Practicals

Question 1

How do you view a specimen using a light microscope?

Answer 1

1. ) get thin slice of specimen.
2. ) pipette 1 drop of water on clean slide to secure specimen. Tweezer specimen on slide.
3. ) add stain if is transparent, methylene stains dna.
4. ) lower cover slip w no air bubbles over specimen w mounted needle and clip onto stage.
5. ) select lowest power objective lens.
6. ) use coarse adjustment knob to move stage up and down almost to focus.
7. ) adjust focus w fine adjustment knob and measure FOV
8. ) for greater magnification shift to higher power objective lens.

Question 2

Magnification

Answer 2

Image size / actual size

Question 3

Investigation into effects of pH on enzyme activity

Answer 3

Put a drop of iodine into every well in tile.
Heat beaker of water to set temp (35?) to remain constant.
Put 3cm cubes of amylase solution in boiling tube and 1 of buffer solution and put in water for 5 mins
Use clean syringe for starch solution and set timer
Use continuous sampling every 10 secs onto spotting tile to time how long it takes for iodine to stay brown (no starch left)
Repeat w different buffer solution

Question 4

Rate

Answer 4

1000/ time

Change / time

Question 5

Test for reducing sugars

Answer 5

1 add Benedict’s reagent to a sample and heat in water bath (75 degrees)

A positive test results in a higher precipitate.

Question 6

Color for high reducing sugars

Color for low reducing sugars

Answer 6

High = red

Low = blue

Question 7

Test for starch

Answer 7

Add iodine.

Starch present = color change to blue black color

Question 8

Test for lipids

Answer 8

(Emulsión test)

1. Shake substance w ethanol until dissolved
2. Pour in water

Lipids present = milky emulsion
More lipids= stronger white color

Question 9

Test for proteins

Answer 9

(Biuret test)

1. Add potassium hydroxide to substance to make alkaline
2. Add copper sulfate

No protein = remains blue
Protein = purple color