VCE Biology Question Thread

[Sine]

They are released from the cell and bind to receptors on the same cell

that is correct

[Acegtr]

hi, is the purpose of the lymphatic system (other than delivering leukocytes) to clean up after an immune response? i assume that once leukocytes deal with pathogens, they can't just hang around and so lymphatic vessels take them away
also, are there any other functions of the lymphatic system that I'm missing?

[whys]

hi, is the purpose of the lymphatic system (other than delivering leukocytes) to clean up after an immune response? i assume that once leukocytes deal with pathogens, they can't just hang around and so lymphatic vessels take them away
also, are there any other functions of the lymphatic system that I'm missing?

The best way to think of the lymphatic system is as our own personal sewerage system. The lymph (the fluid that travels in the lymphatic vessels) remove cellular waste and debris, aid in the immune response as a mode of transport for immune cells, play a role in metabolism (absorbing fats) and contribute to the maintenance of fluid homeostasis within the body. Once leukocytes deal with pathogens, they 'commit suicide'. If they remain in the blood, lymph or the infection site, they can continue to carry out the immune response and end up damaging our own tissue. Thus, they undergo apoptosis. A few cells will remain, and these are what we call memory T and B cells, which will retain immunological memory and respond to the same antigen if encountered once more.

[Acegtr]

ohhh ok makes sense. thanks!

[p0kem0n21]

Hey guys, are reflex arcs still examinable as per the current study design? They are kind of similar to cell signaling (but not really at the same time), so I just want to check to make sure. Thanks 

Edit: Another question. How long do antibodies generally last in the blood? I thought they only last for a few months, but according to 2003 exam 1 q7a (section B), they can even last for a year. Do they stay in the blood that long, or is this because plasma cells in the bloodstream are still alive and secreting these antibodies? Or is there some other reason? Once again, thanks

[specimen]

For our SACS if we did the Unit 4 poster SAC in unit 3, would it count towards our unit 3 or unit 4 GA thing in our study score?

[Harrycc3000]

For our SACS if we did the Unit 4 poster SAC in unit 3, would it count towards our unit 3 or unit 4 GA thing in our study score?

unit 4

[-Lilac-]

Edit: Another question. How long do antibodies generally last in the blood? I thought they only last for a few months, but according to 2003 exam 1 q7a (section B), they can even last for a year. Do they stay in the blood that long, or is this because plasma cells in the bloodstream are still alive and secreting these antibodies? Or is there some other reason? Once again, thanks

Antibody levels in the blood can really depend on the pathogen you are dealing with/the individual as there can be different immune responses generated (tbh why there are different antibody responses isn't that well understood). But usually, plasma cells in the blood stay around anywhere from weeks to a few months and produce antibodies. There are also long-lived plasma cells in the bone marrow that can stay around and produce antibodies for many years/decades.

hi, is the purpose of the lymphatic system (other than delivering leukocytes) to clean up after an immune response? i assume that once leukocytes deal with pathogens, they can't just hang around and so lymphatic vessels take them away
also, are there any other functions of the lymphatic system that I'm missing?

Just adding another thought here cause I find this quite cool (but not really important for VCE).

The lymphatic system also allows us to detect a huge range of potential antigens as it concentrates the lymphocytes into small compartments (lymph nodes) and brings the antigen to them. As the antigen drains to them, we can keep every individual lymphocyte clone with a specific receptor shape in really low numbers and then have clonal expansion upon recognition. If we didn't concentrate the lymphocytes, we would have to have each clone in much higher numbers as the chance of the lymphocyte coming across its antigen randomly in the vessels across the body is very low. And as a result, we wouldn't have room in our system for many different clones, and thus our ability to recognize different antigens would be greatly decreased.

[PhoenixxFire]

Hey guys, are reflex arcs still examinable as per the current study design? They are kind of similar to cell signaling (but not really at the same time), so I just want to check to make sure. Thanks 

They are not assessable

[Chocolatepistachio]

if someone could help with this question

[PhoenixxFire]

^This isn't in the scope of bio.

The 4 macromolecules are proteins, carbohydrates, nucleic acids, and lipids.
The structures shown have carbon, hydrogen, and oxygen. Does that help tell you what type it is?

[Chocolatepistachio]

So it would be either carbohydrates or lipids but how do know which one

[whys]

I'll give you a hint. 9 is a fatty acid and 10 is glycerol. When they combine, what do they form?

[Chocolatepistachio]

So it would be lipids

[Chocolatepistachio]

For this question wouldn't it be D as it has the most amount of starch hydrolysed