Cells and energy for high-school biology: study cards over three tiers, the tricky ones, a practice quiz at three levels — Foundation, On-Level, and Challenge — and a lab where you label an animal cell, label photosynthesis and respiration as a matched pair, graph an enzyme's rate against temperature, and argue from three yeast bottles what the balloon is measuring. Work here, or print it and use a pencil — both count.
Light arrives. Photosynthesis packs its energy into glucose — a stable molecule that keeps.
Glucose is the savings account and ATP is the cash the cell actually spends. Energy FLOWS through — sun to sugar to ATP to heat, and out. Matter, meanwhile, cycles: the same carbon atoms go round and round.
What people get wrong
⚠️People often think…
Plants do photosynthesis and animals do respiration.
Plants do BOTH. Every plant cell needs ATP to run, day and night, and only respiration makes ATP. Photosynthesis fills the pantry; respiration is what cooks from it.
Plants respire too. Every cell needs ATP.
⚠️People often think…
A tree’s mass comes out of the soil.
Weigh the pot before and after — the soil barely changes. Most of that wood is carbon the tree pulled out of the AIR as CO₂. A tree is built largely from thin air and water.
The mass comes from the air.
⚠️People often think…
In osmosis, water moves toward the pure water.
Water follows the SOLUTE — it moves toward wherever there is more dissolved stuff. Salt outside a cell pulls water out and shrivels it; pure water outside pushes water in.
Water follows the solute.
⚠️People often think…
A denatured enzyme has been used up.
Enzymes are never used up — that is the whole point of a catalyst. Denaturing is a SHAPE change from heat or pH, and once bent out of shape it usually stays that way. The molecule is still there; it just no longer fits.
Denaturing bends the shape. Nothing is consumed.
Follow the energy, follow the matter
1Watch one
A plant is left in the dark for a week. What runs out first, and why?
In the dark, photosynthesis stops — no light, no new glucose.
Respiration does NOT stop. Every cell keeps needing ATP.
So the plant keeps spending its stored glucose and never refills it.
The stored sugar runs out, then the plant starves. Income stopped; expenses did not. ✓
2Do one with me
Fill in where the energy and matter go.
The molecule a cell actually spends is
Most of a tree’s mass comes from the
In osmosis, water moves toward the higher
💬One sentence, then you move on
Why do plants need to do respiration if they make their own sugar?
3Try one
A cell is put in salty water. Which way does water move?
I want a hint first
Water goes where the solute is. The salt is on the outside.
💬Last one — then you're done here
Why does energy flow through while matter cycles?
Where this goes
Where this lives
Why a wound needs protein and calories to heal, why a fever above about 104 is dangerous, why salting a slug kills it, why food has calories on the label at all.
What this feeds
Next unit is ecosystems and human impact — how the energy these cells capture moves through living communities.
Name one place you have seen osmosis without calling it that.
One card at a time — tap “Show me” to check yourself, then Next. Start at Foundation; when those feel easy, climb.
Helpful Hints
🪜 Cells and energy — the ladder
Every living thing is made of cells, and every cell comes from a cell → the membrane is selectively permeable: diffusion and osmosis move things for free, active transport spends ATP → organelles divide the work: nucleus holds DNA, ribosomes build proteins, chloroplasts make sugar, mitochondria make ATP → enzymes speed every reaction and quit when their shape is lost → photosynthesis stores light energy in glucose; respiration releases it as ATP — the products of one are the reactants of the other → cells build tissues, organs and systems that keep the organism alive.
Membrane, organelles, enzymes, the two equations, the ladder up.
🤝 The whole idea
A cell is a bag of water that keeps itself different from the water around it, and the whole story of energy on Earth runs through two reactions that mirror each other.
Store it in sugar. Spend it as ATP.
⚠️ Tricky ones
Plants do BOTH photosynthesis and respiration — every plant cell needs ATP, day and night.
A tree’s mass comes from the AIR (CO₂), not the soil. The soil barely loses weight.
Energy FLOWS through (sun → sugar → ATP → heat, gone). Matter CYCLES (carbon goes around).
Osmosis is water following SOLUTE. Salt outside pulls water out; pure water outside pushes it in.
Denaturation is a SHAPE change. The enzyme isn’t used up — it’s bent, and usually stays bent.
Glucose is the fuel; ATP is the cash the cell actually spends.
🔬 The organelles — the chart
Part
Job
Plant, animal, or both?
Remember it by
cell membrane
selectively lets things in and out
both
the gate
nucleus
holds DNA; directs the cell
both (eukaryotes)
the plans
mitochondrion
cellular respiration → ATP
both
the power plant
chloroplast
photosynthesis → glucose
plants and algae only
the solar panel
ribosome
builds proteins from RNA
both (and prokaryotes)
the factory
endoplasmic reticulum
finishes and moves proteins and lipids
both
the hallway
cell wall
stiff outer support
plants (and fungi, bacteria)
the fence
vacuole
stores water and waste
both; huge in plants
the water tank
Chloroplasts and the wall are the plant-only rows — a classic test question.
🎯 How the test will ask
A labeled cell with letters — “which structure makes ATP?” (mitochondrion).
A rate-vs-temperature curve — “explain the drop after the peak.” (denaturation).
“Write the equation for photosynthesis and identify the reactants.”
A cell in salt water — “predict and explain what happens to its volume.”
“Where does a plant’s mass come from? Support with evidence.”
“Describe how two organ systems interact to deliver oxygen to a cell.”
✅ Can you…
Name six organelles and their jobs, and say which two are plant-only?
Explain selectively permeable, diffusion and osmosis?
Write both equations and say why they are a matched pair?
Read an enzyme graph and name the optimum and the denaturation cliff?
Argue from data where a tree’s mass comes from?
Trace cells → tissues → organs → systems → organism with one example?
Pick your level
Look back at anything you missed — the hint that appeared is exactly what to reread tonight.
How sure did you feel?
Lab
Work like a scientist: label the diagrams, turn the table into a graph, then write a claim with evidence and reasoning. Every lab checks itself on the spot, and hints are free.
Your practice never leaves this device. There is no account and no sign-in. Your work is saved in this browser only, and you can erase it whenever you want.
Your practice record — saved on this device
This is your record of the module on screen — it stays here and goes nowhere. Independent means you got it right on the first tap; supported means you got it after the explain-and-retry, or marked ‘I had it’ on a revealed answer. Both count, and neither is a grade. If your teacher asks, copy the row or show them this screen.
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The answer key is for a teacher: it prints only from here, for the unit on screen. Print the study packet prints the study pages and a blank quiz — never the answers.