state safety precautions of investigating effect of alcohol on cell membrane
1- wear eye protection
2-take care handling sharp materials such as cork borers and knife, always cut on tile
3-ethanol is flammable so keep away from naked flames
4- don’t handle electric plugs or sockets with wet hands
5-wash hands with soap after experiment ends
why does beetroot appear red
as it contains a red pigment called betalain which is a large molecule and doesn’t pass through cell membrane
how can we tell if cell membrane is damaged
betalain will pass through cell membrane and get out of the cell
state the relationship between temperature and % of light transmission and state a reason for your answer
as temperature increases % of light transmission decreases, why?
as when temperature increases molecules gain kinetic energy so rate of diffusion increases, and the cell membrane’s protein’s tertiary structure is altered causing permeability to increase so more pigment diffuses outside so solution becomes darker so less light is transmitted
devise an investigation to investigate effect of temperature on cell membrane permeability
1- prepare 7 water baths set at a range of temperatures from 10 to 70 degrees Celsius
2-measure temperature of water baths using a thermometer for precise readings
3-add the same volume of water to each test tube
4- cut 7 cylinders of beetroot of the same dimensions using a cork borer, a knife and a white tile and wash them thoroughly with water until the water runs clear
5- add one beet root cylinder to each test tube and leave in water bath for 15 minutes
6-set colorimeter to blue-green filter and zero % transmission by adding distilled water to colorimeter cuvette
7- transfer liquid from each test tube to colorimeter cuvette and take readings of percentage transmission
devise an investigation to investigate effect of alcohol on cell membrane permeability
1- prepare 5 test tubes containing same volume of ethanol at different concentrations 1%, 2%, 3% etc..
2- cut 5 cylinders of beetroot in equal dimensions using cork borer, knife, ruler and white tile
3-place one cylinder in each test tube and leave for 15 minutes, shake once then remove cylinders and keep the supernatant liquid
4- set colorimeter to blue green filter and 0% transmission by adding distilled water to a blank cuvette
5-transfer the liquid from test tubes to colorimeter cuvettes and take % transmission and record the results in a table
state the reason that when alcohol concentration increases % of light transmission decreases
as ethanol is non polar and the phospholipid bilayer is non polar so ethanol dissolves lipids from phospholipid bilayer so structure of cell membrane will be altered and there will be gaps in cell membrane causing red pigment to leak so solution darkens causing percentage
of light transmission to decrease
state controlled variables of the experiment and how they were controlled
1-the part of beetroot is taken from the core
2- same age, variety and storage time of beetroot (obtain from the same branch)
3-time the beetroot was soaked in water
4-surface area and volume of beetroot cylinders
suggest why test tubes were placed in water baths 5 minutes before cylinders were added
as temperature must be equilibrated to ensure the test tubes contain water at the correct temperature before experiment begins for valid results
why were the beetroot cylinders washed with distilled water and dried before experiment began
to remove excess surface pigments from cut at the age as it would distort transmission readings giving inaccurate results
