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
To investigate photosynthesis in pondweed how would you vary CO2 concentrations
Use different masses of sodium bicarbonate to vary concentrations
To investigate photosynthesis in pondweed how would you measure rate more accurately
Collect gas in inverted cylinder
Measure volume of oxygen evolved per unit time
Tell me photosynthesis equation
6CO2 + 6H2O –> C6H12O6 + 6O2
[6] Design investigation to determine the rate of photosynthesis changes as light intensity changes
Change light intensity by changing distance lamp is from pondweed
Use same species of pondweed
Repeat each distance 3 times and calculate an average
Measure amount of bubbles produced over 5 minutes
Ensure same size of plant/number of leaves
Ensure same volume of water/concentration of CO2
In the pea seed respiration practical how could you show energy has been released
Measure the change in temperature in each thermos flask
Heat not transferred to surroundings as flask insulated
Only see temperature rise in alive pea seed conditions as other seeds are dead so only alive seeds are releasing energy
In the pea seed respiration practical how could you show CO2 produced
Use delivery tube to collect any produced gas in each flask
Gas can be bubbled through limewater
if CO2 present = lime water would go from clear to cloudy
In the pea seed respiration practical why are there 2 thermos flasks
One flask is a control experiment
Identical to original experiment
But without independent variable (be specific to question in exam for variable)
In the pea seed respiration practical why are peas soaked in Milton fluid
Peas are soaked in the bleach
Kills any bacteria
As bacteria would respire and affect results
[6] Adding water to a powder called sodium metabisulphite will release sulphur dioxide gas.
Devise a laboratory investigation to find out the effect of sulfur dioxide gas on the heat release by germinating seeds
Change conditions of seeds
One batch exposed to SO2 and one not exposed to SO2
Use same species/type of seed
Repeat each condition 3 times
Measure temperature change
Using thermometer
Ensure same thermos flask to contain seeds
Ensure same moisture/humidity/light intensity/starting temperature
State an alternative solution to measure CO2 concentration
Use hydrogen carbonate indicator
Turns yellow when CO2 concentration increases
Stays red if no CO2 present
In concentration of CO2 of inhaled/exhaled air practical give 2 possible solutions to test for it
Limewater
Hydrogen Carbonate Indicator
State 2 differences between inhaled air and exhaled air
Concentration of carbon dioxide (low in inhalation, high in exhalation)
Exhaled air is warmer than Inhaled air
Why does breathing rate increase during exercise
Increased concentration of CO2 in blood
Carbon dioxide excreted more rapidly
Increases heart rate
Increased breathing rate supplies more O2 to muscles for aerobic respiration
How can we tell if a seed has germinated
Radicle/shoot/root is seen
Why is oxygen needed for germination
For aerobic respiration to release energy
Why is warmth needed for germination
Optimum temperature for enzymes
Why is water needed for germination
To activate enzymes
What happens to ovary after fertilisation
Ovule becomes a seed
Ovule wall becomes a seed coat
Ovary becomes a fruit
Why do fewer seeds germinate when stored in wet and warm conditions
There are more bacteria in these conditions so seeds could get diseased
A student investigates the oxygen absorbed by germinating seeds at different temperatures
Suggest why the student opens the tap after obtaining one set of results
To repeat readings
Allow oxygen in for aerobic respiration
Prevent anaerobic respiration
A student investigates the oxygen absorbed by germinating seeds at different temperatures
What is the function of soda lime
Absorbs CO2
Why is the rate of oxygen absorption greater at 22 degrees C than 12 degrees C
More respiration
Enzymes have more kinetic energy
More collisions
So more enzyme substrate complexes are formed
Aerobic Respiration Equation
C6H12O6 + 6O2 –> 6CO2 + 6H2O
Anaerobic Respiration Equation in Fungi and Plants
Glucose –> Ethanol + Carbon Dioxide
Anaerobic Respiration Equation in Animals
Glucose –> Lactic Acid
[3] Describe a method to measure mean number of weeds in each field
Use a quadrat
Count number of weeds in quadrat
Use random coordinates in fields to place quadrat down in
Repeat process 3 times
[5] Discuss if biological control is better at controlling weeds than chemical control (pesticides)
*Before using own knowledge compare data in the table for discuss questions
Biological control doesn’t need to be reapplied - insects can reproduce
Biological control less risk of pollution
Biological control less risk of resistance but Chemical control - weeds can grow resistance to pesticides
Biological control is specific - doesn’t affect other food chains
Biological control methods cause no bioaccumulation (no harmful chemicals built up in weed tissue)
But Biological control could become a pest
Chemical control can contaminate soil
Describe a method to measure the percentage of a stone wall covered by lichen
Measure area of lichen
Measure total area of stone
Repeat 10 times and calculate mean
Natural Selection example….
Plant with a short growing season survive drought
Eutrophication example….
Growth of algae in rivers polluted by fertiliser
Insect pollination example….
Pollen transferred from one plant to another by an insect
Active Transport example….
Absorption of nitrate ions from soil using ATP
Describe a method the scientist could use to compare the population of the grass species at 50 m and 100 m from the mine
Use tape measure
And quadrat
Count the number of species on quadrat
Repeat 10 times
In the anaerobic respiration of glucose and yeast suspension practical why is layer of oil added
Prevent entry of oxygen
Ensuring anaerobic respiration
In the anaerobic respiration of glucose and yeast suspension practical how could you measure rate of respiration
Number of bubbles produced in 30 minutes in test tube of limewater
In the anaerobic respiration of glucose and yeast suspension practical why does a student boil and cool glucose before yeast added
Boiled To remove oxygen
Kill bacteria
Then Cooled so enzymes don’t denature
And so yeast doesn’t die
In the anaerobic respiration of glucose and yeast suspension practical how could you modify experiment instead of counting bubbles.
Use a Measuring cylinder
To measure volume
In the anaerobic respiration of glucose and yeast suspension practical give function of the water bath
Control and maintain constant temperature
Explain how named conditions in industrial fermenter are controlled
Steam applied before usage kill unwanted microorganisms leaving only water
Stirrers ensure mixture is evenly distributed
Cooling Jacket maintains optimum temperature stops enzymes denaturing
Air filters prevent contamination and keep aseptic conditions
Explain how bacteria have evolved so antibiotics are less effective
Mutation in bacteria
Can create a resistance to the antibiotics
Only resistant bacteria survive
Resistant bacteria reproduce
Pass on the allele
So resistant bacteria increase in population
Explain rate of respiration of yeast as temperature increases from 45 degree C to 60 degrees C.
Increased temperature = breaks bonds
Change in shape of active site
Enzyme denatures
Substrate can no longer bind with enzyme
