Experiments Unit 1

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  • Created by: neet
  • Created on: 20-12-12 19:52

Measure Initial Rate of an Enzyme-controlled React

  • Set up experiment for the breaking down of hydrogen peroxide into water and oxygen
  • Measure (the volume) amount of oxygen given off in the first minute
  • Divide the volume of oxygen produced by the time to get the initial rate of reaction
  • More oxygen given off = faster initial rate of reaction
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Effect of Caffeine on the heart rate of Daphnia

  • Make up a range, atleast 5, of caffeine solutions with different concentrations and one control with no caffeine
  • Transfer a Daphnia into the dimple of a cavity slide
  • Place slide under microscope and focus on heart beating
  • Count the number of heartbeatd in 10 seconds and multiply by 6 to give rate per min
  • Repeat 10 times using same concentration but different Daphnia each time
  • Keep other factors the same (e.g temperature and volume of caffeine solution)
  • Repeat procedure with other concentrations
  • Compare results by drawing a graph
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Measure amount of vitamin C

  • Make up several, atleast 6, vitamin C solutions of different concentrations
  • Measure out a set volume of DCPIP into a conical flask
  • Add one of the vitamin C solutions to the DCPIP, drop by drop, using a pipette
  • Gently shake the conical flask for a set length of time after each drop
  • When solution turns colourless, record the volume (no. of drops)
  • Repeat experiment with the same solution twice more
  • Find average of results
  • Make sure other variables are kept constant (e.g temperature)
  • Repeat procedure with each solution
  • Use results to make a line graph showing calibration curve
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Effect of temperature on permeability

  • Cut 5 equal sized pieces of beetroot
  • Rinse them to remove any pigment released during cutting
  • Place the five pieces in five different test tubes each with 5cm^3 water
  • Place each test tube in water bath at different temperatures e.g 10, 20, 30, 40, 50 for same length of time
  •  Remove the pieces of beetroot so only solution is left
  • Use colorimeter to calculate intensity of the solution

More light absorbed by colorimeter = More pigment released = Higher permeability

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Increasing temperature increases permeability

Temperatures below 0 degrees:

Permeability is high, phospholipids dont have energy so can't move very much, membrane is rigid, carrier proteins and channel proteins deform, ice crystals form and pierce membrane

Temperatures between 0 - 45 degrees:

Phospholipids gain more energy so they can move around more so become more permeable

Temperatures above 45 degrees:

Phospholipid bilayer startd to melt, water inside the cell expands putting pressure on the membrane, Channel proteins and carrier proteins deform so they can't control what enter or leaves cell

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