AP Bio, but it actually makes sense.
Practice questions written like the real exam, with a short explanation after every one you miss.
It's all free until January, and you don't need an account.
Which description correctly identifies the tertiary structure of a protein?
Every wrong answer gets explained.
Each one starts with the answer. Then it shows why the one you picked looked right, so the same trick doesn't get you in May.
Why not CSo close. H-bonds along the backbone make helices and sheets, which is secondary. Tertiary needs the R groups.
B. Tertiary structure is the whole chain's 3D shape, held in place by its R groups interacting.
RememberBackbone → secondary. Side chains → tertiary. Extra chains → quaternary.
Mistakes you repeat get their own list.
Some wrong ideas come up again and again in different topics. Pick the same one twice and it goes on a short list on your Learn page, by name. Tap it to practice just that trap.
The same 5 questions for everyone, every day.
They go from easy to brutal. Post your grid in the group chat, or send a friend your set and see who actually knows cell respiration.
We grade your free response, point by point.
Free response is half your AP score. Type an answer and you get back every rubric point, marked, with the reason you got it or didn't. Better to lose that point here than in July.
- All six types of AP Bio free-response questions
- Or check your own answer against a model one, for free
Your first 3 grades are free.
A student grows radishes in 20 pots. Ten get fertilizer, ten don't. After three weeks, the student weighs each radish dry.
- Identify the control group.“The 10 pots that got no fertilizer.”Right: it's the baseline the fertilized pots are compared against.Point earned
- State the dependent variable.“The dry mass of the radishes.”Point earned
- Predict the result if the fertilizer works.“Fertilized radishes end up heavier.”Point earned
- Justify your prediction.“Fertilizer is good for plants.”Needs the mechanism: more nitrogen means more amino acids and nucleotides, so more new tissue.No point
A full practice exam, timed like the real one.
60 questions in 90 minutes, on a clock that doesn't pause. Flag the hard ones and come back to them. When you hand it in, you see the AP score you're on track for and the unit that cost you the most.
Your first one is free.
All of Cramfox is free until January.
Everything Free until January
- Every explanation, every lesson, the Daily 5 and challenges
- Unlimited practice, with no 10-a-day cap
- Unlimited unit tests and full-course tests
- Unlimited timed practice exams: the full multiple-choice section on the real clock
- Your predicted score broken down unit by unit
- Free-response grading with no 3-grade limit: every rubric point scored, with the reason for it
Questions
Is it free?
Yes, all of it, until January: unlimited practice, unit and course tests, timed practice exams, and point-by-point grading on your free-response answers. You don't need an account to start.
What happens in January?
Pro comes back for the AP season. Until then, everything is on for every student, with nothing to buy.
What does it cover?
All 8 units and 60 topics of AP Biology, written for the current course. That includes the 2025–26 changes to Unit 1.
Is this official College Board material?
No. Every question is original, written to match how the exam asks things. The College Board isn't affiliated with Cramfox.
Does it work on my phone?
It was built for your phone first. It works on a laptop too, with keyboard shortcuts.
Start with five questions.
You don't need an account or a card. Pick your unit and go.
Start practicing