Required Practicals and 6-mark questions Flashcards
How would you use a light microscope to observe plant tissues?
- Use tweezers to place the onion tissue flat on a microscope slide
- Place a drop of iodine onto the tissue
- Lower a glass cover slip onto the tissue, making sure no bubbles form
- Place slide on microscope stage and observe using lowest-power objective lens
- Focus on the image and zoom in until you can see the structure of the cells
How would you use a light microscope to observe animal tissues?
- Use a cotton bud to scrape the inside of your cheek
- Smear it on the centre of the microscope slide
- Place a drop of methylene blue onto the tissue
- Lower a glass cover slip onto the tissue, making sure no bubbles form
- Place slide on microscope stage and observe using lowest-power objective lens
- Focus on the image and zoom in until you can see the structure of the cells
How would you investigate the effect of different concentrations of water on the mass of potato?
- Cut cylinders of potato, of equal length, and then record their mass
- Place the potato cylinders into beakers containing different concentrations of water and leave for about 30 minutes
- Record the mass of the potato cylinder at the end of this period of time
How would you test for starch?
- Use a pipette to add 2 drops of the solution into the well of a spotting tile
- Add 2 drops of iodine solution
- If starch is present, a blue-black colour will be produced
How would you test for glucose?
- Add 1cm^3 of the solution to a boiling tube
- Add 1cm^3 of Benedict’s reagent
- Place in 80 degree water bath for 5 minutes
- If glucose is present, an orange-red precipitate will form, if not the solution will remain blue
How would you test for proteins?
- Add 2cm^3 of the solution to a test tube
- Add 2cm^3 of biuret solution
- If protein is present, the mix will turn light purple, if not it will turn cloudy blue
How would you test for oil lipids?
- Half fill a test tube with water
- Add a drop of solution and mix it in
- Place your thumb over the top and shake the test tube
- If oils are present an emulsion will form, making the water go cloudy
How would you investigate the effect of pH on the rate of reaction of amylase?
- Add 10cm^3 of a 4% starch solution to a boiling tube
- Add 10 drops of iodine solution and stir with a glass rod
- In a separate test tube, add 2cm^3 of a 2% amylase solution
- Add 5cm^3 buffer solution to the test tube with amylase
- Leave both tubes in a water bath at 35 degrees for 2 minutes
- Take a spotting tile and add 1 drop of iodine solution to each well
- After 2 minutes, mix the contents of the tubes while keeping them in the water
- Using a glass rod, place a drop of the solution into a well every 30 seconds
- When the iodine does not change colour, you know the reaction has finished
How would you investigate the effect of antibiotics and antiseptics on bacterial growth?
- You will be provided with an agar plate that has a culture of bacteria
- Without removing the lid, mark the underside of the plate with lines that divide the plate into three equally sized sections, and a dot in the middle of each of these three sections.
- Put different antiseptics or antibiotics on to three equally sized filter paper discs, either by soaking the discs in the liquid, or pasting cream onto the disc.
- Carefully lift the lid of the agar plate, and place the discs above the dots.
- Incubate the plate at 25°C for 48 hours - this provides ideal growing conditions for the bacteria
- Measure the diameter of the clear zones
- The larger the clear zone, the more effective the
antiseptic/antibiotic is against the bacteria
How would you investigate the effect of light intensity on rate of photosynthesis?
- Cut a piece of pond weed and submerge it in a boiling tube
- Place a tank of water between the boiling tube and a lamp
- Position the boiling tube so it’s 50cm from the lamp
- Turn the lamp on and wait 2 minutes
- Make sure the temperature of the water in the boiling tube remains constant by monitoring it with a thermometer
- Count the number of bubbles released in a minute. Do this 3 times to work out a mean
- Repeat the experiment with distances of 40, 30, 20 and 10cm
How would you investigate the effects of a factor on human reaction time?
- The tester holds a 30cm ruler vertically by the 30cm end above the subject’s hand
- Without warning, the tester lets go of the ruler and the subject tries to catch it as soon as possible
- Record the distance the ruler fell before being caught
- Repeat this and calculate a mean
- Repeat the whole experiment with caffeine
Reflex arcs
Reflexes are very fast and are automatic; this allows the body to protect itself
When touching something hot, a sensory nerve is stimulated
This sensory neuron carries an impulse to the spinal cord
It passes from neuron to neuron via a synapse
It bypasses the brain
It goes around the spinal cord via a relay neuron
It travels back down a motor neuron
The motor neuron will stimulate a muscle and cause a response
Explain how controlling the levels of carbon dioxide, water and the temperature will affect the growth of plants
Plants use carbon dioxide in photosynthesis
Carbon dioxide + water → oxygen + glucose
Light is needed for this process
carbon dioxide, water and the temperature are all limiting factors.
Increasing carbon dioxide or water will increase the rate of
photosynthesis but only up to a point when other factors become
limiting.
Temperatures are limiting if it is too low (not enough energy for the
reaction to take place) or too high (enzymes denatured)
How can human insulin be made through genetic engineering?
Enzymes are used to cut out the human gene that produces insulin
This is inserted into a bacterial plasmid DNA
The bacteria now produce human insulin
Large volumes of bacteria can be grown, producing large volumes of insulin
This can be purified and used
Evaluate the use of genetic testing
Good points include; being able to plan for any future disease; certainty over what is going to happen; being able to make an informed choice about having children who may inherit the gene;
Bad points include; mental health issues if testing positive, lack of healthy future; health insurance cost may increase; loss of privacy over genetic information.
