Unit 3 Flashcards
1
Q
How might you carry out the Benedicts test?
A
Create solution. Add equal amount of reagent to solution. Shake + heat in water bath. Partially quantitative.
2
Q
What is the test for reducing sugars?
A
Benedicts test
3
Q
What is the test for non-reducing sugars?
A
Modified Benedicts test
4
Q
How might you carry out the modified Benedicts test?
A
Hydrolyse by boiling in dilute HCL. Once cooled, neutralise with sodium hydrogen carbonate. Check with pH paper and repeat Benedicts test.
5
Q
What are the results of the Benedicts test?
A
Blue - green - yellow - orange - brick red precipitate.
6
Q
What is the test for proteins?
A
Biuret test. Detects presence of peptide links.
7
Q
How might you carry out the test for proteins?
A
Create solution. Add potassium hydroxide to substance, then add copper sulphate + shake.
8
Q
What are the results of the test for proteins?
A
Blue - lilac
9
Q
What is the test for lipids?
A
Emulsion test
10
Q
How might you carry out the test for lipids?
A
Add sample to ethanol + shake, allow to settle, empty liquid into test tube w/water.
11
Q
What are the results of the test for lipids?
A
Clear/colourless - milky white emulsion.
12
Q
What is the test for glucose?
A
Clinistix
13
Q
How might you carry out the test for glucose?
A
Dip stick into substance and wait for a few minutes.
14
Q
What are the results of the test for glucose?
A
It will change colour and the level can be found by checking the label on the bottle.
15
Q
What is paper chromatography used for?
A
Identifying different amino acids. More soluble substance travels further.
16
Q
How might you carry out paper chromatography?
A
Cut paper to size, add solvent to tank + saturate atmosphere (Lid on), draw base line, add spot of solution + mark with x, repeat x5 for conc spot, place in tank with line above solvent, Draw line on solvent front before reaches top of paper (solvent travels up with dissolved AA’s). Allow to dry + spray with ninhydrin in fume cupboard. Heat gently. Circle spots + calculate Rf.
17
Q
How do you find the Rf value of an amino acid you tested using paper chromatography?
A
Distance moved by spot/distance moved by solvent..
18
Q
What is the test for starch?
A
Iodine
19
Q
How might you carry out the test for starch?
A
Add a few drops of iodine to the food sample.
20
Q
What are the results of the test for starch?
A
Yellow/brown to blue/black.
21
Q
Will hydrophilic amino acids prefer to stay in the stationary phase or the mobile phase?
What about hydrophobic amino acids?
What would their Rf values be?
A
Stationary phase, lower.
Mobile phase, higher.
22
Q
How might you determine the effects of pH on enzyme activity? Which pH works best?
A
Jelly cubes in different pH buffers with a protease in a water bath of optimum temp (35c). Test percentage transmission with a colorimeter. The pH with the lowest percentage transmission as the dye is released and less light can pass through. Control temp, enzyme vol + conc + substrate vol + conc.
23
Q
Where is trypsin found? What is its optimum pH?
A
Small intestine. pH 7
24
Q
How might you determine the effects of temperature on enzyme activity? Which temperature works best?
A
Mix starch + amylase at required temp + place at 5 diff temps in thermostatically controlled water bath with iodine. Use a colorimeter to measure their percentage transmission. The temperature with the highest percentage transmission is the optimum temperature as the starch is not present according to the iodine. pH, enzyme volume + conc + substrate vol + conc must be controlled.
25
How does a colorimeter work?
Measures change in intensity of light as it passes through a solution. They can record the amount of light absorbed by solution (absorbance) or amount that passes through (transmission). The light that isn't absorbed passes onto a photo-sensitive light + electrical current in converted into digital signal. Must be calibrated by blank solution (100% transmission)
26
What is a calibration curve?
A graph of known quantities. Allows colorimeter readings to be expressed in substrate concs. Used for calcing spec quantities. Start with known conc of starch, make range of concs, measure % transmission for each value + plot graph with transmission of y axis + conc on x axis.
27
How might you immobilise lactase to create lactose free milk?
