MS-LS1-2: Modeling How a Cell and Its Parts Work Together
In plain English: MS-LS1-2 is the NGSS middle school performance expectation that asks students to develop and use a model of how a cell works as a whole and how its parts help. Students build and test models of the cell membrane and cell wall and explain how the nucleus, chloroplasts and mitochondria support the whole cell. It is usually taught in grade 6, 7 or 8 life science.
Develop and use a model to describe the function of a cell as a whole and ways the parts of cells contribute to the function.
Clarification Statement: Emphasis is on the cell functioning as a whole system and the primary role of identified parts of the cell, specifically the nucleus, chloroplasts, mitochondria, cell membrane, and cell wall.
Assessment Boundary: Assessment of organelle structure/function relationships is limited to the cell wall and cell membrane. Assessment of the function of the other organelles is limited to their relationship to the whole cell. Assessment does not include the biochemical function of cells or cell parts.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Students develop and use models of a cell as a working whole. A cell is the smallest unit of a living thing, and on its own it takes in materials, gets energy, gets rid of wastes, grows and divides. The parts inside a cell with special jobs are called organelles. Students test physical models of the cell membrane and the cell wall, build scale models, and use plant and animal cell models to explain how the nucleus, chloroplasts and mitochondria help the whole cell. They also critique an analogy model and revise it.
The NGSS Clarification Statement says: "Emphasis is on the cell functioning as a whole system and the primary role of identified parts of the cell, specifically the nucleus, chloroplasts, mitochondria, cell membrane, and cell wall." The Assessment Boundary says: "Assessment of organelle structure/function relationships is limited to the cell wall and cell membrane. Assessment of the function of the other organelles is limited to their relationship to the whole cell. Assessment does not include the biochemical function of cells or cell parts." So this lesson connects structure (what a part is like) to function (its job) only for the cell wall and the cell membrane. For the nucleus, chloroplasts and mitochondria, it asks only how each one helps the cell as a whole. The chemical reactions inside cells, and how organelles are built inside, are beyond this standard and do not appear in any activity, homework or quiz item. All data on this page are invented for teaching and labeled as invented; sizes are typical rounded values. Students do the practice of developing and using models: they build, test, compare, critique and revise them.
Learning Objectives
By the end of this lesson, students will be able to:
Describe the cell as a system that takes in materials, gets energy, grows and divides
Use physical models to explain how the structure of the cell membrane and the cell wall fits their functions
Explain how the nucleus, chloroplasts and mitochondria each help the cell as a whole
Compare plant and animal cell models and use them to make predictions
Critique a cell model, including its scale, and revise it
Prior Knowledge Required
Students should already be comfortable with:
Living things are made of one cell or many cells MS-LS1-1
Plants get the materials they need for growth chiefly from air and water 5-LS1-1
Show a photo of a single green pond cell next to a photo of a leaf. Remind students that in MS-LS1-1 they saw that some organisms are just one cell. Ask:
Warm-Up Prompt
"A one-celled pond organism has to do everything to stay alive. Make a list of the jobs it must do. Then draw a quick sketch of the cell and add a part for each job."
Collect the job lists (take in water and food, get energy, keep its insides together, get rid of wastes, grow, make copies of itself). Keep the sketches: students revise them at the end of the lesson.
Direct Instruction15 minutes
The cell as a system. A system is a group of parts that work together. Show Diagram 1 and introduce the five parts. The cell membrane is a thin, flexible layer around every cell; it lets some materials in and out and keeps others in or out. The cell wall is a stiff layer outside the membrane in plant cells; it is made of tough fibers with tiny openings between them, so it supports and protects the cell while water passes through. The nucleus holds the instructions the cell needs to grow and divide, and it directs the cell's activities. Chloroplasts, found in plant cells and other green cells, capture light energy and use it to make food (sugar) for the cell. Mitochondria (one is a mitochondrion), found in plant and animal cells, release the energy stored in food so the whole cell can use it. The jelly-like material that fills the cell is the cytoplasm.
The whole cell: a root cell with no chloroplasts
Model what a cell deep in a plant root does over one day.
