Some biology practical doubts

[blabla]

You said..

while you said

isn't that quite different?

the second ones right in my opinion - in the site i got this info from, they added this amount to 2 cm depth of protein sample, and they used 10% KOH solution. We probably wont be given this concentration anyway in the exam - at least in our school we are given 5% KOH. So I'd go for the 2nd option!

 

[rana]

SOURCES OF ERRORS!
1.temp nt controlled
2.pH not controlled or nt measured accurately
3.difficulty in judging the colour.
4.difficulty in having the same time
5.inaccuracy in preparing serial dilution
6.inaccuracy of equipment, fr e.g. pipette/syringe
7.too short time.
8.evaporation of the solution which can cause the concentration to change.

LIMITATIONS OF ERRORS!
1.measure the volume accurately using syringe with narrow range of calibration
2.repeat more times at each pH/conc./temp
3.use range of pH/conc./temp
4.accurate specific measuring devices
5.use colorimeter to measure the degree of colourness.
6.use buffer to control pHs
7.use of water bath/thermostat to control temp
8.use thermometer to measure the temp.
9.thermostatically controlled environment.
10.repeat with each conc.
11.volume of the sample(e.g. enzyme/substrate) must be the same..cuz as volume increases, conc also increases
12.keep only one factor different, and all others must be the same.

Reliability.....take minimum of 3 readings!
repeat with mre pH/conc/temp
and find out their mean
Accuracy.....seing electronic thermostat
use of pippettes instead of measuring cylinders

KEY
1)read the whole question till the end
2)decide number of readings to take
3)don't go for more or less than 3 readings per conc/vol of any ques.
4)make a table
5)write down the UNITS in each coloumn of the table...e.g. conc/cm^3 , temp/°C

MICROSCOPY!!!

1)propotion of thickness must be correct.
2)draw the organelles where u see them, dont just draw anywhere within the cell! never draw what u know.
3)whenever u see the plant cells, draw the cell walls.
4)IN PLAN DIAGRAMS, NO DRAWING OF ANY CELLS, AND NO SHADING...if u'll do either of them, u'll lose the whole mark!!
5)when asked to draw 2 cells, draw the ones that are easiest to draw. and dont draw more then 2 cells!
6)fraw the adjacent (touching) cells.
7)drawing should be large, unshaded.
8)in plan diagrams show the relative thickness of each layer.
9)draw the exact shape, if its oval or round or has wavy outlines
10)label the diagram...simplest thing to label is cytopasm, nucleus and cell membrane.
11)if its a trachea cell, then label goblet cells, cilia, blood vessels, muscular tissue, cartilage cells (lacunae)
12) when asked to compare 2 diagrams....make a table (drawing a table itself has 1 mark!)....put atleast one similarityMAKING TABLES
iNDEPENDENT Variable in the first column....and observations or dependent variables in other columns.....
in question 1 of exam..two kinds of questions cn be set....one involving quantitative observations like most enzyme experiments and other involving qualitative observations like food-tests...as far as observations for qualitative data are concerned...these will include most probably color changes during course of investigation...so a likely error for these experiments cn be difficulty in judging b/w different colors with your improvement being the use of colorimeter to measure color intensity.....
i have some notes for biology practicals, i would like to share it here hope it helps!
GRAPHS!
1.the value which is varying is always on the y-axis while the constant value is on the x-axis.
2.no unbroken lines
3.it must be neat and thin
4.the points can be joined using a ruler or by hand
5.do not draw beyond the plotted points.

Hi!
Could anyone please tell me some sources of errors and improvements of experiment relating to enzymes and rate of reaction ??

Pretty Pretty Pleeeease....

6.blobs or centre points more than 1mm are NOT acceptable
7.if zero is present in the reading, ur graph MUST pass through zero.
8.label both axis!
9.use appropriate units
10.use appropriate scale
11.use sharpened pencil to plot
12.plot the dots within circles, of equal sizes, must be clear and not too big.

Hi!
Could anyone please tell me some sources of errors and improvements of experiment relating to enzymes and rate of reaction ??

Pretty Pretty Pleeeease....

