Biological molecules Flashcards
Triglycerides how are they formed
Formed by the condensation of 1 molecule of glycerol and 3 fatty acids.
The condensation reaction between glycerol and a fatty acid (RCOOH) forms an ester bond
Triglycerides properties related to structure
They have a high ratio of C-H bonds to C atoms in the hydrocarbon tail so they release more energy than the same mass of carbohydrates.
They are insoluble in water (clump together as droplets) so no effect on the water potential of the cell.
Phospholipids what are they
1 molecule of glycerol, 2 fatty acids, a phosphate-containing group.
Phosphate head, fatty acid tails
Phospholipids properties related to structure
Phosphate heads are polar/hydrophilic so they are attracted to water. Orients to the aqueous environment either side of the membrane
Fatty acid tails are non-polar/hydrophobic so they are repelled by water. Orients to the interior of the membrane so that it repels polar/charged molecules.
Phospholipids what do they do
Forms bilayer in the cell membrane, allowing diffusion of non-polar/small molecules
Triglycerides what do they do
Triglycerides are energy-storage molecules
Saturated fatty acids
No C=C bonds in hydrocarbon chain; all carbons fully saturated with hydrogen
Unsaturated fatty acids
One or more C=C double bonds in hydrocarbon chain
Emulsion test for lipids
1.) add ethanol and shake (to dissolve lipids)
2.) add water
3.) positive test: milky/cloudy white emulsion
Condensation reaction
Joins 2 molecules together
Eliminates a water molecule
Forms a chemical bond
Hydrolysis reaction
Separates 2 molecules
Requires addition of a water molecule
Breaks a chemical bond
Glycogen structure and function
Energy store in animal cells
Polysaccharide of α-glucose with C1-C4 and C1-C6 glycosidic bonds, so it is branched
Glycogen structure related to function
Branched; can be rapidly hydrolysed to release glucose for respiration to provide energy
Large polysaccharide molecule, cannot leave cell
Insoluble in water; water potential of cell is not affected, therefore there is no osmotic effect.
Polymer of glucose so easily hydrolysed
Glucose (polymer) so provides respiratory substrate for energy (release);
Starch structure and function
Energy store in plant cells
Polysaccharide of α-glucose. Mixture of amylose and amylopectin.
Amylose has C1-C4 glycosidic bonds so it is unbranched, whereas amylopectin has C1-C4 and C1-C6 glycosidic bonds so it is branched
Structure of starch related to its function (amylose)
Helical; compact for storage in the cell
Large polysaccharide molecule; cannot leave the cell
Insoluble in water, does not affect the water potential of the cell so there is no osmotic effect