HS-LS1-6: Explaining How Sugar Atoms Build Amino Acids and Other Molecules
In plain English: HS-LS1-6 is the NGSS high school performance expectation that asks students to construct and revise an evidence-based explanation of how carbon, hydrogen and oxygen atoms from sugar combine with other elements, such as nitrogen and sulfur, to form amino acids and other large carbon-based molecules. Evidence comes from models, simulations and tracer data. It is usually taught in Biology.
Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules.
Clarification Statement: Emphasis is on using evidence from models and simulations to support explanations.
Assessment Boundary: Assessment does not include the details of the specific chemical reactions or identification of macromolecules.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Plants make sugar by photosynthesis, but a plant is not made of sugar: it is made of proteins, fats, DNA, cellulose and many other carbon-based molecules. In this lesson students build an explanation, backed by evidence, of how the carbon, hydrogen and oxygen atoms in sugar are rearranged and combined with other elements (nitrogen, sulfur, phosphorus) to make amino acids and other large molecules. They take inventories of atoms with model kits, run a bead simulation of a tracer experiment, analyze invented tracer and growth data, and revise their explanations each time new evidence arrives. The same ideas apply to animals, which break down the molecules in their food and rebuild the atoms into their own molecules.
The official Clarification Statement reads: "Emphasis is on using evidence from models and simulations to support explanations." The Assessment Boundary reads: "Assessment does not include the details of the specific chemical reactions or identification of macromolecules." So students track where atoms come from and where they go, never the steps of a pathway, and no item asks them to classify a molecule from its structure. Molecule names such as protein or fat appear only as examples. Balanced atom inventories in the model kit activity show where atoms end up; the real pathways take many steps and are beyond this standard.
Learning Objectives
By the end of this lesson, students will be able to:
Use an atom inventory to decide which elements in an amino acid or other carbon-based molecule can come from sugar and which must come from other sources
Analyze tracer data and simulation results as evidence that carbon from sugar ends up in amino acids and proteins
Use growth and composition data to explain why a plant needs nitrogen and sulfur from the soil to turn sugar into proteins
Construct a written explanation, supported by evidence, of how atoms from sugar become part of large carbon-based molecules
Revise an explanation when new evidence contradicts it, and say what changed and why
Prior Knowledge Required
Students should already be comfortable with:
Photosynthesis makes sugar from carbon dioxide and water MS-LS1-6
Food is rearranged by chemical reactions into new molecules MS-LS1-7
Atoms are rearranged, not created or destroyed, in chemical reactions MS-PS1-5
Reading a chemical formula such as C6H12O6 as a count of atoms
Show a bag of sugar next to a handful of dried beans. Remind students that the bean plant made the beans starting from sugar it built in its leaves.
Warm-Up Prompt
"A bean seed is rich in protein, and every protein contains nitrogen. The bean plant made its sugar from carbon dioxide and water, which contain no nitrogen. Write your best explanation of how the plant made its protein. What evidence would convince you that your explanation is right?"
Record explanations on chart paper and label this "Version 1". Students will return to it twice. Many students say the plant pulls protein out of the soil or that sugar turns into protein by itself; do not correct them yet.
Direct Instruction15-20 minutes
Sugar is a supply of atoms and energy. Cells break sugar molecules apart and rearrange their carbon, hydrogen and oxygen atoms into new molecules. Many of those new molecules also need other elements. Every amino acid contains nitrogen, and a few also contain sulfur. DNA contains nitrogen and phosphorus. Plants take these elements from the soil as nitrate or ammonium (N), sulfate (S) and phosphate (P). Amino acids are then linked into proteins. The balance of atoms always holds: no atom is made or lost, it only moves to a new molecule. Use Diagram 1 to trace the path of the atoms.
How we know. Scientists follow atoms with tracers: they give an organism carbon or nitrogen in a form that can be detected later, and then look for it in different molecules. Growth experiments with and without an element and measurements of what plants are made of add more evidence.
Atom inventory: what sugar can supply
Compare the formula of glucose, C6H12O6, with the formula of the amino acid glycine, C2H5NO2.
Result: Carbon, hydrogen and oxygen could all come from sugar, but glucose has no nitrogen. The N must come from somewhere else, such as nitrate or ammonium a plant absorbs from the soil. One glucose has enough carbon for 3 glycine, and those 3 need 3 N atoms from outside.
