Prelim Biology (1 Viewer)

[TurkStyle]

Hi Guys i Need help with my Pratical Assesment please tell me what to do for each section or any one u can be bothered (especially the ones in red) to tell me about. Please tell me how to set out a Practical like start with aim and so on.

Related Syllabus Outcomes:

Organisms are mmade of cells that have similar structural charecteristics

Membranes provide seperation from and links with the external enviroment

Task Outline:
1)Plan, choose equipment and resources and perform a first-hand investigation to identify the following substances: glucose, starch, lipids, proteins, chloride ions and lignin.
2)Process information from secondary sources to identify mitochondria, chloroplasts, golgi bodies, lysomes, endoplpasmic reticulum, ribosomes, nucleus, nucleolus, and cell membranes.
3)Describe the current model of the cell membrane and explain how it accounts for the movement of substances in and out of the cells.
4)Perform a first hand investigation to model the selectively permeable nature of a cell membrane.
5)Compare the processws of diffusion and osmosis

thankyou.

 

[TurkStyle]

its never too late to answer to anyone of these

 

[lyounamu]

its never too late to answer to anyone of these

Since I don't see anyone helping you out. I better help you out.

1)
– Glucose Test:
§ Place 4 ml of sample in a test tube
§ Add 4 ml of Benedict’s solution
§ Heat gently in a water bath
§ If the solution turns orange-brown, there is glucose present
– Starch Test:
§ Place sample in a test tube
§ Add 5 drops of iodine solution
§ If the iodine turns purple, there is starch present
– Lipid Test:
§ Place a drop of sample on a piece of brown paper
§ If the paper becomes clear, the substance is a lipid
– Protein Test:
§ Place 4 ml of sample in a test tube
§ Add 5 ml of sodium hydroxide and 5 drops of copper sulfate (this is called the Biuret solution)
§ If the solution becomes light purple, there is protein present
– Chloride Ions Test:
§ Place 4 ml of sample in a test tube
§ Add 4 drops of silver nitrate
§ If the solution turns milky white (precipitate formed), chloride ions are present
– Lignin Test:
§ Add 3 drops of toludine blue to the sample
§ If the toludine changes from blue to blue-green, lignin is present

2) Use the micrograph to analyse different part of the cell. You should be familiar with all the features and how they look like. For example, mitochondria is made up of two membranes (inner & outer membrane). Inner membrane is greatly folded and increases its surface area for many chemical reactions to occur. Mitrochondria looks like a sausage.

3) The current model of the cell membrane is called the fluid mosaic model. According to this model, cell membrane is a thin sheet that consists of two thin layers (bilayer) of special lipid called phopholipid. The bilayer is very fluid and lipids can move about easil.y Other lipds such as cholestral are also found in it. Proteins are scattered throughout the membrane. The cell membrane is 40% lipid and 60% protein.

4) Perform a first hand investigation to model the selectively permeable nature of a cell membrane:
An experiment was performed as follows:
 A cellulose bag was filled with starch solution
 It was placed in a jar of water with iodine present
 Left overnight, the starchy solution in the cellulose bag turned purple
 This proved that the iodine solution travelled through the bag (by osmosis)
 This successfully modelled the selectively permeable nature of the cell membrane
 The cellulose bag was the cell membrane and the starch was the cytoplasm

5)
Diffusion:
Involves random movement of particles
Movement of substance from high concentration to low concentration
Requires no energy Requires no energy
Does not need to involve a differentially permeable membrane
Involves liquids and gases

Osmosis:
Involves random movement of particles
Movement of substance from high concentration to low concentration
Always involves a differentially permeable membrane
Involves only water

 

[TurkStyle]

hi lyounamy do u have any pracs that u have done in the past you can send to me cause im not quite sure about how to structure one like what to write ina conclusion etc..

 

[lyounamu]

hi lyounamy do u have any pracs that u have done in the past you can send to me cause im not quite sure about how to structure one like what to write ina conclusion etc..

Sorry. I have them but I don't have them in my computer.

However, you should structure them like:

• Aim
• Background information
• Materials
• Method
• Result
• Discussion
• Conclusion

If I can write it up, I will send you one. I doubt I will be able to do that...

 

[TurkStyle]

wow man ure a hero.
thank you very much.

 

[lyounamu]

wow man ure a hero.
thank you very much.

You're welcome.

 

[elz11]

just a question - if you are testing for glucose in an apple - then would you put a small apple piece in a test tube, add benedict's solution to the test tube and heat it?

 

[Trans4M]

hmm if u can u should try to convert it to solution ro something

like try crushing the apple with pestle and mortar and then get the juice extract put into test tube. Then add benedict solution and warm it up.

 

[elz11]

Ohh okay that makes sense. thanks
but for starch testing, you can use the full apple piece right?

 

[Trans4M]

i am not too sure about that but still try to make a solution if u can as u see it more clearly. I am usually told to make it a solution unless testing for lipids which u dont need really.