VCE Biology Question Thread

[vox nihili]

True or false: the folding of a protein into its functional 3D shape takes place on the ribosomes.

False yeah?

False-ish. Go with false, that's the answer they're looking for

[johnhalo]

Hey guys,
I'm having a bit of trouble understanding the two types of facilitated diffusion - carrier and channel mediated.

I have a couple of questions:
1) Is there a difference between molecules going through channel and carrier proteins? In other words, what determines a molecule going through the channel or carrier protein?
2) Can molecules go through both a channel and a carrier protein? In other words, can a molecule use a channel or a carrier protein, or are there specific molecules that can only go through each protein channel?

I may have been a bit confusing in my explanation, so if you need clarification I'll be happy to try explain again!

Thanks in advance guys

[TheAspiringDoc]

Hey guys,
I'm having a bit of trouble understanding the two types of facilitated diffusion - carrier and channel mediated.

I have a couple of questions:
1) Is there a difference between molecules going through channel and carrier proteins? In other words, what determines a molecule going through the channel or carrier protein?
2) Can molecules go through both a channel and a carrier protein?

I may have been a bit confusing in my explanation, so if you need clarification I'll be happy to try explain again!

Thanks in advance guys

Q1: If going through channel, then molecule is polar. If going through carrier, it is going against the concentration gradient.
Q2: I find this a bit vague/ambiguous. But sure, I guess something could theoretically. But in reality it (and the other same molecules) only would either go through one at a certain time because if you can go through channels, then why bother going through carriers and using ATP?
I think this is right but could someone else confirm?

[johnhalo]

Q1: If going through channel, then molecule is polar. If going through carrier, it is going against the concentration gradient.
Q2: I find this a bit vague/ambiguous. But sure, I guess something could theoretically. But in reality it (and the other same molecules) only would either go through one at a certain time because if you can go through channels, then why bother going through carriers and using ATP?
I think this is right but could someone else confirm?

Thanks for replying,

In reply to q2, I was told (and have read) that carrier proteins do not necessarily need ATP to work, so can be used passively. But when active transport happens, then an input of ATP is needed since active transport only happens through carrier proteins. Correct me if I'm wrong.

[TheAspiringDoc]

Thanks for replying,

In reply to q2, I was told (and have read) that carrier proteins do not necessarily need ATP to work, so can be used passively. But when active transport happens, then an input of ATP is needed since active transport only happens through carrier proteins. Correct me if I'm wrong.

Oh yeah, you're right. Sorry, I'm not sure yet then. I'll take a look around but hopefully someone else can assist

[johnhalo]

Oh yeah, you're right. Sorry, I'm not sure yet then. I'll take a look around but hopefully someone else can assist

I've been stuck on this for ages, but my assumption is that it doesn't matter and that molecules that can't diffuse through the plasma membrane can go through any of these channels regardless. However, it also doesn't make sense since there are two types of proteins in which molecules can go through the bi-layer. Thanks for the help

[melons]

I've been stuck on this for ages, but my assumption is that it doesn't matter and that molecules that can't diffuse through the plasma membrane can go through any of these channels regardless. However, it also doesn't make sense since there are two types of proteins in which molecules can go through the bi-layer. Thanks for the help

As far as I'm aware, carrier proteins can be used without ATP for passive transport, but for active transport need ATP.
So it can be used differently depending on the conditions.

In answer to question 2, I would say that molecules could use either the carrier or channel protein depending on which direction they are travelling through the plasma membrane. Not sure if I interpreted the question correctly though.

[vox nihili]

Hey guys,
I'm having a bit of trouble understanding the two types of facilitated diffusion - carrier and channel mediated.

I have a couple of questions:
1) Is there a difference between molecules going through channel and carrier proteins? In other words, what determines a molecule going through the channel or carrier protein?
2) Can molecules go through both a channel and a carrier protein? In other words, can a molecule use a channel or a carrier protein, or are there specific molecules that can only go through each protein channel?

I may have been a bit confusing in my explanation, so if you need clarification I'll be happy to try explain again!

Thanks in advance guys

1. The key difference between channel and carrier proteins is their tertiary structures. Channel proteins, quite literally, form a channel through the plasma membrane. If the right molecule can fit into the channel, it will simply fall through. Carrier proteins, on the other hand, must be deformed to pass through a molecule. Such that, the shape of the carrier protein changes as it conveys its cargo across the membrane.
Whether or not a molecule goes through a carrier or a channel protein depends really on what's available. There are some molecules (e.g. ions) that tend to go through channels and so on, but really there isn't a solid way of differentiating between the two.

2. Theoretically, yes. Not sure I can think of an example of something that actually does though.

[davenguyen1997]

Hello guys
Assume that somebody is diving at middle of the ocean then suddenly he has a cut from a dry coral.This is what I think about the cut, I think that he is in a hypertonic environment .Therefore, the water inside his body will be dry out to the ocean from the cut, also the Sodium Chloride from the ocean will diffuse simultaneously into his body from the cut.Am I wrong anywhere? Thank you so much.

