Your private tutor for AP Biology.

Sam teaches every topic out loud, marks up the textbook page as he goes, draws it on the board, and checks you’ve got it before moving on.

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Water’s Polarity

One of water’s important properties is that it is composed of polar molecules: the hydrogen and oxygen within water molecules (H2O) form polar covalent bonds. While there is no net charge to a water molecule, the polarity of water creates a slightly positive charge on hydrogen and a slightly negative charge on oxygen, contributing to water’s properties of attraction. Water’s charges are generated because oxygen is more electronegative than hydrogen, making it more likely that a shared electron would be found near the oxygen nucleus than the hydrogen nucleus, thus generating the partial negative charge near the oxygen.

As a result of water’s polarity, each water molecule attracts other water molecules because of the opposite charges between water molecules, forming hydrogen bonds.

Water also attracts or is attracted to other polar molecules and ions. A polar substance that interacts readily with or dissolves in water is referred to as hydrophilic (hydro- = “water”; -philic = “loving”).

A water molecule

The whole course, in order. Nothing skipped.

8units

60topics

571teaching steps

three steps, that's it

From hello to exam-ready

Sign in and say hi

He teaches, topic by topic

The whole course in order, out loud, from the real textbook page. Short pieces, with a quick question after each one.

Practice until it sticks

Exam-style questions, a test for every unit, and honest results. Then he goes back over whatever you missed.

what it’s like

A lesson is a conversation.

You’re never just watching. This is the real lesson screen: pick any part to see it.

Enzymes

Enzymes are macromolecules—most often proteins—that speed up chemical reactions by lowering activation energy barriers.

A substance that helps a chemical reaction to occur is a catalyst, and the special molecules that catalyze biochemical reactions are called enzymes. Almost all enzymes are proteins, made up of chains of amino acids, and they perform the critical task of lowering the activation energies of chemical reactions inside the cell.

Activation energy, with and without an enzyme

Sam’s replies to answers are written live, so his words here are examples.

how he teaches

He explains it first. Then he asks.

Like a good tutor at your kitchen table: one idea at a time, and no moving on until it has landed.

that’s you, asking anything

He talks you through it

Every idea out loud, in plain words. Subtitles stay on, and you can stop him to ask anything.

He marks the real page

Underlines and circles land on the textbook line at the moment he says it.

He draws it on the board

Each diagram builds up while he explains it, so you see how the parts connect.

He checks you've got it

A quick question after each idea. Miss it, and he explains it a new way.

and the rest of the job

Everything a great tutor would do

He finds your weak spots

Anything you partly got or got wrong is saved. He brings it back and teaches it again before asking.

He picks up where you left off

“Right, we were in the middle of this part: The Punnett square.”

To the sentence, not just the lesson.

You build real graphs

Axes, scale, points and error bars, marked the way the exam marks them.

You’re in charge

Just say it, and he does it.

“Repeat that”
“Go back”
“Take me to lipids”
“Test me”
“Pause 5 minutes”

He explains it another way

Still stuck? First plainer words, then a different angle, then an analogy. He tells you what you’d mixed up, too.

what's covered

Every single topic

All 8 units of AP Biology, in the order of the official course. Open any unit to see its topics.

Topics: 60
Teaching steps: 571
Exam-style questions: 480
Free-response sets: 8

Contents

1Chemistry of Life7 topics

1.1Structure of Water and Hydrogen Bonding
1.2Elements of Life
1.3Introduction to Macromolecules
1.4Carbohydrates
1.5Lipids
1.6Nucleic Acids
1.7Proteins

2Cell Structure and Function10 topics

2.1Cell Structure and Function
2.2Cell Size
2.3Plasma Membrane
2.4Membrane Permeability
2.5Membrane Transport
2.6Facilitated Diffusion
2.7Tonicity and Osmoregulation
2.8Mechanisms of Transport
2.9Cell Compartmentalization
2.10Origins of Cell Compartmentalization

3Cellular Energetics5 topics

3.1Enzymes
3.2Environmental Impacts on Enzyme Function
3.3Cellular Energy
3.4Photosynthesis
3.5Cellular Respiration

4Cell Communication and Cell Cycle6 topics

4.1Cell Communication
4.2Introduction to Signal Transduction
4.3Signal Transduction Pathways
4.4Feedback
4.5Cell Cycle
4.6Regulation of Cell Cycle

5Heredity5 topics

5.1Meiosis
5.2Meiosis and Genetic Diversity
5.3Mendelian Genetics
5.4Non-Mendelian Genetics
5.5Environmental Effects on Phenotype

6Gene Expression and Regulation8 topics

6.1DNA and RNA Structure
6.2DNA Replication
6.3Transcription and RNA Processing
6.4Translation
6.5Regulation of Gene Expression
6.6Gene Expression and Cell Specialization
6.7Mutations
6.8Biotechnology

7Natural Selection12 topics

7.1Introduction to Natural Selection
7.2Natural Selection
7.3Artificial Selection
7.4Population Genetics
7.5Hardy-Weinberg Equilibrium
7.6Evidence of Evolution
7.7Common Ancestry
7.8Continuing Evolution
7.9Phylogeny
7.10Speciation
7.11Variations in Populations
7.12Origins of Life on Earth

8Ecology7 topics

8.1Responses to the Environment
8.2Energy Flow Through Ecosystems
8.3Population Ecology
8.4Effect of Density on Populations
8.5Community Ecology
8.6Biodiversity
8.7Disruptions in Ecosystems

good questions

Before you start

No, Sam is an AI tutor. The lessons themselves are written in advance and are the same for every student. The AI is there to listen to your answers, judge them honestly, answer your questions and explain things again.

Yes. Every Essential Knowledge statement in the official AP Biology course description is taught, in the same order, across all 8 units.

The topics follow the official course description, and the words he underlines come straight from a free, peer-reviewed AP Biology textbook. Details are at the bottom of this page.

Nobody can honestly promise a score. Sam can teach you the whole course, show you exactly what you're missing and keep working on it with you. The rest is up to you.

It works best that way, because explaining an idea is how you find out whether you've got it. If you can't talk right now, you can type instead.

A computer or phone with a web browser and an internet connection. There's nothing to download. Subtitles are on by default.

He remembers. Next time you come back to the sentence you left on, not the start of the lesson.

We ask for as little as we can: a first name and a Google sign-in. No ads, and we don’t sell your data. You can delete your account and everything in it from Settings. Read the privacy policy.

No. TutorFit is independent and isn't affiliated with or endorsed by the College Board.

AP Biology, and only AP Biology for now. We wanted to get one course completely right.

Sam’s ready when you are.

Your first lesson is about water, and why it explains almost everything alive.

Start your first lesson

Your private tutor for AP Biology.

From hello to exam-ready

Sign in and say hi

He teaches, topic by topic

Practice until it sticks

A lesson is a conversation.

He explains it first. Then he asks.

He talks you through it

He marks the real page

He draws it on the board

He checks you've got it

Everything a great tutor would do

He finds your weak spots

He picks up where you left off

You build real graphs

You’re in charge

He explains it another way

Every single topic

Before you start

Is Sam a real person?

Does it really cover the whole course?

Where does the teaching come from?

Will it get me a 5?

Do I have to talk out loud?

What do I need to use it?

What if I leave in the middle of a lesson?

Is it safe for students under 18?

Is this official AP material?

Which subjects can I study?

Sam’s ready when you are.