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Random biology questions before the exam

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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:

--- Quote from: lanvins on June 07, 2008, 10:02:46 pm ---What actually are C3 and C4 plants?

--- End quote ---

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

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