Mix alginate + lactase, add food colouring, place small beads in calcium chloride with a syringe, then allow to harden and pass milk through beads. Test with clinistix to ensure glucose is present so lactose has been broken down.
28
How might we investigate the distribution of catalase in soaked pea and temperature on this reaction?
Test for catalase by crushing a soaked pea and adding hydrogen peroxide. Test seed coats and cotyledons separately for catalase. Boil each pea and place at different temperatures.
29
What is alcoholic fermentation? Equation?
In anaerobic conditions yeast cells break down sugar into ethanol and carbon dioxide.
Glucose -> Ethanol + Carbon Dioxide + Energy
30
How might we test the specificity of enzymes?
Add yeast to different solutions of sugars. Test how the measurement of liquids changes.
31
How might you prepare a slide to look at in a microscope?
Place a small amount of the substance onto a slide, add a drop of water/iodine onto it and add a cover slip.
32
How do you use a stage micrometer?
You must first calibrate the stage scale with the eyepiece scale so that the size of the divisions in the eyepiece are known at high and low power.
33
How do you calibrate an eyepiece graticule?
Align the top of both scales. Count the number of divisions on the eyepiece graticule that add up to a fixed number of divisions on the stage micrometer. You know it's the eyepiece as when you move focus knob, it doesn't change.
34
Why might a student blot dry potato cylinders before weighing after having them placed in a sucrose solution?
To ensure that the change in weight was due to changes in potato mass/osmosis, not due to outside liquid.
35
On a graph of percentage gain in mass vs percentage sucrose solution in an experiment on potato cylinders, how might you find what the concentration of cell sap was?
The point of equilibrium where osmosis is not occurring and there is no change in mass. This is the natural state of the potato so is the sap conc.
36
How do you know what the average solute potential of an onion cell is when on a graph of solute potential v plasmolysed cell percentage?
The point where 50% of cells are plasmolysed shows the average solute potential of onion cells which is equal to sucrose solute potential. Solute potential of sucrose at that conc can be calculated from conversion table.
37
How might you perform a root tip squash?
Grow beans in tray for 7-8 days, place section of lateral white root which is actively dividing in boiling tube with acetic orcein stain + heat @ 60 for 30 mins to soften + stain tissue. Cut off very end of root tip which is dividing. Then prepare a microscope slide and tap on cover slip or roll over with fist to squash root to get a single layer of cells. View and find out how long each stage of mitosis occurs for.
38
What is the formula to find out how long each stage of mitosis took in a root tip squash?
Percentage of cells at stage x 1440 minutes = number of minutes per that stage.
39
What is a block diagram?
Diagram which is used to show tissue layers, not individual cells.
40
How do you draw a block diagram?
Accurate rep, proportionality, smooth lines, pencil, ruled line for label,
41
What does annotate mean?
Label cell and give a short description of its role.
42
What does hydrogencarbonate indicator test for?
CO2
43
What are the colours of hydrogencarbonate indicator:
Less CO2
Normal CO2
High CO2
Purple, orange-red, yellow.
44
What is a simple respirometer used for?
Measure RQ of germinating seeds or small animals (mealworms + woodlice) Measures changes in gas pressure inside apparatus.
45
Describe how a respirometer experiment can be carried out.
Potassium hydroxide solution in tube to absorb CO2, equal volume of water in other tube to ensure temp/pressure changes act equally on both sides of manometer + cancel out. Wire basket into KOH tube, both tubes in water bath at 20c with taps closed for 15 mins. As respire, take up O2 + give out CO2 which is absorbed causing pressure to fall so fluid of manometer rises. Rise is recorded + O2 volume used is calculated by divide mean rise by time taken. Syringe used to reset fluid. KOH then removed + replaced with water + experiment repeated giving measure of CO2 produced. If CO2 produced = O2 used, no change in manometer levels. If more CO2 produced than O2 used, liquid in KOH tube falls.
46
What is a respirometer?
Device used to measure rate of respiration of living organism by measuring rate of exchange of O2/CO2. When respiring, it uses O2 + produces CO2 + total gas volume stays same. KOH absorbs CO2 + so volume gas decreases, decreasing pressure. Rate pressure falls = respiration rate.
