1. AICE Biology Lab Review AS Paper 3
Adapted from Ms. Evans GHS

2. Metric Units (Length) kilometer (km) = 1,000 m (1 X 103 m)
meter (m) = 1 m
centimeter (cm) = 0.01 m (1 X 10-2 m)
millimeter (mm) = m (1 X 10-3 m)
micrometer (um) = m (1 X 10-6 m)
nanometer (nm) = m (1 X 10-9 m)
**To convert between units, move the decimal right if you are making it smaller. Move it left if making it large.
Keep track of units

3. A. Cell Structure
Use a graticule and stage micrometer to measure cells and be familiar with units
(mm, µm, nm)
Example:
A lysosome measures 0.4 µm in diameter. What is the diameter in nm?
A 4nm
B 40 nm
C 400 nm
D 4000 nm

4. Calibrating an Eyepiece Graticule
Images from “Measuring” Leica microsystems

5. Measuring With A Graticule
Images from “Measuring” Leica microsystems

6. Measuring With A Graticule: PRACTICE
The diagram shows a graduated slide, with divisions of 0.1 mm viewed using an eyepiece graticule.
Pollen grains were grown in a sugar solution and viewed using the eyepiece graticule. Diagram 1 shows the pollen grains at first and diagram 2 shows them after four hours.

7. Difference Between Magnification & Resolution
Magnification: zooms in, makes small objects larger to see detail
Resolution: The shortest distance that can be distinguished between two objects

8. Calculating Magnification
Magnification = Image / Actual
Example 1:
The diagram is a plan of a transverse section through a leaf, drawn using a x 5 eyepiece and a x 8 objective lens of a microscope.
The actual distance across the leaf section is 7.5mm. What is the magnification of the diagram?
A x5 B x 8 C x D x 40

9. Calculating Magnification
Magnification = Image / Actual
Example 3:
The diagram shows a drawing of an electronmicrograph.
What is the approximate length of one mitochondrion in this cell? (Assume the line = 7mm)
A 5 to 6 µm
B 7 to 8 µm
C 8 to 10 µm
D 10 to 15 µm

10. (e) Compare & contrast the structure of typical animal & plant cells
A. Cell Structure
(e) Compare & contrast the structure of typical animal & plant cells

11. A. Cell Structure
(f) Draw plan diagrams of tissues (including transverse section of a dicotyledonous leaf) and calculate the linear magnification of drawings.

13. B. Biological Molecules
Carry out tests for reducing and non reducing sugars (including semi quantitative use of the Benedict’s test)
the iodine in potassium iodide test for starch,
the emulsion test for lipids and the
biuret test for polypeptides.

14. Benedict’s Test for reducing sugars
Mix equal amounts of test solution and Benedict’s.
Heat until nearly boiling for color change.
Identify relative concentrations of reducing sugars based on degree of color change.

15. Benedict’s Test for reducing sugars
Here’s a good example of some possible test solutions

16. Testing for non reducing sugars (sucrose)
If you get a negative result for your Benedict’s test, you can rule out the presence of reducing sugars like glucose, fructose & lactose, but further testing is needed to rule out sucrose.
There method to test for Non-reducing sugars: Acid Hydrolysis.

17. Testing for non reducing sugars (sucrose): Acid Hydrolysis
After a neg result, get a fresh solution and add dilute HCL. Heat for 10 minutes to break any glycocidic bonds present.
Then, add Hydrogen Carbonate to your sample until it ceases to fizz. This neutralizes the HCL in your sample.
Now, add Benedicts Solution to your sample and heat for minutes.
If you see a color change where you previously had a negative test, this is a positive test for non-reducing sugars (eg. sucrose) or starches in the solution.
Use the IKI test to narrow down your results
+positive IKI means you have either starch only or a mixture of starch & sucrose
-Neg. IKI means you have sucrose only.

18. Iodine in Potassium Iodide (IKI) test for starch
Iodine solution (IKI) reacts with starch to produce a dark purple or black color.
Right: distilled water and IKI
Left: starch solution and IKI - Iodine turns dark in the presence of starch.

19. Emulsion Test for Lipids
This one can be difficult to interpret. Look closely for small droplets of oil suspended in the emulsion.