Result: Water and other materials from the soil pass through the cell wall and membrane. The root cell has no chloroplasts, so food (sugar) made in the leaves is carried down to it and enters through the membrane. Mitochondria release energy from that food. The cell uses the energy to grow and, when the nucleus directs it, to divide. Every part is needed, and the whole cell also depends on leaf cells.
Scale model: making a cell big enough to see
A leaf cell is about 50 µm long (1 µm, a micrometer, is one thousandth of a millimeter). The class builds a model 10,000 times actual size. Its nucleus is about 8 µm across.
Result: Model cell: 50 µm × 10,000 = 500,000 µm = 50 cm long, half the length of a meter stick. Model nucleus: 8 µm × 10,000 = 80,000 µm = 8 cm across.
Structure and function: membrane versus wall
The membrane is about 0.008 µm thick. The wall of a leaf cell is about 0.4 µm thick. Find their thicknesses in the same 10,000× model.
Result: Membrane: 0.008 × 10,000 = 80 µm = 0.08 mm, thinner than a sheet of paper, so it is thin and flexible. Wall: 0.4 × 10,000 = 4,000 µm = 4 mm, like stiff cardboard. The wall is 0.4 ÷ 0.008 = 50 times thicker, which fits its job of support.
Predicting with the model: a muscle cell in a sprint
Use the animal cell model to predict what changes in a leg muscle cell when a runner starts to sprint.
Result: The cell must shorten again and again, so it needs energy much faster. Its many mitochondria release energy from food faster, and its membrane takes in more food materials and lets more wastes out. The parts change their work together so the whole cell can do its job.
Comparing plant and animal cell models
List the parts in each model in Diagram 1.
Result: Both have a cell membrane, a nucleus, mitochondria and cytoplasm. Only the plant cell has a cell wall and chloroplasts. An animal cell has no wall, so its flexible membrane lets it change shape, as a muscle cell does when it shortens.
After each example ask: "Which part of the model shows this, and what would happen to the whole cell if that part stopped working?" Remind students that a model is a tool for explaining and predicting; it is never exactly like the real thing.
Guided Practice15 minutes
Pairs use the invented observations of four mystery cells below to identify each cell and to explain what the whole cell does. They compare their answers with Diagram 1.
Guided practice data (invented): four mystery cells seen in micrographs (photos taken through a microscope)
Cell
Cell wall?
Chloroplasts per cell
Nucleus?
Mitochondria per cell
1
Yes
45
Yes
about 200
2
Yes
0
Yes
about 150
3
No
0
Yes
about 2,500
4
No
0
Yes
about 300
Sort the cells: which two are plant cells, and which two are animal cells? Name the evidence (a wall, chloroplasts).
Cell 2 is a plant cell with no chloroplasts. Where in a plant could it come from, and where does it get its food?
Cell 3 has the most mitochondria, about 2,500 ÷ 300 ≈ 8 times as many as cell 4. Which cell probably uses energy fastest? Is cell 3 more likely a muscle cell or a fat storage cell?
Every cell in the table has a nucleus. What would happen to any of these cells if its nucleus were removed?
Independent Practice10 minutes
Each student uses Diagram 2, invented counts of chloroplasts in cells from four parts of a bean plant, to extend the model. They write a paragraph that answers: "Why do cells in the upper leaf layer have the most chloroplasts, and how do root cells stay alive with none?" The paragraph must name the chloroplasts, the mitochondria and the whole plant cell, and it must use at least two numbers from the graph.
Closure5 minutes
Students return to their warm-up sketches and revise them: add and label the membrane, the wall (if it is a plant cell), the nucleus, chloroplasts and mitochondria, with one arrow or note per part that shows how it helps the whole cell. Exit ticket: "Which cell part would you remove from your model to show a cell that cannot control what enters it? Explain."
Differentiation Strategies
For Struggling Students
Give a part-and-job card set (five parts, five jobs) to match before students build or draw a model
Provide a model frame: "The ___ is like ___ because both ___. It helps the whole cell by ___."
