exam questions

• lipids are classed as more energy rich storage compounds than carbs, why?

  -       Because lipids contain a lower proportion of oxygen than carbohydrates

  -       Lipids can be hold more compactly with a relatively large amount of energy being stored per gram than carbs
• describe the role of the ester bond within lipids and the mode of ester bonds formation and breakage.

  -       Role of ester bond is to join a fatty acid and glycerol 

  -       Formed via esterification/ condensation-water molecule release 

  -       Broken by hydrolysis-using a molecule of water

   
• role of lipids within an animal’s body(4)

  -       Energy storage=e.g., fat under skin and around major organs 

  -       Insulation=fat under skin, around nerve axons e.g., myelin sheath, to maintain body temp 

  -       Cellular structure=phospholipids in cell membranes, cholesterol in cell membranes

  -       Protection= fat around major organs act as shock absorber.
• describe how diagram would be different if one of the fatty acids was unsaturated(2)

  • there would be double bond between carbon atoms
  • a kink in the fatty acid chain forms
• explain the effect that large quantities of this lipoprotein would have on blood cholestrol levels(4)

  • increased blood cholestrol levels
  • because the triglyceride is saturated- the lipoprtein is an LDL
  • LDLs move cholestrol from liver to blood stream
  • LDL bind to receptors on cell membrane, LDLs can accumulate in blood if receptors overloaded
• explain why high levels of sugar in a persons diet could lead to obesity(3)

  • high sugar levels means energy inputs may be larger than energy outputs
  • therefore, excess energy is converted to fat
  • leading to weight gain
  • overtime individuals BMI may exceed 30 to be obese