Tracer evidence for sulfur
Invented data: mustard seedling roots are given sulfate made with a detectable form of sulfur. After 24 hours, of the labeled sulfur that has been built into molecules, 55% is in free amino acids, 40% is in proteins and 5% is in other sulfur-containing molecules. None is in sugars or starch.
Result: 55% + 40% + 5% = 100%. Sulfur from the soil joins carbon-based molecules to form the few amino acids that contain sulfur, and these become part of proteins. Sugars contain no S, so finding none of the label there fits the explanation.
Composition of dry plant matter
Typical approximate values for dry plant matter are 45% carbon, 45% oxygen, 6% hydrogen, 1.5% nitrogen and about 2.5% other elements. A bean plant has a dry mass of 40 g.
Result: Carbon 0.45 × 40 = 18 g, oxygen 18 g, hydrogen 2.4 g, nitrogen 0.6 g, other 1.0 g. About 96% of the dry mass is C, H and O, the elements in sugar; a small but necessary share comes from the soil.
Revising a historical explanation
In the 1600s, Jan Baptist van Helmont planted a 5 lb willow in 200 lb of dried soil and gave it only water for 5 years. He reported that the tree grew to about 169 lb 3 oz while the soil lost only about 2 oz, and he concluded that the tree was made from water.
Result: The tree gained about 164 lb, and the soil loss was less than 0.1% of that gain, so soil cannot be the main source. Later evidence revised his explanation: most of the dry mass is carbon taken from CO2 in the air, built into sugar and then into other molecules; water supplies hydrogen and some oxygen.
Animals rebuild molecules too
A student eats rice (mostly starch) and beans (rich in protein). The body breaks the starch into sugar and the proteins into amino acids.
Result: Some sugar carbon is used to build fat, and amino acids are rebuilt into the student's own proteins. The body can make some amino acids from sugar carbon and nitrogen taken from other amino acids, but not all of them, so some must come from food. Atoms are rearranged, never created.
After each example, ask: "What is the evidence, and which part of our Version 1 explanation does it support or contradict?" Have students write "Version 2" of the class explanation before guided practice.
Guided Practice15 minutes
Pairs analyze an invented tracer data set. A wheat seedling was given carbon dioxide made with a detectable form of carbon for one minute, then normal air. Samples taken later show where the labeled carbon is. The same data are graphed in Diagram 2.
Guided practice data: labeled carbon in a wheat seedling (invented)
Time after labeling
In sugars (%)
In amino acids (%)
In proteins (%)
In other molecules (%)
1 minute
85
5
0
10
10 minutes
60
20
5
15
60 minutes
40
22
18
20
24 hours
20
10
35
35
Check that each row adds to 100%. What does that tell you about the labeled atoms?
Describe the order in which the label appears in sugars, amino acids and proteins. Which group is labeled first?
The share in amino acids rises and then falls, while the share in proteins keeps rising. Explain this pattern with a model in which atoms move from one group to the next.
Write "Version 3" of the class explanation. It must cite two numbers from the table and say what the data cannot show (for example, where the nitrogen came from).
Independent Practice10-15 minutes
Each student analyzes invented data from radish plants grown for three weeks in water with dissolved nutrients. One group of plants had a complete nutrient solution; the other had the same solution with no nitrogen. Both had the same light and air.
Independent practice data: radish plants after 3 weeks (invented, per plant)
Solution
Dry mass (g)
Protein (g)
Sugar and starch (g)
Complete
2.4
0.50
0.20
No nitrogen
0.9
0.06
0.30
Students compute protein and sugar-plus-starch as a percent of dry mass for each group, then write an explanation that answers: "The plants without nitrogen still made sugar. Why did they build so little protein?" The explanation must name the evidence and connect it to the atoms in amino acids.
Closure5 minutes
Exit ticket: "The amino acid asparagine is C4H8N2O3. Which of its atoms could come from sugar? How many atoms in each molecule must come from elsewhere, and from where?" (C, H and O could come from sugar; the 2 N atoms must come from another source, such as nitrate or ammonium in the soil.) Students compare the class explanation from Version 1 to Version 3 and write one sentence about what changed.
Differentiation Strategies
For Struggling Students
Give an atom inventory table with columns for C, H, O, N and S and a row for sugar, so students fill in counts before explaining
Provide an explanation frame: "The carbon in the protein came from ___. The nitrogen came from ___. My evidence is ___, which shows ___."