47
Why should temp be controlled in a respirometer experiment?
Affects resp rate + change gas volume due to expansion or contraction.
48
How would you make a 0.1% solution from a 1% starch solution?
1cm3 of starch solution and 9cm3 of distilled water.
49
State 2 precautions for accuracy when making serial dilutions.
Use a clean pipette + ensure the suspension is thoroughly mixed.
50
Describe how serial dilutions can be used to create a calibration curve with a colorimeter.
Use colorimeter to find percentage transmission of each dilution + record. Create a graph of % transmission against starch conc. Each solution less concentrated than one before by set dilution factor. (e.g. DF 10, each 10x less conc)
51
Why might systematic sampling be used on a rocky shore to sample seaweed?
There is gradation/zonation (of conditions) up the shore/
| an environmental gradient exists/area to be sampled is not homogenous.
52
Why might students avoid placing transect tape over rock pools when sampling seaweed?
It isn't representative of the shore.
53
When preparing an enzyme experiment, which of these should not be controlled:
Temp, enzyme conc, substrate conc + substrate volume.
Enzyme concentration.
54
Suggest how you could modify an experiment to measure enzyme activity in terms of froth height and O2 production.
Collect O2 gas produced + measure its volume in mm3 with a gas syringe.
55
How can you be sure which is the eyepiece graticule and which is the stage micrometer?
When you increase the magnification or move the stage, only the stage micrometer will change.
56
Once the eyepiece graticule has been calibrated, describe how you would use it to determine the mean length of pre prepared Elodea cells, as accurately as possible.
Select suitable reference point for measuring cell length, e.g. middle lamella, measure length of cell in s.e.u. using highest appropriate power, convert s.e.u. to μm + measure appropriate num of cell lengths + calc mean length.
57
What is a reducing sugar? e.g.
A sugar that can donate electrons to/reduce Benedicts reagent. Monosaccharide sugars + some disaccharide sugars (maltose).
58
What is a non-reducing sugar? e.g.
Gives an initially negative Benedicts test, but after being hydrolysed into constituent monosaccharides with HCL + neutralised with Na HydrogenCarbonate, it gives a positive. e.g. sucrose, most disaccharide sugars.
59
How might you determine the effect of substrate conc on enzyme activity?
e.g. range of starch concs in amylase. Control temp, enzyme vol + conc, substrate vol + pH. Set water bath to 35c.
60
How might you determine the effect of enzyme conc on enzyme activity?
Temp, substrate vol + conc, enzyme vol + pH are controlled. 35c water bath.
61
pH
Indication of the conc of H2 ions in a solution. Acidic solutions have a higher conc.
62
What are simple (arithmetic) dilutions?
100%, 80% e.g. Useful when investigating enzyme/substrate conc. e.g. 60% solution conc = 60cm3 solution + 40cm3 water.
63
What is a serial dilution?
Each solution across series is less concentrated than previous by set factor. e.g. dilution factor x2 doubles dilutions. (each conc is half of previous) Advantage is a large range of concs is produced. Used for calibration curves.
64
What are the main steps in using a colorimeter?
```
Calibration (weak solution iodine considered blank/100% transmission if using amylase breaking down starch)
Choose filter (Max change in transmission, whichever colour is opposite end of spectrum)
Improve accuracy (Clean cuvettes, fill to right level, ensure orientation correct, re-calibrate after each go)
```
65
How do you draw a graph?
Independent variable on y axis, dependent variable on x axis. Use / for units. Join points with straight lines usually.
66
Independent Variable
| Dependent Variable
The thing you measure.
| The thing you change.
67
When might you use a line of best fit?
Constructing graphs of enzyme reactions over time using colorimeter readings, determine water + solute potential.
68
Line graphs
Used when Independent + dependent variables are continuous + probably a casual link between the 2. e.g. IV change causes DV change.
69
Bar Charts
Used when IV is discontinuous/categoric. e..g. plant/solution type tested. Space between bars.
