Required practicals

Question 1

Describe how you prepare a microscopy

Answer 1

1. add a drop of water to the middle of a clean slide
2. cut up an onion and peel off the epidermis and place on slide
3. add drop of iodine solution
4. place cover slip on at an angle

Question 2

Why do you have to stain a microscope with iodine?

Answer 2

highlights objects by adding colour

Question 3

Why do you have to place the cover slip on at an angle?

Answer 3

so there are no air bubbles

Question 4

How should you draw your microscope observations?

Answer 4

• use sharp pencil
• clear unbroken lines
• do not shade
• write title and magnification
• label important features with straight lines

Question 5

What are some examples of a culture medium?

Answer 5

• nutrient broth solution
• agar jelly

Question 6

What are a-septic techniques used for culturing microorganisms?

Answer 6

• sterilise petri dish and culture medium by heating to high temperature
• sterilise inoculating loop through blue flame
• tape lid onto petri dish
• store petri dish upside down

Question 7

What is an inhibition zone?

Answer 7

clear area where the bacteria have died

Question 8

what temperature should you culture microorganism at school and why?

Answer 8

25 degrees because harmful pathogens are more likely to grow above this temperature

Question 9

why should you tape the lid onto the petri dish?

Answer 9

to stop microorganisms from the air getting in

Question 10

why should you store the petri dish upside down?

Answer 10

to stop drops of condensation from falling onto the agar surface

Question 11

Describe the osmosis practical

Answer 11

1. cut up a potato into cylinders and get some beakers with different sugar solutions in them and one should be water for control
2. measure the mass of the cylinders then leave on cylinder in each beaker for about 24 hours
3. take them out, dry them with a paper towel and measure their masses again

Question 12

What are the variables in the osmosis practical?

Answer 12

• dependent variable- chip mass
• independent variable- concentration of solution
• control variable- everything else

Question 13

What errors may arise in the osmosis practical?

Answer 13

• if potato cylinders have not fully dried, the excess water would’ve given it a higher mass
• if water evaporated from the beakers the concentration of the sugar solution will change

Question 14

Describe the required practical for the effect of pH on amylase

Answer 14

1. put a drop of iodine solution in every well of a spotting tile
2. put a Bunsen burner on a heat proof mat and place a tripod and gauze over it with a beaker of water and heat to 35 degrees
3. use syringe to add 1 cm^3 of amylase and the same amount of buffer solution with a pH of 5