Let students use the 10,000× scale only, with a printed table for converting µm to cm
For Advanced Students
Ask students to design a better membrane model than the tea bag, one that lets water in but keeps a colored solution in, and to explain its limits
Have students choose their own scale for a cell model that must fit on a desk, then calculate the model size of every part
Ask students to model a one-celled organism that has both chloroplasts and the ability to swim, and explain how each part helps it survive
Assessment Guidance
What to Look For
Check that students tie each part to the whole cell ("the mitochondria release energy the whole cell uses to grow"), not just to a vocabulary word. For the membrane and wall, look for structure linked to function: thin and flexible with control over what passes, stiff and fibrous with openings for support. Watch for students who put chloroplasts or a wall in animal cells, who think plant cells have no mitochondria, or who treat an analogy as exact. In scale problems, check units and the powers of ten.
02
Classroom Activities
3 Activities
1
Tea Bag Membrane Model
25 minPairs
Pairs test three "bags" as models of a cell boundary. Each holds the same amount of loose tea and sits in a cup of room-temperature water. Pairs score the color of the water on a 0-5 scale card every 5 minutes and look for tea leaves in the water.
Procedure
Cup A: a paper tea bag. Cup B: 1 teaspoon of loose tea in a zip bag, zipped shut. Cup C: 1 teaspoon of loose tea in a piece of mesh produce bag tied with string.
Pour 250 mL of room-temperature water into each cup at the same time and start the timer.
At 0, 5, 10 and 15 minutes, hold each cup against white paper and score the color (0 = clear, 5 = darkest card). Record whether any leaves are floating loose in the water.
Safety: use only room-temperature water, do not drink the tea, and wipe up spills right away.
Sample Data (invented)
Color scores at 0, 5, 10 and 15 minutes. Cup A: 0, 1, 2, 3, no loose leaves. Cup B: 0, 0, 0, 0, no loose leaves. Cup C: 0, 2, 3, 4, many loose leaves.
Discussion Questions
Only Cup A changed color but kept its leaves inside. Which part of a cell does the paper tea bag model best, and why?
Cup B never changed color. What would happen to a real cell whose boundary let nothing in or out?
Cup C let both the color and the leaves out. Why would a cell with a boundary like this not survive?
Name one way the tea bag is not like a real cell membrane.
Modification for Distance Learning
Students run the test at home with any tea bag, a sandwich bag and a piece of loosely woven cloth, photograph each cup every 5 minutes, and post their scores.
2
Berry Basket Cell Wall Model
20 minGroups of 3
Groups compare two model plant cells. Each "membrane" is a quart zip bag holding 500 mL of water. One bag sits alone on the table; the other sits inside a plastic berry basket, a stiff "cell wall" with openings. Groups stack textbooks on each and measure the model's height.
Procedure
Fill two quart zip bags with 500 mL of water each and zip them shut, pressing out the air.
Lay one bag flat on a tray. Put the other inside an upright berry basket on a second tray.
Measure each model's height with a ruler. Then lay one textbook on top, measure, and repeat with 2 and 3 books (lay the books on the basket's top edge).
Pour a cup of water through an empty berry basket over a tray and watch where it goes.
Safety: keep the trays on the floor or a low table, and stack the books gently so they do not slide.
Sample Data (invented)
Height in cm with 0, 1, 2 and 3 books. Bag alone: 6.0, 4.0, 3.0, 2.5. Bag in basket: 6.0, 6.0, 6.0, 5.9. Water poured into the empty basket ran straight out through its openings.
Discussion Questions
With 3 books, the bag alone lost 3.5 cm of height and the basket model lost only 0.1 cm. What does the stiff basket do for the bag inside it?
Water ran straight through the basket. Why is it important that a real cell wall lets water through?
Animal cells have no wall. What can an animal cell do that a plant cell, held in its stiff wall, cannot?
Challenge Variation
Groups predict, then test, what happens with a basket that has much larger holes (or a cardboard box with no holes). They explain which version is the best model of a real cell wall and why.
3
Model Critique: Is a Cell Like a Stadium?
20 minGroups of 3-4
An analogy compares something new to something familiar. Groups get a card that compares a plant cell to a sports stadium, decide where the analogy works and where it fails, and write a better version.
