Practicals Flashcards
Investigate how the rate of photosynthesis is dependent on light intensity- 6 marker
I would Add water to a beaker, and add sodium hydrogen carbonate which provides carbon dioxide.
I would add a piece of pondweed plant to the beaker ( make sure that I cut the end of the pondweed plant which ensures that the xylem tubes are open so there will be er oxygen and water movement: oxygen bubbles escape more easily, so I’ll be able to see the bubbles clearly.) make sure that the cut end is facing upwards.
Place an inverted funnel on the pondweed plant and add a test tube on top of the funnel to count the oxygen bubbles being produced.
Place a lamp at a fixed distance of 30cm (acts as light energy)
Start a stopwatch and count the number of OB being produced in 60 seconds.
Repeat this process for 3 times and calculate an average result.
Place the lamp at a closer distance (10cm) and count the number of OB being produced in 60 seconds, I would realize that the amount of OB increased since the light intensity increased so there will be a faster rate of photosynthesis.
Make a table and record the results of distance vs the amount of OB produced, then I would plot the results in a graph.
What is the independent variable, DV and CV of the photosynthesis practical? How to improve accuracy and reliability for this study?
IV- what you change. (Distance)
DV- what you measure. (amount of oxygen bubbles produced)
CV- what you keep the same. (Volume of water, concentration of sodium hydrogen carbonate, etc)
You can improve accuracy by using a gas syringe instead of counting the OB ( which can measure the volume of gas in a chemical reaction) for precise results
Repeat the experiment at different distances ( 10cm, 20, 30)and calculate an average.
Control the temperature by using a water bath to ensure the temperature is steady.
Investigate the effect of exercise on heart rate ( make a practical procedure) 6 marker-
Measure student A resting heart rate by using 2 fingers ( middle and index finger) and pressing gently on your wrist or on your neck. And record on a table your resting heart rate.
I would make student A Perform an exercise; jogging for 4 minutes
Immediately after measure their heart rate for 1 minute by using a heart monitor and record the number of heart beats in 60 seconds on the table.
Rest for 3 minutes and measure your heart rate again after recovery and record it by writing it down on the table.
Repeat this process again with student B, to ensure a wide range of results. Repeat 3 times to ensure accuracy.
Calculate the average heart rate for each stage (resting, immediately after exercise, and during recovery).
Compare the results of your heart rate before exercise and after exercise and plot a graph of heart rate vs exercise based on your results.
What is the IV, DV, CV In this investigation?
IV- the amount of exercise being done
DV- heart rate
CV- same type of exercise, the food intake of the students prior to the investigation, method of measuring the heart rate, the temperature of the environment, etc.
Why is an LED lamp used instead of a normal lamp? Why is an LED lamp used for the experiment?
In an LED lamp, we can keep the temperature constant since light is being released without too much heat, so only light is affecting photosynthesis, which makes it a fair test, since in a normal lamp as light intensity increases, heat increases. Which is not a fair test since we don’t know what affected the rate of photosynthesis.
Led lamp is used since it prevents the denaturing of enzymes in the plant, and helps maintain the water temperature stable.
What are we using the scalpel for in the Osmosis Practical?
To make sure we cut even pieces of potato, all of them should be the same size, length and width. to ensure the surface area is the same for osmosis, because if it wasn’t it wouldn’t be a fair test.
What does a positive/ negative answer indicate whilst you’re calculating the percentage change in mass for the potato cylinders in the osmosis practical?
Positive answer- indicates that the potato gained mass/ water ( water molecules move in)
Negative answer- shows that the potato lost water ( water moves out of the potato)
How to calculate percentage change?
Final - Initial divided by initial x 100
What does the point where the line crosses 0% mean? For the osmosis practical?
That’s the isotonic concentration, in which there is no net movement of water.
Why use % change instead of just mass change? Why are using the same sized potatoes important?
Because it standardizes results of different sized potato’s.
To make sure that the only factor that is affecting the potatoes mass is the sucrose concentration, and not because its size.
As sucrose concentration increases, the percentage change decreases, why?
The water molecules move out the potato, causing the overall mass to decrease.
What is the risk assessment for the osmosis practical-
When using the scalpel, cut away from your fingers.
Use a cutting board.
How does using more concentrations of sucrose relate to accuracy?
The more variety of concentrations you use, the more reliable and accurate the graph is.
Why does the frequency of breathing increase whilst exercising?
The muscles are working harder and aerboically respiring since there needs to be oxygen being delivered to the muscles and carbon dioxide to be removed to keep up with the high energy demand the body requires, if the body cannot meet the energy demand then the muscles will anaerobically respire which produces lactic acid.
What are some variables from the students from the exercise investigation that have to be controlled to be able to ensure a fair test?
Students should be similar size, same fitness level, same gender, age
Investigate the effect of exercise on breathing-
Workout student A’s breathing rate whilst he’s resting.
Count the number of breaths student A has taken in 15 seconds and multiply that by 4 to obtain the breathing rate in a minute.
I would repeat this process 2-3 times to calculate an average, and ensure accuracy.
Student A will perform an exercise for a set time of 4 minutes, immediately after the exercise, I would count the number of breathes taken in 15 seconds and multiply that by 4 again.
I would repeat this step every minute for 5 minutes after the exercise, to see how breathing rate changes gradually after exercise back to the normal breathing rate.
