Bio Tool #29 · Schwebach SOL Review · Biology Unit 3 · SOL BIO.2e
Sun to Sugar to ATP: Cell Energy for the Biology SOL
Cell energy is one sentence long: light energy is stored in sugar by the chloroplast and released as ATP by the mitochondrion. On the test form Virginia released in 2026, three questions came from this unit, and photosynthesis turned up inside questions from other units as well.
Warm up on three questions
Answer them before reading further and write down your score. The same three come back at the end.
Part of the common SOL review at Battlefield High School, where these pages began. Know these and you have covered what the school review covers.
Schwebach Recommendation
Not stressed in most reviews, but the state results or the gap between the course and the state guide say it matters. Each one says why it is here.
Sun to sugar to ATP, in five ideas
Idea 1BIO.2e · LT 3.1Battlefield review
ATP releases energy by losing its last phosphate
ATP carries three phosphate groups in a row. When a cell needs energy right now, it snaps off the last phosphate, and the energy in that bond goes to work: a muscle contracts, a pump moves an ion. What remains is ADP, a battery with one charge spent. Energy from glucose puts the phosphate back on, so a cell rebuilds the same ATP thousands of times instead of using it up.
On the test
The trap is the recharge. Adding a phosphate to ADP stores energy; removing one from ATP releases it.
Draw it
Draw ATP as a string of three beads. Snip the last bead and draw a spark labeled “energy for work.” Label what is left “ADP,” then draw an arrow back to ATP labeled “energy from glucose.”
A leaf builds sugar from carbon dioxide and water, powered by light
A plant builds sugar out of two plain molecules: carbon dioxide pulled from the air through its leaves and water drawn up from the soil. Out come glucose, which holds the energy, and oxygen, which leaves through the same leaf openings. Light is not one of the ingredients. It is the power source, and its energy ends up stored in the bonds of the sugar. The molecules you breathe out are the ones a plant takes in.
On the test
A diagram will show arrows going into and out of a leaf or a chloroplast. Sort by direction: what the plant brings in is a reactant, what it makes or lets go is a product, and light is the energy that drives the change.
Draw it
Draw a leaf. Add arrows: carbon dioxide in from the air, water up from the roots, sunlight striking the top, glucose stored inside, oxygen out. Circle the sunlight and write “energy, not an ingredient.”
Idea 3BIO.2e · BIO.1 · LT 3.2Battlefield reviewSchwebach Recommendation
Photosynthesis runs as fast as its scarcest supply allows
More light speeds photosynthesis up, and so does more carbon dioxide, until some other supply runs short and the rate levels off. Water matters too: a wilting plant closes its leaf openings and stops taking in carbon dioxide. Temperature works through the enzymes inside the chloroplast, so a little warmth helps and too much heat slows everything down. On the SOL this idea usually arrives as a graph, so practice reading where a rate curve rises and where it flattens.
On the test
Rate questions come as a table or a graph. Where the numbers stop climbing, the factor being changed is no longer the limit; something else has run short.
Draw it
Sketch a graph with “light” along the bottom and “oxygen bubbles per minute” up the side. Draw a line that rises, then goes flat. Label the flat part “something else is running short.”
Every cell starts breaking down glucose the same way, in the cytoplasm. If oxygen is there, the mitochondria finish the job and the cell gets back about 36 ATP from one glucose. If oxygen runs out, the cell stops early and ferments, which keeps the first step going for only 2 ATP. Your muscles in a hard sprint make lactic acid this way; yeast makes alcohol and carbon dioxide, which is why bread rises. A cell living on 2 ATP per glucose burns through sugar far faster to keep up.
On the test
Look for the word oxygen in the question. With oxygen: mitochondria and about 36 ATP. Without it: fermentation in the cytoplasm, 2 ATP, and sugar used up much faster.
Draw it
Draw one glucose at a fork in the road. One path: “oxygen → mitochondrion → about 36 ATP.” The other: “no oxygen → fermentation → 2 ATP,” splitting into “muscle: lactic acid” and “yeast: alcohol + carbon dioxide.”
