Required Practicals

Question 1

Required practical 1 : investigation into the effect of a named variable on the rate of an enzyme controlled reaction . What is the method for ph

Answer 1

1. Cut 2cm cube of fresh potato and place in a conical flask with 2cm^3 ph buffer
   2.put the bung securely in the flask - twist and push cafefully
   3.half fill a bowl with water and a measuring cylinder and invert it over the bowl of water and the end of the rubber tubing in the measuring cylinder
   4.measure 2cm^3 hydrogen peroxide into the 2cm^3 syringe . Push the plunger on the syringe and immediately start the stop clock
   5.repeat with different PH buffers
2. Plot a graph with oxygen produced against ph

Question 2

required practical 2 : mitosis in an alium root tip

Answer 2

procedure
1) cut off about 1cm from several root tips of some growing garlic roots. choose root tips which are white and have a firm rounded end , tips that are turning brown will give poor results
2) put the root tips into a hollow glass block containing 2cm3 1M hydrochloric acid for exactly 5 min
3) put the root tips in cold water for 5 min then dry with filter paper
4)transfer one of the root tips to a clean microscope slide . cut about 2-3 mm from the rounded growing tip
5) press down hard onto the slide with coverslip and add one small drop of toluidine blue and leave to stain for a few minutes
6)cover with coverslip and can blot if excess dye.
7) view under microscope

Question 3

For beetroot practical , the student put the same volume of water in each tube , explain why it was important that he controlled this experimental value

Answer 3

If there’s too much water the concentration of pigment will be lower so solution will appear lighter (harder to compare solutions colour ) and therefore we use the same volume so results are comparable

Question 4

How could the student monitor the temp

Answer 4

Take readings using a thermometer

Question 5

Suggest how the increase in temperature of the water caused the release of the red pigment

Answer 5

As the temperature increases , this causes damage to the cell surface membrane and therefore the membrane proteins denature and increased fluidity as there’s damage to the the phospholipid bilayer