Topic 2 Flashcards

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1
Q

Describe the permeability of cell membrane experiment: stage 1, obtaining beetroot solution

A
  • Use a scalpel to cut 5 equal sized pieces of beetroot on a cutting board
  • Rinse pieces to remove pigment released in cutting
  • Use a measuring cylinder to measure out 5cm3 of water
  • In 5 different test tubes
  • Place the test tubes into water baths at different temperatures
  • Place 5 pieces of beetroot in 5 different test tubes for same length of time using stopwatch
  • Remove beetroot from tubes leaving just coloured liquid
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2
Q

Describe the permeability of cell membrane experiment: stage 2, using the calorimeter

A
  • Switch calorimeter on and allow 5 minutes for it to stabilise
  • Set up calorimeter using blue filter
  • Use pure water to calibrate machine to zero
  • Use pipette to transfer sample of liquid from first of beetroot test tubes to clean cuvette [3/4 full]
  • Put cuvette in calorimeter and record absorbance of coloured solution
  • Repeat for remaining test tubes
  • Plot graph of temperature vs absorbance
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3
Q

What is the relationship between light absorbance and permeability of the membrane? 4

A
  • The higher the absorbance reading
  • Less light passed through
  • More pigment released
  • Higher permeability of membrane
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4
Q

Why is beetroot used to investigate cell membrane permeability?

A

It has a purple pigment that leaks out of the cell membrane according to its permeability

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5
Q

Explain how to investigate the effect of enzyme/substrate concentration on enzyme controlled reactions

A
  • Set up five concentrations of catalase/hydrogen peroxide depending on what’s tested
  • Add a set volume and known concentration of hydrogen peroxide to a boiling tube
  • Keep pH constant by adding buffer solution
  • Set up apparatus with upside down measuring cylinder in trough of water connected to boiling tube with delivery tube
  • Use pipette to add known concentration and volume of catalase
  • Quickly attach bung and tube
  • Measure volume of oxygen produced in measuring cylinder every 10 seconds for first minute of reaction
  • Use stopwatch to measure time
  • Plot data on graph of volume of oxygen produced vs time
  • Draw tangent to determine initial rate of reaction
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