70
Scattergrams
Used when IV + DV are continuous but not necessarily casual link between them. e.g. num of species in quadrat/soil pH.
71
How might you calculate the rate of change from a graph showing a linear relationship?
e.g. O2 vol produced by catalase over time. Vol O2 produced at 2 times on graph + divide diff in O2 production by time in seconds. Average rate expressed in cm3s-1.
72
Tables
Used to record info.
73
Homogenisation
Cell fractionation. Breaking up + mixing of material to give uniform preparation. Can be done using mortar + pestle/blender.
74
Centrifugation
Place prep In centrifuge tubes + spin at high speed. Causes larger particles to sediment while smaller at top in supernatant. Each tube must be counterbalanced by tube containing same vol/mass of material.
75
What is the triangle for magnification?
I/AxM
Image/Actual x Magnification
e.g. Magnification = Image/Actual
76
How do you measure the average water potential of cells in plant tissue?
Sections of tissue placed in diff concs. Some gain water, some loss water (osmosis). When solute potential of external solution equal to water potential of plant tissue, no mass change. Add water + diff sucrose solutions to beakers + add weighed sample of tissue. After 24 hours, remove + reweigh. Calc % change mass + create graph. Where line crosses x axis, solute pot of solution is same as water potential of tissue. No net osmosis.
77
How can you determine av solute potential of cells at incipient plasmolysis?
Add tissue to pure water so turgid, place in beakers of water or diff sucrose solutions, leave 30 mins, remove + view. Tally num plasmolysed + turgid. Draw percentage plasmolysis graph.
78
How might we use a colorimeter to investigate the effect of a factor (temp) on permeability of CSM (beetroot)?
Cut sections of beetroot, rinse in water beaks + repeat until water clear. Set up water baths of diff temps, add water to diff tubes + place in bath, leave 5 mins then add beetroot. Leave 10 mins. Set up colorimeter with distilled water for blank at 100% transmission. Sample water in cuvettes with colorimeter + draw % transmission graph.
79
What is the dorsal side of the heart?
The back of the heart.
80
Which is the ventral side of the heart?
The front of the heart.
81
Density
Num individuals present. Frame quadrats used.
82
Percentage Cover
Mainly for plants. Est, percentage area of quadrat covered by species. Usually rounded to nearest 10%. Less than 5% rounded to 1%.
83
Frequency
Species recorded as present/absent at each sampling point.
84
Pin Frame/Point Quadrat
Has large pins which can be lowered onto ground. Species present if pin touches it.
85
Random Sampling
Uniform area/not clear pattern in species distribution. Avoids bias + ensures sample's representative. Divide sample area into grid using tape at right angles + gen random coordinates using calculator. May put master tape in line with other tape at right angles along this line.
86
Systematic Sampling
Used where there's zonation. Along line/transect. Line/belt/interrupted belt transect.
87
Line Transect
Sampling continually/at intervals along line. Individuals touching line recorded.
88
Belt Transect
Sampling along line using quadrats end to end so it's continuously sampled.
89
Continguously
Continuously (end to end)
90
Interrupted Belt Transect
As belt but sample at intervals. Appropriate for long distances.
91
Abiotic
Non-living/physical factors. e.g. soil moisture, soil organic content, soil temp, soil pH + light intensity.
92
Edaphic
Factors relating to the soil.
93
Biotic
Living. e.g. competition, grazing, predation, light intensity at ground level in wood because of trees.
94
How would you measure soil moisture content?
Collect soil sample using soil auger, weigh, dry in oven until constant mass + calc % soil moisture content.
95
Soil Auger
Instrument which can bore down into soil, when removed from ground, sample can be removed from curls. Can remove soil across range of depths, not just at surface.
96
Percentage Soil Moisture Content Formula
((Initial soil mass - soil mass after drying)/initial soil mass) x 100%
97
How would you measure soil organic content?
Place dry soil in crucible + reweigh, burn off humus with bunsen burner, mix soil at intervals so all organic content burnt, allow to cool, burn + reweigh to constant mass. Calc % organic content.