Start with physical model pieces before formulas, and color-code nitrogen and sulfur so the outside elements stand out
For Advanced Students
Ask students to design a second tracer experiment that would show where the nitrogen in a protein comes from, and to predict its results
Have students use the composition values in the third worked example to estimate how much nitrogen a field of plants removes from the soil, and connect this to why farmers add fertilizer
Ask students to find one weakness in the bead simulation and change a rule to fix it
Assessment Guidance
What to Look For
Check that explanations follow atoms: carbon, hydrogen and oxygen from sugar, other elements from the soil or from food. Look for evidence cited by number or observation, not only by name. Listen for the ideas that sugar turns into protein with nothing added, that plants take protein or most of their mass from the soil, and that atoms are created. In revisions, look for students who say which evidence made them change which part. Do not assess the steps of the chemical reactions or ask students to identify types of macromolecules; the Assessment Boundary rules both out.
02
Classroom Activities
3 Activities
1
Model Kit Atom Inventory: From Glucose to Amino Acids
20 minPairs
Pairs build a glucose molecule with a model kit, take it apart and use its atoms, together with nitrogen supplied as ammonia pieces, to build amino acids. The model shows that every atom is accounted for and that sugar alone cannot make an amino acid.
Materials per Pair
6 carbon, 18 hydrogen, 6 oxygen and 2 nitrogen pieces, with bonds (or gumdrops in four colors and toothpicks)
A card with the formulas of glucose (C6H12O6), ammonia (NH3) and the amino acid alanine (C3H7NO2)
Procedure
Build one glucose molecule and two ammonia molecules from your pieces. Check that you used every piece.
Take the molecules apart and build as many alanine molecules as you can. Build water (H2O) from any atoms left over.
Fill in an inventory table: atoms at the start, atoms in the alanine, atoms in the water. The totals must match.
Answer: which atoms in each alanine came from sugar, and which could not have?
Safety: if you use gumdrops, do not eat them after they have been handled and passed around; toothpick points face down on the desk.
Discussion Questions
How many alanine molecules did one glucose and two ammonia make, and what was left over?
What would stop you from building a third alanine, even if you had more carbon?
The model builds alanine in one move. A real cell uses many steps and helper molecules. What does the model get right anyway? (The steps themselves are beyond this standard.)
Modification for Distance Learning
Students use a free online molecule builder or draw circles for atoms, and submit their completed inventory table.
2
Tracer Bead Simulation: Follow the Labeled Carbon
20 minGroups of 3-4
Groups simulate a tracer experiment. Red beads are carbon atoms that entered the plant as labeled CO2. Each round, beads move from the CO2 cup to the sugar cup, from sugar to amino acids (each picks up a blue nitrogen bead) and from amino acids onto a protein string. Groups record where the labeled beads are after each round and graph the results.
Materials and Rules
Per group: 20 red beads, 15 blue beads, three cups labeled CO2, sugar and amino acids, and a string for the protein chain.
Start with all 20 red beads in the CO2 cup. Each round, in this order: move up to 2 red beads (with their blue beads) from amino acids onto the string; move up to 3 red beads from sugar to amino acids, adding one blue bead to each; move up to 5 red beads from CO2 to sugar.
Run 6 rounds and record the count in each place after every round.
Safety: keep beads in cups or trays and pick up any on the floor at once, since they are a slipping hazard.
Sample Data (from the rules)
Round 1: CO2 15, sugar 5, amino acids 0, protein 0
Round 2: CO2 10, sugar 7, amino acids 3, protein 0
Round 3: CO2 5, sugar 9, amino acids 4, protein 2
Round 4: CO2 0, sugar 11, amino acids 5, protein 4
Round 5: CO2 0, sugar 8, amino acids 6, protein 6
Round 6: CO2 0, sugar 5, amino acids 7, protein 8
Discussion Questions
In which round does the first labeled bead reach the protein string? Why can it not happen sooner?
After round 4 the CO2 cup is empty, but the sugar count starts to fall. Explain why.
How many blue beads did you use by the end of round 6? What do they stand for, and what would happen to the simulation if you ran out?
Compare your graph with Diagram 2. Name one way the simulation is like the real tracer data and one way it is not.
Modification for Distance Learning
Students run the same rules in a spreadsheet, one row per round, and graph the four columns.
