous environments (what wouldhappen in non-aqueous environments? In seas ofliquid ammonia?)