 

[blabla]

anybody got any good lung slides? they're soo weird...cant figure them out :\

 

[Saad (سعد)]

yeah this is what i meant thank you....so we can leave the vascular bundle position and identify it by label only?

If only vascular bundle is visible, then you can draw a line like this:

VB }---------- Label

'VB' is your Vascular Bundle on your drawing/photomicrograph.

However, if xylem, phloem, cambium, sclerenchyma etc. are visible inside the vascular bundle, then instead of labelling 'Vascular Bundle', label each of the four subunits of the V.B. individually.

Hi!
Could anyone please tell me some sources of errors and improvements of experiment relating to enzymes and rate of reaction ??

Pretty Pretty Pleeeease....

Its actually based on what the practical involved, exactly. For example, if you were measuring the color change of, say, Iodine, you would commonly make an error in judging the color - and its improvement could be using a colorimeter. If you were cutting potato pieces; then all the pieces were not uniformly cut, etc. and its improvement could be using a micrometer or a cork borer to cut it to same length.

Beware of writing factors affecting all solutions equally as 'errors' - such as temperature, pH, evaporation of water from the containers (if unlidded/uncovered) etc. These may work in some cases, where they don't affect all solutions/etc. equally, but not when they do so. Use your head here and be careful.

When preparing serial dilutions using syringes, there could be an air bubble trapped in the syringe, or the solutions not accurately prepared. This could be avoided by using a pipette or a more accurate measuring device.

Things which often work as improvements are using a wider range of concentrations of enzyme/substrate/independent variable, and taking more replicates for each concentration.

But it all depends on what the actual procedure is.

Hope that helps!

 

[raamish]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_s11_ms_31.pdf

1b(iii) what is the relationship of absorbance of light here?

Also, in diagram of a vein tunica intima should be double layered like the epidermis in plants or should it be a single line?
will cell surface membrane be double layered also?

 

[Saad (سعد)]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_s11_ms_31.pdf

1b(iii) what is the relationship of absorbance of light here?

Also, in diagram of a vein tunica intima should be double layered like the epidermis in plants or should it be a single line?
will cell surface membrane be double layered also?

When the protein denatures, it coagulates (forms 'clots'). The more protein that is coagulated due to the presence of CuSO4, the greater the optical density of the solution (the less light will pass/more light will be absorbed).

For example, the optical density of a glass of pure water is much less, as light can pass through it. Its greater when you put a handful sand into it; then, very small amounts of light will pass, the rest is absorbed, and you can't see through the sand.

Dunno about the artery, I haven't studied that yet at all. o_o Could use help there too.

 

[raamish]

When the protein denatures, it coagulates (forms 'clots'). The more protein that is coagulated due to the presence of CuSO4, the greater the optical density of the solution (the less light will pass/more light will be absorbed).

For example, the optical density of a glass of pure water is much less, as light can pass through it. Its greater when you put a handful sand into it; then, very small amounts of light will pass, the rest is absorbed, and you can't see through the sand.

Dunno about the artery, I haven't studied that yet at all. o_o Could use help there too.

thnx ok how do we differentiate b/w macrophages and neutrophils in microscope

 

[narutogirl]

umm..I have a huge doubt in how trachea is supposed to be drawn under these markings
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Biology%20(9700)/9700_w11_ms_34.pdf

I really need this to be understood :S :S :S..help T__T
and the alveoli, how is it drawn...??

 

[blabla]

thnx ok how do we differentiate b/w macrophages and neutrophils in microscope

http://classes.midlandstech.edu/carterp/Courses/bio211/chap17/Slide3.JPG

 

[AhmedNES]

how can u do serial dilution plz i need help and how to calibrate microscope.

 

[raamish]

http://classes.midlandstech.edu/carterp/Courses/bio211/chap17/Slide3.JPG

thnx got it. ok in artery and vein which tunica media is thicker and which tunica externa is thicker ? can u also post a link to a a lung?

 

[Saad (سعد)]

how can u do serial dilution plz i need help and how to calibrate microscope.

Bismillahir-Rahmanir-Raheem.

Let's say you have 1.0 mol dm-3 sucrose solution, and you are required to make five serial dilutions of it.

