SBI4U Biology: the course map (27 ideas across biochemistry, metabolism, molecular genetics, homeostasis and population dynamics), vocabulary against mechanism, the diagrams to redraw from memory, and the data-analysis questions

SBI4U is Ontario's Grade 12 university biology: biochemistry, metabolic processes (respiration and photosynthesis), molecular genetics, homeostasis and population dynamics. Our map has 27 ideas in teaching order. Each idea is two things to learn, the vocabulary (terms you must name) and the mechanism (a process you must explain in order), and the way to own a mechanism is to redraw it from memory until the arrows are right. Here is the map, the diagrams and the plan.

What SBI4U is, and what it assumes (Grade 12 biology in Ontario)

SBI4U is the course code for Biology, Grade 12, University Preparation, in the Ontario Ministry's science curriculum. Its prerequisite is SBI3U, the Grade 11 university biology course. The Ministry's document organises the course in strands lettered A to F; strand A is the scientific-investigation skills that run through everything, so the content map below starts at B.

The chemistry it uses is Grade 11 chemistry: bonding, polarity, solutions and a working idea of pH. SCH4U's organic chemistry helps with the biomolecules strand, because functional groups and condensation reactions come up, but it is not required, and the biochemistry unit teaches the chemistry it needs. Some schools recommend Grade 11 chemistry alongside; the only formal prerequisite is SBI3U.

Where it leads: first-year biology, and the life-science and health-science programs that ask for it. The two strands that matter most there are molecular genetics and metabolism, which is worth knowing when you decide where to spend the extra hour.

The course map: 27 ideas in the order they are taught

These are our own titles for the ideas, grouped by the Ministry's strand letters, in the order most classes teach them.

B. Biochemistry

1. The four classes of biological macromolecule
2. Water, hydrogen bonding and the chemistry of life
3. Protein structure: primary to quaternary
4. Enzymes, active sites and the induced-fit model
5. Enzyme inhibition and feedback regulation
6. Membrane structure and transport across membranes

C. Metabolic processes

7. ATP and the energy currency of the cell
8. Glycolysis
9. The Krebs cycle
10. The electron transport chain and chemiosmosis
11. Anaerobic respiration and fermentation
12. The light-dependent reactions
13. The Calvin cycle

D. Molecular genetics

14. The structure of DNA
15. DNA replication
16. Transcription
17. Translation and the genetic code
18. Mutations and their consequences
19. The control of gene expression
20. Biotechnology and genetic engineering
21. Patterns of inheritance

E. Homeostasis

22. Homeostasis and negative feedback
23. The nervous system and the action potential
24. The endocrine system and hormonal control
25. The kidney, osmoregulation and excretion

F. Population dynamics

26. Population growth models and carrying capacity
27. Community interactions

Copy the 27 lines onto one page and keep it at the front of the binder. As the semester goes on, mark each idea can do, shaky or cannot, in pencil, and change the marks as they change. That page is the course on one screen, and chapter 3 of the free playbook is the method for keeping the marks honest.

Vocabulary against mechanism: every idea is both

Biology has a trap that maths does not. Every idea on the map is two things, and the first one hides the second.

The vocabulary is the set of terms you must be able to name and define: glycolysis, pyruvate, NADH, codon, anticodon, allosteric site. After one careful read the terms feel learned, because you recognise them on the page. Recognition is not the exam. The exam asks you to produce the term from its definition, or the definition from the term, with the page closed, and recognition does not survive that.

The mechanism is the process you must be able to explain in order: what happens first, where it happens, what goes in, what comes out, what the next step takes from it. Rereading never builds a mechanism, because a paragraph you read is in the author's order and the exam asks for it in yours, from a blank start. This is why rereading fails biology specifically: the vocabulary gives a feeling of progress that the mechanism never earns.

So every idea gets two passes. The vocabulary goes on recall cards, a question on the front and the term or definition on the back, spaced over days; how to write a card that forces recall has the rules, and the main one is that the front never gives the back away. The mechanism is learned by redrawing it from a blank page and checking against the book, which is active recall with a pencil.