3
Explain, Then Revise: Evidence Cards
25 minGroups of 3-4
Groups write an explanation of where the atoms in a pumpkin's proteins came from, then receive evidence cards one at a time. After each card they keep, change or cross out parts of their explanation and note which card caused each change. The final explanation is posted with its revision history.
Evidence Cards
Card A (observation): A pumpkin grows from a seed of about 0.2 g to a fruit of about 10 kg in four months, while the soil level in the patch barely changes.
Card B (invented tracer data): Labeled carbon given to pumpkin leaves only as CO2 in the air is found a week later in the proteins and fats of the fruit.
Card C (invented yeast data): Yeast cells were grown for 2 days at the same temperature. With sugar and ammonium sulfate (a nitrogen and sulfur source), the count rose from 1 million to 40 million cells per mL. With sugar only, it rose to 3 million. With ammonium sulfate only, it rose to 1.2 million.
Card D (composition): Dry pumpkin tissue is mostly carbon, oxygen and hydrogen, with a few percent nitrogen and small amounts of sulfur and phosphorus.
Discussion Questions
Which card made your group change its explanation the most, and what did you change?
At Card C, the sugar-only yeast grew 3 times and the complete flask grew 40 times. What does the gap tell you about what sugar can and cannot supply?
Which card, if any, would you ask for more evidence about, and what investigation would you run?
Challenge Variation: Live Yeast Test
With the teacher, groups test Card C themselves. Mix 1 g dry baker's yeast into 200 mL warm (not hot) tap water with 10 g sugar, with and without 1 g food-grade yeast nutrient (sold for home baking and brewing), and compare cloudiness after 24 and 48 hours against a printed scale. Safety: wear goggles; use only food-grade materials and label every cup; cover cups loosely with foil and never seal a container, because yeast give off carbon dioxide gas; do not taste anything; pour the mixtures down the sink with plenty of water and wash hands afterward.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Where the Atoms in Large Carbon-Based Molecules Come From
Sugar made in photosynthesis supplies carbon, hydrogen and oxygen. Cells rearrange these atoms into fats, starch and cellulose, and combine them with nitrogen and sulfur from the soil to make amino acids, which are linked into proteins. DNA also needs nitrogen and phosphorus. The arrows show where atoms go, not the chemical steps, which are beyond this standard.
Diagram 2: Labeled Carbon Moving Through a Wheat Seedling
The guided-practice tracer data, drawn to scale. Students use the order and timing of the label in each group of molecules as evidence for their explanation. About a third of the label ends up in other molecules, which the graph does not break down.
04
Homework Assignment
~30 min
HS-LS1-6 Homework: Following Atoms from Sugar to Large Molecules
Directions: All data sets are invented for practice unless a problem says otherwise. You do not need to know the steps of any chemical reaction. For every explanation, name your evidence and say what it shows.
Part 1: Atom Inventories (Problems 1-2)
The amino acid serine is C3H7NO3, and palmitic acid, a building block of many fats, is C16H32O2. (a) For each molecule, list the elements that could come from sugar and any that must come from another source. (b) What is the smallest whole number of glucose molecules (C6H12O6) that could supply the carbon for one palmitic acid molecule? (c) Explain why a plant grown with no nitrogen could still make palmitic acid but not serine.
A protein is a chain of 250 amino acids. Every amino acid contains at least one nitrogen atom, and 12 of the amino acids in this protein each contain one sulfur atom. (a) What is the smallest number of nitrogen atoms in the protein? (b) How many sulfur atoms does it contain? (c) Explain why a plant given light, air and pure water, but no soil or nutrients, could make sugar for a while but could not make this protein.
Part 2: Analyze the Evidence (Problems 3-4)
Mice were fed glucose made with a detectable form of carbon. After 6 hours, the labeled carbon was found in: blood sugar 30%, exhaled CO2 45%, fat in the liver 10%, muscle protein 5%, other molecules 10%. (a) Check that the shares add to 100%. (b) What percent of the label ended up in fat or protein? (c) Construct an explanation of how carbon from the glucose ended up in muscle protein, and name the other element that had to be added. (d) Where did the largest share go, and what process explains it?
Corn seedlings were grown for four weeks in a complete nutrient solution or in the same solution without sulfur. Complete: dry mass 3.2 g, protein 0.64 g. No sulfur: dry mass 1.8 g, protein 0.18 g. (a) Find protein as a percent of dry mass for each group. (b) Explain the difference using what you know about the atoms in amino acids. (c) Name one variable that must be kept the same for the comparison to be fair.
