VCE Biology Question Thread

[Callum@1373]

I think you may have misinterpreted my question. What I meant is, is there always an organic molecule bonded to the phosphate (other than the glycerol of course!)

Ah yep I getcha, not on every occasion there is an R or organic molecule group, but pretty sure that's well beyond the scope of VCE bio cos the course doesn't go into the specifics of it

[vox nihili]

I think you may have misinterpreted my question. What I meant is, is there always an organic molecule bonded to the phosphate (other than the glycerol of course!)

Ah yep I getcha, not on every occasion there is an R or organic molecule group, but pretty sure that's well beyond the scope of VCE bio cos the course doesn't go into the specifics of it

Absolutely beyond the VCE course. Plenty of people with degrees in the life sciences probably wouldn't know that.

Phospholipids always have something else attached to the phosphate.

[TheAspiringDoc]

"The fluid mosaic model explains various observations regarding the structure of functional cell membranes. The model, which was devised by SJ Singer and GL Nicolson in 1972, describes the cell membrane as a two-dimensional liquid in which phospholipid and protein molecules diffuse easily." - wikipedia.

I thought that because phospholipids are amphipathic (or is it philic or do they mean the same thing ) they'd struggle to get through the hydrophilic 'head' section. And as for the proteins, don't they need help getting across the membrane (remind me, what is the diff between carrier and channel proteins?)

Thanks everyone for your help - I really appreciate it!

[Biology24123]

I thought that because phospholipids are amphipathic (or is it philic or do they mean the same thing ) they'd struggle to get through the hydrophilic 'head' section.

Thanks everyone for your help - I really appreciate it!

What do you mean by the phospholipid struggling to get through?

[TheAspiringDoc]

What do you mean by the phospholipid struggling to get through?

struggling to get through the cell's phospolipid bilayer membrane

[vox nihili]

"The fluid mosaic model explains various observations regarding the structure of functional cell membranes. The model, which was devised by SJ Singer and GL Nicolson in 1972, describes the cell membrane as a two-dimensional liquid in which phospholipid and protein molecules diffuse easily." - wikipedia.

I thought that because phospholipids are amphipathic (or is it philic or do they mean the same thing ) they'd struggle to get through the hydrophilic 'head' section. And as for the proteins, don't they need help getting across the membrane (remind me, what is the diff between carrier and channel proteins?)

Thanks everyone for your help - I really appreciate it!

Really interesting question, shows that you're really thinking about this and that you've grasped the VCE knowledge exceptionally well.

BEYOND VCE

There are three different proteins called flippases (ATP-dependent phospholipid translocases), floppases and scramblases. Without getting bogged down in the details, these proteins facilitate the movement of phospholipids across the membrane. Otherwise, as you rightly pointed out, they would be stuck on either side of the membrane, unable to flip sides.

[Biology24123]

struggling to get through the cell's phospolipid bilayer membrane

Right. I get it

[TheAspiringDoc]

BEYOND VCE

Phosphate groups in a phospholipid have two free -OH groups. These can react with different organic molecules, effectively attaching them to the phospholipid. The presence of these groups changes the function of the phospolipids. For instance, one phospholipid (phosphatidylserine) has the amino acid serine attached to the phosphate group; if this phospholipid is found on the outside of the plasma membrane, it serves as a signal of apoptosis thereby attracting phagocytes to engulf the cell.

In regards to Mr. TRav's diagram, I thought that one of the fatty acid tails is always saturate and one isn't (in phospholipids, that is)?

Also, I may be reading it wrong, but on the website from wich this diagram is from, it even says "have a saturated fatty
acid (no double bonds between carbons) on C-1 and an unsaturated fatty acid (double
bonds between carbons) on C-2 of the glycerol backbone."

So what's what?

[vox nihili]

Are glycolipids formed this way

Sorry I didn't see this last night. Nailed it, that's absolutely right.

(Image removed from quote.)

In regards to Mr. TRav's diagram, I thought that one of the fatty acid tails is always saturate and one isn't (in phospholipids, that is)?

Also, I may be reading it wrong, but on the website from wich this diagram is from, it even says "have a saturated fatty
acid (no double bonds between carbons) on C-1 and an unsaturated fatty acid (double
bonds between carbons) on C-2 of the glycerol backbone."

So what's what?

Hmmm not entirely sure to be honest. Phospholipids vary greatly with respect to the fatty acids they contain.

[TheAspiringDoc]

Notes say: "Relenza: A drug designed to bind to neuramidase on the surface of influenza virus preventing the release of virions and stopping the replication and spread of the virus."

Is it supposed to say neuraminidase?

[sunshine98]

Notes say: "Relenza: A drug designed to bind to neuramidase on the surface of influenza virus preventing the release of virions and stopping the replication and spread of the virus."

Is it supposed to say neuraminidase?

Yep you are correct ( totally checked my notes to see this ) Remember , however , that you do not need to know these specifics. My teacher taught this as a means of helping us understand rational drug design and that should be ur priority , rather than the specifics of relenza.

[vox nihili]

Notes say: "Relenza: A drug designed to bind to neuramidase on the surface of influenza virus preventing the release of virions and stopping the replication and spread of the virus."

Is it supposed to say neuraminidase?

Yes it is. Could have googled this one though!

[TheAspiringDoc]

Yes it is. Could have googled this one though!

I did, and although google suggested 'neuraminidase', if you press 'show results for neuramidase' you still get heaps of results spelt that way which relate to influenza

[vox nihili]

I did, and although google suggested 'neuraminidase', if you press 'show results for neuramidase' you still get heaps of results spelt that way which relate to influenza

Bloody hell... :|

[geminii]

I always get this mixed up...would someone be so kind as to explain the difference between glucose, glucagon and glycogen? Thanks!