The Analogy Card
The stadium's outer concrete wall is the cell wall.
The ticket gates, where staff let fans in and keep others out, are the cell membrane.
The control room, which holds the event plans and directs the staff, is the nucleus.
The solar panels on the roof, which turn sunlight into power stored in batteries, are the chloroplasts.
The generators that use the stored power to run the lights, screens and gates are the mitochondria.
Tasks
For each pair, write one way the stadium part is like the cell part and one way it is not.
Find the biggest weakness. (Hint: a real membrane surrounds the whole cell, but a stadium has only a few gates. A stadium does not grow or divide into two stadiums.)
Revise the analogy or draw a new model that fixes at least two weaknesses, and present it to another group.
Discussion Questions
The card has five parts and five matches. Which match do you think is weakest, and why?
A stadium is not alive. Which jobs of a whole cell does the analogy leave out completely?
Would the same analogy work for an animal cell? Which two parts would you take away?
Modification for Distance Learning
Groups build the critique on a shared slide, with one slide per part, and record a two-minute presentation of their revised model.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Plant Cell and Animal Cell Models
Simplified models, not to scale. Both cells have a cell membrane, a nucleus and mitochondria. Only the plant cell has a stiff cell wall outside its membrane and green chloroplasts. The muscle cell model shows many mitochondria because muscle cells use energy quickly.
Diagram 2: Chloroplasts in Cells from Four Parts of a Bean Plant (Invented Data)
Invented mean counts from 10 cells per plant part, drawn to scale. Cells in the upper leaf layer, which get the most light, have the most chloroplasts; root cells, which grow in the dark soil, have none. Root cells still need energy, so they rely on food made in the leaves.
04
Homework Assignment
~30 min
MS-LS1-2 Homework: Using Models of the Cell
Directions: All data are invented for practice, and sizes are typical rounded values. Remember 1 cm = 10,000 µm and 1 mm = 1,000 µm. Show your math, and in every explanation say how the part helps the whole cell.
Part 1: Building and Testing Models (Problems 1-3)
You are building a model of a leaf cell 5,000 times actual size. The cell is 60 µm long, its nucleus is 10 µm across and each chloroplast is 6 µm long. (a) Find the model size of each part in cm. (b) The cell membrane is about 0.008 µm thick. How thick should it be in your model, in mm? (c) Pick a material for the membrane and one for the cell wall, and explain how each material matches the real part's structure and job.
A class measured the cell wall thickness in four plant parts (invented, rounded): leaf cell 0.2 µm, apple flesh cell 0.3 µm, oak wood cell 4 µm, flax stem fiber 6 µm. (a) How many times thicker is the flax fiber wall than the leaf cell wall? (b) Which two plant parts most need support to hold the plant up? (c) Use the data to explain how the structure of the cell wall fits its job.
A pond alga with chloroplasts is grown in two jars (invented data). Jar 1, on a sunny windowsill: 100 cells per drop on day 0 and 400 on day 14. Jar 2, in a dark closet: 100 cells per drop on day 0 and 60 on day 14. (a) By what factor did the cells in Jar 1 increase? (b) By what percent did the cells in Jar 2 decrease? (c) Use a cell model to explain the difference, naming the chloroplasts and the mitochondria.
Part 2: Parts Working for the Whole Cell (Problems 4-6)
Invented, rounded counts of mitochondria per cell: heart muscle cell 4,800; liver cell 1,600; skin cell 300; fat storage cell 150. (a) How many times as many mitochondria does a heart muscle cell have as a skin cell? (b) Rank the cells from most to fewest mitochondria. (c) What does the ranking suggest about how fast each kind of cell uses energy? Explain using the job of mitochondria.
Ana builds a plant cell model: a shoebox (cell wall), a balloon inside it (cell membrane), a large bead (nucleus) and six green buttons (chloroplasts). (a) Which of the five parts from this lesson is missing? Why does the whole cell need it? (b) A real cell wall has openings. What could Ana change so her shoebox wall models this? (c) Name one strength of her model and one way it is not like a real cell.
