Biology Practicals (Paper 1 atm Only) Flashcards
Test for Glucose/Sugar
Add ________’s Solution to food sample
Place in __ degrees C water ____ for _ minutes
Sugar present = colour change from ____ to brick __
_____/Orange/______ = ________ result but _____ concentration of sugar present
Add Benedict’s Solution to food sample
Place in 80 degrees C water bath for 5 minutes
Sugar present = colour change from blue to brick red
Green/Orange/Yellow = positive result but lower concentration of sugar present
Test for Starch
Add few drops ______ Solution to food sample on ________ tile
Starch present = colour change from ______ to ____/_____
Add few drops Iodine Solution to food sample on spotting tile
Starch present = colour change from orange to blue/black
Test for Proteins
If sample _____ - add _cm^3 _____ to food sample and _____
Add _____ volume of dilute _________ _________ and _____
Add _ drops _% ______ _______ solution
Protein present = pale ______ colour present
If sample solid - add 2cm^3 water to food sample and shake
Add equal volume of dilute potassium hydroxide and shake
Add 2 drops 1% copper sulfate solution
Protein present = pale purple colour present
Test for Lipids
________ Test
Place food sample in ____ ____
Add pure _______
_____ to _______ any lipid in _______
Add _____ volume of _____
Lipids present = ________ forms = cloudy _____ colour
Emulsion Test
Place food sample in test tube
Add pure ethanol
Shake to dissolve any lipid in alcohol
Add equal volume of water
Lipids present = emulsion forms = cloudy white colour
What enzyme digests starch into
Enzyme = Amylase
Broken down to Maltose
A variable to control with enzyme activity
Temperature - optimum temperature most effective temperature for enzymes
[6] Design investigation to find best temperature for removing protein stains by using washing powder that contains protease enzyme.
Use a range of temperatures from 20-60 degrees C at 5 degrees C intervals
Use same concentration of enzyme and mass of washing powder
Repeat each temperature for the practical 3 times and calculate mean
Measure area of the stain 30 minutes after cleaning it
Ensure same pH of washing powder or same type of clothing material
Ensure same area or mass of protein stain
How does temperature affect rate of diffusion
@Higher Temperatures
Molecules = more kinetic energy
So move faster
Diffusion happens faster
How does distance affect rate of diffusion
Greater Distance
= Smaller surface area to volume ratio
Substance has less area to diffuse across
So slower diffusion rate
How does visking tubing allow osmosis to occur
Only allows small soluble molecules to pass
Such as Glucose and Water
So Osmosis can occur
How to investigate rate of osmosis with visking tubing practical
Change concentration of sucrose solution in visking tubing
Or temperature of water
Height of liquid rises into capillary tube if osmosis faster
Height falls if osmosis slower
How can potato chips be used to measure rate of osmosis
Placed in sucrose or salt solutions of different concentrations
Osmosis occurs until water potential of tissue + solution = same
Measure the mass change
Why are you drying cylinders of potato before measuring the final mass of potato after practical
Remove surface moisture
That would alter results
So valid comparison could be made
Define Osmosis
Movement of water molecules from high to low water potential via a partially permeable membrane
For potato osmosis practical:
If solution has a high water potential then….
Water will move into potato chip
Mass of chips will increase
For potato osmosis practical:
If solution has a low water potential then….
Water will move out of potato chip
Mass will decrease
Plant cells are described as ______ when soaked in pure water
turgid
Plant cells are described as ___________ when soaked in concentrated salt or sugar solution
plasmolysed
Animals cells (rbc) described as _____ when they are full of water molecules
Lysed
Rbc can burst
They have no cell wall to protect cell
Animals cells (rbc) described as _________ when they not filled with water molecules
Shriveled
To investigate photosynthesis of a leaf why is leaf placed in boiling water
Kills the leaf
Stops any chemical reactions occuring
To investigate photosynthesis of a leaf why is leaf placed in hot ethanol
The boiling ethanol dissolves chlorophyll and removes green colour from leaf
Turns white to easy see change colour
To investigate photosynthesis of a leaf why do you rinse the leaf
Rehydrate and soften leaf
To investigate photosynthesis of a leaf how do you remove CO2 before testing
Destarch leaf
Expose one side of leaf to sodium hydroxide
Absorb CO2 in air
To investigate photosynthesis of a leaf why do you place leaf in dark room before experiment
Destarch leaf
Free from starch at the start of the experiment
To investigate photosynthesis in pondweed how would you change light intensity
Move distance of a lamp