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Biology Practical notes!!

K

Keki_kulz

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filza94 said:
Ok Duh we're getting urease & urea tomorrow in Bio 33, Now what wud be the Improvements, Sources of error & Limitations for the experiment below?
Enzyme Concentration

In this investigation, we will examine what happens to the rate of a reaction when the amount of enzyme is reduced. We will use urease, an enzyme that converts urea to ammonia. The ammonia causes the pH of the water to increase (it becomes more basic). You will be able to tell when a reaction occurs because the urea solution also contains a pH indicator that is becomes yellow in acid but turns red when the solution becomes basic.

The object of this experiment is to measure the amount of time it takes for the solution to turn red if less enzyme is used.

C1. Create a hypothesis regarding the the amount of urease and the rate of reaction of Urea.

C2. Obtain four test tubes and add 2 cm of urea to each.

C3. Label three of these tubes 1 through 3; the remaining tube will not be used; it will serve as a control.

C4. Have your lab partner start timing as you add 15 drops of urease to tube #1 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C5. Add 5 drops of urease to tube #2 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C6. Add 1 drop of urease to tube #3 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C7. Record your results in the answer sheet.

C8. Did using less enzyme produce a reaction?

C9. What was the effect of using less enzyme in your experiment? If your experiment did not work as expected, what should have happened?

C10. In general, what happens to the rate of reaction as the amount of enzyme is decreased?

C11. Do your results support your hypothesis? Explain.
Click to expand...


do u have any idea about 34?
 
S

Sarah_3420

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guys any help please? what came in p 31 or 33 that might tell us wuts coming in 32 ? tmoro is the exam :/
 
Gehad Mohamed

Gehad Mohamed

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libra94 said:
i have some notes for biology practicals, i would like to share it here :D 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.
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.

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 similarity
ERRORS IN MESUREMENTS!
1)irregular in shape
2)difficulty in focusing
3)preperation is squashed

and yeahhhh one more thingg, the values must be whole numbers!!! e.g if its 8.5mm u round it off to a whole number which is 9!!
Click to expand...
Thanks sooooooo much
 
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SAtheXtreme

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kitkat <3 :p said:
can anyone tell me how to make a plane diagram and sources of error in it please :(
Click to expand...


Usually you get a specimen on a slide or a photomicrograph to draw a plan diagram.

For a low power drawing

1. you must not draw individual cells when drawing a plane diagram.

2. draw only the outline of tissues.(don’t shade, draw thinner continuous lines.)

3. When drawing a specimen on a slide you can use high power to clearly see where the edges of

tissues.

4. Your drawing should cover more than the half of the space given.


When labelling(if you are asked to do so….)

1. label using a pencill and make sure the end of the line exactly touches the structure.

2. write the labels horizontally and outside the drawing itself.

3. Don't cross over the lines when labelling.

Hope this helps:)
plan diagram.jpg
 
K

kitkat <3 :P

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SAtheXtreme said:
Usually you get a specimen on a slide or a photomicrograph to draw a plan diagram.

For a low power drawing

1. you must not draw individual cells when drawing a plane diagram.

2. draw only the outline of tissues.(don’t shade, draw thinner continuous lines.)

3. When drawing a specimen on a slide you can use high power to clearly see where the edges of

tissues.

4. Your drawing should cover more than the half of the space given.


When labelling(if you are asked to do so….)

1. label using a pencill and make sure the end of the line exactly touches the structure.

2. write the labels horizontally and outside the drawing itself.

3. Don't cross over the lines when labelling.

Hope this helps:)
View attachment 40979
Click to expand...
THank u sooo much it really helped jazakAllah :)
 
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