Strand	Vocabulary (cards)	Mechanism (redraw)
Biochemistry	monomer, polymer, condensation, hydrolysis, peptide bond, active site, substrate, competitive and non-competitive inhibitor, phospholipid, osmosis	how each macromolecule is built from its monomers; how an inhibitor changes the rate; how each of the five transport types moves a substance
Metabolic processes	glycolysis, pyruvate, NADH, FADH₂, Krebs cycle, electron transport chain, chemiosmosis, ATP synthase, photosystem, Calvin cycle	where each stage happens, what goes in, what comes out, how many ATP; what crosses between the light reactions and the Calvin cycle
Molecular genetics	nucleotide, antiparallel, helicase, DNA polymerase, leading and lagging strand, mRNA, codon, anticodon, ribosome, operon, allele, genotype, phenotype	the fork during replication; the flow from DNA to protein; how a repressor turns a gene off; the ratios a cross produces
Homeostasis	negative feedback, set point, resting potential, threshold, depolarization, neurotransmitter, hormone, target cell, nephron, filtration, reabsorption	the feedback loop with its sensor, control centre and effector; the action potential in order; what the nephron does to the filtrate along its length
Population dynamics	exponential growth, logistic growth, carrying capacity, limiting factor, predation, competition, symbiosis	why a population's growth curve bends; how an interaction changes both populations over time

The eight diagrams to redraw from memory

Eight diagrams carry most of the mechanism marks in the course. Each one is a redraw task: blank page, draw from memory, label everything, compare with the textbook, circle every missing or wrong label, and redraw tomorrow. Spacing the redraws over days is what makes the second attempt stick.

1. The four macromolecules with their monomers. Carbohydrates from monosaccharides, proteins from amino acids, nucleic acids from nucleotides, lipids from glycerol and fatty acids, with the bond that joins each pair named.
2. Protein structure's four levels. The amino-acid sequence; the helix and the pleated sheet; the folded shape with the bonds that hold it; two or more chains together. What breaks when a protein denatures.
3. The membrane with the five transport types. The bilayer with its proteins, and simple diffusion, facilitated diffusion, osmosis, active transport and bulk transport, each with its direction against the gradient and whether it costs ATP.
4. The respiration overview. Glycolysis in the cytoplasm, pyruvate oxidation and the Krebs cycle in the matrix, the electron transport chain on the inner membrane, with the ATP and NADH counts at each stage.
5. The chloroplast. The light reactions in the thylakoid membranes, the Calvin cycle in the stroma, and the two things that cross between them.
6. The replication fork. Both strands, the leading strand built continuously and the lagging strand in fragments, with the enzymes named at the point where each works.
7. Transcription and translation. The flow from a gene to a protein: DNA to mRNA in the nucleus, mRNA to a chain of amino acids at the ribosome, with the codon table used once to read three codons.
8. The action potential graph. Membrane potential against time: the resting potential near −70 mV, the threshold, depolarization as sodium enters, repolarization as potassium leaves, the brief hyperpolarization, and the return to rest.

Why redraw from memory rather than annotate the textbook's figure? Karpicke and Blunt (2011) had students study a science text either by recalling it with the text closed or by building a concept map with the text open, and tested them a week later. The recall group did better, and did better even on the questions that asked them to draw a concept map. Drawing with the book open is studying; drawing with it closed is testing, and testing is what builds the memory.

Worked examples: one mechanism, one data question

Respiration, redrawn (ideas 8 to 10)

Here is diagram 4 in words, with the counts a student is expected to carry, so you can check your own redraw against it.

Glycolysis, in the cytoplasm. One glucose (six carbons) is split into two pyruvate (three carbons each). It costs 2 ATP and makes 4, so the net gain is 2 ATP, and it makes 2 NADH. No oxygen is used at this stage.

Pyruvate oxidation, in the mitochondrial matrix. Each pyruvate loses a carbon as CO₂ and becomes acetyl-CoA, making 1 NADH each: 2 NADH and 2 CO₂ per glucose.

