biology practicals

Question 1

practical for investigating effect of temperature on enzymes

Answer 1

mix
10cm3 of 10% starch suspension
+ 5cm3 of 5% amylase
in a boiling tube
heat in water bath
every minute take 1 drop of the mix
add to 1 drop of iodine solution
in spotting tile
when digestion is complete
iodine solution will stay orange
(no starch)
repeat using water baths at different temperatures

Question 2

practical for effect of pH on enzymes

Answer 2

add 10 potato disks to 20cm3 catalase
measure the volume of gas is 5 min
the pH can be altered ->
by adding different volumes of a weak acid or alkali
use universal indicator paper to detect the pH of the solution each time

Question 3

explain the process of photosynthesis

Answer 3

the suns energy hits the plants which contain chloroplasts which contain chlorophyll which converts energy to glucose which is photosynthesis

Question 4

*yellow outside of leaf green inside of leaf

explain why the yellow region of the leaf hasn’t produced sugar

Answer 4

the yellow region has no chloroplasts so there is no starch there, meaning it will not turn blue-black when iodine is present

Question 5

why are food chains no more than 5 trophies levels?

Answer 5

energy that is not passed on is lost as heat energy, or is in teeth&bones which are not digestible. only 10% of energy is passed on.

Question 6

formula for photosynthesis

Answer 6

6CO2 + 6H2O -> 6O2 + C6H12O6

Question 7

test for starch in a leaf

Answer 7

boil in water w beaker & Bunsen
boil leaf in ethanol within water 78C
colour change so see iodine
rinse the leaf in cold water
drop on iodine solution
Orange to blue black = starch present

Question 8

pondweed

Answer 8

further away less light absorbed for photosynthesis