VCE Biology Question Thread

[Yacoubb]

4) how would I relate the structure of lipid molecules to the function.
I know lipids are glycerol attached to three fatty acids or phosphate group or carbohydrate group but how would I link it to function?

I would imagine this would be relevant more so to phospholipids. The hydrophilic phosphate head & the hydrophobic fatty acid chains enable the movement of lipid-soluble materials into the cell. I believe VCAA 2008 q1 had this! Should check it out

[mondray]

Hi all,
I got my first prac sac write up for bio and I didnt do year 11 bio :/
We did an investigation on movement across the a plasma membrane. For the first part, we did diffusion of glucose and for the second part we did diffusion of iodine into a starch solution. The cell membrane was represented by a dialysis tube.
For my hypothesis, Im not too sure how to word it. Are there any examples or suggestions any could give me? ANy help would be appreciated, thanks

[Yacoubb]

Hi all,
I got my first prac sac write up for bio and I didnt do year 11 bio :/
We did an investigation on movement across the a plasma membrane. For the first part, we did diffusion of glucose and for the second part we did diffusion of iodine into a starch solution. The cell membrane was represented by a dialysis tube.
For my hypothesis, Im not too sure how to word it. Are there any examples or suggestions any could give me? ANy help would be appreciated, thanks

What were the contents of the dialysis tube?

[cosine]

4) how would I relate the structure of lipid molecules to the function.
I know lipids are glycerol attached to three fatty acids or phosphate group or carbohydrate group but how would I link it to function?

Thanks in advance

Well, there are three main types of lipids: Phospholipids, triglycerides and glycolipids

- Phospholipid: The plasma membrane of every living cell is composed of a phospholipid bilayer. Hence, phospholipids are an important biamacromolecule in biological membranes - in other terms, their function is structural components of the membrane. To relate their structure to the function, phospholipids are amphiphatic (partially soluble) meaning they have a region that can be dissolved in water (the phosphate head) and a region which cannot be dissolved in water (the fatty acid chains). This simple reason contributes to the fact that the phosphate head always faces out to the hydrophillic regions, and the fatty acid chains are always isolated from watery regions. Because of this phenomenon, it forms a bilayer, and as a result acts as a boundary for the cell.

- Triglycerides: Most common form of lipids, their main functions include thermal insulation and are a rich source of energy. They are composed of a gylcerol backbone and TRI - three fatty acid chains.

- Glycolipids: They are found on the plasma membrane. Glyco - carbohydrate, lipid - fat. Hence, a glycolipid is basically a carbohydrate chain attached to the glycerol backbone instead of the phosphate group, so remember that it still has two fatty acid chains. Their main function is to provide energy for the cell, and to act as markers for cellular recognition.


Hope I helped, correct me if im wrong anywhere, as im still in year 12 doing bio!

[mondray]

What were the contents of the dialysis tube?

My apologises, I should have been more precise!
First Experiment - Glucose solution in the dialysis tube submerged into a beaker of water
Second experiment - Starch solution in the dialysis tube submerged into a beaker of water containing iodine

[bts]

Anyone know any good links of vids for the role mRNA, rRNA and tRNA in the process of producing proteins from DNA?

Cheers

[Bestie]

Well, there are three main types of lipids: Phospholipids, triglycerides and glycolipids

- Phospholipid: The plasma membrane of every living cell is composed of a phospholipid bilayer. Hence, phospholipids are an important biamacromolecule in biological membranes - in other terms, their function is structural components of the membrane. To relate their structure to the function, phospholipids are amphiphatic (partially soluble) meaning they have a region that can be dissolved in water (the phosphate head) and a region which cannot be dissolved in water (the fatty acid chains). This simple reason contributes to the fact that the phosphate head always faces out to the hydrophillic regions, and the fatty acid chains are always isolated from watery regions. Because of this phenomenon, it forms a bilayer, and as a result acts as a boundary for the cell.

- Triglycerides: Most common form of lipids, their main functions include thermal insulation and are a rich source of energy. They are composed of a gylcerol backbone and TRI - three fatty acid chains.