A student claims, "Plant cells don't need mitochondria, because their chloroplasts make their food." Write a claim, evidence and reasoning response. Use at least two pieces of evidence from this lesson's models and data.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Scale and Data Calculations
Model sizes, ratios and percents correct, with units
Correct method with one unit or arithmetic error
Structure and Function (Wall, Membrane)
Links a property (stiff, thin, flexible, has openings) to the job it allows
Names the job but not the property, or the reverse
Parts and the Whole Cell
Explains how each part named helps the cell as a whole survive, grow or divide
Names parts and jobs without linking them to the whole cell
Using and Critiquing Models
Uses the model to explain or predict, and names a strength and a limit
Describes the model without using it or judging it
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data are invented for practice, and sizes are typical rounded values. Questions ask how each part helps the cell as a whole, and how the structure of the cell wall and membrane fits their jobs. 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
Which cell part controls which materials enter and leave every cell?
Answer: A
The cell membrane surrounds every cell and lets some materials through while keeping others in or out. Choice C is wrong because the wall is found only in some cells and lets water and most dissolved materials pass freely; it supports rather than controls. Choice B directs the cell's activities but is not its boundary.
Question 2 of 20 · Multiple Choice
A plant cell has a stiff layer outside its membrane, made of tough fibers with tiny openings. How does this structure help the cell?
Answer: C
This is the cell wall. Tough fibers make it stiff, so it supports and protects the cell, and its openings let water and dissolved materials through. Choice D describes what a flexible membrane without a wall allows. Choice A is the job of chloroplasts, and choice B is the job of the nucleus.
Question 3 of 20 · Multiple Choice
The leaves of a houseplant are covered with foil for a week. What happens in the leaf cells under the foil?
Answer: D
Chloroplasts need light to make food. Under the foil, the whole cell must live on food it stored earlier, released by its mitochondria. Choice B mixes up the jobs: mitochondria release energy from food but do not use light. Choice A is not supported: the wall does not depend on light.
Question 4 of 20 · Multiple Choice
Which observation shows that a cell came from an animal rather than a plant?
Answer: C
Plant cells have a stiff wall outside the membrane; animal cells have only the membrane. Choices A and B describe parts that plant and animal cells both have, so they cannot tell the two apart. Choice D is also true of every cell.
Question 5 of 20 · Multiple Choice
A class builds a cell model 10,000 times actual size. A human egg cell is about 120 µm across. How wide is the model? (1 cm = 10,000 µm)
Answer: B
Model size = 120 µm × 10,000 = 1,200,000 µm, and 1,200,000 ÷ 10,000 = 120 cm, about the height of a 7-year-old. Choice C converts with 1 cm = 1,000 µm, a factor of 10 too large. Choice A divides by 100,000 instead of 10,000. Choice D divides by 100 instead of 10,000.
Question 6 of 20 · Multiple Choice
A coffee filter lets water and the dissolved brown color through but holds back the coffee grounds. Of the four cell parts below, which one does the filter model best?
Answer: B
Like the membrane, the filter lets some materials through and holds others back. Choices A, C and D are parts whose jobs have nothing to do with letting materials through. The filter is only a rough model: a real membrane is far more selective, and it can keep out even some small dissolved materials that a filter would let pass.
Question 7 of 20 · Multiple Choice
A model plant cell keeps its shape under a heavy book only when its bag "membrane" sits inside a stiff box. What does the box model, and what is that part's job?
Answer: C
A stiff outer layer that keeps the cell from being crushed models the cell wall, whose job is support and protection. Choice B names the part the bag already models. Choice A gives the nucleus a job it does not have. Choice D has no link to keeping shape.
Question 8 of 20 · Multiple Choice
A student's animal cell model has a nucleus, mitochondria, a membrane, a cell wall and chloroplasts. What should the student change?
Answer: D
Animal cells have no cell wall and no chloroplasts, so both should come out. Choice A removes parts that animal cells do have. Choice C would make the model worse: animal cells need their flexible membrane, and they have no wall at all.
