Grade 12 · University
SBI4U Grade 12 Biology, worked through with a live AI tutor
SBI4U is molecular and it is dense: the metabolic-processes unit alone asks you to follow glycolysis, the Krebs cycle and the electron transport chain, then run photosynthesis in the other direction. It is also the course university life-science programs assume, so the level of detail is closer to first-year than to Grade 11. The tutor can trace a pathway with you on the whiteboard and quiz the steps until they hold without notes.
Prerequisite: SBI3U (Grade 11 Biology, university preparation)
What SBI4U covers
The strands of SBI4U Biology, in our words rather than the Ministry’s. Your teacher’s course outline decides the order and the weight.
Biochemistry
The four macromolecule families and their building blocks, enzyme structure and activity, factors that affect enzymes, and membrane structure and transport.
Metabolic processes
Cellular respiration in its aerobic and anaerobic forms, photosynthesis, the role of ATP, and how energy moves through a cell.
Molecular genetics
DNA structure and replication, transcription and translation, gene regulation, mutations, and the techniques and ethics of biotechnology.
Homeostasis
Feedback systems, the nervous, endocrine and excretory systems, and how the body holds internal conditions steady when the outside changes.
Population dynamics
Population growth models, carrying capacity, interactions between species, and how human populations differ from other species' patterns.
Curriculum reference: Ontario Ministry course page, checked .
Where students get stuck
Where the ATP in cellular respiration actually comes from
Glycolysis and the Krebs cycle make only a few ATP directly. Most of the yield comes from the electron transport chain, which uses the NADH and FADH2 made earlier to pump protons and drive ATP synthase. If the exam asks why oxygen matters, the answer is that it is the final electron acceptor; without it the chain stops and the cell falls back to fermentation.
Transcription versus translation
Transcription copies a gene from DNA into messenger RNA in the nucleus. Translation reads that mRNA three bases at a time at a ribosome and builds a protein. Codons belong to mRNA; anticodons belong to transfer RNA. Keeping the location, the input and the output of each straight answers most of the questions in the unit.
Negative feedback, with a real example
A change is detected, a response pushes the variable back toward its set point, and the response stops when it gets there. Blood glucose after a meal: the pancreas releases insulin, cells take up glucose, glucose falls, insulin release slows. Positive feedback amplifies instead, as in labour contractions, and is rarer, which is why the course dwells on the negative kind.
Logistic growth and carrying capacity
Exponential growth assumes unlimited resources; logistic growth adds a ceiling. The curve is steepest at half the carrying capacity, where the population is large enough to grow fast but not yet crowded, and it flattens as density-dependent limits bite. Questions that give you a population and a capacity are asking where on that curve you are.
How a session on SBI4U works
- 1
Bring the actual problem
Share your screen, upload the page, or hold it up to the camera. The tutor reads the SBI4U question itself instead of your retyped version of it.
- 2
Talk it through on the whiteboard
You explain where you got to, out loud. The tutor writes the next step on a shared board while it talks, and asks you to take the one after that.
- 3
Try the next one yourself
Generate a practice set on the same topic, with full worked solutions that show the method rather than only the answer.
It starts in Learn mode: concepts first, the answer as a last resort. The tutor is not a Ministry resource and does not replace your teacher’s course outline.
SBI4U questions
Does the tutor follow the Ontario SBI4U curriculum?
It works from your textbook, your notes and your assignment, and from the five SBI4U strands: biochemistry, metabolic processes, molecular genetics, homeostasis and population dynamics. It is not an official Ministry resource.
Can the tutor help me learn the pathways?
Yes. It can walk glycolysis, the Krebs cycle, the electron transport chain or the Calvin cycle step by step on the whiteboard, then turn your notes into flashcards and practice quizzes so the steps hold under test conditions.
Do I need SCH3U or SCH4U alongside SBI4U?
Not as a prerequisite. The biochemistry unit is easier with Grade 11 chemistry behind you, and many university life-science programs require SCH4U separately, so check the program's admission page.
Stuck on SBI4U tonight
Bring the question from your own textbook or assignment. Talk it through out loud and watch it worked out step by step on a whiteboard.
Free Trial