hi, does tissue / blood rejection (after transfusion) cause the humoral or cell-mediated response? i came across a vcaa question which says it's only cell-mediated but i don't understand why?
VCE Biology Questions Thread
bioho4
Tbh this question is very similar to: Are viruses eliminated by the humoral response or the cell mediated response?
In theory both are activated.
But I think the more prominent one would be the cell mediated response. Because it seems more likely that the different markers on the transplant would be recognized as an intracellular threat rather than an extracellular threat, because its on a cell rather than in the blood (where the humoral response is more efficient), like you won't really have the donors cells floating around in the blood, though the humoral response would still be initiated.
Hence, I would talk about the cell mediated response rather than the humoral if no information is provided. However, VCAA is very specific in the language it uses for example in the sample exam 2022, 4c short answer, it specifically mentions the response against an intracellular pathogen (cell mediated) so I think if this question was to be asked there would be more context behind it to determine which pathway of the adaptive response needs to be mentioned.
Hey!
Just wondering what the difference between NADP+ and NAD+is?
And does glucose make ATP? Or does it get converted into ATP?
Hi bioho4! Can you please reference the particular VCAA question? Context is always useful.
The answer to your question actually depends on what is being transplanted/transfused.
- If it is a tissue transplant, the immune reaction to the tissue would be a Cell-Mediated response.
- If it is a blood transfusion, the immune reaction to the mismatched red blood cells would be a Humoral response.
That's not to say either won't induce both, though.
chimichurri
NADP+ has an extra phosphate group; and is used in photosynthesis.
NAD+ is used in cellular respiration.
Hey chimichurri!
I wouldn't worry about the specific chemistry involved.
Just know that they pretty much fulfil identical roles -- acting as electron/proton carriers/donors. With the difference being that NADPH is for Photosynthesis whereas NADH is for Cellular Respiration.
Also it seems like you should revise Cellular Respiration overall 
(Glucose is broken down to make energy to synthesise ATP)
Sorry there chimichurri I missed that second part! Moskva Is right!
In Photosynthesis: water is split using sunlight; and this releases electrons. These electrons are used to load NADP+ into NADPH. Also, hydrogen ions (H+) are released. These build up on one side of the membrane, creating a 'proton gradient'. (Since there is a lot of them on one side, they want to diffuse to the otherside). They then pass through this protein called ATP Synthase, which acts like a watermill; adding the third phosphate group to ADP; forming ATP!
This ATP is then used up in the light independent stage - which produces glucose.
So while photosynthesis does produce ATP; it's only in the first light dependent stage. There is none left over at the end!
This may sound similar to the Electron Transport Chain! In fact: it is! Except the direction of H+ ion flow is the opposite, and other reactions happen (Such as FADH, etc...) and the H+ ions come from the NADH/FADH produced in the krebs cycle etc... (instead of water).
Moving back a bit, during glycolysis (when glucose is split); it produces two 'pyruvate' molecules;
The thing is, it also takes two ATP to do this. So it is really a net 2 ATP produced (as it takes 2, but makes 4). Note that the atoms in glucose aren't being made into ATP; it's just the electrons!
Hence in photosynthesis: Sunlight & Water --> e- --> ATP....... --> Glucose
And in Cellular Respiration: Glucose --> e- --> ATP
So it's the electrons from ATP that are transferred. Not the ATP molecules!
I don't think you need to know all that btw... 
Secondary responses are extended cellular responses to an antigen utilising specified cells such as Phagocytes and Monocytes while primary responses are shorter lived and more often preventative toward antigens such, (skin, stomach acid etc).
7 days later
Hi, RBCs aren't nucleated therefore they don't have MHC 1 markers. So how are they identified as self/non-self? And how can blood transplants be rejected from the recipient's body?
- Edited
RBCs don't have MHC/HLA markers but some will have "red cell antigens". Most times these atigens will fall under either type-A or type-B (there are a few minor ones but they are very very uncommon so don't worry about it).
You may have heard of the term "blood type", which can be either O, A, B or AB (for all intents and purposes).
- People with type-O blood type have no red cell antigens on their red blood cells.
- People with type-A blood type have type-A antigens on their red blood cells.
