BIOLOGY MOCK 2023 A LEVEL QUESTIONS

• Give 3 structural features found in all virus and describe the function of one of these features:

  • genetic material
  • capsid
  • attachment protein
  • attachment protein binds To receptors on cell
• Explain why viruses are described as acellular or non living:

  • acellular = no cell surface membrane
  • non living = no metabolism
• Give one reason why antibiotics are not affective against viruses:

  • doesn’t have cell wall
• Give 3 ways structure of chitin is similar to cellulose :

  • joined by glycosidic bonds
  • glucoses flipped 180
  • have beta glucose
• Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect:

  • tracheoles highly branched
  • so short Diffusion pathway
• Explain the importance of xylem being kept open aw a continuous tube:

  • allows unbroken water column
  • cohesion from hydrogen bonds between water molecules
  • evaporation causes tension in column
• Describe 2 functions of golgi apparatus

  • packages transport protein
  • forms and releases vesicles
• Explain why damage to the cell lining the ileum reduces absorption of the products of digestion and why this reduces absorption of water:

  • reduced surface area
  • decreases water potential in ileum
  • so water moves out cell into ileum by osmosis
• Suggest how passive immunity would work and which patient should be offered this anti toxin antibody:

  • antibody causes phagocytosis, destruction of toxins
  • anti toxin prevents chance of diarrhoea
  • offered to patients with diarrhoea
• Describe how the anti toxin would be digested:

  • Peptide bonds hydrolysed
  • endopeptidases break internal peptide bonds
  • exopeptidases break terminal peptide bonds
  • membrane bound dipeptidases break dipeptides into amino acids
• how exposure to CO affects the loading and unloading Of Oxygen by haemoglobin:

  • Less O loaded at high Partial pressure compared with no CO
  • at low partial pressure haemoglobin has higher affinity for O
  • haemoglobin has more O at low partial pressure
• Cells in drawing A can be identified with those treated with MiTMAB:

  • cytoplasm stop dividing
  • 2 nuclei in cell
• Suggest how MiTMAB can cause dynamin to become inactive;

  • MitMAB binds to dynamin away from active site
  • changes the shape of dynamins active site
  • fewer enzyme substrate complexes are formed
• Suggest what is on the test line at T and explain what causes the line to appear in a positive test:

  • antigen at T bonds to substrate
  • Enzyme complex forms colour change
• Suggest one reason why a line at C shows the test has worked:

  • blood sample moved above T
• Suggest why the fused cells allow continuous production of monoclonal antibodies:

  • cancer cells divide rapidly
  • B cells produce monoclonal antibodys
• Suggest how this would affect the return of tissue fluid into the capillaries:

  • increases water potential of blood
  • less water returns to blood by osmosis
• Describe how quarternary protein is formed from its monomers:

  • amino acids join by peptide bonds
  • by condensation reaction
  • secondary formed by hydrogen bonding
  • tertiary formed by interaction between R groups
  • quarternary toiler by bonds between polypeptides
• Describe the structure of DNA and a chromosome:

  • polymer of nucleotides
  • deoxyribose, phosphate, nitrogenous base
  • phosphodiester bonds between nucleotides
  • double helix held by hydrogen bonds
  • DNA associated with histones/proteins
  • during mitosis, chromosomes consist of 2 chromatids at a centromere