bio core practicals

Question 1

what’s the microscopes core prac?

Answer 1

1. take a specimen of cells
2. add a drop of water or stain onto the slide
3. place specimen on the drop of water/stain
4. lower a coverslip on top to hold the specimen in plac

Question 2

iodine test for starch
benedict’s reducing sugars

Answer 2

add some drops of iodine solution to food and if there’s starch it’ll turn blue-black

when food solution is mixed with an = volume of benedict’s solution and placed in a hot water bath it causes a reduction reaction.

blue = no reducing sugars
green = little
orange = more
red = lots

Question 3

biuret test for protein?
ethanol emulsion test for fats?

Answer 3

potassium hydroxide is mixed with a solution of the food , then 2 drops of copper sulphate is added
purple indicates protein

food is mixed with ethanol and shaken, fats and oils dissolved in the ethanol float to surface forming a cloudy emulsion.

Question 4

core prac for osmosis?

Answer 4

1. label sep boiling tubes with the sucrose concentrations of each solution u will test.
2. cut potato slices the same size using a borer
3. blot each potato peice dry. M&R its mass and put it in an empty tube.
4. fill each tube with appropriate concentrations, cover potatos w solution
   5.leave 15mins, blot, M&R mass again, use formula

Question 5

why is ethanol used in the core prac?
why is detergent used?
why is salt used?
protease

Answer 5

to cause the DNA to precipitate
it breaks down cell membranes
it makes the DNA more likely to clump together
breaks down proteins

Question 6

how to extract dna?

Answer 6

-dissolve salt in water and washing up liquid, stir till salt dissolves
-mash strawrberrys and add the solution made
-place in water bath, filter mixture + collect filtrate
-add protease, tilst BT pour in ice cold ethanol slwoly

Question 7

control variable
independent variable
dependent

Answer 7

doesn’t change
you change
changes because u have changed the independent variable