Biological Molecules

• What is the charge of oxygen in a H2O molecule?

  Slightly negative
• Why is ice less dense than liquid water?

  The hydrogen bonds between molecules in ice are slightly further apart than the average distance between liquid water molecules
• What is an advantage to living organisms of ice being less dense than water?

  Ice floats and forms an insulating layer on top of ponds, maintaining a constant temperature for organisms
• Why is water a good solvent?

  It's polar so other charged molecules are attracted to it
• Why is water's high specific heat capacity useful for organisms?

  It can be used as a coolant, to buffer temperature changes during chemical reactions and to provide a constant temperature for aquatic organisms
• Why is water cohesive and adhesive?

  Water is cohesive because the hydrogen bonds mean water molecules are attracted to one another. Water is adhesive because it can be attracted to other polar molecules.
• Why is it useful to organisms that water is cohesive and adhesive?

  Water acts as a good transport medium. These properties also mean that it can move upwards through narrow tubes via capillary action.
• What are 3 examples of hexose monosaccharides?

  Glucose, fructose, galactose
• What is a hexose monosaccharide?

  One with 6 carbon
• What is a pentose monosaccharide?

  One with 5 carbons
• What are 2 examples of pentose monosaccharides?

  Ribose and deoxyribose
• What is the difference between alpha and beta glucose?


  The OH group is below Carbon 1 on alpha, and above it on beta
• Why is glucose soluble in water?


  Because it contains OH groups which make it polar
• What is the bond between two monosaccharides called?

  Glycosidic bond
• What is the disaccharide version of alpha glucose?

  Maltose
• What is a reaction which creates water called?

  A condensation reaction
• What is the addition of water to a disaccharide in order to split it into 2 monosaccharides called?

  Hydrolysis
• What is the test for reducing sugars called?

  Benedict's test
• What is Benedict's Reagant?


  An alkaline solution of Copper (II) Sulfate
• What colour would blue Benedict's Reagant change to if reducing sugars are present?


  Red
• Are all monosaccharides reducing sugars?

  Yes
• Are most disaccharides reducing or non-reducing sugars?

  Non-reducing
• Why does Benedict's Reagant turn red when reducing sugars are present?


  Because the blue Cu2+ ions have an electron is added to form brick red Cu+ ions
• What is the method for testing for reducing sugars?

  1. Add 2cm cubed of a food sample (liquid or crushed with water)

  2. Add 2cm cubed of Benedict's Reagant

  3. Place the test tube in an 80C water bath
• What is the method for testing for a non-reducing sugars?

  1. Confirm that the sugar is not a reducing sugar

  2. Add 2cm cubed of food sample in liquid form to a test tube

  3. Add 2cm cubed of hydrochloric acid

  4. Place in 80°C hot water bath for 5 minutes

  5. Remove and slowly add sodium hydrogencarbonate until the solution is neutral

  6. Re-test the solution using the Benedict's test
• How can you make the Bendict's Test quantitative?

  Use a colorimeter to test the transmission of red light in the solutions. More reducing sugars= more red light
• What are 2 examples of biosensors?

  Pregnancy test, blood sugar monitor
• What is an analyte in a biosensor?

  The sample containing the molecule you are testing for
• What is the receptor in a biosensor?

  The part which interacts with the molecule you are testing for
• What is the transducer in a biosensor?

  Detects the change in the receptor and provides a response
• What does the display in a biosensor do?

  Gives a visual representation of the change in the receptor
• What colour does iodine change to when starch is present?

  Changes to black because iodine molecules become trapped in the helix of the starch
• What is the polysaccharide version of beta glucose called?

  Cellulose
• Which two polysaccharides make up starch?

  Amylose and amylopectin
• What percentage of starch is amylopectin and what percentage is amylose?

  20-30% amylose

  70-80% amylopectin
• What type of glucose are amylose and amylopectin made up of?

  Alpha glucose
• What general structure are cellulose molecules?

  Long, unbranched chains of beta glucose
• Why are cellulose molecules straight?

  The bonds between the glucose molecules are straight
• What are the strong fibres formed by cellulose chains feld together by hydrogen bonds called?

  Microfibrils
• Why is cellulose suitable for use in cell walls?

  It's microfibril structure makes it strong enough to provide structural support for cell walls