Pharmacognosy is the one paper where a right answer can still cost you marks if you cannot explain why bentonite refuses to settle in water or why amylose turns iodine blue-black. In PCG 212 – Pharmacognosy Practical I, you (a 200 Level student in the ABUAD College of Pharmacy) are examined as much on lab reasoning as on recall. This EverythingABUAD guide takes each practical topic on the second-semester outline and shows you the exact points where the reasoning is tested.
The trap in this course is treating it as pure memorisation. Sedimentation rate is a simple mass-over-time sum, but the follow-up asks you to name the mineral from its behaviour. A microscope question looks trivial until you have to justify why safranin and not water. So this page explains the concept behind each topic in plain language, then lets you test yourself on original practice questions with fully worked answers. The complete workbook sits in the interactive reader further down, free to read online or download.
- Course: PCG 212 – Pharmacognosy Practical I
- College / Department: College of Pharmacy / Pharmacy
- Level / Semester: 200 Level, Second Semester
- Topics covered: Mineral Matters & Sedimentation, Crude Drug Evaluation & Diagnostic Characters, The Compound Microscope, Starch (Composition, Properties & Uses), Unorganised Crude Drugs & Gums, and Chemical Identification Tests
- Best for: Continuous assessment + final exam revision
Topics Covered in PCG 212
1. Mineral Matters & Sedimentation
Pharmaceutical mineral matters like kaolin, talc, chalk and bentonite are judged partly by how fast they settle out of water. The sum itself is easy: sedimentation rate is mass divided by the time taken to settle fully. What examiners really test is your reading of the result. A dense, gritty powder drops quickly, while bentonite barely settles at all because it absorbs water and swells into a gel that stays dispersed. Exam tip: remember that particle size, density and shape control the rate, never the mineral's chemical source, and that solubility plays no part because these minerals are essentially insoluble.
2. Crude Drug Evaluation & Diagnostic Characters
A crude drug is authenticated by its characters, and you need to keep two families of them straight. Features you can judge with your senses, colour, odour, taste and texture, are macroscopic or organoleptic characters. Features you can only see down a microscope, such as stomata, trichomes and crystal inclusions, are pharmacognostic characters. Exam tip: when a question describes a plant part rich in stomata, venation, chlorophyll and a cuticle, the answer is a leaf, and true conducting tissue is always xylem and phloem together. Collenchyma, sclerenchyma and parenchyma are supporting or ground tissue, not vascular.
3. The Compound Microscope
Half the practical marks in this section come from knowing the instrument, not the specimen. The eyepiece usually magnifies ten times, and total magnification is that figure multiplied by the objective in use. The diaphragm in the substage condenser controls how much light reaches the lenses, so it sets brightness and contrast. Exam tip: pair each detail with its reason. Safranin stains cell walls and nuclei red so internal structure shows up, and glycerol is added before mounting because it is viscous and keeps the wet mount from drying out under the coverslip during examination.
4. Starch: Composition, Properties & Uses
Starch is a large polysaccharide macromolecule built from glucose units, and it is roughly 80% amylopectin (branched) and 20% amylose (linear). That split matters for the classic iodine test: the linear amylose helix traps iodine to give the intense blue-black colour, while branched amylopectin only tints it reddish-purple. Exam tip: tie the theory to its pharmaceutical use. Starch works as a tablet binder, as a disintegrant that swells to break tablets apart in gastric fluid, and as a dusting powder, so a question on its role in a formulation is really asking which of those three properties applies.
5. Unorganised Crude Drugs & Gums
Unorganised (acellular) crude drugs have no organised cellular structure. Gums, resins, waxes and fixed or volatile oils all belong here, and a manufactured tablet never does. You should know their sources and quirks: tragacanth is a dried exudate from Astragalus species and flocculates when acid is added, while acacia produces its gum as a protective response to injury, a process called gummosis. Exam tip: watch the "all of them are" style question. These drugs are not uniformly white in colour, and collection, storage and processing all affect their quality, so an "except" option there is usually a distractor.
