biology paper 1 doubts

[♥Яαηõõşḧ♥]

At low power, u can see the cytoplasm with many dense granular bodies (refer to june 2012 question 2.)
At high power u can see, chloroplasts, nucleus, starch grains, vacuoles. u cant see the ER, ribosomes, mitochondria, lysosomes or cell membrane

june 2010*

 

[Irfan1995]

Can someone please make a list of organelles that can be viewed with a light microscope?

Very few:
1) Mitochondria
2) Chloroplasts
3) Nucleus
With very high magnifications, you can see the following:
4) Centriole (only one, not two)
5) Golgi apparatus (although it's a bit blurry)
6) Nucleolus.

You can see pretty much anything longer than half the wavelength of violet light. The wavelength of violet light is about 400 nm, so you can see anything bigger than 200 nm.

 

[NouranAyman]

At low power, u can see the cytoplasm with many dense granular bodies (refer to june 2012 question 2.)
At high power u can see, chloroplasts, nucleus, starch grains, vacuoles. u cant see the ER, ribosomes, mitochondria, lysosomes or cell membrane

at low magnification example 400X we can see only nucleus??

 

[Irfan1995]

http://www.google.mu/imgres?hl=en&client=firefox-beta&hs=lqx&sa=X&rls=org.mozilla:en-USfficial&biw=1280&bih=673&tbm=isch&prmd=imvns&tbnid=ju0rTU86mNVzTM:&imgrefurl=http://www.chembio.uoguelph.ca/educmat/phy456/456lec01.htm&docid=p0RMccoFY2lDWM&imgurl=http://www.chembio.uoguelph.ca/educmat/phy456/gif%255Csheet1.gif&w=444&h=332&ei=YuifULSbLNHirAfq4ICADA&zoom=1&iact=rc&dur=5&sig=118127656486629011851&page=1&tbnh=131&tbnw=176&start=0&ndsp=18&ved=1t:429,r:0,s:0,i:68&tx=123&ty=99
that's what i'm talking about...check it out. you'll see..

That's what I meant! An partially positive hydrogen atom DOES NOT form a hydrogen bond with an ADJACENT atom, but it can form a hydrogen bond with a much further one.

 

[Kumkum]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w10_qp_12.pdf
please help me with question number 9....
i don't understand

 

[NouranAyman]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w09_qp_11.pdf can someone explain Q 20 and Q 26

 

[railey]

Hope you guys are all ready for tomorrows Multiple-guess. BEST OF LUCK TO EVERYONE TAKING THE EXAM, and inshallah Allah (S.w.t) Will get us all a good mark.

 

[NouranAyman]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w10_qp_12.pdf
please help me with question number 9....
i don't understand[/quote
yeah please someone explain this question! its soo freakin weirdd

 

[♥Яαηõõşḧ♥]

at low magnification example 400X we can see only nucleus??

no low magnification is x10, u can only see the nucleus

 

[Irfan1995]

alright lisn! W is tissue fluid cuz they said that W has no plasma protein and no red blood cells while for Y and X blood pressure of blood entering the capillary should be higher than that leaving capillary and also blood entering capillary has a pressure higher than that of tissue fluid while Z is lymph as they said it lacks red blood cells but they didnt say about plasma protein as lymph has less plasma protein but it only lacks in RBCs so the answer is D

Actually, just because W doesn't have any plasma protein doesn't mean that it's automatically tissue fluid. It could also be lymph.
You can't also say that Z is lymph because it lacks RBCs, because tissue fluid doesn't have any RBCs as well. Also, lymph has NO plasma protein at all.

 

[xtremeforums]

Very few:
1) Mitochondria
2) Chloroplasts
3) Nucleus
With very high magnifications, you can see the following:
4) Centriole (only one, not two)
5) Golgi apparatus (although it's a bit blurry)
6) Nucleolus.

You can see pretty much anything longer than half the wavelength of violet light. The wavelength of violet light is about 400 nm, so you can see anything bigger than 200 nm.

In november 10 variant 1 question 1...
The answer is D. Stating that mitochondria are not visible under high power x400 light microscope.
Can u please clarify that?

 

[♥Яαηõõşḧ♥]

Hope you guys are all ready for tomorrows Multiple-guess. BEST OF LUCK TO EVERYONE TAKING THE EXAM, and inshallah Allah (S.w.t) Will get us all a good mark.

thanks... best of luck to u too, inshallah we'll all do great !!!!

 

[xtremeforums]

At low power, u can see the cytoplasm with many dense granular bodies (refer to june 2012 question 2.)
At high power u can see, chloroplasts, nucleus, starch grains, vacuoles. u cant see the ER, ribosomes, mitochondria, lysosomes or cell membrane

Thanks!!

 

[yashi30]

That's what I meant! An partially positive hydrogen atom DOES NOT form a hydrogen bond with an ADJACENT atom, but it can form a hydrogen bond with a much further one.

right... we were both talking about the same thing.

though my point is how come the secondary structure is affected? because these 2 groups are still there and can form hydrogen bonds.

 

[Irfan1995]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_11.pdf can someone explain Q 20 and Q 26

20) Interphase occupies over 90% of a cell's time. With cancers, they divide uncontrollably, so cell divisions are almost one after the other, so they have a much shorter interphase time.
26) Only pressure potential can be positive, so that means only X can be the pressure potential.
Also, you must know that water potential = solute potential + pressure potenial.
Solute potential and water potential is always negative.
A very negative number plus a positive number will always give a smaller negative number (for example, -200 + 50 = -150)
So the total water potential would be Y and the solute potential would be Z

 

[Irfan1995]

In november 10 variant 1 question 1...
The answer is D. Stating that mitochondria are not visible under high power x400 light microscope.
Can u please clarify that?

Hmm, mitochondria are about 0.5 micrometers long. And my school's lab have microscopes that reach up to x400 and I can see them with no problem (although they are a bit tiny)

 

[Irfan1995]

right... we were both talking about the same thing.

though my point is how come the secondary structure is affected? because these 2 groups are still there and can form hydrogen bonds.

I don't really understand your question

 

[xtremeforums]

Hmm, mitochondria are about 0.5 micrometers long. And my school's lab have microscopes that reach up to x400 and I can see them with no problem (although they are a bit tiny)

hmmm.. x400 means using the x40 lense on the microscope right? because x10 is the fixed magnification of the ocular. Am i right?

Anyway, lets just stick to mitochondria not being visible with a light microscope... ?

 

[NouranAyman]

20) Interphase occupies over 90% of a cell's time. With cancers, they divide uncontrollably, so cell divisions are almost one after the other, so they have a much shorter interphase time.
26) Only pressure potential can be positive, so that means only X can be the pressure potential.
Also, you must know that water potential = solute potential + pressure potenial.
Solute potential and water potential is always negative.
A very negative number plus a positive number will always give a smaller negative number (for example, -200 + 50 = -150)
So the total water potential would be Y and the solute potential would be Z

thank you so much

 

[♥Яαηõõşḧ♥]

Hmm, mitochondria are about 0.5 micrometers long. And my school's lab have microscopes that reach up to x400 and I can see them with no problem (although they are a bit tiny)

doesnt high power here mean that the objective lens is x40 and the eyepeice lens is x10.... In any microscope when the x40 lens is used mitochondria are not visible, right??