20. Biuret Test for peptide bonds (protein)
+ Positive test is lavender to purple,
1st: Add KOH
2nd: Add drops of
CuSO4 to see if
a purple layer forms
Negative is sky blue
Record this as sky
blue, not No Reaction

21. 2 types of glucose: Describe the ring forms of alpha and beta glucose.
Alpha and beta glucose differ only in the direction that -H and -OH groups point on carbon 1. Alpha glucose has an -OH [hydroxyl] group that points "downwards", away from the ring, whereas the -OH on carbon 1 of beta glucose is above the ring.

22. (c) Describe the formation and breakage of a glycosidic bond.

23. (d) describe the molecular structure of starch (amylose & amylopectin), glycogen & cellulose and relate these structures to their functions in living organisms.

24. Starch (amylose & amylopectin)
Function: store energy for plants
Structure: many glucose molecules in a lattice configuration (crisscrossing)

25. Glycogen Function: Store glucose in animals
Structure: Highly branched glucose polymer

26. Cellulose Function: Structural support in plants
Structure: straight chain polymer, and each cellulose molecule is long and rod-like. This differs from starch, which is a coiled molecule. This is why cellulose cannot be broken down into its glucose subunits by any enzymes produced by animals.

27. Triglyceride Structure: glycerol & 3 fatty acids
Function: Energy storage; saturated (bad) & unsaturated (better) fats

28. Phospholipid
Structure: phosphate group as a “head” (hydrophilic) with 2 fatty acid tails (hydrophobic); both bonded to a molecule of glycerol
Function: Makes cell membranes with differing abilities to allow diffusion of materials across and allows solubilities in both oil & water

29. Peptide Bonds
(f) describe the structure of an amino acid and the formation & breakage of a peptide bond.

30. Amino Acids
20 of them

31. Peptide Bond

32. (g) explain the meaning of the terms primary,
secondary,
tertiary, and
quaternary structure of proteins and describe the types of bonding (hydrogen, ionic, disulphide and hydrophobic interactions) that hold the molecule in shape.

34. Primary Structure
Covalent bonding between adjacent -amino acids = peptide bonds

35. Secondary Structure
The helix is stabilized by hydrogen bonding between amine and carbonyl groups of the same polypeptide chain. The pleated sheet is stabilized by hydrogen bonds between the amine groups of one chain and the carbonyl groups of an adjacent chain.

36. Tertiary Structure
Tertiary structure is largely maintained by disulfide bonds. Disulfide bonds are formed by covalent bonding.
Hydrogen bonds
Hydrophobic and hydrophilic interactions between R groups

37. Quaternary Structure
Hydrophobic interaction is the main stabilizing force for subunits in quaternary structure.
Two or more strands of amino acids will assemble so that their exposed hydrophobic sections are in contact.

38. Hemoglobin
(h) describe the molecular structure of hemoglobin as an example of a globular protein, and of collagen as an example of a fibrous protein & relate these structures to their functions.

39. Haemoglobin
Made of 4 polypeptide chains: 2 alpha & 2 beta globin chains
The folded helices form a pocket that holds the working part of each chain, the heme which holds the iron.
Function: to carry oxygen to cells, which
binds to the oxygen in the heme group.

40. Collagen
Fibrous proteins generally exist as water-insoluble strands (as opposed to globular "ball-shaped" proteins which are soluble in water.)
The chains have a high percentage of hydrophobic amino acids that allows them to coalesce into strong linear chains
They are found in joints, ligaments, tendon, muscle, connective tissue, the skin and other tissues that are exposed to heavy mechanical stress,
Examples of these proteins are the collagens found in connective tissue

41. C. Enzymes
(d) Investigate and explain the effects of temperature, pH, enzyme concentration, and substrate concentration on the rate of enzyme - catalysed reactions, and explain these effects.

45. E. CELL AND NUCLEAR DIVISION (Mitosis)
(d) *describe, with the aid of diagrams, the behaviour of chromosomes during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell membrane, centrioles and spindle (names of the main stages are expected);

46. Plants: Monocots versus Dicots
The flowering plants (angiosperms) are classified as either monocots or dicots based on characteristics of their pollen, leaves, roots, stems and flowers.
Monocots include lilies, corn, rice, palms and grasses.
Dicots include pretty much everything else- including all woody plants.