[Buttercrisis]

Hi, I just had some questions is anyone could help me...
1. For RNA, my teachers have always told me that the complimentary base pairs are A-U and C-G but how can they have pairs when it's single stranded? Like it doesn't have another strand to pair with?
2.  In the phospholipid bilayer, why is the head polar, while the tails are non-polar? Because doesn't that mean that even if water can get through the head, it won't be able to get through the middle of layer (non-polar tails)?
3. Can a protein that stops at secondary or tertiary structure, or even primary structure (can it stop there?) be considered complete?
4. I read a document written by a teacher in the US and he said that for covalent bonds, because they're strong they can't be formed spontaneously and are formed through use of enzymes. But when I searched the internet for more info relating to it I couldn't find anything which said the same thing; I was just wondering if maybe that information was wrong?
Thanks! If you could help me, that'd be great.

[vox nihili]

Hi, I just had some questions is anyone could help me...
1. For RNA, my teachers have always told me that the complimentary base pairs are A-U and C-G but how can they have pairs when it's single stranded? Like it doesn't have another strand to pair with?
2.  In the phospholipid bilayer, why is the head polar, while the tails are non-polar? Because doesn't that mean that even if water can get through the head, it won't be able to get through the middle of layer (non-polar tails)?
3. Can a protein that stops at secondary or tertiary structure, or even primary structure (can it stop there?) be considered complete?
4. I read a document written by a teacher in the US and he said that for covalent bonds, because they're strong they can't be formed spontaneously and are formed through use of enzymes. But when I searched the internet for more info relating to it I couldn't find anything which said the same thing; I was just wondering if maybe that information was wrong?
Thanks! If you could help me, that'd be great.

1. During transcription they base pair to DNA
2. The reason for their polarity just comes down to the fact that the heads are charged and the tails are long alkane chains. Water can get through because it can, effectively, sneak past the tails.
3. A protein can't stop at a level of structure. All proteins have primary, secondary and tertiary structure. These structures are just a description of the shape of a protein at any given point (or its amino acid constituents in the case of primary structure). A protein can't be without shape
4. The information is very wrong.

[plsbegentle]

Hello guys
Assume that somebody is diving at middle of the ocean then suddenly he has a cut from a dry coral.This is what I think about the cut, I think that he is in a hypertonic environment .Therefore, the water inside his body will be dry out to the ocean from the cut, also the Sodium Chloride from the ocean will diffuse simultaneously into his body from the cut.Am I wrong anywhere? Thank you so much.

i have no idea what ur talking about, but diffusion is the movement of molecules from a region of high concentration to a region of low concentration.
Osomosis is a special type of diffusion, its the net movement of free water molecules from a dilute (weak) solution to a strong solution through a partically permeable membrane.You also mentioned about hypertonic reaction which i think u were on the right track when u said "will diffuse simultaneously into our body from the cut",(instead of in, its out) basically hypertonic reaction is when water leaves the cell via omosis due to the strong concentration outside of the cell. An example would be potato cells placed in a sucrose solution. The potato cell will obiosuly shrink in size due the strong sucrose solution because water wants to leave the cell. The other osmosis reactions are hypotonic where water enters the cell causing it to expand or even burst open and isotonic where solute concentration is equal in both the cell and the solution, therefore the movement of water is stable. If your still unsure, try videos on youtube such as crashcourse or khan academy, both provide very good content on osmosis and diffusion!

[Gogo14]

What are monounsaturated, polyunsaturated lipids and transfatty acids?

Also, why is cholesterol not a steroid, but a sterol lipid?

[davenguyen1997]

i have no idea what ur talking about, but diffusion is the movement of molecules from a region of high concentration to a region of low concentration.
Osomosis is a special type of diffusion, its the net movement of free water molecules from a dilute (weak) solution to a strong solution through a partically permeable membrane.You also mentioned about hypertonic reaction which i think u were on the right track when u said "will diffuse simultaneously into our body from the cut",(instead of in, its out) basically hypertonic reaction is when water leaves the cell via omosis due to the strong concentration outside of the cell. An example would be potato cells placed in a sucrose solution. The potato cell will obiosuly shrink in size due the strong sucrose solution because water wants to leave the cell. The other osmosis reactions are hypotonic where water enters the cell causing it to expand or even burst open and isotonic where solute concentration is equal in both the cell and the solution, therefore the movement of water is stable. If your still unsure, try videos on youtube such as crashcourse or khan academy, both provide very good content on osmosis and diffusion!

Thanks a lot the answer has a lot of signification for me. 😊

[TheAspiringDoc]

What are monounsaturated, polyunsaturated lipids and transfatty acids?

Also, why is cholesterol not a steroid, but a sterol lipid?

Monounsaturated = One carbon in it doesn't have its full hydrogen capacity so is double bonded to adjacent carbon
Polyunsaturated is the same, but just lots of the carbons aren't full with hydrogens

I thought cholesterol was a steroid?
edit: apparently a sterol is a modified steroid, and cholesterol is indeed a sterol.