VCE Biology Question Thread

[biy]

Could you say that the difference between tertiary and secondary structure of proteins is that secondary structure is the result of hydrogen bonding between different funcitonal groups (amine, carboxyl groups) of different amino acids in the polypeptide chain, which can result in alpha helices and beta pleated sheets. Whereas the tertiary structure is the consequence of the R-group interractions of different amino acids in a polypeptide chain, including hydrophobic and hydrophillic attractions, hydrogen bonding and covalent bonds between disulfide bridges.

[vox nihili]

Could you say that the difference between tertiary and secondary structure of proteins is that secondary structure is the result of hydrogen bonding between different funcitonal groups (amine, carboxyl groups) of different amino acids in the polypeptide chain, which can result in alpha helices and beta pleated sheets. Whereas the tertiary structure is the consequence of the R-group interractions of different amino acids in a polypeptide chain, including hydrophobic and hydrophillic attractions, hydrogen bonding and covalent bonds between disulfide bridges.

That's exactly it. Secondary structure refers to the interactions between the backbone and tertiary between the R groups.

[Jay.C]

Hey guys, just wondering which organelles and parts of a cell are useful to determine whether mitosis is occurring?

[jyodesh.com]

During mitosis the nucleus will degrade and you'll get compaction of the DNA into chromosomes. Centromeres will migrate to opposite poles of the cell and you'll get formation of the mitotic spindle. Its pretty obvious when it happens.

https://www.youtube.com/watch?v=P7m3WfzgZdI

[cosine]

The image attached asked how glucose diffused through the cell membrane. It says that glucose uses protein channels, If I were to write it diffuses down it's concentration gradient through carrier proteins, would this still be correct? Because I have learnt that protein channels facilitate small ions and minerals, whereas protein carriers facilitate small hydrophilic substances such as glucose.

Anyone? Thanks

[grannysmith]

The image attached asked how glucose diffused through the cell membrane. It says that glucose uses protein channels, If I were to write it diffuses down it's concentration gradient through carrier proteins, would this still be correct? Because I have learnt that protein channels facilitate small ions and minerals, whereas protein carriers facilitate small hydrophilic substances such as glucose.

Anyone? Thanks

Yeah protein channels/carriers pretty much the same thing in VCE. You'd still get the mark I reckon.

[cosine]

What happens during the passage of an action potential along the axon of a neuron? Doesn't the membrane become polarised, when the ions get pumped in, is it 3 Na+ ions inside the cell, and 2 K+ ions outside? If so, isn't this only facilitated diffusion, as it's going along the concentration gradient?

Thanks

[cosine]

How do phagocytes such as macrophages know exactly where/what a foreign pathogen is? Is it because the MHC markers of the phagocyte detect the foreign antigens on the pathogen, and hence engulf it? Also, if this is true (not sure, so what im gonna say might also be wrong), is phagocytosis non-specific, although it responds to antigens, because every response is the same to any type of antigen? Like whether it's a bacterium, or a virus, it would still engulf it the same way, so it's non-specific. But specific immunity is when SPECIFIC antibodies are made for an antigen?

My main question is if you cannot be bothered reading that above : do phagocytes interact with antigens, and upon not recognising them, engulf the pathogen?

Thank you

[sunshine98]

How do phagocytes such as macrophages know exactly where/what a foreign pathogen is? Is it because the MHC markers of the phagocyte detect the foreign antigens on the pathogen, and hence engulf it? Also, if this is true (not sure, so what im gonna say might also be wrong), is phagocytosis non-specific, although it responds to antigens, because every response is the same to any type of antigen? Like whether it's a bacterium, or a virus, it would still engulf it the same way, so it's non-specific. But specific immunity is when SPECIFIC antibodies are made for an antigen?

My main question is if you cannot be bothered reading that above : do phagocytes interact with antigens, and upon not recognising them, engulf the pathogen?

Thank you

Yes! 
Phagocytosis is considered to be apart of the second line of defence, and hence is nonspecific.

