Biology/Physics ATP Preparation Thread

[abcde]

Not that tough!

 

[intelnehalem]

Oh Great ! So when will you be posting them ? Are they available on internet ??

I might be able to post it soon ! Need to get my camera back though They are not available in the net btw
and yeah, I'll post the answer to that question now!

 

[KarachiRocker]

Please be fast.. We ( atleast I ) need them badly.

 

[intelnehalem]

This is the circuit diagram and how the experiment is carried out.
At room temperature, take the readings from the ammeter . Voltage is constant at 5V from the DC supply.
Increase the temperature by 5C , observe the thermometer scale reading(line of sight has to be in line with the meniscus) to make sure the temperature is right. ALWAYS STIR BEFORE TAKING A TEMPERATURE READING
Now, measure and record the value of current from the ammeter.
Repeat the above for more temperatures .
Safety precaution: Water bath is used to prevent direct contact of heat to thermistor as well as to provide a uniform temperature.
Now , record your values in a table .( Temp/C, Voltage/V, Current/A and Resistance/ohms as headings)
Calculate resistance using R=V/I
Plot a graph of temperature vs Resistance (resistance on Y axis, temp on x axis)
From the graph it can be seen that resistance decreases with temperature!
Correct me if I am wrong :beer:

 

[KarachiRocker]

Great dude !

 

[intelnehalem]

Please be fast.. We ( atleast I ) need them badly.

I'll try and upload them by tonight

 

[abcde]

Absolutely correct!

 

[workaholic]

Well the above question(thermistor one) appeared in Nov04. In the mark scheme it was written that you could make your readings more accurate by using "tight connections" and "tap meters". What do they mean? I have asked this before but still I dont have the answer. Plz help!!!!!! :Search:

 

[KarachiRocker]

Thanks in Advance

 

[intelnehalem]

Great dude !

Thanks dude ! I hope we could discuss as many questions as possible
Another bio question

Design an experiment to show that biological washing powders are more efficient at removing blood stains and fatty deposits than normal washing powder

 

[intelnehalem]

Well the above question(thermistor one) appeared in Nov04. In the mark scheme it was written that you could make your readings more accurate by using "tight connections" and "tap meters". What do they mean? I have asked this before but still I dont have the answer. Plz help!!!!!! :Search:

oh was it in that paper? I ,too, have no idea what tap meters and tight connections mean ! Sorry dude

 

[abcde]

Well the above question(thermistor one) appeared in Nov04. In the mark scheme it was written that you could make your readings more accurate by using "tight connections" and "tap meters". What do they mean? I have asked this before but still I dont have the answer. Plz help!!!!!! :Search:

Sometimes, the needle of an ammeter/voltmeter/galvanometer gets stuck in one position. This would give inaccurate readings during the experiment so by tapping them, the needle becomes mobile again and gives the accurate reading.
I think tight connections are there to minimise the resistance of the circuit. correct me if I'm wrong.

 

[intelnehalem]

Answer to the biological washing powder question:
Biological washing powders contain enzymes! [YOU NEED TO KNOW THIS TO ANSWER THE QUESTION]
Take 2 equal sized material of the same type ex: Cotton
Create an equally sized blood stain/fatty deposit on both the 2 clothes.
Take 2 basins(or any suitable container) with equal amounts of water at the same temperature (suitably room temperature)
Add equal amounts of biological washing powder and normal washing powder to each of the 2 basins and stir to equally distribute.
keep the experiment in the same conditions(atmospheric) for the same period of time
Compare the size of the stain of the 2 materials (one which was in biological washing powder and the other in normal washing powder)
The cloth which was in biological washing powder would have a smaller stain than the other since enzymes are present in biological washing powders.
Biological washing powder contains Proteases (digests proteins ex: Blood) and Lipases (digests lipids ex: fatty deposits) mostly! (amylase may also be present)
repeat the experiment for further accuracy

 

[abcde]

Good! But don't write "digests proteins e.g. blood." Instead, it should be digests proteins e.g. those present in blood plasma.

