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Biology Practical 33!

Abood_spicy

Abood_spicy

Messages
3
Reaction score
16
Points
13
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!!
 
Jassim

Jassim

Messages
100
Reaction score
142
Points
53
Guys, try googling plan diagrams AND slides for yeast, artery, lungs, capillary and lymphocyte, macrophages, neutrophils. For plant cells google slides of potato, onion epidermis, VASCULAR BUNDLE and a general plant cell. This saves time and helps you identify the slides in the paper. For question 2, the contrast part, unless only differences asked, give only 1 similarity and the rest differences. Depending on what's given you could write about numbers, size, folds, location, thickness, shape, cilia, granules, vacuoles. Also be able to differentiate the stages of cell division if given.
For plan diagrams use microscope power x10.
For cell details use x40.
 
Jassim

Jassim

Messages
100
Reaction score
142
Points
53
Yeast can carry out
anaerobic respiration, known as fermentation. Knowing that yeast is a
living thing I can predict that:

Yeast respires best at room temperature (35-37°C)

I came to this prediction because most living things do respire best
at this temperature.

Yeast respires anaerobically, this is known as fermentation, the
equation for it is:


C6H12O6 CO2


I can now also predict that bubbles of CO2 will be produced.
------------------------------------------------------------

As I'm going to have high temperatures of water in this experiment I
can predict that there may be a drop in the number of C02 produced
because the high temperatures will denature the enzymes in yeast. The
way in which it works is that:

[IMAGE]



Method
======

Equipment I will need for this investigation will be:

· Dried Yeast

· Rubber Bung

· Plastic Beaker

· Delivery Tube with bung

· 2 Boiling tubes

· Sugar



I first collected a beaker of warm water from the water bath and
poured it into a boiling tube ¼ full. I then put 1g of sugar to it,
put a bung in it then shook until it dissolved. Then I put 1g of yeast
in and did the same. Next I removed the bung and fit a delivery tube,
I stood the tube in the remaining warm water in the beaker and placed
the other end of the delivery tube into Tube B which was ½ filled with
cold water. I waited 10 minutes to let the reaction take place after
which I noticed a stream of bubbles coming out of the delivery tube
(CO2). I recorded the amount of bubbles in 30 seconds and put it into
a results table. Although CO2bubbles were seen in the yeast mixture,
Tube B was needed to show them clearly and make them countable. I then
cleaned everything and repeated it but with different temperatures of
water in the plastic beaker, the temperatures were: 20ºC, 25ºC, 30ºC,
35ºC, 40ºC, 45ºC, 50ºC and 55ºC. I chose precise measurements of the
yeast using an electric balance to get precise and accurate results.
To make it a fair test I had the same amount of measurements for
everything in each experiment. Things that were controlled in the
experiment were:

· Amount of yeast

· Amount of water

· Amount of sugar

This was to make it a fair test; this left the temperature of the
water as the only variant. I measured the temperature of the water
with a thermometer to get accurate readings.



Results
=======

No. Gas bubbles given off (CO2)

Temp (ºC)

1st Recording

2nd Recording

3rd Recording

Average


I chose this range of measurements to show clearly the best
temperature that yeast respires at; from this I can plot a graph to
further clarify the best temperature. Several experiments were done,
and an average was taken to get more accurate and precise results.



Conclusion
==========

Firstly from the graph I can see that

· The peak is at 45ºC

· There is a gradual rise up to 45ºC

· There is a steep fall after 45ºC

I can conclude from this investigation that yeast respires best a
45ºC, but further analysis of my graph shows a steep fall after this
point, as I predicted (see prediction) this is a result in the enzymes
becoming denatured, so the reaction stopped. My prediction also said
the best temperature would be 35-37ºC but because different enzymes
work at different temperatures the best temperature was slightly
higher. Also because the higher the temperature the more energy
particles have to move around resulting in an increase in collisions,
therefore a better chemical reaction. Apart from my prediction on the
best temperature my conclusion fully supports my prediction, bubbles
of C02 were produced and the enzymes did denature at a high
temperature resulting in the reaction eventually stopping.



Evaluation
==========

My results were reliable, as I had no anomalies, if I had they would
have been visible in my graph, I had also strictly controlled the
amounts of water, sugar and yeast in my method resulting in valid data
to make a reliable conclusion. To improve this investigation I could
see if more sugar affected the rate of respiration, carried out more
experiments with lower temperatures of water e.g. 15ºC, 10ºC, 5ºC and
even 0ºC, this would give me a better graph showing me a full gradual
rise up to 45ºC. I could also have used better equipment, instead of
the delivery tube I could have used a burette, this would have made
counting the bubbles easier making my results more accurate. I could
have also had the end of it in a beaker of limewater then if it turned
cloudy/ milky it would have proved that the bubbles were CO2, as this
is the test for carbon dioxide. Some things that helped me do a good
investigation were preliminary work I had done before the experiments.
I went through the stages of setting up my equipment, what I should do
and also the amounts of yeast, sugar and water I should use, and also
a sensible range of water temperatures. I had also completed a
computer simulation of the experiment to give me better knowledge of
what I was doing.
 