47. The three tissue systems in the plant body

48. Vessel element (xylem cell)
Sieve tube element
Tracheid (xylem cell)
Vessel element (xylem cell)
Phloem tissue

49. Xylem Tissue
Tracheid
Vessel element

50. Phloem Tissue
Sieve tube element
Companion cell

51. Dicots

52. Dicot Root Cross Section (cs)

53. Dicot Stem

54. Dicot Leaf These leaves have a more obvious mid-rib (central vein)
Veins are perpendicular to the central vein.
40x . This image shows the large central vein (vascular tissue) in the middle of a dicot leaf. The white areas inside the leaf are air spaces, which allow the cells to take up carbon dioxide gas for photosynthesis. The rows of elongated cells near the top surface of the leaf are the palisade layer, where most of the photosynthesis takes place.
40x . This image shows the large central vein (vascular tissue) in the middle of a dicot leaf. The white areas inside the leaf are air spaces, which allow the cells to take up carbon dioxide gas for photosynthesis. The rows of elongated cells near the top surface of the leaf are the palisade layer, where most of the photosynthesis takes place.

55. Mesophyte Dicot Leaf: Ligustrum
Mesophytic leaves are adapted to average conditions. Note the well differentiated mesophyll with a palisade mesophyll on the upper surface and the spongy mesophyll below.

56. Mesophyte Leaf: Prunus (Laurel)
At 3 different magnifications

57. Stomata
Identify the guard cells that both form the stoma and regulate its size.

58. Hydrophytes: Water Loving Plants
Hydrophytic leaves are adapted to an aquatic existence. Note that the upper palisade mesophyll is well developed for photosynthesis while the lower portion of the mesophyll is very loosely arranged. Stoma are located in the upper epidermis.

59. Xerophytes : Ammophilia (Marram Grass)

60. More Xerophytes: Oleander 200X

61. More Xerophytes: Oleander 400X

62. G. Transport: Mammals
(l) *describe the structures of arteries, veins and capillaries and be able to recognise these vessels using the light microscope;

63. Artery & Vein Cross section Comparison

64. H. GAS EXCHANGE
(a) *describe the structure of the human gas exchange system, including the microscopic structure of the walls of the trachea, bronchioles and alveoli with their associated blood vessels;
(b) *describe the distribution of cartilage, ciliated epithelium, goblet cells and smooth muscle in the trachea, bronchi and bronchioles;

65. Trachea

66. Lung Tissue

67. J. IMMUNITY / Mammalian Transport
(n) *describe the structure of red blood cells, phagocytes and lymphocytes and explain the differences between blood, tissue fluid and lymph; (Transport)
(a) *recognise phagocytes and lymphocytes under the light microscope;
Blood smear Medium Lymphocyte (yellow)
Neutrophils (green)
Bar = 50 Microns (µm)

68. AICE Biology Lab Review: Biological Molecules
Prepared by Ms. Evans at GHS
Lab Review ppt: Biological Molecules & Enzymes

69. B. Biological Molecules
(a) carry out tests for reducing and non-reducing sugars (including semi-quantitative use of the Benedict’s test), the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins;
Lab Review ppt: Biological Molecules & Enzymes

70. Benedict’s Test: Reducing & Non Reducing Sugars, Round 1
Testing for simple sugars: Benedict's Reagent, round 1
Procedure:
Add Benedicts reagent to sample, place in waterbath until just boiling.
Left to right:
Benedict's reagent (BnR),
potato extract + BnR,
onion extract + BnR,
5% glucose + BnR.
RESULTS:
Aqua-blue = negative.
Green to Yellow to orange = positive.
Note: to detect the simple sugar sucrose, you must do round 2 test
Lab Review ppt: Biological Molecules & Enzymes

