bio practicals Flashcards
Effect of Caffeine on Daphnia Heart Rate METHOD
1.Remove 1 Daphnia and place it in distilled water for 5 minutes to acclimatize.
2.Transfer the Daphnia onto a cavity slide under a microscope.
2.Observe and count the number of heartbeats for 30 seconds, then multiply by 2 to obtain beats per minute.
Repeat with 2 more Daphnia. Repeat again, this time with small concentration of caffeine solution in place of distilled water. Carry out for 5 concentrations of caffeine = 3 repeats at 3 concentrations.
- Measuring the Vitamin C Content in Fruit Juice
Method:
pipette 1cm3 blue DCPIP into test tube. Using burette (or accurate pipette) add 1% vitamin C standard solution drop by drop. Shake tube gently after each drop. Continue until the colour changes from blue to colourless. Record volume of solution needed to decolourise the DCPIP. Repeat further 2 times and calculate mean result (calibration). Repeat procedure with different fruit juices. If using whole fruit or veg you must prepare a juice / extract first. Compare volumes needed to change colour of DCPIP (blue to colourless) with standard Vitamin C.
- Effect of Alcohol on Cell Membranes
Method:
Cut beetroot into 1 cm pieces using a cork borer and soak in distilled water overnight.
Blot dry and place in 5 different alcohol concentrations.
Leave for 30 minutes, then remove beetroot pieces.
Shake tubes to disperse the pigment.
Use a colorimeter to measure % absorbance at 490 nm.
Repeat for all concentrations and record results.
- Effect of Enzyme Concentration on Rate of Reaction
Prepare 5 different enzyme concentrations (e.g., catalase).
Set up a gas syringe or measuring cylinder in water to measure oxygen.
Allow materials to acclimatize for 5 minutes.
Add a known volume of enzyme to 10 cm³ of hydrogen peroxide in a test tube.
Immediately seal the test tube with a bung and start a stopwatch.
Measure oxygen volume produced per minute.
Repeat twice for accuracy and repeat for all enzyme concentrations.
- Observing Mitosis (Root Tip Squash)
Cut 1-2 cm of root tip from garlic.
Place in acetic alcohol for 10 minutes.
Transfer to ice-cold distilled water for 4-5 minutes.
Heat in 1M HCl at 60°C for 5 minutes.
Stain with acetic orcein for 2 minutes.
Place a coverslip and squash the root tip gently.
Observe under a microscope and count cells in different mitotic stages.
- Effect of Garlic & Mint on Bacterial Growth
Prepare agar plates and inoculate with a bacterial culture to form a lawn.
Soak filter paper discs in garlic/mint extracts.
Place discs on agar plates using sterile forceps.
Incubate plates upside-down at 25°C for 24 hours.
Measure the zone of inhibition (ZOI) diameter.
Repeat for reliability.