Question 9 of 20 · Multiple Choice
A student's scale model shows the cell membrane as a 2 cm thick foam layer and the cell wall as a sheet of plastic wrap. What is the main problem with the model?
Answer: A
A real cell wall is stiff and many times thicker than the thin, flexible membrane, so the model has the two reversed. Choice B would remove the part that controls what enters the cell. Choice D is wrong because plastic wrap is neither stiff nor full of openings, so it does not model a wall.
Question 10 of 20 · Multiple Choice
Which statement best describes a cell as a whole?
Answer: D
A cell is a system: its parts work together so the whole cell can take in materials, get energy, grow and divide. Choice A ignores that the parts depend on each other, for example mitochondria need the food that chloroplasts make. Choice B is wrong because a cell without a membrane or mitochondria also dies.
Question 11 of 20 · Multiple Choice
Scientists cut an amoeba (a one-celled organism) into two pieces. The piece with the nucleus grows and divides. The piece without the nucleus lives a few days but never divides. What does this show?
Answer: A
Only the piece with the nucleus could grow and divide, which fits the nucleus holding the instructions for these jobs. Choice D is contradicted: the piece with the nucleus kept living. Choice B is wrong because the piece without a nucleus had a membrane and still failed.
Question 12 of 20 · Multiple Choice
Why can water pass through a plant cell's cell wall even though the wall is stiff?
Answer: D
The wall is a mesh of tough fibers with tiny openings, so it is stiff but lets water through, like the berry basket model. Choice C is backward: the wall is much thicker than the membrane. Choice A is wrong because a wall that dissolved could not support the plant.
Question 13 of 20 · Multiple Choice
A white blood cell squeezes between other cells to reach an injury. Which feature of animal cells makes this possible?
Answer: C
With only a thin, flexible membrane on the outside and no stiff wall, an animal cell can change shape. Choice A would prevent squeezing. Choice B is wrong because animal cells have no chloroplasts, and choice D describes something a nucleus does not do.
Question 14 of 20 · Multiple Choice
In a model 20,000 times actual size, how thick is a cell wall that is really 0.3 µm thick? (1 mm = 1,000 µm)
Answer: B
0.3 µm × 20,000 = 6,000 µm, and 6,000 ÷ 1,000 = 6 mm. Choice A divides by 10,000 instead of 1,000. Choice C divides by 100. Choice D divides 0.3 by 20,000 instead of multiplying.
Question 15 of 20 · Short Answer
Develop a model: describe or sketch what moves into and out of a leaf cell over a sunny day, and name the part that helps with each step.
A good model shows: water and materials entering through the cell wall and then the membrane (which controls what gets in); chloroplasts using light to make food; mitochondria releasing energy from that food for the whole cell; wastes leaving through the membrane; and the nucleus directing growth and division. Arrows should show direction.
Question 16 of 20 · Short Answer
Invented counts of mitochondria per cell: Cell X 150, Cell Y 3,600, Cell Z 900. Which cell probably does the most work? How many times as many mitochondria does it have as Cell X? Explain.
Cell Y. It has 3,600 ÷ 150 = 24 times as many mitochondria as Cell X. Mitochondria release energy from food for the whole cell, so a cell with many more of them can use energy faster, as a hard-working cell must.
Question 17 of 20 · Short Answer
A student says, "A cell is like a brick house." Give one way this analogy works and two ways it fails.
Works: the walls of a house, like a plant cell wall, give support and shape. Fails: (1) a brick house cannot grow or divide into two houses, but a cell can; (2) bricks let almost nothing pass, but a cell's boundary lets materials in and out; also, animal cells have no wall at all.
Question 18 of 20 · Short Answer
Explain why a cell whose membrane is torn open cannot survive, even if all its other parts are fine.
The membrane holds the cell's contents together and controls what enters and leaves. With a torn membrane, the cytoplasm and parts spill out and harmful materials get in, so the nucleus, mitochondria and chloroplasts can no longer work together. The whole cell depends on the boundary.
Question 19 of 20 · Short Answer
An animal cell 20 µm wide is modeled as a ball 25 cm (250,000 µm) wide. What is the scale factor? How wide should the model nucleus be, in cm, if the real nucleus is 6 µm across?