71. Benedict’s Test: Reducing & Non Reducing Sugars, Round 2
A Negative result in round one DOES NOT mean an absence of carbohydrates!!
Sucrose is a non-reducing Sugar & can only be detected by doing round 2 of Benedict’s testing (Acid Hydrolysis)
Procedure:
Perform round 1 of Benedict’s Testing. Negative result indicates either no carbohydrate OR Non-reducing Sugars (Sucrose or starch).
How would you test for the presence of starch???
Perform Round 2 of Benedict’s Testing to see if you have sucrose if Starch test is Negative.
Lab Review ppt: Biological Molecules & Enzymes

72. Sample Procedure for Benedict’s Test for Non Reducing Sugar
In a test tube place 5 cm3 solution, add 3 cm3 Benedict's reagent to the solution in the test tube and place the tube in the boiling water bath for five minutes.
Add 1 cm3 dilute hydrochloric acid to the solution solution in your test tube. Note the time and place in the water bath
After 10+ minutes, remove the tube from the water bath & cool it under the tap. Neutralize the acid by adding solid sodium bicarbonate, a little at a time, until the addition of one portion produces no fizzing.
With a dropping pipette place 3 cm3 Benedict's solution in test tube & return to the water bath and heat for five minutes.
A color change indicates that there was Non reducing sugar present. How would you verify that your solution was sucrose & not starch???
Lab Review ppt: Biological Molecules & Enzymes

73. Benedict’s Testing: Sample Question 1
Solutions of four food substances are tested for sugars. The table shows the colours of the solutions after testing.
Which food is a non-reducing sugar?
Lab Review ppt: Biological Molecules & Enzymes

74. Benedict’s Testing: Sample Question 2
Four sugar solutions were tested with a standard Benedicts solution. The table shows the colour of the solutions after testing.
What is the best interpretation of the results?
Lab Review ppt: Biological Molecules & Enzymes

75. Testing for Starch IKI (Iodine in Potassium Iodide)
Left to right:
IKI only,
starch solution,
starch solution + IKI.
RESULTS: Yellow-orange = negative.
Purple-black = positive.
Lab Review ppt: Biological Molecules & Enzymes

76. Emulsion Testing for Lipids
Sample Procedure:
Add 2cm3 fat or oil to a test tube containing 2cm3 of absolute ethanol. Dissolve the lipid by shaking vigorously. Add an equal amount of cold water.
Observation: A cloudy white suspension.
Basis of test:
Lipids are immiscible with water. Adding water to a solution of the lipid in alcohol results in emulsion of tiny droplets in the water which reflect light and give a white , opalescent appearance.
Lab Review ppt: Biological Molecules & Enzymes

77. Testing for Polypeptides (proteins) Biuret’s Reagent
Left to right:
Biuret's reagent (BrR),
water + BrR,
egg albumin solution,
egg albumin solution+ BrR.
RESULTS:
Denim-blue = negative.
Lavender = positive.
Lab Review ppt: Biological Molecules & Enzymes

78. Acid hydrolysis then Benedict’s
Identify each sample
Food tests are carried out on four unknown chemicals. The chart below shows the results of each test.
Solution
Benedict’s Test
Acid hydrolysis then Benedict’s
IKI
Biuret
Emulsion A X + B C D
(KEY: + = positive result , X = negative result)
Lab Review ppt: Biological Molecules & Enzymes

79. Measuring Color in Dependent Variables
Color standards
Carry out macromolecule test on set of solutions with KNOWN concentrations (you make these)
Use excess of your indicator
This produces a range of colors (and you know the concentrations)
Stand this in a test tube rack
Now test your unknown sample
Compare sample to your known concentrations and determine the concentration of your sample
Terms to use
Simple words: red, blue, purple, green
Qualify with “pale” or “dark”
Use +, ++, +++ to show intensity (include a key)
State actual color…do not say “no change”

80. Recording Quantitative Results
Descriptions of what you see
Use simple language
Avoid terms that would be difficult to understand (ex. yellowish-green)
Should say “this tube is darker or lighter green than tube 1”
Never state “no change” say the color
Example…if there was no reaction to benedicts solution, you would state, “the tube remained blue”

81. Tools to Measure Dependent Variable
Colorimeter
Measures color changes
Quantitative measurements of color intensity in solution
Good way to “improve reliability” of experiment
Uses cuvettes that contain solution
Deeper colors absorb more light
Important to choose suitable color of light to shine through (opposite of the color of solution)