NaNinG

NaNinG

Messages
122
Reaction score
1,495
Points
143
Jassim said:
Yeast can carry out
anaerobic respiration, known as fermentation. Knowing that yeast is a
living thing I can predict that:

Yeast respires best at room temperature (35-37°C)

I came to this prediction because most living things do respire best
at this temperature.

Yeast respires anaerobically, this is known as fermentation, the
equation for it is:


C6H12O6 CO2


I can now also predict that bubbles of CO2 will be produced.
------------------------------------------------------------

As I'm going to have high temperatures of water in this experiment I
can predict that there may be a drop in the number of C02 produced
because the high temperatures will denature the enzymes in yeast. The
way in which it works is that:

[IMAGE]



Method
======

Equipment I will need for this investigation will be:

· Dried Yeast

· Rubber Bung

· Plastic Beaker

· Delivery Tube with bung

· 2 Boiling tubes

· Sugar



I first collected a beaker of warm water from the water bath and
poured it into a boiling tube ¼ full. I then put 1g of sugar to it,
put a bung in it then shook until it dissolved. Then I put 1g of yeast
in and did the same. Next I removed the bung and fit a delivery tube,
I stood the tube in the remaining warm water in the beaker and placed
the other end of the delivery tube into Tube B which was ½ filled with
cold water. I waited 10 minutes to let the reaction take place after
which I noticed a stream of bubbles coming out of the delivery tube
(CO2). I recorded the amount of bubbles in 30 seconds and put it into
a results table. Although CO2bubbles were seen in the yeast mixture,
Tube B was needed to show them clearly and make them countable. I then
cleaned everything and repeated it but with different temperatures of
water in the plastic beaker, the temperatures were: 20ºC, 25ºC, 30ºC,
35ºC, 40ºC, 45ºC, 50ºC and 55ºC. I chose precise measurements of the
yeast using an electric balance to get precise and accurate results.
To make it a fair test I had the same amount of measurements for
everything in each experiment. Things that were controlled in the
experiment were:

· Amount of yeast

· Amount of water

· Amount of sugar

This was to make it a fair test; this left the temperature of the
water as the only variant. I measured the temperature of the water
with a thermometer to get accurate readings.



Results
=======

No. Gas bubbles given off (CO2)

Temp (ºC)

1st Recording

2nd Recording

3rd Recording

Average


I chose this range of measurements to show clearly the best
temperature that yeast respires at; from this I can plot a graph to
further clarify the best temperature. Several experiments were done,
and an average was taken to get more accurate and precise results.



Conclusion
==========

Firstly from the graph I can see that

· The peak is at 45ºC

· There is a gradual rise up to 45ºC

· There is a steep fall after 45ºC

I can conclude from this investigation that yeast respires best a
45ºC, but further analysis of my graph shows a steep fall after this
point, as I predicted (see prediction) this is a result in the enzymes
becoming denatured, so the reaction stopped. My prediction also said
the best temperature would be 35-37ºC but because different enzymes
work at different temperatures the best temperature was slightly
higher. Also because the higher the temperature the more energy
particles have to move around resulting in an increase in collisions,
therefore a better chemical reaction. Apart from my prediction on the
best temperature my conclusion fully supports my prediction, bubbles
of C02 were produced and the enzymes did denature at a high
temperature resulting in the reaction eventually stopping.



Evaluation
==========

My results were reliable, as I had no anomalies, if I had they would
have been visible in my graph, I had also strictly controlled the
amounts of water, sugar and yeast in my method resulting in valid data
to make a reliable conclusion. To improve this investigation I could
see if more sugar affected the rate of respiration, carried out more
experiments with lower temperatures of water e.g. 15ºC, 10ºC, 5ºC and
even 0ºC, this would give me a better graph showing me a full gradual
rise up to 45ºC. I could also have used better equipment, instead of
the delivery tube I could have used a burette, this would have made
counting the bubbles easier making my results more accurate. I could
have also had the end of it in a beaker of limewater then if it turned
cloudy/ milky it would have proved that the bubbles were CO2, as this
is the test for carbon dioxide. Some things that helped me do a good
investigation were preliminary work I had done before the experiments.
I went through the stages of setting up my equipment, what I should do
and also the amounts of yeast, sugar and water I should use, and also
a sensible range of water temperatures. I had also completed a
computer simulation of the experiment to give me better knowledge of
what I was doing.
Click to expand...



Thanx a lot dear.....u sure are helping.
Gudluck wid ur exams ....:)
 
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