Topic 2: Beetroot core practical Flashcards
Beetroot cells contain large red pigment molecules called _________ in their _________.
betalains
vacuole
Normally, the betalains cannot pass through the ________ ________ (tonoplast) or the _______ _________. These membranes are not __________ to betalains.
vacuole membrane
cell membrane
permeable
But when beetroot cells are exposed to certain temperatures or put in alcohol this disrupts the vacuole membrane and the cell membrane (they become _________) and betalains can ______ through these membranes and leave the cell.
permeable
diffuse
Define diffusion in terms of betalains
1 point
- the betalains move from where they are in HIGH concentration inside the cell, to where they are in LOWER concentrations outside the cell, down the concentration gradient.
What happens when there is no longer a diffusion gradient? (in terms of betalains diffusing)
(2 points)
- Eventually an equilibrium will be reached between the inside of the cell and the outside of the cell
- even though the betalains are moving through the disrupted membrane in both directions, there is no NET movement (movement happens at the same rate in both directions).
What is the aim of the beetroot practical?
1 point
- To investigate the effect of temperature on the permeability of beetroot membranes
The _______ _____ the solution, the more betalain molecules have been able to move through the vacuole and cell membranes, so the more disrupted the membranes are and the ________ the membrane ____________.
darker pink
greater
permeability
Key Summary: What is the method for the beetroot practical?
7 steps
- Tissue named (e.g. beetroot, red cabbage) – controlled variable - pieces cut to same surface area & from same species of beetroot & same part of beetroot.
- Soak overnight and rinse to wash betalains off the beetroot pieces.
- Place one beetroot piece in water in at each temperature.
- Independent variable = temperature - 5 different temperatures for validity + control (normal temperature for beetroot) so 6 in total - 0, 10, 20, 30, 40, 50 (or alcohol concentrations – 0%, 1%, 2%, 3%, 4%, 5%) using {water bath to maintain different temperatures / dilution of same alcohol stock solution}.
- Controlled variable eg. same length of TIME in water bath – same {time of 30 minutes/ VOLUME of water in tube} – measure with pipette 5cm^3 (same temperature using water bath at 10⁰C if changing {ethanol/alcohol} concentration).
- Dependent variable = measure absorbance using a colorimeter, with blue-green filter, as a measure of membrane permeability (higher absorbance = higher membrane permeability).
- Repeat 5 times FOR EACH TEMPERATURE – identify anomalies, obtain 3 concordant results, calculate mean, increases reliability.
A _____ ______ filter ( ____ nm) is used - wavelength of light that the pink solution absorbs the most. This maximises the ________ of the results.
blue green
490
accuracy
A beam of ______ passes through the ______, through the _________ ________ and to the _________. The meter records the amount of _______ absorbed by the ________.
light
filter
beetroot solution
photocell
light
solution
The more concentrated (darker) the pink solution, the _______ the absorbance.
higher
(the effect of temperature on membrane permeability in beetroot practical)
Below 0 degrees C, ___ _________ may form and pierce the membrane, this may __________ the membrane permeability.
ice crystals
increase
Key Summary: What is the effect of temperature on membrane permeability?
(5 steps)
- INCREASED KINETIC ENERGY INCREASES MOVEMENT OF PHOSPHOLIPIDS
- Membrane PROTEINS ARE DENATURED (look at data if given to determine temperature at which this happens)
- More denaturation of proteins and disruption of membrane at higher temperatures
- Vacuole membrane and cell membrane break down, so are disrupted and become more permeable to betalains
- Betalains can escape FROM THE VACUOLE AND THE CELL through vacuole and cell membranes
(beetroot practical)
Name the independent variable (1 point)
How can it be varied? (2 points)
What is the control? (1 point)
- temperature
- 5 different temperatures + 1 control
- Using WATER BATHS at 0, 10, 20, 30, 40, 50 degrees C.
- control - usual temperature for growing beetroot (10 degrees C)
(beetroot practical)
Name the dependent variable (1 point)
How can it be measured? (1 point)
- % absorbance of the solution around the beetroot piece
1. Measured using a COLORIMETER
Why is using a colourimeter (to measure the % absorbance of the solution around the beetroot piece) better than just deciding which solution is darkest by eye?
(2 points)
- Colourimeter gives QUANTITATIVE data - numbers (colours are qualitative data)
- LESS SUBJECTIVE (as different people could rank colours differently)
(beetroot practical)
What are the controlled organism variables?
(7 points)
- SAME SURFACE AREA (size) of beetroot pieces - measured using cork borer and ruler
- same species of beetroot - ideally cloned plants, so genetically identical
- same age of beetroot – seeds sown and beetroot picked at same time
- same growth conditions eg. soil pH, soil minerals
- same part of beetroot used eg. core
- same storage temperature
Betalains are released when {cells / vacuole membranes} are cut and damaged, even though the membrane permeability has not changed.
How can we make sure there are no betalains on the surface of the beetroot piece before it is placed in the water? (1 point)
What if there are betalains on the surface of the beetroot piece when it is placed in the water? (1 point)
- SOAK AND RINSE BEETROOT PIECES to remove betalains from damaged (cut) cells before placing in water
- if they are not washed they would make the solution darker pink (higher absorbance), suggesting a higher permeability than there actually is
How is the surface area of beetroot pieces controlled? (1 point)
- Cut cylinders or cubes to the same size using a cork borer, ruler and sharp scalpel
Why is the surface area of beetroot pieces controlled? (2 points)
- If the area is larger there is more {surface area / more tissue} for betalains to be lost from,
- so solution will be darker (higher absorbance)
How is the same beetroot {part/age/species/storage temperature} controlled? (3 points)
- grow beetroot plants from seeds from same packet.
- sown and harvested at the same time.
- stored in same conditions.
Why is the beetroot {part/age/species/storage temperature} controlled? (1 point)
- Different {beetroots/parts of beetroot/ages} may have different {numbers or sizes of cells/number of betalains}
(beetroot practical)
What are the controlled procedural variables & how are they controlled?
(3 points)
- Same VOLUME of water - 5cm3 measured using graduated pipette
- Incubation time - 30 minutes measured using stopclock
- Same {wavelength/filter} in colorimeter - set to 490nm
(beetroot practical)
What are the controlled environmental variables & how are they controlled?
(1 point)
- SAME pH OF WATER that beetroot pieces are placed in - use a BUFFER