Part 3: Construct and Revise (Problems 5-6)
A student explains: "A tree's wood is made mostly of minerals from the soil." New evidence: (1) dry wood is about 50% carbon by mass; (2) a potted tree gained 12 kg of dry mass in 6 years while the dry soil in the pot lost 0.05 kg; (3) soil minerals contain little carbon. (a) How much carbon is in the 12 kg of new dry wood? (b) The soil loss is what percent of the gain? (c) Revise the student's explanation, keeping any part the evidence supports.
Plan an investigation that uses nitrate made with a detectable, non-radioactive form of nitrogen to test the claim: "The nitrogen in the proteins of wheat grains comes from nitrate in the soil." Describe (a) the groups you would compare, (b) what you would measure and when, (c) the results that would support the claim and the results that would contradict it, and (d) one safety or ethics step for the lab work.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Atom Inventory
Correctly separates atoms that sugar can supply from those that must come from elsewhere; counts correct
Correct idea with one counting error
Use of Evidence
Cites specific numbers from the data and says what each shows
Mentions the data without numbers or without linking them to the claim
Explanation
Explains the path of atoms from sugar to the large molecule, including added elements
Explanation is correct but skips where the added elements come from
Revision and Planning
Revision states what changed and which evidence caused it; plan has a comparison group and clear predictions
Revision or plan is present but incomplete
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Data sets are invented unless a question says otherwise. No question asks for the steps of a chemical reaction. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
The amino acid proline is C5H9NO2. Compare it with glucose, C6H12O6. Which element in proline must come from a source other than sugar?
Answer: D
Proline contains one nitrogen atom, and glucose has none, so the nitrogen must come from another source. Choices A, B and C name elements that glucose does contain and can supply.
Question 2 of 20 · Multiple Choice
The amino acid methionine is C5H11NO2S. Which of its atoms must come from sources other than sugar?
Answer: B
Sugar supplies only C, H and O, so the N and S must come from elsewhere, for a plant from nitrate or ammonium and sulfate in the soil. Choice D ignores the two elements that sugar lacks. Choice A names elements that sugar does contain.
Question 3 of 20 · Multiple Choice
In a tracer study, carbon given to a plant only as CO2 shows up first in sugars, later in amino acids and later still in proteins. Which explanation do these data best support?
Answer: C
The order in which the label appears matches a path from sugar to amino acids to proteins. Choice A reverses the order in the data. Choice D is false: proteins are carbon-based molecules.
Question 4 of 20 · Multiple Choice
The amino acid valine is C5H11NO2. At least how many glucose molecules (C6H12O6) are needed to supply the carbon for 6 valine molecules?
Answer: A
Six valine molecules contain 6 × 5 = 30 carbon atoms, and each glucose has 6, so 30 ÷ 6 = 5 glucose molecules. Choice C is the number of carbon atoms, not molecules. Choice B assumes one glucose per amino acid.
Question 5 of 20 · Multiple Choice
Dry plant matter is typically about 1.5% nitrogen by mass. About how much nitrogen is in a plant with a dry mass of 50 g?
Answer: C
1.5% of 50 g is 0.015 × 50 = 0.75 g. Choice A uses 15% instead of 1.5%. Choice D treats the percent as a number of grams.
Question 6 of 20 · Multiple Choice
Wheat plants grown in a solution with no nitrogen made plenty of sugar but very little protein. Which explanation best fits these data?
Answer: B
The plants still made sugar, so the missing piece was nitrogen, which every amino acid needs. Choice C contradicts the data, since the plants made plenty of sugar. Choice A is wrong because the plants had light.
Question 7 of 20 · Multiple Choice
A student claims: "Plants get the carbon in their proteins from the soil." Which new evidence would most directly require the student to revise this claim?
Answer: D
If plants with no soil and no carbon in their root solution still build carbon-rich proteins, the carbon cannot have come from the soil, which contradicts the claim. Choice C is true but is about nitrogen and sulfur, not carbon. Choices A and B do not trace carbon at all.
Question 8 of 20 · Multiple Choice
An amino acid sample is analyzed and found to be 32.0% carbon, 6.7% hydrogen, 42.6% oxygen and 18.7% nitrogen by mass. Which conclusion does this evidence support?
