Practicals Flashcards
What is the aim of the cheek cell slide practical?
Use microbiological techniques to prepare and view cheek cell slides.
List the equipment for cheek cell slides.
Cotton bud, disinfectant, microscope slide, cover slip, mounted needle, methylene blue, light microscope.
Outline the method to prepare cheek cell slides. - 10 steps
Add methylene blue to slide.
Swab cheek with cotton bud.
Dab bud in dye, then place in disinfectant.
Lower cover slip carefully to avoid air bubbles.
Blot excess stain.
Set on microscope stage.
Start with x10 objective lens.
Adjust coarse/fine focus.
Switch to high power (x40), focus again.
Identify & draw 3–4 cells.
Give a risk for the cheek cell slides practical
Methylene blue is an irritant. Avoid contact with skin.
What is the aim of food tests practical?
Test for starch, reducing sugars, lipids, and protein in food samples.
Equipment list for food tests.
Iodine, Benedict’s solution, Biuret reagent, ethanol, spotting tile, test tubes, sugar paper, water bath, pipettes, beaker.
How is starch tested?
Add iodine to food sample in test tube.
If starch present, turns brown → blue-black.
How is reducing sugar tested (Benedict’s test)?
Add Benedict’s solution to food.
Heat in water bath.
Brick red precipitate = sugar present.
Describe the emulsion test for lipids.
Add ethanol to food sample.
Add water.
White emulsion = lipids present.
What is the sugar paper method for lipids?
Rub sample on paper, allow to dry. Translucent spot = lipids.
Describe the Biuret test for protein.
Add Biuret solution.
Shake and wait.
Blue → purple = protein present.
Name one source of error and one safety precaution for food test using Biuret.
Error: Subtle colour changes if low concentration.
Safety: Biuret = corrosive. Use goggles.
What is the aim of the sampling techniques practical?
Compare biotic and abiotic factors in different habitats.
What equipment is used in this practical?
Quadrat, tape measures, pen, paper, soil pH kit, thermometer, umbrella, random number generator.
Describe method 1 (random sampling). - sampling techniques
Use random coordinates to place quadrat.
Count target species.
Repeat 10 times.
Estimate population size using:
(Total area ÷ quadrat area) × mean per quadrat.
Describe method 2 (along transect).- sampling techniques
Lay tape from tree into open area.
Place quadrat at 0 cm.
Count plant species.
Test abiotic factor (e.g. pH, light).
Move 5 m, repeat.
Repeat until end of line.
Describe method 3 (insects). - sampling techniques
Place umbrella under branch.
Shake.
Count and identify insects.
Release them.
Name one source of error and one risk for sampling techniques
Error: Only one transect = unreliable.
Risk: Insect stings or plant allergies.
What is the aim of the Enzyme-Controlled Reactions (Catalase) experiment?
Investigate enzyme-controlled reactions using catalase in potato.
What is the independent variable in the Enzyme-Controlled Reactions (Catalase)
Hydrogen peroxide concentration.
What is measured? - Enzyme-Controlled Reactions (Catalase)
Volume of oxygen released.
Describe the method. - Enzyme-Controlled Reactions (Catalase)
Label tubes with H₂O₂ %s.
Cut equal potato pieces.
Add to H₂O₂ in flask with bung.
Collect gas in measuring cylinder.
Record oxygen after 5 mins.
Repeat for each %.
How do you calculate rate of reaction?
Rate = volume of oxygen ÷ 5 (cm³/min).
Give 2 controlled variables. - Enzyme-Controlled Reactions (Catalase)
Temperature, potato length.
One risk in this practical? - Enzyme-Controlled Reactions (Catalase)
H₂O₂ is an irritant — wear goggles.
Aim of this practical? - photosynthesis
Investigate how light intensity affects photosynthesis (pondweed).
What is the dependent variable? - photosynthesis practical
Number of bubbles produced per minute.
What is the method? Photosynthesis
Place pondweed in tube 10 cm from light.
Add sodium hydrogen carbonate.
Count bubbles in 1 min.
Repeat at 20, 30, 40 cm.
What is the equation for light intensity?
Light intensity = 1 ÷ distance²
One extension for this practical? - photosynthesis practical
Test different pondweed species.
One hazard? - photosynthesis practical
Hot lamp, allergy to pondweed.
What is the aim? -Physiology, Responses, Respiration
Measure changes in pulse and breathing before/after exercise.
How do you measure pulse rate?
Press wrist.
Count beats for 1 minute.
Exercise, then repeat.
How do you measure ventilation rate?
Use spirometer and nose clip.
Time 1 min, count breaths.
Exercise, repeat measurement.
One risk and one source of error? - Physiology, Responses, Respiration
Risk: Exercise may be unsafe for asthmatics.
Error: Exercise intensity may vary by person.
What is the aim of the microbiological techniques practical?
Investigate the effects of antimicrobial agents (using a plant extract) on microbial growth using aseptic techniques.
Name 4 pieces of equipment used in the microbiological techniques practical.
Bacterial stock, petri dishes with growth medium, plastic spreader, syringes.
What is the first step to maintain aseptic conditions in this practical?
Perform all steps near a Bunsen flame on a blue flame to prevent contamination.
Perform all steps near a Bunsen flame on a blue flame to prevent contamination.
Use a syringe to transfer 0.1 cm³ of bacterial stock 10 cm above the agar.
What is used to spread bacteria evenly on the agar?
A plastic spreader.
What is done to the petri dish lid after spreading bacteria?
Place the lid on and dispose of the spreader safely.
How is the petri dish divided and labelled?
Divide the base into 4 sections and label them; one section is used as control.
How is the plant extract prepared?
Grind a plant using pestle and mortar, then add 10 cm³ of sterile water.
How are paper discs prepared?
Soak sterile filter paper discs in the plant extract.
How are the discs applied?
Place the discs on the labelled sections of the petri dish.
What must be done after adding discs to petri dishes?
Incubate upside down for 48 hours.
What is measured at the end of the experiment? - Microbiological Techniques
Diameter of the clear zone around each disc.
What are 2 sources of error in this practical? Microbiological Techniques
Petri dish contamination, irregular shape of clear zones.
Name 2 safety precautions for this practical. Microbiological Techniques
Tie back hair near Bunsen flame; disinfect all surfaces after experiment.
What is the aim of the osmosis practical?
Investigate osmosis in plant tissue by measuring change in mass of potato cylinders.
What are 3 key pieces of equipment used?
Potato, sucrose solutions, electronic balance.
What concentrations are the 7 sucrose solutions?
0.0M, 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, 0.6M.
What is the size of each potato cylinder used?
50 mm in length.
How much solution is used per beaker?
50 cm³.
How long are potato cylinders left in solution?
30 minutes.
What is done after removing the cylinders?
Blot dry, weigh again, and record final mass.
What calculation is performed at the end? - potato osmosis practical
Percentage change in mass = (final mass - initial mass) ÷ initial mass × 100.
Give one source of error in the osmosis practical.
Potato pieces may have different water potentials depending on where cut.
Name one risk and its precaution in this practical. - osmosis practical
Sharp tools (scalpel, cork borer) – handle carefully to avoid cuts.
