AS level biology help plz...

The topic is fluid mosaic model. Any help on the following two questions would be much appreciated.

1.Red blood cells were mounted on microscope slides in various solutions. They were examined by the light microscope.
What concusion could be drawn about the cell suface membrane from folowing observation?
When mounted in a detergent solution, the slide appeared yellow-red colour; individual cells could not be seen.

2. Some hormones are steroids, small lipid-soluble molecules; others are proteins. Suggest an explanation for the fact that sex hormones get into cells while hormones such as insulin remain outside.

Reply 1

Revenged

yaz203

The topic is fluid mosaic model. Any help on the following two questions would be much appreciated.

1.Red blood cells were mounted on microscope slides in various solutions. They were exaqmined by the light microscope.
What concusion could be drawn about the cell suface membrane from folowing observation?
When mounted in a detergent solution, the slide appeared yellow-red colour; individual cells could not be seen.

2. Some hormones are steroids, small lipid-soluble molecules; others are proteins. Suggest an explanation for the fact that sex hormones get into cells while hormones such as insulin remain outside.

1) What observation?

2) Steriods hormones, such as oestrogen, are lipid soluble so they can diffuse through the membrane. Insulin, is not lipid soluble and so cannot diffuse through the cell membrane...

Background information:

Steriods, such as oestrogen, therefore have "intracellular" receptors, which are located in the nucleus of the cell... They have slow responces...

Most things are not lipid soluble and can't diffuse through the membrane... The receptors are therefore located in the cell membrane... In the case of insulin, insulin binds to the receptor, part of the receptor is phosphorylated (phosphorous is added) and later a protein in the cell is phosphorylated...

This is only one mechanism of action of receptors... Others, like (nicotinic) acetylcholine receptor, causes opening of ion channels and others have complex intracellular responces... Don't worry, you don't need to know this for A-level...

Reply 2

yaz203

Thanks for your help.
The observation of the red blood cell being mounted in a detergent solution, the slide appeared yellow-red colour; individual cells could not be seen. What conclusion of the cell membrane can be made from this?

Reply 3

Revenged

yaz203

The detergent would break up the plamsa membrane... The contents of the cell would leak out, which is why you can't see any cells after the detergent has been added...

Reply 4

fettucini

Ayiyiyiyiyi! I got a D in A level biology :smile:

I don't understand a word of what has been posted above-lmao!

Reply 5

yaz203

thanks a lot revenged i understand it all apart from the reason why the detergent would break up the plama membrane.

Reply 6

Revenged

yaz203

thanks a lot revenged i understand it all apart from the reason why the detergent would break up the plama membrane.

detergents interfere with the arrangement of phospholipids in the plasma membrane...

polar heads are normally on the outside whereas the hydrophobic tails are in the inside of the membrane...

detergents interfere with this arrangement cauaing the membrane to break up...