1. Label 5 test-tubes/beakers with 1.0, 0.1, 0.01, 0.001, and 0.0001. Put 10cm3 of the 1.0 mol dm-3 solution from the main solution you are provided, into the beaker labelled 1.0
2. Take 1 cm3 from the 1.0mol dm-3 solution and put into the beaker labelled 0.1. Add 9 cm3 of water. Now you have 10 cm3 of 0.1 mol dm-3 solution.
3. Take 1 cm3 from the beaker labelled 0.1 which you used prepared in step 2, and add it to the beaker labelled 0.01. Then, once again, add 9cm3 of water.
4. Take 1 cm3 from the beaker labelled 0.01 which you used prepared in step 3, and add it to the beaker labelled 0.001. Then, once again, add 9cm3 of water.
5. Finally, take 1 cm3 from the beaker labelled 0.001 which you used prepared in step 4, and add it to the beaker labelled 0.0001. Then, once again, add 9cm3 of water.

And now, you have all five serial dilutions prepared.

Oh, and if you're told to make serial dilutions differing in halves - such as 1.0, 0.5, 0.25, 0.125 and 0.0625, then instead of taking 1 cm3 of the solution and 9 cm3 of distilled water, take 5 cm3 of the solution and 5 cm3 of distilled water.

And what do you mean by calibrating a microscope? You mean using the eyepiece graticule and stuff?

Anyways, hope that helped insha'Allah!

 

[narutogirl]

Bismillahir-Rahmanir-Raheem.

Let's say you have 1.0 mol dm-3 sucrose solution, and you are required to make five serial dilutions of it.

1. Label 5 test-tubes/beakers with 1.0, 0.1, 0.01, 0.001, and 0.0001. Put 10cm3 of the 1.0 mol dm-3 solution from the main solution you are provided, into the beaker labelled 1.0
2. Take 1 cm3 from the 1.0mol dm-3 solution and put into the beaker labelled 0.1. Add 9 cm3 of water. Now you have 10 cm3 of 0.1 mol dm-3 solution.
3. Take 1 cm3 from the beaker labelled 0.1 which you used prepared in step 2, and add it to the beaker labelled 0.01. Then, once again, add 9cm3 of water.
4. Take 1 cm3 from the beaker labelled 0.01 which you used prepared in step 3, and add it to the beaker labelled 0.001. Then, once again, add 9cm3 of water.
5. Finally, take 1 cm3 from the beaker labelled 0.001 which you used prepared in step 4, and add it to the beaker labelled 0.0001. Then, once again, add 9cm3 of water.

And now, you have all five serial dilutions prepared.

Oh, and if you're told to make serial dilutions differing in halves - such as 1.0, 0.5, 0.25, 0.125 and 0.0625, then instead of taking 1 cm3 of the solution and 9 cm3 of distilled water, take 5 cm3 of the solution and 5 cm3 of distilled water.

And what do you mean by calibrating a microscope? You mean using the eyepiece graticule and stuff?

Anyways, hope that helped insha'Allah!

That was very helpful, if my first concentration is 5%, then i will make...5.0, 0.5,0.005.0.0005,0.00005. using the same way. (they will usually make it clear how they want the serial dilution to be done in the exam, right?

U seem to be really good at this bio practical stuff that i seem to have some sort of disability with it X,D
Can you pretty pretty please draw an alveoli for me, there is a big chance it might come tomorrow and I have no clue how the hell is it drawn T__T

 

[Saad (سعد)]

That was very helpful, if my first concentration is 5%, then i will make...5.0, 0.5,0.005.0.0005,0.00005. using the same way. (they will usually make it clear how they want the serial dilution to be done in the exam, right?

U seem to be really good at this bio practical stuff that i seem to have some sort of disability with it X,D
Can you pretty pretty please draw an alveoli for me, there is a big chance it might come tomorrow and I have no clue how the hell is it drawn T__T

o.o Yes, use that method and make those concentrations the same way. Beware; only use this method when they say 'produce a range of concentrations using serial dilution'. They can also ask you make 5 different concentrations with equal intervals, of something, from the original solution; such as giving you 1.0 mole dm-3 sucrose and then you may have to make 0.8, 0.6, 0.4, 0.2 and 0.0 for the practical - the method of doing that is different. Read the paper; they will usually make it clear.