The Krebs cycle, in the matrix. Each acetyl-CoA turns the cycle once, so two turns per glucose. Per glucose the two turns give 2 ATP, 6 NADH, 2 FADH₂ and 4 CO₂. By now all six carbons of the glucose have left as CO₂: 2 from pyruvate oxidation and 4 from the Krebs cycle.

The electron transport chain and chemiosmosis, on the inner mitochondrial membrane. The NADH and FADH₂ hand their electrons to the chain; the energy pumps protons into the space between the membranes; the protons flow back through ATP synthase, which makes most of the cell's ATP. Oxygen is the final electron acceptor and becomes water.

The total. Current textbooks put the yield at about 30 to 32 ATP per glucose; older books said 36 to 38, which assumed every NADH bought a full 3 ATP and ignored the cost of moving molecules across the membranes. If your textbook gives a number, use that number on the exam, and know why the two figures differ: it is a classic explain-the-difference question.

The redraw check: did your overview put glycolysis outside the mitochondrion? Did the counts at each stage add up to the 2 ATP, 2 ATP and then most of the rest? Did oxygen appear only at the end? A missing location is a missing mark.

A genetics calculation and a population calculation (ideas 21 and 26)

A monohybrid cross. Two heterozygous parents, Aa × Aa. Each parent passes A or a with equal chance. The four combinations, each with probability 1/4, are AA, Aa, aA and aa. Genotypes: 1 AA : 2 Aa : 1 aa. If A is dominant, AA and Aa look the same, so the phenotypes are 3 dominant : 1 recessive. The probability that a given offspring shows the recessive phenotype is 1/4. The common wrong line is writing 1/3, from counting the recessive among the three visible categories instead of the four equally likely outcomes.

Exponential growth. A bacterial culture of 100 cells doubles every 20 minutes. How many cells after 2 hours, if nothing limits growth? Two hours is 120 minutes, and 120 ÷ 20 = 6 doublings. N = 100 × 2⁶ = 100 × 64 = 6,400 cells. Check it by doubling step by step: 200, 400, 800, 1,600, 3,200, 6,400. After another two hours the same rule gives 6,400 × 64 = 409,600, and that is the point of the question: real populations stop following the exponential curve because food, space and waste become limiting. The growth curve bends and levels off at the carrying capacity, which is the logistic model, and an exam question that gives you a graph of a population levelling off is asking you to name that and explain why.

The data-analysis questions, and how they are marked

Every SBI4U test has questions that hand you a graph or a table and ask what it shows. Markers look for three moves, in order.

Read the axes and the units before the trend. Say what is on each axis and in what unit. A rate of reaction against temperature is a different question from a rate against substrate concentration, and the first sentence of your answer should show you noticed which.

Describe the trend with numbers from the graph. Not "it goes up"; "the rate rises from about 2 units at 10 °C to about 8 units at 35 °C, then falls to near 0 by 50 °C." The numbers are the evidence that you read the graph rather than guessed the shape.

Explain the trend with a mechanism from the course, in order. The rise: more kinetic energy, more collisions between enzyme and substrate. The fall: the enzyme denatures, the active site changes shape, the substrate no longer fits. A description without a mechanism is half marks; a mechanism without the numbers is half marks the other way.

Practise with any graph in your textbook: cover the caption, write the three moves, then uncover and compare. Ten minutes a graph, two graphs a week, and by the exam the routine is automatic.