[cosine]

Yes! 
Phagocytosis is considered to be apart of the second line of defence, and hence is nonspecific.

So is what I said right? Because I made that up, my teacher could not answer it for me so I took my logic to it... Phagocytes interact with antigens, but because they do not recognise them, they engulf?

Sounds good, thanks sunshine98

[Dkontro]

What happens during the passage of an action potential along the axon of a neuron? Doesn't the membrane become polarised, when the ions get pumped in, is it 3 Na+ ions inside the cell, and 2 K+ ions outside? If so, isn't this only facilitated diffusion, as it's going along the concentration gradient?

The membrane depolarises as sodium ions are pumped in and re-polarises as potassium ions leave. The sodium potassium pump uses ATP to pump sodium back out of neuron and potassium back into the neuron. It isn't facilitated diffusion as there is a high concentration of sodium on the outside of neuron.

Thanks

[cosine]

No one answered  me

What happens when an action potential passes along an axon in terms of the ions coming in and out? I know that Sodium ions rush in, and Potassium ions rush out. Because the sodium ions are going from the outside the neuron and into it, from a high concentration to a low one, would this be considered facilitated diffusion? My teacher says it's active transports, because energy is required, but how can energy be required if the ions are going from high to low concentration?

Thanks guys

[jyodesh.com]

No one answered  me

What happens when an action potential passes along an axon in terms of the ions coming in and out? I know that Sodium ions rush in, and Potassium ions rush out. Because the sodium ions are going from the outside the neuron and into it, from a high concentration to a low one, would this be considered facilitated diffusion? My teacher says it's active transports, because energy is required, but how can energy be required if the ions are going from high to low concentration?

Thanks guys

During the action potential, it would be facilitated diffusion. Na+ ions travel into the cell through voltage gated Na_v channels. Potassium ions travel out of the cell through voltage gated K_v channels. What your teacher might be thinking about is the Na+/K+ antiporter thats constantly working to transport the sodium out of the cell and potassium into the cell against their electrochemical gradient (and thus requiring ATP).

[BakedDwarf]

Is this correct?
The major histocompatibility complex (MHC) is a cluster of tightly linked genes on chromosome 6 that code for MHC antigens that are attached to the surface of body cells; MHC antigens are marker proteins that enable the body to distinguish its own cells from foreign matter.
There are two types of MHC markers:

- MHC class I markers are found on all body cells that have a nucleus; they present foreign
 antigens to B and T cells

- MHC class II markers are found on all B and T lymphocytes and on some macrophytes

Can someone explain how MHC class I markers specifically present foreign
 antigens to B and T cells
?

Also, do we have to know what interleukins are? If so, what are they? (not sure if they were in my textbook or i just missed them)

[cosine]

Is this correct?
The major histocompatibility complex (MHC) is a cluster of tightly linked genes on chromosome 6 that code for MHC antigens that are attached to the surface of body cells; MHC antigens are marker proteins that enable the body to distinguish its own cells from foreign matter.
There are two types of MHC markers:

- MHC class I markers are found on all body cells that have a nucleus; they present foreign
 antigens to B and T cells

- MHC class II markers are found on all B and T lymphocytes and on some macrophytes

Can someone explain how MHC class I markers specifically present foreign
 antigens to B and T cells
?

Also, do we have to know what interleukins are? If so, what are they? (not sure if they were in my textbook or i just missed them)

MHC Class I markers are on every nucleated cell in the body. These are NOT responsible for presenting antigens. These MHC Class I markers are 'tagged' or 'labelled', meaning that they have these specific MHC markers so that all the other cells of the body can recognise them as self, and so they do not get destroyed.

MHC Class II markers are found on B Lymphocytes, T lymphocytes, Macrophages and Dendritic cells. These cells actually have both MHC Class I and MHC Class II. These Cells engulf foreign pathogens, digest them with their lysosomes, and present antigenic fragments on the Class II markers.