Also, almost always, one needs a control solution. This would be 0.0 mol dm-3 of sucrose solution whether 'serial dilution' or 'dilution of equal intervals' method is used; 0.0 mol dm-3 is obviously, distilled water.

I'm good at theory Al-Hamdulillah, I'm mediocre at actual performance. That's what counts.

And I can't draw you an alveolus for several reasons reasons; one, ever since I was a kid, I never figured out how to use the Microsoft Paint feature; two, I don't have a scanner, so I can't hand-draw it and scan it; three, even if I could, I don't know how to draw it myself. I haven't even looked at the slides questions yet; I'm going to spend the night doing that insha'Allah.

Sorry.

 

[narutogirl]

I can't draw you an alveoli for several reasons reasons; one, ever since I was a kid, I never figured out how to use the Microsoft Paint feature; two, I don't have a scanner, so I can't hand-draw it and scan it; three, even if I could, I don't know how to draw it myself. I haven't even looked at the slides questions yet; I'm going to spend the night doing that insha'Allah.

It's okay, I was sorta pushy going to several posts and asking... and not getting answered. Felt frustrated and that is helped by the fact that I am freaking out because I suck at practical and have astigmatism, so enjoying the pain of not seeing the slide properly :'C

 

[Saad (سعد)]

It's okay, I was sorta pushy going to several posts and asking... and not getting answered. Felt frustrated and that is helped by the fact that I am freaking out because I suck at practical and have astigmatism, so enjoying the pain of not seeing the slide properly :'C

Don't worry about being astigmatic (I'm about 90% sure I'm astigmatic too, I just forget what the eye-doctor exactly said since I see him like once in a year and a half. >.>) Just don't remove your glasses when looking at the slide like most people do. It'll be a bit uncomfortable, but you'll see it properly.

 

[AhmedNES]

how can u do serial dilution whrn u have a 1.5% concentation stock solution plz answer.

 

[Saad (سعد)]

how can u do serial dilution whrn u have a 1.5% concentation stock solution plz answer.

The same way as explained above with 10%.

The way of making serial dilutions is the same no matter what the concentration of the stock solution is - take 1 cm3 of the original solution and 9cm3 distilled water each time, or 5 cm3 of either one, depending on the question.

In the example I gave above, just put 1.5% instead of 10%. Then you'll have 1.5% --> 0.15% --> 0.015% --> 0.0015% --> 0.00015 (or the fifth solution may the control; 0.0% - depends on the question).

Hope that helped insha'Allah.

 

[raamish]

The same way as explained above with 10%.

The way of making serial dilutions is the same no matter what the concentration of the stock solution is - take 1 cm3 of the original solution and 9cm3 distilled water each time, or 5 cm3 of either one, depending on the question.

In the example I gave above, just put 1.5% instead of 10%. Then you'll have 1.5% --> 0.15% --> 0.015% --> 0.0015% --> 0.00015 (or the fifth solution may the control; 0.0% - depends on the question).

Hope that helped insha'Allah.

hey saad help me real quick. could u post your plan diagrams of artery and vein and bronchiole and trachea. really cant understand how many layers there will be in them and their labelling?

 

[raamish]

The same way as explained above with 10%.

The way of making serial dilutions is the same no matter what the concentration of the stock solution is - take 1 cm3 of the original solution and 9cm3 distilled water each time, or 5 cm3 of either one, depending on the question.

In the example I gave above, just put 1.5% instead of 10%. Then you'll have 1.5% --> 0.15% --> 0.015% --> 0.0015% --> 0.00015 (or the fifth solution may the control; 0.0% - depends on the question).

Hope that helped insha'Allah.

please reply quickly. if u cant post your diagrams(although if u can plzz) then tell me the layers of bronchiole and trachea for e.g. trachea has epithelium then cartilage(i dont know in which layer) . After that i am confused which layers will come. HELPPPP