82. Dilutions Simple Dilution Serial Dilution
Unit volume of liquid of interest is combined with an appropriate volume of solvent liquid to achieve desired concentration
“1 to 5” dilution means:
1 unit of solute AND 4 units of solvent for a total volume of 5 units
A series of simple dilutions which amplifies the dilution factor quickly beginning with a small quantity of material
The solute for each step comes from the previous dilution

83. Concentration
The concentration of a solution is the amount of a substance present in a given volume of solvent.
concentration = amount ÷ volume
Usually measure the amount in moles and the volume in dm3
Concentration of a substance is usually expressed in mol dm-3

84. Concentration
Concentration of a solution is the amount of stuff dissolved in a given volume of a solvent
Most commonly given as a percentage on the Cambridge exam

85. 1 cm3 = 1 mL

86. Simple Dilution
A simple dilution is one in which a unit volume of a liquid material of interest is combined with an appropriate volume of a solvent liquid to achieve the desired concentration
The dilution factor is the total number of unit volumes in which your material will be dissolved
The diluted material must then be thoroughly mixed to achieve the true dilution
Use simple dilution procedures when asked to MAKE A RANGE OF CONCENTRATIONS
You will determine the % concertation and then show how you made them
Hint:
1% solution = 1 gram of something dissolved in 100 mL of water
Or 1 mL of something dissolved in 100mL of water

87. Serial Dilution
A serial dilution is simply a series of simple dilutions which amplifies the dilution factor quickly beginning with a small initial quantity of material
Source of dilution material (solute) for each step comes from the diluted material of the previous dilution step

88. Warm Water Bath Materials Measure temperature carefully
Large beaker of water
Thermometer
Ring stand
Bunsen burner
Wire gauge
Thermometer clamp
Measure temperature carefully
Use thermometer in water
Cannot touch bottom of beaker of water or the side
Read thermometer while it is in the water
Allow test tubes in warm water bath to reach same temp as water
Should measure actual temp of liquid in tubes

89. Accuracy, Precision, Reliability
How true measurement is
Depends on the calibration of instrument you are using
Precision
Ability of the measuring instrument to give the same reading every time you use it
Doesn’t have to be the “true” value
Repeatable, reproducible
Reliability
Degree of trust you have in the instrument
If measurements are reliable, then you expect to get same measurements in repeated experiment on that tool
Affected by ACCURACY and PRECSION and TYPE of measurements being taken
Best way to deal with poor reliability: REPEAT readings several times (multiple trials at same time)

90. Preparing Tables Create a data table ALWAYS
Make table BEFORE you start
Independent Variable should be in the FIRST column
The readings/measurements you take in the next columns
Sometimes second column will be dependent variable
Sometime you will have multiple columns because you need to calculate the dependent variable
Lines should be clearly drawn with a ruler and pencil
Each column must be FULLY headed including the unit of measurement
Use a slash or brackets to denote the unit…be consistent
length of stem/mm OR length of stem (mm)
Don’t use slash to denote “per”…use negative exponents (-1) or the word “per”
Velocity/ms-1 OR velocity/m per s
DO NOT put units in the boxes with the actual measurements (only in headings)

91. Percentage of Glucose Solution (%) Time for color change (seconds)
Preparing Tables
Percentage of Glucose Solution (%)
Time for color change (seconds)
1.000
0.750
0.500
0.250
0.125

92. More on Tables If you have to do calculations….
Use significant figures
Answers should have same amount of sig figs as measurements in calculations
Keep same decimal places throughout table

93. Suggesting Improvements
How could you get more valid or reliable result?
Suggest controlling certain variables better in your experiment
You MUST state how you would better control the variable
Examples:
Using a thermostatically controlled warm water bath instead of Bunsen burner
Using a colorimeter instead of color standards
DO several more repeats of experiments to get an average

98. Practice Problems Set 5: #4 Serial Dilution (Nov. 2013 Simple Dilution)

100. Word choice

101. “You” Or really any other pronouns for that matter
“You can’t see a ribosome with a light microscope.”

