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?)