 

[intelnehalem]

Tips on testing for Reducing Sugar/lipids/Protein/Starch
Starch:
Crush and grind a given solid sample
either you can make a solution with this or you can directly proceed to adding Iodine solution
Place the sample on a WHITE TILE (important!!)
Add Iodine SOLUTION (iodine disqualifies, it should be iodine solution)
Colour change:
red brown to blue black if starch is present

Reducing sugars:
Always for solutions only
If solid sample, crush and grind add 2cm3 of water and make a solution
Add equal amounts of Benedicts solution(if you have a 2cm3 solution, you have to add 2cm3 of benedicts )
HEAT over a WATER BATH
Colour change if reducing sugar is present:
blue to green/yellow/orange if only a little concentration of reducing sugar present in test solution
otherwise it is blue to BRICK RED PRECIPITATE!!

Proteins:
Add 2cm of Sodium/Potassium Hydroxide solution into the sample
Add a few drops of Copper sulphate solution using a pipette into the test tube containing the sample
If proteins are present:
Colour change is blue(due to Copper sulphate) to purple/mauve/lilac!

Lipids:
If it is a DRY solid, crush and grind the sample
Place it in a DRY test tube (have to be dry otherwise the experiment will be inaccurate)
add about 2cm3 of ethanol to the test tube containing the dry sample
pour ONLY THE LIQUID PART OF THE SAMPLE SOLUTION containing ethanol into another test tube containing 2cm3 of water!
If Lipids/fats are present, a cloudy EMULSION is formed

We tend to forget some of these minute details so I though of writing them down !

 

[intelnehalem]

Good! But don't write "digests proteins e.g. blood." Instead, it should be digests proteins e.g. those present in blood plasma.

Actually, blood cells contain protein too Haemoglobin in RBCs is also a protein, They are also digested by the enzymes. If the stain is dry, the liquid part of the blood would have evaporated, so I don't think it would be appropriate to refer to blood plasma ! I should have mentioned dry stains in my answer though

 

[abcde]

Thanks a lot, intel!

 

[intelnehalem]

Thanks a lot, intel!

My pleasure to be able to help !

 

[intelnehalem]

Here is another question which many might like!

You are given a pure bred plant that produces white flowers and another plant which produces Pink flowers.This is a result of co-dominance between 2 alleles. Describe how you would carry out a detailed investigation to show that Pink flowers are an intermediate phenotype. Give all the test crosses which you may use.

hint(this question might be tough): you have to use 2 crosses

 

[intelnehalem]

Here is another question which many might like!

You are given a pure bred plant that produces white flowers and another plant which produces Pink flowers.This is a result of co-dominance between 2 alleles. Describe how you would carry out a detailed investigation to show that Pink flowers are an intermediate phenotype. Give all the test crosses which you may use.

hint(this question might be tough): you have to use 2 crosses

To do this, you have to cross the pure bred white flowering plant with the pink flowering plant. To prevent self pollination, remove stamens and transfer pollen grain manually if possible from White flowers to Pink flowers or vice versa. After fertilization and seeds produced, plant them in a suitable area.
Cross:
Parent Phenotype: White X Pink
Genotype: CwCw x CrCw
Gametes : (Cw) (Cw) x (Cr) (Cw)
F1 Genotype: CrCw CwCw CrCw CwCw
Phenotype: Pink White Pink White

Phenotypic ratio- Pink:white = 1:1 observed within the plants

Obtain 2 Pink flowering plants and allow them to pollinate (explained above) After fertilization, plant the seeds and observe the results. A phenotypic ratio of PINK:RED:WHITE =2:1:1 observed
Parent Phenotype: Pink X Pink:
Genotype: CrCw x CrCw
Gametes : (Cr) (Cw) x (Cr) (Cw)
F1 Genotype: CrCr CrCw CrCw CwCw
Phenotype: RED PINK PINK WHITE

From here we can observe that Red and White are dominant phenotypes and present only when homozygous condition occurs. Hence we can conclude that Pink flowered plants are an intermediate since they occur only when in heterozygous condition.
More details possible ! I will edit when I have some more time