6. Chemical Identification Tests
A few colour and precipitate tests recur throughout the practical, and you are expected to state both the method and what a positive result looks like. Fehling's test, made by mixing equal volumes of Fehling's A and B, gives a brick-red precipitate of cuprous oxide when reducing sugars are present. The ferric chloride test gives a blue, green or purple colour with phenolic compounds. Exam tip: learn which class each reagent detects, because the multiple-choice version simply swaps the reagent and asks what it confirms. Fehling's means reducing sugars, ferric chloride means phenolics, and iodine means starch.
Sample Practice Questions (With Answers)
Here are a few sample questions, written in our own words, with the reasoning spelled out so you understand the why and not just the letter:
Q1. A 2.0 g mineral-matter sample settled completely in 6 minutes 40 seconds in 400 mL of water. What is its sedimentation rate?
Answer: Convert the time first: 6 min 40 s = 400 s. Sedimentation rate = mass ÷ time = 2.0 g ÷ 400 s = 0.005 g/s (5 × 10⁻³ g/s). Note that the 400 mL of water is context only, the rate depends on mass and settling time.
Q2. Of kaolin, talc, bentonite and chalk, which fails to settle out in water because of its swelling behaviour, and why?
Answer: Bentonite. In water it absorbs liquid and swells enormously into a colloidal, gel-like suspension rather than dropping to the bottom. That swelling keeps the particles dispersed, so under ordinary conditions it does not sediment the way the denser kaolin, talc and chalk do.
Q3. Which component of starch produces the blue-black colour with iodine, and roughly what proportion of starch is it?
Answer: Amylose, which makes up about 20% of starch (amylopectin is the other ~80%). Its long linear helix traps iodine molecules inside the coil to give the intense blue-black. Branched amylopectin cannot do this and only gives a reddish-purple tint, which is why the blue-black is the standard confirmatory test for starch.
Q4. You perform Fehling's test on a sample and get a brick-red precipitate. What class of substance does this confirm, and what is the precipitate?
Answer: It confirms reducing sugars. The reducing sugar reduces the cupric (Cu²⁺) ions in the deep-blue reagent to a brick-red precipitate of cuprous oxide (Cu₂O) on heating. Non-reducing sugars and starch give no precipitate, so a clear blue solution is a negative result.
How to Study PCG 212 Effectively
- For every sedimentation question, write the time in seconds first, then apply rate = mass ÷ time, and be ready to name the mineral from how it behaves (swelling suggests bentonite, grittiness chalk, a soapy feel talc).
- Build one comparison table of the four mineral matters (kaolin, talc, chalk, bentonite) listing feel, settling behaviour and a distinguishing test, and review it until you can rebuild it from memory.
- Learn each microscope part with its function attached (diaphragm controls light, eyepiece ×10, safranin stains structure, glycerol keeps the mount wet), because that is how the questions are framed.
- Memorise the three identification tests as reagent-to-result pairs: Fehling's to reducing sugars, ferric chloride to phenolics, iodine to starch.
- Fix the starch granule shapes in your head (maize is angular/polygonal with a stellate hilum, potato oval with an eccentric hilum, wheat lenticular), since identification by exclusion is a standard practical.
- Use this guide to understand each concept first, then work the full workbook below under timed, closed-book conditions to test recall.
Download the Full PCG 212 Practice Workbook
Once you have the concepts above, put them to the test. The interactive reader below holds our complete set of PCG 212 practice questions with a full worked answer key, grouped by topic. Read it straight on the page or save it for offline revision in the days before your exam.
Frequently Asked Questions
Is this PCG 212 material free?
It is, in full. Reading it on the page and downloading the workbook cost nothing, and there is no sign-up wall. EverythingABUAD keeps its study aids open to every ABUAD student.
Will these exact questions appear in my exam?
No. This is an original revision set written from scratch by our student team and worded in our own way to match the PCG 212 topics. It is a study aid, not a leaked paper and not a prediction of what your examiner will set.
Do I need to memorise botanical names for the starch practical?
Yes, the maize-starch practical expects you to give Zea mays L. (family Poaceae) along with its granule features and uses, and to contrast it with potato and wheat starch. Learn the botanical name, family and source for each starch on your outline, and confirm the exact list with your lecturer's current course outline.
About this resource: All summaries, explanations, study tips, and practice questions on this page were written, paraphrased, and adapted by the EverythingABUAD student team to support exam revision. This is an original study aid, not an official ABUAD document, and it is not a prediction of any future exam.