I would then make a table and record my results.
Then I would repeat this process for student B.
Why does exercise increase heart rate?
So that glucose is delivered to the muscles
When you’re analysing data of heart rate vs time, if the recovery rate is faster in student B than in student A, what does that prove?
Student B shows higher level of fitness.
Why do we use multiple participants for studies such as the effect of heart rate on exercise?
Increases reliability, since we get a wide range of results, which reduces the effect of anomalies which gives us more valid results so we’ll have accurate data for calculating averages.
Why do we keep the temperature constant for the photosynthesis In the practical?
Because the enzymes in the plant will denature at higher temperatures than usual, the temp should be kept constant for a steady rate of photosynthesis.
What is the risk assessment in the enzyme practical?
General point in all practicals you can mention- care whilst dealing with water and electrical equipment ( electrical water baths, electricity,etc)
You need to wear safety goggles since iodine solution may irritate the eyes, also wear gloves since it may cause skin irritation. And hot water from the water bath if it were to splash, the safety goggles protect your eye
The enzyme amylase breaks down starch into what?
Maltose and glucose
If starch is present, what would be the colour of the reagent? What colour would it then be when it has been broken down by amylase?
Blue or black
The colour of the iodine wells will not change, it will be orange- brown when it has been broken down.
What happens when you grind food with ethanol then add water?
Cloudy emulsion/ cloudy white colour forms which indicates fat is present
Why do you never fill a test tube to the top with reagants?
Since a spillage of the contents can occur, which can damage your hand and cause a possible rash/reaction
What is the role of amylase enzyme?
It controls the breakdown of starch in our digestive system.
It helps breakdown starch (complex sugars) into simple sugars during digestion
Why do you mix the starch and amylase solution together?
So that the amylase breaks down the starch
The student made this conclusion.
‘The best temperature for lipase is 40
°C.’
Suggest why this conclusion may not be correct. 2 marks
Mean results of 40 and 50 degrees are similiar, so 40 can’t be the best.
The students have not tested between 40 and 50, so 45 degrees can be the best optimum temperature.
Why is amylase activity low at pH 4?
The amylase enzyme gets denatured due to the high acidic environment, and the shape of its active site changes causing the subtrate to not be able to fit properly.
What data would you collect for the enzyme practical?
How long does it take for starch to dissapear/ be broken down by amylase
What are the control variables for the amylase enzyme practical? Independent? Dependent?
The volume of starch and amylase, the concentration of the PH, time intervals between testing. These all need to be kept the same.
Independent- the temperature or PH
Dependent- measuring the time it takes for starch to be broken down by amylase.
What does a shorter time taken for starch to be broken down indicate?
It indicates a faster enzyme activity
What are buffer solutions used for?
To maintain the PH of a solution by reducing H+ ions, or adding them
What is an antiseptic?
It’s a chemical agent that helps to slow down or stop the growth of microorganisms around external surfaces.
What are aseptic techniques? When do you use them? What does sterile mean?
Washing hands, sterilizing equipment, sanitizing the surfaces all procedures you need to take whilst dealing with a bacterial culture.
Sterile- totally clean
What can you do to avoid contamination during the microbe practical?
The lid of the agar growth stays on at mostly all times, even when you’re placing the discs you keep them halfway open to limit the exposure of bacteria to the external surfaces.
Why should we use the same strains of bacteria in the agar?
So all bacteria would be the same so we know that the type of bacteria will not be a limiting factor/ something that can affect the results.
If we use different kinds of bacteria, it will all respond differently to the antibiotic.
What is the difference between bacterial strain and bacterial culture?
BS- a specific type of bacteria., has specific characteristics.
BC- many living bacterial cells grown from the specific strain of bacteria.
What type of data will u collect in the microbe practical?
I would measure the Diameter of the clear zones around the antibiotic disc, to see which antibiotic was most effective in killing bacteria.
After Joshua has sealed the lid with tape, but not sealed fully to prevent the anaerobic growth of bacteria, he has placed the Petri dish upside down, why?
To stop condensation into dripping down into the agar.
When you’re analysing data and you’re comparing the sizes of inhibition zones, if an antibiotic disc has produced a bigger zone, what does that mean? What conclusion can you come to with this information?
That bacterial colonies are not allowed to grow on that zone.
Bigger percentage of bacteria have been killed, hence the antibiotic disc is more effective
Conclusion- some antibiotic discs are more effective than others.
What are the CV, IV,DV of the microbe practical?
CV- same bacterial strain, disc size, agar type, incubation time
IV- The type of antibiotic discs
DV- measuring the diameter of clear zones around the antibiotic disc
Explain simply the process of microbe practical- (they don’t ask to create a procedure)
Put STERILE agar into a Petri dish ( agar has nutrients which encourages growth of bacteria)
Take a sterile swab and dip it into the bacterial culture and spread it around the agar. Place 4 black dots, use STERILE FORCEPS to Place antibiotic discs on the black dots.
Seal the lid with tape but not fully to prevent the anaerobic growth of bacteria.
Place upside down to stop condensation from dripping down into the agar.
Incubate for 2 days then look and calculate for the ZONES OF INHIBTION
What is the risk assessment for microbe practical?
Use sterile equipment to avoid contamination, wash hands (aseptic techniques), seal the Petri dish to prevent contamination