Answer: A
Nearly a fifth of the mass is nitrogen, an element glucose lacks, so that part came from another source. Choice B ignores the nitrogen. Choice D confuses percent by mass with number of atoms; this composition matches glycine, C2H5NO2, with 2 C and 1 N.
Question 9 of 20 · Multiple Choice
Which model best describes how atoms from sugar become part of a protein?
Answer: C
Sugar is a source of atoms that are rearranged, and other elements are added to make amino acids. Choice A describes a sugar chain, which has no nitrogen and is not a protein. Choice B has atoms of one element turning into another, which chemical reactions cannot do.
Question 10 of 20 · Multiple Choice
A cat eats only meat, which is mostly protein and fat, yet its liver stores glycogen, a large molecule built from sugar units. Which explanation fits?
Answer: B
Atoms from food molecules can be rearranged into new kinds of molecules, including sugar built from the carbon in amino acids. Choice D contradicts the observation. Choice C is wrong because sugar units contain only C, H and O.
Question 11 of 20 · Multiple Choice
A seedling grows from a 0.3 g seed to a plant with 30 g of dry mass, while the soil loses 0.4 g. Which source supplied most of the added dry mass?
Answer: A
The plant gained about 29.7 g, but the soil lost only 0.4 g and the seed had only 0.3 g, so most of the mass came from carbon (and oxygen) in CO2 built into sugar, together with hydrogen from water. Choice B cannot account for more than 0.4 g. Choice C is limited to 0.3 g.
Question 12 of 20 · Multiple Choice
Chlorophyll is a large carbon-based molecule that contains one magnesium atom. Which investigation would best test whether spinach needs magnesium from its roots to make chlorophyll?
Answer: D
Changing only the magnesium supply and measuring chlorophyll tests the claim directly. Choices A and B measure growth, which many factors affect, and do not change magnesium at all. Choice C measures water content, not chlorophyll.
Question 13 of 20 · Multiple Choice
In a class simulation, 30 labeled carbon beads start as CO2. After 4 rounds there are 6 in CO2, 10 in sugar, 8 in amino acids and 6 in protein. What percent of the labeled beads are in amino acids or protein?
Answer: C
8 + 6 = 14 of 30 beads, and 14 ÷ 30 ≈ 46.7%. Choice A counts only the protein beads (6 of 30). Choice B counts only the amino acid beads. Choice D counts the beads still in CO2 and sugar.
Question 14 of 20 · Multiple Choice
A student's model shows "sugar + nitrogen → amino acids → proteins" but does not show where the nitrogen comes from. Which revision would improve the model most for a plant?
Answer: B
Plants take up nitrogen mainly as nitrate or ammonium through their roots, so an arrow from the soil completes the atom path. Choice A has one element turning into another. Choice C is wrong because sugar has no nitrogen.
Question 15 of 20 · Short Answer
The amino acid tyrosine is C9H11NO3. What is the smallest number of glucose molecules that could supply the carbon for 2 tyrosine molecules, and how many nitrogen atoms must come from another source?
Two tyrosine molecules contain 2 × 9 = 18 carbon atoms, and 18 ÷ 6 = 3 glucose molecules. Each tyrosine has one N, so 2 nitrogen atoms must come from another source, such as nitrate or ammonium.
Question 16 of 20 · Short Answer
Invented tracer data for a sunflower given labeled CO2: after 1 hour, 70% of the label is in sugars, 15% in amino acids, 3% in proteins and 12% in other molecules; after 1 day, 25% in sugars, 20% in amino acids, 30% in proteins and 25% in other molecules. By what factor did the protein share grow, and what explanation do the data support?
The protein share grew from 3% to 30%, 10 times. The label moved out of sugars and into amino acids and proteins, which supports the explanation that carbon from sugar made in photosynthesis is built into amino acids and then proteins. The data cannot show where the nitrogen came from.
Question 17 of 20 · Short Answer
A student writes: "Plants make amino acids with nitrogen that their leaves take in from the air." Plants grown in normal air but with a nitrogen-free root solution make very little protein. Use this evidence to revise the explanation.
If the leaves could get enough nitrogen from the air, plants in normal air would make normal amounts of protein. They do not, so the nitrogen for amino acids comes mainly from the roots, as nitrate or ammonium. Revised: "Plants combine carbon, hydrogen and oxygen from sugar with nitrogen taken up by their roots to make amino acids."
