Biological molecules 2a

• Why is water a dipolar molecule?

  The oxygen atom has a slight negative charge while the hydrogen atoms are slightly positively charged, so it has negative and positive poles
• What is a hydrogen bonding in water?

  The positive pole of one water molecule is attracted to the negative pole of another. They are relatively weak bonds but in water, there are huge numbers creating a significant force responsible for many of water’s unusual properties
• High specific heat capacity 


  Acts as a buffer against sudden temperature changes
• High specific Latent heat of vaporisation

  results in sweating being effective at cooling the body
• strong cohesion and surface tension in water

  Allows water to be pulled up xylem tissues in continuous columns in plants
• Solvent


  It’s a polar molecule so polar Substances dissolve in water easily so metabolic reactions can take place faster in solution. Substances can be transported easily around organism
• Metabolite


  Used in many metabolic reactions like hydrolysis and formed in condensation reactions. Also used in photosynthesis
• What is a polymer?


  A polymer is a large molecule made up of repeating subunits called monomers.
• What reaction joins monomers together?

  Condensation reactions
• Polymers are broken into monomers through which reaction?

  Hydrolysis
• What are the 3 monosaccharides?

  Glucose, fructose, galactose
• Chemical formula of monosaccharides?

  C6H12O6
• What makes maltose?


  Maltose is made from two glucose molecules.
• Sucrose?


  Glucose + fructose
• lactose?


  Glucose + galactose
• What are the 2 isomers of glucose?

  Alpha glucose and beta glucose.
• What is the difference between alpha and beta glucose?

  The main difference between alpha and beta glucose is the position of the hydroxyl group on the first carbon atom. In alpha glucose, the hydroxyl group is below the ring, while in beta glucose, it is above the ring.
• Two monosaccharides joined together is called what?

  Disaccharide
• What is the bond Called between monosaccharides?

  Glycosidic bond
• What are the 3 polysaccharides?

  Starch, glycogen, cellulose
• What are they used for?

  Starch and glycogen- energy storage

  Makes plant cell walls (structural)
• Polysaccharides are monomers of either alpha glucose or beta glucose. Cellulose is made from beta glucose whereas starch and glycogen are made from alpha glucose
• Starch and cellulose are found in plant cells, glycogen in animal cells
• What two polymers is starch made from?

  Amylose and Amylopectin
• What does amylose form.?

  A compact helical chain to store large numbers of glucose molecules in a small space
• Amylopectin?


  Branched so allows amylopectin to be quickly hydrolysed by amylase enzymes to form maltose then glucose for respiration
• Describe structure of glycogen

  More branches than amylopectin so an energy storage molecule in animals found in liver and muscle cells.
• Why are starch and glycogen both suited to their function?

  • Coiled so compact and so store lots of glucose in a small space
  • large and insoluble so can’t diffuse out cells
  • insoluble so no osmotic effect
  • Glycogen and amylopectin both quickly hydrolysed to provide glucose for respiration. Branching creates more ends available to enzymes
  • inert so not involved in cell’s chemical reactions
• How do two beta glucose molecules link together?

  the molecule on the left has to flip over
• Why is cellulose suited to its function?

  Major component of plant cell wall

  • made of straight unbranched chains
  • chains run parallel to each other and h bonds form cross linkages between chains
  • Many h bonds collectively are strong and so provide high tensile strength making cell wall rigid and prevents osmotic lysis
  • cellulose molecules are grouped to form microfibrils
• What is the test for starch?

  The test for starch is the iodine test, which turns the starch solution blue-black in colour from brown/orange
• What’s the test for reducing sugars?

  Benedict's test.

  add benedicts

  heat

  sample goes from blue to brick red
• Test for non reducing sugars?

  Sucrose is a non-reducing sugar

  Boil sample with dilute acid like HCL

  neutralise with alkali

  Reheat with Benedict’s solution so it will now turn brick red due to sucrose being hydrolysed into its monosaccharides glucose and fructose
• What are some issue with the Benedict's test?

  Non specific- a positive result only tells us a reducing sugar is present but not which one

  It’s qualitative- colour change is used to determine the result so no value is obtained for the concentration of reducing sugar. The test can be described be as semi-quantitative because the colour change depends on the amount of reducing sugar present. Allows an estimate for how much reducing sugar is present. e.g red = high

  Subjective
• How can a biosensor be useful?

  it can test for specific sugars e.g a glucose biosensor will only detect glucose and no other sugar.
• What can a colorimeter do?

  It can quantify results. A serial dilution of a glucose solution can be carried out producing a set of known concentrations. Carry out Benedict’s and measure colour intensity using the colorimeter. A calibration curve is then produced. Absorbance on x axis, concentration on y axis
• Role of hydrogen ions

  Affect pH levels
• Role of iron ions

  Component of haemoglobin in red blood cells
• Role of phosphate ions

  Component of DNA, ATP and phospholipids and to make molecules more reactive
• Role of sodium ions

  Co transport with glucose and amino acids in small intestine