How to study SBI4U

• Cards for the vocabulary, spaced. A new card tonight comes back tomorrow, then in three days, then in a week. Roediger and Karpicke (2006) found that students who recalled material remembered more a week later than students who reread it, even though the rereaders felt more confident at the time. The feeling is the trap; the card with the answer covered is the fix.
• The eight redraws on a rotation. One a day, so each comes round about once a week, more often for the ones you got wrong.
• Mechanisms explained aloud. Talk the Krebs cycle through to a wall with no notes, in order, then open the book and find the step you skipped. Teaching it out loud is the method.
• Mixed question types in review sessions. Name it, explain it, read the graph, all in one sitting, on ideas from different strands. Rohrer and Taylor (2007) found that students who practised problems shuffled by type did worse in practice and better on the test a week later than students who practised them in blocks; the exam is shuffled, so practise shuffled.
• Memory techniques for the few exact lists. The order of the stages in respiration, the four levels of protein structure, the parts of the nephron in sequence. Memory techniques cover the few lists that need them; most of the course is mechanism, not list.
• The biology method, whole. How to study biology is vocabulary plus mechanism as a weekly routine, and the grid in a study plan you will keep is where the routine lives beside your other courses.

A week-by-week plan for a semester (and the SBI4U exam review)

Eighteen weeks, one semester. Each row names the ideas, the cards to make, the diagram to redraw and the data question to practise. A missed week moves forward; it never resets the plan.

Week	Ideas	Cards	Redraw	Data question
1	1, 2	macromolecules, monomers, hydrogen bonding	the four macromolecules (1)	a solubility or boiling-point table
2	3, 4	protein structure, active site, induced fit	protein structure (2)	rate against temperature
3	5	inhibitor types, feedback inhibition	the inhibitor's effect on a rate curve	rate against substrate concentration, with and without an inhibitor
4	6	membrane terms, the five transport types	the membrane (3)	water movement against solute concentration
5	7, 8	ATP, glycolysis	respiration overview (4), glycolysis half	ATP yield table
6	9, 10	Krebs, chain, chemiosmosis	respiration overview (4), whole	oxygen use against time
7	11, 12	fermentation, light reactions	the chloroplast (5), light half	yeast gas production against sugar
8	13, review	Calvin cycle	the chloroplast (5), whole	photosynthesis rate against light intensity
9	14, 15	DNA structure, replication enzymes	the replication fork (6)	a melting-temperature or base-composition table
10	16, 17	transcription, codon, anticodon	transcription and translation (7)	a codon table used to read a sequence
11	18, 19	mutation types, operon terms	the operon's on and off states	protein output with and without a repressor
12	20	biotechnology terms	a gel or a cloning workflow in steps	a gel electrophoresis result
13	21	inheritance terms	a cross set up and solved	offspring ratios from a cross
14	22, 23	feedback terms, action potential terms	the action potential graph (8)	membrane potential against time
15	24	hormone and target terms	a feedback loop with its hormone named	blood glucose against time after a meal
16	25	nephron terms	the nephron along its length	filtrate composition along the nephron
17	26, 27	growth models, interactions	both growth curves on one axis	a population levelling off
18	Exam	the shaky cards only	the eight diagrams, one each	three graphs, three moves each, timed

Week 18 is the one-week exam plan: a diagnostic over the 27 ideas on day seven, spaced sessions on the shaky and cannot lists, a timed run two days out, a light review the night before, and sleep.

What carries into first year

The molecular genetics and metabolism strands are first-year biology's core, taught again at twice the depth and three times the vocabulary. The students who find first year manageable are not the ones who memorised the most in Grade 12; they are the ones who arrive with the habit of redrawing a process from memory and checking it, because that habit scales to a mechanism of any length. Build it on the Krebs cycle this year and it is ready for whatever first year puts in front of it.

The course on one screen

• Five strands: biochemistry (1 to 6), metabolic processes (7 to 13), molecular genetics (14 to 21), homeostasis (22 to 25), population dynamics (26 and 27).
• Every idea is two things: vocabulary on recall cards, spaced; mechanism redrawn from a blank page.
• Eight diagrams on a rotation: macromolecules, protein levels, the membrane, respiration, the chloroplast, the replication fork, DNA to protein, the action potential.
• Three moves on every graph: axes and units, the trend with numbers, the mechanism in order.
• The counts to carry: glycolysis 2 ATP net and 2 NADH; about 30 to 32 ATP per glucose in total, or your textbook's number.
• The ratios to carry: Aa × Aa gives 1 : 2 : 1 and 3 : 1.