- Glycolipids: They are found on the plasma membrane. Glyco - carbohydrate, lipid - fat. Hence, a glycolipid is basically a carbohydrate chain attached to the glycerol backbone instead of the phosphate group, so remember that it still has two fatty acid chains. Their main function is to provide energy for the cell, and to act as markers for cellular recognition.


Hope I helped, correct me if im wrong anywhere, as im still in year 12 doing bio!

Do I have to remember all that?

[cosine]

My apologises, I should have been more precise!
First Experiment - Glucose solution in the dialysis tube submerged into a beaker of water
Second experiment - Starch solution in the dialysis tube submerged into a beaker of water containing iodine

First experiment:

It is hypothesised that if the concentration levels glucose are higher in the dialysis tube as to the beaker of water, then the osmotic pressure will increase the rate of osmosis into the dialysis tube.

I havent had much experience with hypothesis before, so please correct me if im wrong, thanks.

[Yacoubb]

My apologises, I should have been more precise!
First Experiment - Glucose solution in the dialysis tube submerged into a beaker of water
Second experiment - Starch solution in the dialysis tube submerged into a beaker of water containing iodine

No worries

Experiment 1:
There would be a net movement of glucose out of the dialysis tube, from an area of high glucose concentration to an area of low glucose concentration, by diffusion.

Could you maybe give me a little more info on experiment 2?

[cosine]

Do I have to remember all that?

Well its not a matter of remembering it, but by learning the concepts and why they happen - such as WHY phosopholipids form a bilayer instead of a single layer - will actually solidify your knowledge.

[mondray]

No worries

Experiment 1:
There would be a net movement of glucose out of the dialysis tube, from an area of high glucose concentration to an area of low glucose concentration, by diffusion.

Could you maybe give me a little more info on experiment 2?

Thanks heaps Yacoubb and Cosine

2) You will investigate the movement of starch, water and iodine across a membrane. Iodine is a yellow chemical which turns blue/black when in the presence of starch. Dialysis tubing containing a solution of starch will be placed in a beaker of water containing some iodine.

[cosine]

No worries

Experiment 1:
There would be a net movement of glucose out of the dialysis tube, from an area of high glucose concentration to an area of low glucose concentration, by diffusion.

Could you maybe give me a little more info on experiment 2?

This was what I was refering to before, clearly from my hypothesis i assumed that the semi permeable membrane would not freely allow glucose diffusion, so as you said before the rate of osmosis is more rapid, hence why there is net movement of water molecules inside the dialysis tube in order to reach equilibrium. How exactly are we supposed to know ?

Thanks, I might be overthinking it but it sure is confusing me!

[Yacoubb]

This was what I was refering to before, clearly from my hypothesis i assumed that the semi permeable membrane would not freely allow glucose diffusion, so as you said before the rate of osmosis is more rapid, hence why there is net movement of water molecules inside the dialysis tube in order to reach equilibrium. How exactly are we supposed to know ?

Thanks, I might be overthinking it but it sure is confusing me!

You know what you could actually be right. Perhaps the dialysis tube is only permeable to water. I was thinking the same thing - typically you're looking at osmosis in your sac for movement across the membrane. Was diffusion or osmosis sort of the focus of your experiment??

[cosine]

You know what you could actually be right. Perhaps the dialysis tube is only permeable to water. I was thinking the same thing - typically you're looking at osmosis in your sac for movement across the membrane. Was diffusion or osmosis sort of the focus of your experiment??

If it is the case as i mentioned, could you read my hypothesis and help me out to improve it please

It is hypothesised that if the concentration levels glucose are higher in the dialysis tube as to the beaker of water, then the osmotic pressure will increase the rate of osmosis into the dialysis tube.


Also, what would be the independent and dependent variables in the hypothesis above?

Thanks Yacoubb!!

[vox nihili]

If it is the case as i mentioned, could you read my hypothesis and help me out to improve it please

It is hypothesised that if the concentration levels glucose are higher in the dialysis tube as to the beaker of water, then the osmotic pressure will increase the rate of osmosis into the dialysis tube.


Also, what would be the independent and dependent variables in the hypothesis above?

Thanks Yacoubb!!

You tell us!

IV: what are you, the experimenter, changing?
DV: what are you measuring/looking at?