102. “You” Or really any other pronouns for that matter
“You can’t see a ribosome with a light microscope.”
“Ribosomes cannot be seen using light microscopy.”

103. “Things” and “Stuff” Too ambiguous. What “things”? What “stuff”?
“The cell surface membrane is responsible for keeping stuff inside or outside of the cell”
“Nuclear pores let things in and out of the nucleus.”

104. “Things” and “Stuff” Too ambiguous. What “things”? What “stuff”?
“The cell surface membrane is responsible for keeping stuff inside or outside of the cell”
“The CSM is responsible for regulating what molecules enter and exit the cell.”
“Nuclear pores let things in and out of the nucleus.”
“Nuclear pores allow for particles, like ribosomes and mRNA to exit the nucleus, and for particles like hormones and nucleotides to enter the nucleus.

105. “Things” and “Stuff”
Words to use instead: molecules, macromolecules, the actual name for the “thing”, structure, vesicle

106. “Good” and “Bad”
Less ambiguous, but not appropriate for Cambridge level students in a formal paper
Good: beneficial, necessary
Bad: harmful, unwanted
What is considered “good” to one cell might be “bad” for another cell, so avoid these two words at all costs!

107. “Job”
Cells and organelles don’t have jobs (They can’t quite figure out how to type a resume yet)
“The job of the ribosome is to synthesize proteins”

108. “Job”
Cells and organelles don’t have jobs (They can’t quite figure out how to type a resume yet)
“The job of the ribosome is to synthesize proteins”
“The function of the ribosome is to synthesize proteins.”

109. Shape
Like “good” and “bad” it’s not that this word is ambiguous, but it is generally not used in Biology
Instead: structure, complex, organization

110. Metaphor, Simile, and Analogy
Fine for literature, but not for AICE Biology exams
“The mitochondria is the powerhouse of the cell.”
“The nucleus is like the brain of the cell.”

111. Metaphor, Simile, and Analogy
Fine for literature, but not for AICE Biology exams
“The mitochondria is the powerhouse of the cell.”
The mitochondria creates chemical energy for the cell in the form of ATP.
“The nucleus is like the brain of the cell.”
The nucleus controls the functions of the cell by transcribing DNA

112. Other words to avoid
A lot
Many
Really
Very
Lots
Nice

113. Commonly seen on Paper 2 and Paper 3
Command Words

114. List and State
List: give a number of points, no elaboration is necessary
State: give a concise answer, no supporting argument
“State the advantages of using the light microscope, rather than using the electron microscope, in studies of tissues.”
“State the functions of structures P, Q and R.”

115. Define and Explain
Define: present a formal statement, probably learned by heart
Explain: accompanied by “… what is meant by”, is another way of asking for a definition

116. Outline and Describe Outline: give the main steps or main points
 Describe(1): give a step by step account of a structure or process; detail can be required
“Outline how red blood cells are involved in the transport of carbon dioxide.”

117. Describe(2) and Explain(2)
Describe(2): pick out key points from stimulus material such as a graph or a diagram
Explain: give reasons (often to follow up from describing). This will require knowledge of the underlying theory
“The leaves of the buttonwood trees at the exposed site were significantly smaller than those at the sheltered site. Describe three ways, other than small size, in which leaves are adapted to reduce the rate of transpiration.”
“Explain how capillaries are adapted for their function as exchange vessels.”

118. Discuss and Compare
Discuss: give a critical account – may often require two sides of an argument to be presented
Compare: give similarities and differences

119. Suggest(1) and Suggest(2)
Suggest(1): there is no unique answer
Suggest(2): use knowledge in a novel situation
“People who receive drug treatment for HIV take a mixture of drugs that act in different ways. Suggest the advantage of taking a mix of the drugs shown in Table 4.1.”

120. Measure, Determine, and Calculate
Measure: use a measuring instrument, e.g. protractor, ruler
Determine: in a practical situation, usually implies measuring and then calculating; it could also involve carrying out a procedure before measuring something
Calculate: use a mathematical process to find the answer from given or measured values; always show working

121. Predict and Deduce
Predict: make a logical connection between other pieces of information to produce the required answer
Deduce: make a logical connection between other pieces of information to produce the required answer and include a supporting statement