Carbon goes around the loop; energy passes through once
Carbon moves in a loop, and living things run both halves. Photosynthesis pulls carbon dioxide out of the air and locks its carbon into sugar. Respiration breaks that sugar down and releases the carbon as carbon dioxide again, in every organism that respires: animals, plants, fungi and bacteria. Decomposers return carbon too, and they do it the same way, by respiring as they digest dead matter. Matter cycles around this loop; energy passes through once and leaves as heat.
On the test
When a question asks how living things put carbon back into the air, the answer is respiration, decomposers included. The products of one process are the raw materials of the other.
Draw it
Draw a chloroplast and a mitochondrion side by side. Arrows from the mitochondrion to the chloroplast carry carbon dioxide and water; arrows back carry glucose and oxygen. Draw the sun’s arrow coming in at the top and a heat arrow leaving at the bottom.
Which way is the energy moving? Into sugar is photosynthesis; out of sugar into ATP is respiration.
Is there oxygen? Find the word in the question. It decides between about 36 ATP and 2.
Count what goes in and what comes out. The two equations hold the same six carbons, twelve hydrogens and eighteen oxygens, only in opposite directions.
Find the flat part of the graph. Where a rate stops rising, another factor has become the limit.
Try the checks on the deer question: sunlight reaches clover, the deer eats the clover, the deer runs. Energy moves into sugar in the clover, then out of sugar into ATP in the deer’s muscle, so the answer runs sunlight, sugar in clover, sugar in deer, ATP in muscle. Try that one.
Three Schwebach Recommendations
These three ideas sit at the edge of most reviews, and each one costs students points on the state test.
Recommendation 1Schwebach Recommendation
Some cells photosynthesize with no chloroplasts at all
Why it is here: Gap between the course and the state guide: cyanobacteria are prokaryotes, and Virginia students struggle to classify single-celled organisms that photosynthesize (about a third answered that question correctly on the form released in 2026).
Photosynthesis needs chlorophyll to capture light, not the chloroplast itself. Photosynthetic prokaryotes such as cyanobacteria hold chlorophyll in membranes in their cytoplasm. Chloroplasts likely began as cells like these.
Plants respire too, in every living cell, day and night
Why it is here: A common misconception: students learn photosynthesis for plants and respiration for animals. Plants run both, and a root or a seed in the dark runs on respiration alone.
Leaves make sugar and send it through the plant. Root cells, like all plant cells, use cellular respiration in their mitochondria to break that sugar down and make ATP. Plants respire, day and night, in every living cell.
Without oxygen, a cell burns through sugar much faster
Why it is here: The hardest cell-energy question on the form Virginia released in 2026 asked what an organism does with sugar when there is no oxygen. Fewer than half of Virginia students answered it correctly.
A cell that gets 2 ATP from each glucose instead of about 36 has to break down roughly eighteen times as much sugar for the same energy. That is why a sealed bag of yeast and sugar runs through its sugar quickly, and why a sprinting muscle that has run short of oxygen tires fast.
Battlefield students: if you have the Canvas SOL Review module, the Unit 3 check there walks through the school’s review questions and points back to these ideas.
Where to go after cell energy
The Biology SOL has 45 scored questions. These units carry more of them, and each connects to what you just practiced.
DNA and protein synthesis
About seven questions, the most of any unit. ATP is a nucleotide, a cousin of the building blocks of DNA and RNA.
Virginia also posts its released Biology test so students can practice in TestNav, the system the real test uses. Find it on the Virginia Department of Education’s SOL practice items page, then come back here to study what you miss.
0–5 min · Three warm-up questions on iPads or the paper sheet; students keep their own score.
5–30 min · The five ideas, about five minutes each: say it, draw it together on the board, one check question read aloud with a vote.
30–40 min · Students choose one Schwebach Recommendation, then work the practice set at their own pace.
40–45 min · Retry the warm-up, compare scores, and pick the next unit from the list.
The paper version prints on two pages: five drawing boxes, six practice questions without answers, a study plan and a QR code back here. Practice questions are original and written from the Virginia 2018 Biology Standards of Learning and the VDOE Instructional Guide; they are not produced or endorsed by the Virginia Department of Education. The two labels describe ideas, not questions: “Battlefield review” marks an idea the school’s common review covers, and no question from that review appears on this site.
