AQA Biology A-Level cheat sheet
Biological molecules
, EVERYTHING YOU NEED TO KNOW – SUGARs/CARBOHYDRATEs
• Monomers – Smaller repeating unit from which a larger molecule/polymer is made. Monomers join via condensation reactions (form a chemical bond by lo
water) and tend to separate via hydrolysis (break chemical bond via adding water). Polymer – A larger unit made up from smaller repeating units (monome
Examples of polymers/polysaccharides are:
• MALTOSE (glucose x glucose)
• SUCROSE (glucose x fructose)
• LACTOSE (glucose x galactose).
• They all contain carbon, hydrogen and oxygen. Formed via condensation reaction (loss of H2O) forming a glycosidic bond. *HEXOSE sugars
Starch, consists of 2 polysaccharides.
• Polymer of alpha-glucose
• Amylose – long + UNBRANCHED
• Amylopectin – Long + BRANCHED, has side chains (1,4 & 1,6 glycosidic bonds) – makes molecule compact
• Ends ensure fast enzyme action/hydrolysis/breakdown
• Starch is therefore insoluble, doesn’t affect WP
• Is large so cannot leave/cross cell membranes.
• Glycogen however has lots more 1,4 & 1,6 glycosidic bonding is therefore more highly branched (due to the 1,6) + also compact and coiled, polymer of alph
glucose.
• Cellulose however is a polymer of beta-glucose, has no 1,6 glycosidic bonds. Composed of straight (unbranched + linear) chains, linked by hydrogen bonds
forming microfibrils (strong fibers ensuring structural support, give strength to cell walls).
• In cellulose one of the beta glucose’s carbon 1 hydroxyl groups flipped/inverted by 180* as bonding wouldn’t otherwise occur
Biological molecules
, EVERYTHING YOU NEED TO KNOW – SUGARs/CARBOHYDRATEs
• Monomers – Smaller repeating unit from which a larger molecule/polymer is made. Monomers join via condensation reactions (form a chemical bond by lo
water) and tend to separate via hydrolysis (break chemical bond via adding water). Polymer – A larger unit made up from smaller repeating units (monome
Examples of polymers/polysaccharides are:
• MALTOSE (glucose x glucose)
• SUCROSE (glucose x fructose)
• LACTOSE (glucose x galactose).
• They all contain carbon, hydrogen and oxygen. Formed via condensation reaction (loss of H2O) forming a glycosidic bond. *HEXOSE sugars
Starch, consists of 2 polysaccharides.
• Polymer of alpha-glucose
• Amylose – long + UNBRANCHED
• Amylopectin – Long + BRANCHED, has side chains (1,4 & 1,6 glycosidic bonds) – makes molecule compact
• Ends ensure fast enzyme action/hydrolysis/breakdown
• Starch is therefore insoluble, doesn’t affect WP
• Is large so cannot leave/cross cell membranes.
• Glycogen however has lots more 1,4 & 1,6 glycosidic bonding is therefore more highly branched (due to the 1,6) + also compact and coiled, polymer of alph
glucose.
• Cellulose however is a polymer of beta-glucose, has no 1,6 glycosidic bonds. Composed of straight (unbranched + linear) chains, linked by hydrogen bonds
forming microfibrils (strong fibers ensuring structural support, give strength to cell walls).
• In cellulose one of the beta glucose’s carbon 1 hydroxyl groups flipped/inverted by 180* as bonding wouldn’t otherwise occur