98
Percentage Soil Organic Content Formula
((Dry soil mass - burnt soil mass)/initial soil mass) x 100%
99
What temp should you use when measuring soil moisture content?
105c.
100
What should you do if there's a delay between sampling + testing soil?
Place in plastic bags so no moisture evaps off before measuring.
101
In an experiment where you measure soil moisture content, how might you increase precision, accuracy, validity + reliability?
```
P = Use balance that measures to 2dp.
A = Transport + store soil in plastic bags.
V = Don't compromise on accuracy.
R = Take num of samples + measure edaphic factors as required.
```
102
How do you measure soil pH?
Use soil testing kit (indicator dyes) /pH electrode attached to digital meter.
103
How do you measure soil temp?
Thermometers. Usually special soil thermometer. Need to be left in soil long enough to equilibrate + insert to same depth at diff sampling points.
104
How do you measure light intensity?
Light meter. Many measure light intensity within waveband 400 - 700 nm, which can be used for photosynthesis. Readings expressed in Wm-2. Relative light intensity more meaningful. Light intensity at ground level/light intensity in open x 100%.
105
Pitfall Traps
Capture small animals walking over habitat surface. Sunk into soil so they fall in + can't get out. Ensure it's sunk sufficiently into soil so edge isn't above ground level + check regularly so they're aren't eaten by predators.
106
Sweep Nets
Sample arthropods in tall grass. Sweep side to side through grass so they're captured. Use specific num sweeps + same net size with same mesh size.
107
Pooters
Capture small insects to identify +/or count.
108
How should you present ecological data?
Record in tables, present in graphs. Type depends on data collected. Line graph, histogram, kite diagram (belt transect) or bar chart (interrupted belt transect)
109
Paper Chromatography
Soluble compounds can be separated + identified. Can separate complex organic compounds (mixtures of free amino acids/plant pigments).
Can separate + identify small quantities of solutes in unknown mix.
110
Rf Value
Relative distance an amino acid has moved relative to the solvent front. Always less than 1.
111
Why are colour filters used with a colorimeter?
Max's % transmission/absorbance change over experiment.
112
Quantitative
Numbers, quantity of organisms in a habitat.
113
Qualitative
Where a species is present/absent. Quality.
114
Kite Diagram
Shows num of organisms/% cover for plants against distance along a transect.
115
How might you calculate the rate of something?
Rate = Distance/Time
So maybe difference in amount / time
116
Standard form
E.g. 4 x 10^3 = 4000
| The number ^x determines the number of 0s.
117
Percentage Yield
(Actual yield/theoretical yield) x 100
118
SA:V ratio
E.g. Cube
```
SA = (l x w) x 6
V = l x w x h
```
119
How might you represent a phenotypic ratio?
Punnet Square
120
Probability
The extent to which an event is likely to occur, measured by the ratio of the favourable cases to the whole number of cases.
121
Chance
The possibility of something happening.
122
How do you calculate the median?
Middle number
123
Mode
Most common number.
124
~
Approximately
125
<<
| >>
Much less than
| Much more than
126
When might a line graph be used?
When both variables are quantitative and continuous. Determines the nature of a casual link between an independent variable and a dependent variable.
127
Continuous Variable
Any numerical value is possible, not just whole numbers.
128
Independent Variable
Factor being changed during practical. It goes on the x axis. (Horizontal) Causes a change in the dependent variable.
129
Dependent Variable
Factor being measured in practical. On the y axis. (Vertical)
130
How should a line graph be drawn?
Caption including both variables + biological material being investigated. Both variables with labels and units. (/) Appropriate scales. Usually a straight line rather than a best fit. (Indicates uncertainty as to values not notated on curve)
131
When might you draw a line of best fit?
Sufficient data points to be confident in relational or theoretical considerations predict that they fall on the line. Make calcs by interpolation or extrapolation. E.g. Calibration curve, percentage change in mass + percentage plasmolysis against water potential. Draw when you are going to calculate from graph.
132
How do you determine the colour filter to use during colorimetry?
Blue/green solution - red filter
Red solution - green filter
Yellow/orange solution - blue filter