Question 18 of 20 · Short Answer
A sunflower has 2.0 kg of dry mass, and 45% of that is carbon. How much carbon is in the plant, and how many kilograms of CO2 contain that much carbon? (CO2 is 12.01 ÷ 44.01 ≈ 27.3% carbon by mass.)
Carbon: 0.45 × 2.0 = 0.90 kg. CO2 needed: 0.90 ÷ 0.273 ≈ 3.3 kg. The plant took in about 3.3 kg of CO2 from the air to get that carbon (more, in fact, since some sugar was used for energy).
Question 19 of 20 · Short Answer
Explain how a carbon atom in a sugar molecule made in a bean leaf can end up in a protein in a bean seed. Name each thing that must happen and every element that must be added.
The sugar is moved from the leaf to the developing seed. There it is broken down and its carbon, hydrogen and oxygen atoms are rearranged into carbon skeletons that are joined with nitrogen (and, for a few, sulfur) to form amino acids. The amino acids are then linked into proteins. The nitrogen and sulfur come from outside the sugar.
Question 20 of 20 · Short Answer
A student grows plants in sand watered with a solution that contains every nutrient except nitrogen and sees poor growth. What control group is needed before the student can blame the missing nitrogen, and why?
A group of the same kind of plants in the same sand, light and temperature, watered with the complete solution (with nitrogen). Without it, the poor growth could be caused by the sand, the light or something else; only a difference between the two groups, with nitrogen as the only change, points to nitrogen.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-LS1-6 mean?
HS-LS1-6 asks students to build and revise an explanation, based on evidence, of how atoms from sugar combine with other elements to make amino acids and other large carbon-based molecules. The focus is on following atoms, not on memorizing reactions. The code stands for High School, Life Science, core idea 1 (From Molecules to Organisms: Structures and Processes), performance expectation 6.
Do students need to know the chemical reactions for HS-LS1-6?
No. The official Assessment Boundary says assessment does not include the details of the specific chemical reactions. Students should be able to say which atoms come from sugar, which elements are added and what evidence shows it. Pathways and their steps belong to later courses.
Does HS-LS1-6 require students to identify macromolecules?
No. The Assessment Boundary also excludes identification of macromolecules, so students are not asked to classify a molecule as a protein, fat or carbohydrate from its structure. Teachers can still use those names as examples when they explain where atoms go.
Is HS-LS1-6 taught in Biology or Chemistry?
It is usually taught in Biology, often right after photosynthesis and alongside cellular respiration. It uses chemistry ideas such as reading formulas and conserving atoms, so it connects well with a chemistry course.
Where do plants get the nitrogen for amino acids?
Plants take up most of their nitrogen through their roots as nitrate or ammonium dissolved in soil water. Sulfur comes in as sulfate and phosphorus as phosphate. Animals get these elements from the molecules in their food.
What models and simulations work well for HS-LS1-6?
Atom inventories with model kits, bead or card simulations of tracer experiments, and flow diagrams of atoms work well. The Clarification Statement puts the emphasis on evidence from models and simulations, so have students use a model to explain data and then say where the model falls short.
What does "construct and revise an explanation" look like in class?
Students write an explanation early, then change it as evidence arrives, keeping a record of what changed and why. Numbered versions on chart paper, or crossed-out and rewritten sentences on a worksheet, make the revision visible and assessable.
How does HS-LS1-6 connect to photosynthesis and respiration?
Photosynthesis (HS-LS1-5) makes the sugar, and HS-LS1-6 follows its atoms into other molecules. Cellular respiration (HS-LS1-7) breaks down some of the sugar to release energy, which cells use to build the new molecules. Together the three explain how an organism uses matter and energy.
What mistakes do students often make with HS-LS1-6?
A common mistake is thinking sugar is only a source of energy and not a source of atoms. Others are thinking atoms can be created or turned into other elements, and thinking organisms take in proteins or fats whole and store them unchanged. Ask students to account for every atom to bring these ideas out.
How does HS-LS1-6 connect to other standards?
It builds on middle school ideas about photosynthesis and about food being rearranged into new molecules (MS-LS1-6 and MS-LS1-7). It sits beside HS-LS1-5 and HS-LS1-7, and it leads to HS-LS2-3 and HS-LS2-5, where the same atoms are followed through ecosystems and through the carbon cycle.
07
Related Standards
6 standards
These standards connect to HS-LS1-6: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS1-6Prerequisite
Explain with evidence the role of photosynthesis in cycling matter and energy
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