Practicals

Question 1

practical for effects of excercise

Answer 1

1. Breathing rate measured by counting breaths per minute; heart rate measured on chest heart rate monitor
2. Measure initial BR & HR
3. As a group (for mean & remove random error), first do 5 mins walk then measure BR & HR
4. Then do 5min gentle jog then measure BR & HR
5. Then do 5 min run then measure BR & HR
6. Put 5min resting periods between each exercise
7. Collect mean difference in BR & HR

Question 2

practical for rate of photosynthesis

Answer 2

1. Add pondweed to test tube connected to capillary tube & gas syringe
2. Place white light a certain distance away from pondweed – keep constant
3. Let pondweed photosynthesise for set amount of time – 10mins
4. O2 will be release in gas tube where its length will be measured with a rule – proportional to volume of gas produced
5. Repeat practical with different distance of light source from pondweed
   6.CO2 content of water can be controlled by adding measured amount of sodium hydrogencarbonate to distilled water

Question 3

Microscope practical

Answer 3

1. Place slide on stage and secure with clips if there
2. then select lowest power objective lens and move it using coarse focusing dial to get it as close as possible to slide without touching
   3.then look in eyepiece lens and turn the coarse focus away from slide until it comes into focus
   4.turn fine focus until image clear
   to find magnification multiply eyepiece lens magnification by the objective lens multiplication

Question 4

How to prepare a microscope slide

Answer 4

peel off epidermal tissue using forceps
place sample of water on slide
few drops iodine to solution
lower cover slip onto sample on angle using mounting neeedle

Answer 5

1. Ensure petri dish & culturing medium (agar jelly/nutrient broth solution) is sterilised used high temp.
   o Culturing medium contains carbs, minerals, proteins & vitamins
2. Pass inoculating loop through hot flame – sterilises
3. Dip in microorganism solution/collect microorganism with inoculating loop and transfer onto agar
   . Bacteria forms visible colonies
   . Different bacteria grown in different parts of agar
4. Tape petri dish to close – prevents airborne microorganisms entering
5. Store upside down – prevents condensation dropping onto agar; do not store above 25C – leads to more harmful pathogens
   · Paper discs soaked in different types/concentrations of antibiotic can be added – measure effect with area of inhibition zone

Use agar with even covering
Store at 25C for at least 48hrs
Add dry paper disc (control)

Question 6

Osmosis practical

Answer 6

1. Cut potato into similar sized cylinders using cork borer
2. Have multiple test tubes filled with different sugar/salt solutions (pure -> 1mol/dm3, inc. 0.2mol/dm3)
3. Measure initial mass of potato cylinder
4. Leave PC in test tube for 24hrs
5. Dry and measure mass of PC
   Inc mass = water drawn in from PC low -> high conc.
   Dec mass = water drawn out from PC high -> low conc.

· InV = conc. of solution; DeV = mass of PC; CoV = temp., size of PC, time, type of sugar/salt/potato used
· Errors: PC partly dried; water evaporating from test tube

Question 7

enzymes RP

Answer 7

1. Add a drop of iodine solution into every well of spotting tile
2. Use an electric water bath to maintain a constant temp. of 35oC in a beaker – use thermometer
3. In boiling tube, add 1cm3 of amylase solution & buffer solution of pH 5 – use syringe
4. Put boiling tube into beaker – use test tube holders
5. Add 5cm3 of starch solution into boiling tube – use new syringe
6. Immediately mix contents & start stopwatch
7. Continuously sample mixture to check break down of starch – done by taking fresh sample of mixture every 30s & adding to well of spotting tile – use dropping pipette
   . Starch is no longer present when solution remains browny-orange
8. Repeat with different pH values of buffer solution
   · 𝑅𝑎𝑡𝑒=1000𝑇𝑖𝑚𝑒
   · InV = pH of buffer solution; DeV = rate of reaction; CoV = volume of solutions, temp., type of starch