- People with type-B blood type have type-B antigens on their red blood cells.
- People with type-AB blood type have both type-A and type-B antigens on their red blood cells
Ok, due to Immunological Tolerance, and the relatively conservative nature of these A and B antigens, people with a certain blood type will be able to accept any blood with the same or less antigens. Since they are recognised as self. That is to say, a person with type-A blood will be able to accept Type-O (no antigens, less) and Type-A (same) blood; but not Type-B or Type-AB blood.
Blood transplants are rejected is because the antigens in the transfusion are not recognised as self (i.e. foreign).
EDIT: just to be extra clear, this is quite a simplified view of blood types, as there are more red cell antigens types than just A and B; rhesus factors also need to be taken into consideration (which is technically just another type of antigen).
Ah ok I see,
The VCAA question explicitly states a tissue has entered the body; presumably transplanted but that doesn't really matter.
And, yes, MHC class 1 on the cells of the tissue is what allows Cytotoxic T Cells to recognise them.
Also, the cells themselves aren't considered pathogens, just foreign.
5 days later
- Edited
Just want to confirm if my reasoning is right and ask a question about how index fossils are use to date other fossils found in the same strata:
Firstly radiometric dating is utilized to date igneous rock associated with (near) sedimentary layer that the index fossil is found within, percentage of parent isotope is compared to broken down products, hence using stratigraphy it can be inferred that the age of the index fossil = ____.
Using stratigraphy, the fossil found in the same strata is the same age as the index fossil, ____.
So if the question asked whether using index fossils is absolute or relative (point 2) what would be say?
Relative - because the age of the fossil is being determined by using the index fossil nearby?
or Absolute - because the NUMERICAL value of the fossil is known because of the INDEX fossils whose NUMERICAL age is also known?
Hey tubes!
- Firstly radiometric dating is utilized to date igneous rock associated with (near) sedimentary layer that the index fossil is found within, percentage of parent isotope is compared to broken down products, hence using stratigraphy it can be inferred that the age of the index fossil = ____.
Here you must mention that calculations are made based on the half life of the particular radioisotope measured in the radiometric dating; otherwise, how does the ratio of parent to daughter nuclei help?
It might also be good to mention the type of radiometric dating technique you are referring to (i.e. K-Ar dating), as they all have ranges.
- Using stratigraphy, the fossil found in the same strata is the same age as the index fossil, ____.
Yes, you are correct here as well, but because the unknown fossil is more often than not in another strata from the index fossil used, the index fossils are often used in conjunction with the principle of superposition (which states that rock strata are arranged in a order of progressing age, with the newest at top, in normal conditions). That is to say, if there is a fossil of unknown age and it is found below an index fossil, it can be inferred that the unknown fossil is older than a certain age (i.e. that of the index fossil); and vice versa.
So if the question asked whether using index fossils is absolute or relative (point 2) what would be say?
Relative - because the age of the fossil is being determined by using the index fossil nearby?
or Absolute - because the NUMERICAL value of the fossil is known because of the INDEX fossils whose NUMERICAL age is also known?
Relative. If an index fossil is used it is always relative. Because it is in relation -- or in other words, relative to -- the index fossil (also links back to my previous point that the unknown fossil is more often than not, in a different rock strata to the index fossil, so the approximate numerical age is not known anyway).
Hope this helps 
.
Moskva
Thank you it makes sense. But this VCAA question is kind of confusing, like I understand the answers but I'm confused on how to categorize it. 2018 NHT 7 b and c in which it asks how the ABSOLUTE AGE can be determined using the ancient mollusk (similar to index fossils in the sense of providing RELATIVE age), so it is a relative dating technique that can provide ABSOLUTE AGE or it is an absolute dating technique.
Thank you once again
- Edited
God
Hi,
I agree with your first point. But in that VCAA question by determining absolute age of the igneous rock you could determine the absolute age of the ancient mollusk (as specified in the stem) by using relative dating techniques, since its found in the same stratum (after first using absolute dating techniques on the igneous rock), so would finding the relative age of the ancient mollusk (in the same stratum as the dated igneous rock) be used to determine its absolute age of 50 my???? So is it also possible for it to be the other way around????
So all in all what technique would it be: absolute or relative???