Grade 12 — Term 1
3 study notes · 30 practice questions · Aligned with NIE syllabus
Counted in the Idasara Academy app, which you open with a free account. The free notes, revision, practice and library pages for each lesson are linked below.
This term in the Idasara Academy app has 3 lessons (NIE Units 2, 3). For each lesson, this page gives you the points you must know and one exam-style question with its answer. None of it needs an account.
Lessons in This Term
Cell structure and organization
What you must know
- Organelle membrane counts: Double-membrane organelles are Nucleus, Mitochondrion, and Chloroplast; single-membrane organelles are ER, Golgi apparatus, Lysosome, and Peroxisome; non-membranous structures are Ribosomes, Centrioles, and Cytoskeleton.
- Plant vs Animal cell distinctions: Plant cells possess rigid cellulose cell walls, large central vacuoles, and chloroplasts; animal cells possess centrosomes with centrioles and lysosomes.
- Fluid Mosaic Model of plasma membrane: Phospholipid bilayer with hydrophilic heads facing outwards and hydrophobic fatty acid tails inwards, studded with integral and peripheral proteins, glycoproteins, and cholesterol.
Try one question
Which of the following cellular structures is bounded by a single membrane and contains hydrolytic enzymes active at acidic pH?
- A. Lysosome
- B. Ribosome
- C. Mitochondrion
- D. Peroxisome
Show the answer
Answer: A. Lysosome. Lysosomes are single-membrane-bound cytoplasmic organelles containing acid hydrolases (active at ~pH 4.5-5.0) responsible for intracellular digestion and autophagy.
A model question written by Idasara on the exam pattern. It is not from a past paper.
Chemical and Physical Basis of Life
What you must know
- Biochemical tests identification: Starch = Iodine test (blue-black); Reducing sugars = Benedict's test (brick-red precipitate); Proteins = Biuret test (purple/violet); Lipids = Sudan III / Ethanol emulsion test.
- DNA vs RNA structural distinctions: DNA has deoxyribose, thymine (A-T, G-C), double-stranded double helix; RNA has ribose, uracil (A-U, G-C), single-stranded.
- Enzyme action principles: Protein catalysts that lower activation energy without altering free energy change (ΔG); sensitive to pH, temperature, substrate concentration, and competitive/non-competitive inhibitors.
Try one question
Which physical property of water is primarily responsible for the upward transport of water in the xylem vessels of tall trees against gravity?
- A. Maximum density at 4 °C
- B. High cohesive and adhesive forces
- C. High latent heat of vaporization
- D. High specific heat capacity
Show the answer
Answer: B. High cohesive and adhesive forces. Cohesion (hydrogen bonding between water molecules) forms an unbroken water column, while adhesion (attraction to hydrophilic xylem cell walls) prevents meniscus detachment, enabling transpirational pull according to the cohesion-tension theory.
A model question written by Idasara on the exam pattern. It is not from a past paper.
Diversity of organisms
What you must know
- Alternation of generations: Sporophyte (diploid, 2n) produces haploid spores via MEIOSIS; Gametophyte (haploid, n) produces gametes via MITOSIS.
- Chordate diagnostic characteristics (present at some stage of life): Notochord, dorsal hollow nerve cord, pharyngeal gill slits, and post-anal tail.
- Gymnosperm vs Angiosperm seed reproduction: Gymnosperms have naked ovules on cones and single fertilization; angiosperms have enclosed ovules in ovaries, flowers, and double fertilization.
Try one question
Which substance is the main component of the cell walls of fungi?
- A. Lignin
- B. Cellulose
- C. Peptidoglycan
- D. Chitin
Show the answer
Answer: D. Chitin. Fungal cell walls are made mainly of chitin, a nitrogen-containing polysaccharide. Plant cell walls are made mainly of cellulose and bacterial cell walls of peptidoglycan, while lignin strengthens the walls of some plant tissues such as xylem. None of these three is the main wall material of fungi.
A model question written by Idasara on the exam pattern. It is not from a past paper.
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