Cell Energy: SOL Review
Name ______________________________ Date __________ Warm-up score: before ____ / 3 after ____ / 3
Five ideas · draw each one as we go
1. ATP releases energy by losing its last phosphate
Draw ATP as a string of three beads. Snip the last bead and draw a spark labeled “energy for work.” Label what is left “ADP,” then draw an arrow back to ATP labeled “energy from glucose.”
2. A leaf builds sugar from carbon dioxide and water, powered by light
Draw a leaf. Add arrows: carbon dioxide in from the air, water up from the roots, sunlight striking the top, glucose stored inside, oxygen out. Circle the sunlight and write “energy, not an ingredient.”
3. Photosynthesis runs as fast as its scarcest supply allows
Sketch a graph with “light” along the bottom and “oxygen bubbles per minute” up the side. Draw a line that rises, then goes flat. Label the flat part “something else is running short.”
4. Oxygen decides how much ATP a cell gets back
Draw one glucose at a fork in the road. One path: “oxygen → mitochondrion → about 36 ATP.” The other: “no oxygen → fermentation → 2 ATP,” splitting into “muscle: lactic acid” and “yeast: alcohol + carbon dioxide.”
5. Carbon goes around the loop; energy passes through once
Draw a chloroplast and a mitochondrion side by side. Arrows from the mitochondrion to the chloroplast carry carbon dioxide and water; arrows back carry glucose and oxygen. Draw the sun’s arrow coming in at the top and a heat arrow leaving at the bottom.
Practice · circle your answer, then check online
1. How does an ATP molecule release energy for a cell to use?
By joining with oxygen to form carbon dioxide
By breaking off one phosphate group to become ADP
By absorbing light like chlorophyll does
By adding a phosphate group to become larger
2. Which molecule completes the equation for photosynthesis? 6CO2 + 6H2O + light energy → ______ + 6O2
ATP
C6H12O6 (glucose)
CO2 (carbon dioxide)
Chlorophyll
3. Students placed a sprig of pondweed in water and counted the oxygen bubbles it gave off in one minute at different light levels. Temperature and carbon dioxide were kept the same.
Light level (units)
Bubbles per minute
0
0
200
8
400
15
600
21
800
24
1000
24
Which statement best explains why the bubble count did not change between 800 and 1000 units of light?
The plant stopped making oxygen at high light levels
The extra light was turned into heat instead of sugar
The plant began using all of its oxygen for respiration
Another factor, such as the supply of carbon dioxide, was limiting the rate
4. A cell gets about 36 ATP from one glucose molecule when oxygen is present, and about 2 ATP from one glucose molecule when oxygen is absent. Which statement best describes the effect of oxygen?
Oxygen makes no difference; it only speeds up the process
Without oxygen, the cell gets about twice as much ATP from each glucose
Without oxygen, the cell cannot break down glucose at all
With oxygen, the cell gets about 18 times as much ATP from each glucose
5. A tomato seedling sat in a clear sealed box with a carbon dioxide sensor. A grow light was on from 8 a.m. to 8 p.m. and off overnight.
Time
Light
Carbon dioxide (ppm)
8 a.m.
on
620
2 p.m.
on
410
8 p.m.
on
330
2 a.m.
off
480
8 a.m.
off
600
Which explanation best accounts for the rise in carbon dioxide from 8 p.m. to 8 a.m.?
In the dark, photosynthesis stopped, but the seedling's cells kept carrying out cellular respiration and releasing carbon dioxide
In the dark, the seedling's photosynthesis began making carbon dioxide
The sensor stops working when the light is off
Plants respire only at night, so they release carbon dioxide only in the dark
6. Which statement best compares how matter and energy move through photosynthesis and cellular respiration?
Both matter and energy are recycled over and over between the two processes
Atoms are reused over and over, but energy enters as sunlight and leaves as heat, so it must keep being added
Energy is recycled, but atoms are used up and disappear
Neither matter nor energy moves between the two processes
My plan
☐ Check these six online: scan the code, then tap “All 42 cell energy practice questions.” Write the ones I missed: __________
☐ The one-sentence version of this unit, from memory: ________________________________________________
☐ Next unit I will practice: ☐ DNA and protein synthesis ☐ Ecology ☐ Cells and transport ☐ ______________