Random biology questions before the exam

[lanvins]

What's the difference between natural killer cells and cytotoxic T-cells? Their descriptions are frustrating similiar.

[nancy]

Cytotoxic T-cells are cells that destroy body cells that have been infected by viral particles. Similarly natural killer cells destroy body cells infected with viral particles as well as cancer cells ( cells developing tumors.)
A major differance between cytotoxic T-cells and NK cells is that while cytotoxic t -cells develop a memory response to a particular antigen in the form of T-memory cells, NK cells do not develop a memory response or memory cells.

[lanvins]

what is the relationship between the calvin cycle and the light independent stage of photosynthesis? Do we have to memorise the whole cycle?

What actually are C3 and C4 plants?

[jess3254]

What actually are C3 and C4 plants?

Well, in most plants, initial fixation of carbon occurs via rubisco, the Calvin Cycle enzyme that adds CO2 to ribulose biphosphate. Such plants are called C3 plants, because the first organic product of carbon fixation is a three-carbon compound (3-phosphoglycerate).
Examples of C3 plants would be rice, wheat and soybeans.

C4 plants are called C4 plants before they preface the Calvin Cycle with an alternate mode of carbon fixation that forms a four-carbon compound as its first product.

Here are some websites which explain C3 and C4:
http://wc.pima.edu/~bfiero/tucsonecology/plants/plants_photosynthesis.htm
http://www.slideshare.net/MrDPMWest/ap-bio-ch7-power-point (here's a slide show on photosynthesis)

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html (info on C4 plants)
http://www.geocities.com/profadrian/C3C4Plants.html

Hope that helps

[shinny]

i honestly can't remember much about it so ill just paste u a section from my notes

C3 and C4 Plants
•   C3 plants produce a 3 carbon compound in the step prior to the Calvin cycle.
•   C4 plants produce a 4 carbon compound in the step prior to the Calvin cycle.
•   C4 plants have a different leaf anatomy and can perform carbon fixation in bundle sheath cells.
•   Bundle sheath cells are deeper inside the leaf tissue, and thus, there is a greater CO2 gradient.
•   This causes a faster rate of CO2 uptake, increasing the rate of photosynthesis.
•   C4 plants live in hot climates, and will have their stomata closed for long periods during the day to avoid water loss. This creates the need to increase the rate of photosynthesis.

and im pretty sure theres not even ever been a vcaa question on this so dont worry too much about it

[JL_91]

My teacher said that that whole bit about C3, C4 and CAM plants has been removed from the syllabus, so all I'm going to do is have a brief read over it (just in case!).

The Calvin Cycle basically IS the light-independent stage of photosynthesis..I think! (Correct me if I'm wrong). And yes, I think we need to know the whole process in fair detail, but we don't have to memorise every last thing involved. Just the important ones.

Natural killer cells are non-specific, second line of defence cells that will act on any diseased cell; cytotoxic T cells are specific, third line cells that only act, and only on the specific target cell, when presented with an antigen by an MHC marker (an MHC-antigen complex).

...I'm a bit freaked out by the fact that we're getting 9 short answers on the exam this year, as opposed to 6 or 7. Time management is my #1 weakness! Every time I choose a subject, VCAA seems to choose my year to increase the number of questions on the paper for the first time... lol

[Mao]

how do u know the number of questions ur getting already? if ur basing that off the covers on the vcaa site; theyre not the actual number of marks+questions ur gonna get...it says somewhere in that document

the covers-sheets are what you will be getting
you might be confusing yourself with the sample exam [such as for chemistry], which are not.

[JL_91]

My bad - it has always been 9 questions, I confused myself from something someone else told me and some paper I saw! And yes, the cover sheet is how you find out how many questions/marks you're getting, I didn't get anything from the sample papers.

[shinny]

'Students should note that the number of pages, questions and marks shown for the examination may differ slightly from the number indicated in the actual examination books given to students on the day of the examination.'

straight from the vcaa site. i'm not too sure as to what differ slightly means; but judging from how certain u guys are that it is what we'll be getting, i guess thats just a statement saying don't be surprised IF it does change.

edit: 'SAMPLE Number of questions and mark allocations may vary from the information indicated' is also watermarked onto the cover - but yeh, i assume its just saying it MIGHT change

[BA22]

Cytotoxic T-cells are cells that destroy body cells that have been infected by viral particles. Similarly natural killer cells destroy body cells infected with viral particles as well as cancer cells ( cells developing tumors.)
A major differance between cytotoxic T-cells and NK cells is that while cytotoxic t -cells develop a memory response to a particular antigen in the form of T-memory cells, NK cells do not develop a memory response or memory cells.

The major difference is that Natrual killer cells are non-specific and T-cells are specific. You need to know this, this distinction is key to understanding the multiple layers and specifc function of the immune system

[lanvins]

1. Explain the difference between the patterns of growth of bacteria and viruses after infection of an organism.

2. How does a vaccination give rise to memory T-cells?

[memka]

1. Explain the difference between the patterns of growth of bacteria and viruses after infection of an organism.

Hmmm..something to do with bacteria have their own genetic material so they can reproduce by binary diffussion,
whereas viruses must take over the host cell to reproduce maybe?

2. How does a vaccination give rise to memory T-cells?

A vaccine contains a weakened form of the pathogen (which still has normal antigens).
This causes an immune response to the weakened pathogen, phagocytes engulf the pathogen and present it's antigens to T helper cells.
The Th cells stimulate other B and T cells some of which differentiate into memory cells specific to the pathogen.