The scale factor is 250,000 ÷ 20 = 12,500. Model nucleus: 6 µm × 12,500 = 75,000 µm = 7.5 cm, since 1 cm = 10,000 µm.
Question 20 of 20 · Short Answer
A pond cell has a nucleus, mitochondria, chloroplasts and a cell membrane, but no cell wall. It swims through the water. Use the five-part cell model to explain two things this cell can do and one thing a plant cell can do that it cannot.
It can make its own food in light (chloroplasts) and release energy from that food (mitochondria); it can also control what enters (membrane), grow and divide (nucleus), and, with a flexible membrane and no wall, change shape as it swims. It lacks the support of a stiff wall, so it cannot hold a fixed shape under pressure the way a plant cell can.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS1-2 mean?
MS-LS1-2 asks students to develop and use a model that shows how a cell works as a whole and how its parts help. The named parts are the nucleus, chloroplasts, mitochondria, cell membrane and cell wall. The code means Middle School, Life Science, core idea 1 (From Molecules to Organisms: Structures and Processes), performance expectation 2.
Which organelles does MS-LS1-2 include?
Five parts: the nucleus, chloroplasts, mitochondria, cell membrane and cell wall, as listed in the Clarification Statement. Teachers often mention the cytoplasm because the other parts sit in it. Other organelles may come up in discussion but are beyond this standard.
What is the assessment boundary for MS-LS1-2?
The boundary limits structure-and-function questions to the cell wall and cell membrane. For the nucleus, chloroplasts and mitochondria, students are assessed only on how each part relates to the whole cell. The chemistry of photosynthesis, cellular respiration and other cell reactions is not assessed.
Do students need to know the equations for photosynthesis and respiration for MS-LS1-2?
No. The Assessment Boundary rules out the biochemical function of cells and cell parts. Students should know that chloroplasts use light to make food for the cell and that mitochondria release energy from food for the cell. The chemical equations come later, in MS-LS1-6, MS-LS1-7 and high school biology.
What counts as a model for MS-LS1-2?
Drawings, physical models, scale models, analogies and computer simulations all count. A model is useful when students use it: to explain what the cell does, to predict what happens if a part fails, or to test a property such as how a boundary lets materials through. Students should also say where their model differs from a real cell.
What grade is MS-LS1-2 taught in?
It is a grades 6-8 standard, and states and schools place it differently. Many teach it in grade 6 or 7 life science, right after MS-LS1-1, so students move from "living things are made of cells" to "how does one cell work?" before studying body systems.
What is the difference between the cell wall and the cell membrane?
Every cell has a membrane: a thin, flexible boundary that controls what enters and leaves. Plant cells, and some other cells, also have a cell wall outside the membrane: a thicker, stiff layer of tough fibers that supports and protects the cell and lets water pass through its openings.
What mistakes do students make with cell models?
Common mistakes are putting a cell wall or chloroplasts in animal cells, thinking plant cells have no mitochondria, calling the nucleus the "brain" and stopping there, and drawing a cell as a flat shape when real cells are three-dimensional. Many students also treat an analogy as exact; ask them to name where it breaks down.
Are cell analogies like "the cell is a city" useful?
They help when students critique them. An analogy links each part to something familiar, but it always leaves something out: cities do not divide in two, and a city wall is not the boundary that controls everything entering. Asking students to find and fix the weak spots turns the analogy into real modeling.
How does MS-LS1-2 connect to other standards?
It builds on MS-LS1-1, where students find that living things are made of cells. It prepares students for MS-LS1-3 (cells forming body systems) and MS-LS1-6 and MS-LS1-7 (food and energy in organisms). In high school, HS-LS1-5 and HS-LS1-7 add the chemistry of photosynthesis and respiration.
07
Related Standards
5 standards
These standards connect to MS-LS1-2: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
4-LS1-1Prerequisite
Argue that plant and animal structures support survival, growth, behavior and reproduction
Lesson coming soon
Alongside
MS-LS1-1Parallel
Investigate evidence that living things are made of one cell or many cells
NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.
