Paper 1 Practical Flashcards
(19 cards)
Culturing Microorganisms
What are culture mediums?[1]
They contain carbohydrates, minerals , proteins and vitamins they need to grow. [1]
Culturing Miroorganismisms
Why are cultures of microorganisms are not kept above 25 C in school labs?
In indutsries why are cultures grown in 37 C?.[2]
At 25 C harmful microorganisms are most likely to grow above this temperature.[1]
At 37 C The cultures are incubated at higher temperature so that they can grow a lot faster.[1]
Culturing Microorganisms
When investigating the effect of antibiotics on bacterial growth , state the steps that is needed to be taken for this investigation?.[5]
Place paper discs soaked in different types of antibodies on an agar plate that has an even covering of bacteria. Leave some space between the discs.
The antibotic should soak into the agar jelly and antibiotic resistance bacteria that aren’t affected will continue to grow in the agar around the paper discs, but non- resistant strains will die.
A clear area will be left where the bacteria have died - this is called the inhibition zone .
The paper disc that has not been soaked in an anitibiotic is the control. This makes sue that is due to the antibiotic effect only.
Leave the plate for 48 hours of 25 C.
Culturing microoragnisms.
How could you compare the effectiveness of different antibiotics on bacteria?.[1]
By looking at the relative sizes of the inhibition zones
Culturing microorganisms
How to you get more accurate results when calculating the inhibition zone to compare the effectivness of the antibiotics. ?[1]
What is the equation used to calculate the area of the inhiition zone?[1]
You can use the diameter to caculate the inhibition zone.
Area = pi x [radius] squared.
Osmosis
State the steps needed to observe how sugar solutions affect plant tissue.[6]
You cut up a piece of potato into identical cylinders and get some beakers with different concentrations , one should be sugar and the other one should be pure water. [ This is the independant variable]
You measure the mass of the cylinders using a balance, then leave one cylinder in each beaker for 24 hours.
Dry them with a towel to remove any excess water and meaurse their masses again.
If the cylinders have drawn water by osmosis they will have increase in mass. If the water had been drawn out they will decarese in mass.
You can caulculate the percenatge change in mass and then plot a few graphs.
The dependant varibale is the chip mass and the control variable is he temperature.
Osmosis
State the errors that could occur when investigating how sugar solutions affect plant tissue. [2]
How could you reduce the effect of these errors?.[1]
If some of the potato cylindetrs were not fully dried, the excess water would give a higher mass.
If water evapourated from the beakers, the concentrations of the sugar solutions would change.
Repeating the experiment and calculating th mean percentage change at each concentration.
Investigating Enzymatic Reactions
State relevant steps to investigate the effect of the pH on enzyme activity?. [6]
Put a drop of iodine solution into every well of the spotting tile.
Place a Bunsen burner on a heat proof mat, and a tripod and gauze over the Bunsen burner.
Put a beaker of water on top of the tripod and the gauze, heat the water until it is 35 C.
The control variable is the temperature of the water throughout the experiment.
Use a syringe to add 1 cm[cube] of amylase solution and 1 cm [cube] of a buffer solution with a pH of 5 to a boiling tube. .Use test tube holders, put the tube into the beaker of water and wait for five minutes.
Next use a different syringe to add 5 cm [cube] of a a strach solution to the boiling tube.
Mix the contents of the boiling tube and start the stop clock.
Use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and put a drop in the well. When the iodine solution remains browney - orange, starch is no longer present.
Repaet the whole experiment with buffer solution of different pH values sp see how pH affects the time taken for the starch to be broken down.
How do you calculate the rate of reaction when investigating the enzymatic reactions?. [1]
Rate = 1000/time
Food tests
Mention the steps needed to test for sugars. [4]
Prepare a food sample and trasnfer 5 cm [cube] to test tube.
Prepare a water bath so that it’s set to 75 C.
Add some Benedict’s solution to the test tube [ about 10 drops] using a pipette.
Place the test tube in the water bath using a test tube holder and leave it in for 5 minutes. Make sure it is pointing away from you.
If the food smaple contains suagr the test tube will change form blue to green/yellow/ brick-red.
Food Tests
Which solution do you use to test for starch ?.[1]
If starch is present what is the colour change?[1]
Iodine solution
browney orange - black/blue
Food tests
Mention the steps needed to be taken when testing for proteins. [3]
Prepare a sample of your food and trasnfer 2 [ cm cube] of your sample to a test tube.
Add 2 [ cm cube] of biuret solution to the sample and mix the contents of the tube by gently shaking it.
If the food smaple contains protein the solution will change from blue to purple.
Investigating Enzymatic Reactions
Mention ways you can adjust this experiment. [2]
Control the temerature using a water bath at 35 C. [1]
A colorimeter can be used to meaure the progress of the reaction more accuratelty. [1]
Investigating Enzymatic reactions
If you test at pH 3,4,5,6,7,8,9 and 10, Why don’t we know the exact optimum pH?.[2]
Because although two answers may both show quick reactions (e.g. pH7 and pH8), the actual optimum could be between those number (e.g. pH 7.6) so you need to test different pH’s to find out the exact optimum.
Investigating Enzymatic eaction
Why do you need a water bath?.[1]
To maintain the correct temperature, because temperature affects reaction rate)
Investigating Enzymatic reactions
Name one type of error that can happen during this investigation.[1]
Starting and stopping timers
Food test
Menetion relevant steps to test for protein.[3]
Prepare a sample of your food and transfer 2[cm cube] of your sample to a test tube.[1]
Add 2 cm[cube] of biuret solution to sample and mix the content of the tube by gently shaking it. [1]
If the food sample turns from blue to purple that means protein is present.[1]
Food Tests
Mention the relevant steps to test for lipids.[4]
Prepare a sample of the food you are testing.
Transfer about 5 cm [cube] into a test tube.
Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube.
Sudan III stain solution stains lipids. If the smaple contains lipids, the mixture will seperate out into two layers. The top layer would be red. If there is no lipids present, no seperate red layer will form at the lipids.
Investigating Enzymatic Reactions
Mwntion two control varaibles in this experiment. [2]
The concentration and volume of amylase solution.
