Bio 2019 Paper One

• Give one structural difference between amylose and amylopectin

  Amylose is unbranched

  Amylopectin is branched
• Explain how the structures of amylopectin and glycogen make them suitable for storing energy.

  Branched, can be broken down faster

  Compact, more energy stored

  Large molecules, remain in the cell
• Explain why high levels of sugars in a person’s diet could lead to obesity.

  Energy intake higher then output

  excess energy turned in fat

  leading to weight gain
• Explain why sucralose cannot be broken down by sucrase.

  Sucralose contains chlorine

  shape of the molecule has to be changed

  
• State what is meant by the term gene

  sequence of bases in DNA coding for a sequence of amino acids
• Explain how a change of one amino acid could lead to a change in the structure and properties of the haemoglobin protein.

  changes primary structure

  leading to amino acid having a different R group

  changing the quaternary structure

  meaning haemoglobin may not bond to oxygen
• Devise a method to measure how the concentration of vitamin C changes during the course of a feed.

  five samples of breast milk tested from different points of feed

  volume of DCPIP taken to produce a colour change in milk

  concentration of DCPIP

  compare values with known vitamin C concentrations

  repeat titration to achieve concordant results
• Describe the relationship between the number of months of breastfeeding and childhood obesity.

  • increasing the number of months of breast feeding decreases the percentage of children with obesity
  • large drop in obesity when children are breastfed for 3-5 months

  
• Explain one way in which this investigation could be improved

  same age of onion

  increases validity
• Deduce the effect of increasing the concentration of sodium chloride on the change in mass of the onion tissue.

  2.5% resulted in an increase in mass

  15% / 20% resulted in a loss in mass

  movement of water due to osmosis

  
• Explain why pickling in vinegar would result in anthocyanin pigments leaving the onion cells

  increased permeability of cell surface

  low pH would denature the protein

  as vinegar affects bonds in the protein
• Give one function of the glycoproteins found in the cell surface membrane

  cell recognition
• Explain how the structure of a phospholipid molecule contributes to the partial permeability of a cell surface membrane.

  Phospholipid has a hydrophilic head and a hydrophobic tail

  Allows non-polar molecules to pass

  Polar particles cannot pass through the bilayer
• Compare and contrast the processes of endocytosis and exocytosis.

  Both processes involve vesicles

  Both use ATP

  Exocytosis involves molecules leaving the cell Endocytosis involves molecules entering the cell
• Describe how mRNA is synthesised at a template strand of DNA

  complementary base pairing

  RNA nucleotides joined together by RNA polymerase
• Describe the differences between the structure of DNA and the structure of RNA

  RNA has ribose, DNA has deoxyribose

  RNA is single stranded, DNA is double stranded

  RNA contains Uracil, DNA contains Thymine
• Compare and contrast the process of transcription with the process of DNA replication


  DNA replication uses DNA polymerase, Transcription uses RNA polymerase.

  DNA replication uses DNA nucleotides and Transcription uses RNA nucleotides

  Both involve phosphodiester bonds

  Both use DNA helicase
• Explain how a blood clot could form in a blood vessel

  damage to endothelium exposes collagen

  release of thromboplastin

  thromboplastin catalyses conversion of prothrombin to thrombin

  thrombin catalyses conversion of fibrinogen to fibrin

  fibrin forms a mesh of fibrins and traps red blood cells