Investigating the Effect of Temperature on the Movement of Pigment through Cell Membranes

Investigating the Effect of Temperature on the Movement of Pigment through

Cell Membranes

INTRODUCTION:

The aim of experiment is to prove that temperature effects on a

proteins in cell membranes so that pigment can pass through them

HYPOTHESIS:

On higher temperatures proteins in membranes denature so there is no

barrier to prevent the passage of large molecules

THEORETICAL BACKGROUND:

Certain chemicals and treatments, such as ethanol or high

temperatures, can destroy the partial permeability of cell membrane.

The membranes are still present but behave as if holes have been

punched through them and they no longer provide barrier to the passage

of large molecules such as sucrose. High temperatures and alcohols

denature membrane proteins and increase fluidity of membrane lipids;

alcohols at high concentrations can also dissolve lipids.

In beetroot cells the red anthocyanin pigment occurs in the vacuoles.

Each vacuole is surrounded by a tonoplast membrane and outside of it,

the cytoplasm is surrounded by the plasma membrane. On higher

temperatures proteins loose their ability of control the transport

through cell so any large molecule can pass trough.

APPARATUS AND MATERIALS:

¨ Test tube rack with 10 test tubes

¨ Graduated syringe

¨ Scalpel

¨ Cork borer

¨ Stop watch

¨ Forceps

¨ Colorimeter

¨ Tap root of beetroot

¨ Distilled water

SAFETY:

¨ Carefully use cork borer and scalpel to prevent injuries by cutting

¨ Use Bunsen burner with great precaution to prevent burns or lighting

materials

¨ Water in beaker is very hot so watch out that you don't spill it on

you to prevent burns

¨ Watch out that you don't break any glass apparatus to prevent

cutting

METHOD:

¨ Using a cork borer and scalpel make 10 cylinders of beetroot of 5 cm

length.

¨ Heat 200 cm3 of water up to 85 ºC in 250 cm3 beaker (make sure that

thermometer is in the water).

¨ While heating, with a syringe, put 10 ml of distilled water in 10

test tubes and label them: 85, 80, 75, 70, 65, 63, 60, 55, 50 and 45.

¨ When 85ºC temperature is reached remove the Bunsen burner and put

one beetroot cylinder in the water and leave it there for exactly one

minute.

¨ After one minute use forceps to take it out and put it in a test

tube marked 85.

¨ Put some cold water in the beaker until 80 ºC is reached and t...

... middle of paper ...

...tly changing. In some moments changing would stop but that

isn't reliable sign that that is the right colour density because

after couple of moments changing would start again. Solution is to use

more sensitive equipment or to get colorimeter checked because it

could be broken.

¨ Fifth problem is in humane nature. During the test we had a good

time so occasionally we forgot to take the beetroot out for few

seconds longer than it should be. We didn't pay all attention to

professor so we forgot to shake test tubes before we took the beetroot

out. Also, I didn't take a paper with me during the colour test so

when I got result, occasionally I would forget what it was while I was

going back to my seat. Also there was some noise in the classroom so I

could misunderstand my partners in the experiment when they came with

result.

¨ To be sure in experiment results the best thing is to repeat it at

least once to increase the reliability of them. Now when I know the

whole procedure of experiment, results in repetitive experiment should

be more accurate. Also this is good background to compare how

different concentrations of ethanol effect on the membrane

permeability.