year 2 practicals

Question 1

process for chromatography

Answer 1

extract pigment
draw origin line in pencil
place dots of pigment on origin line
solvent shoudl be below origin line
allow solvent to travel up paper
stop before solvent reaches top of paper
mark position of solvent on paper immediately after.

Question 2

effect of ammonium hydroxide on dehydrogenase enzyme in chloroplasts

Answer 2

photoionisation of chlorophyll and photolysis of water occur during LDR
dehydrogenase activity catalyses NAD accepting these electrons.

DCPIP
blue when oxidised
colourless when reduced
can pick up electrons instead of DCPIP.

ammonium hyrdoxide- alkaline- can denature dehydrogenase enzyme- picks up electrons instead of DCPIP or NAD

Question 3

why must the solution be ice cold?

why were the spinach leaves blended?

why is the solution buffered?

ammonium hydroxide and other electron accepting chemicals are used as weed killers? how will these kill weeds.

Answer 3

to reduce enzyme activity
prevents enzymes damaging chloroplasts released from blending spinach leaves.

to homogenise/break open the cells and release the chlorooplasts

same water potential to prevent water entering or leaving via osmosis and causing lysis or bursting.

prevents LDR
less atp and reduced NAD produced
prevents LIR.
no organic substances e.g. glucose produced.

Question 4

why does liquid containing maggots move towards experimental tube?

Answer 4

oxygen uptake by aerobic respiration
carbon dioxide produced absorbed by potassium hydroxide
decrease in pressure and volume- pressure is higher in control tube- so liquid moves towards experimental tube.

Question 5

rate

Answer 5

volume dividided by time x mass

Question 6

what needs to be recorded to calculate rate of reaction?

Answer 6

diameter of capillery tubing
distance moved by coloured liquid
time

Question 7

chioce chamber practical

null hypothesis

purpose of control

why do you wipe the maze with cotton wool after each maggot has moved along it?

why is it important to repeat with at least 10 maggots?

instead of removing the lid and counting, suggest a better method to improve the accuracy?

Answer 7

null hypothesis- similar no of insects move into light and dark chamber

purpose of control- to show that any difference in movement is due to independent variable

maggot leaves trail of chemicals- affects decision made by other maggots.

to calculate mean and SD to see if difference is signfiicant or due to chance.

open lid and immediately take photo- more accurate as you are measuring distribution of maggots before they have had a chance to move as the lid has been opened.

Question 8

types of sampling

Answer 8

non moving organisms- quadrats
moving organisms- mark release recapture

uniform/equal distribution- quadrats
unequal distribution- transects.

interuppted belt transect- quadratse placed at every position along transect
belt transect- quadrats placed at regular intervals along transect.

Question 9

transect line method

Answer 9

place tape measure at right angle to the shore
place quadrats at regular intervals/every position along transect
measure percentage covert

Question 10

mark release recapture

Answer 10

assumptions-
organisms re distribute evenly
population size remains constant- no births, deaths, migration

process-
capture, mark and release
ensure marking is not toxic/does not increase predation chance or reduce survival chance.
allow time for organisms to redistribute
take second sample and count number marked in second sample
population size= number in first sample x number in second sample/ number marked in second sample.