Horizon Life Science Sample Lessons
This week we learn how cellular respiration releases energy in cells at the chemical, cellular, and body systems levels. We build on what we discovered about photosynthesis in Unit 1 to help students cement their recall of the gases involved. Middle schoolers often forget the word equations and concepts involved once they get to high school, so we approach these in multiple ways for long term recall. Skills learned include analytical reading, doing two inquiry labs, making a graph from a lab, connecting how lungs, blood, and muscles work together during exercise, and mastering vocabulary. Requirements for College Board standards include understanding how carbon and oxygen cycles through different organisms over historical time, which involves applying base ten mathematics to explain how dinosaur breath is likely in our lungs today.
Scroll down for materials and for standards that can be used for the Homeschool Audit documentation.
Students use two lego activities to review photosynthesis and model cellular respiration kinesthetically. They make notes on their models. Students write freeform notes in their lab books in their own words and answer a question about dinosaur breath.
Photosynthesis in chloroplasts of plant cells
Carbon dioxide + water = sugar + oxygen (The sun's energy is stored in the bonds of the sugar molecule)
Cellular respiration in mitochondria of dinosaur cells
Sugar + oxygen = carbon dioxide + water (The sun's energy is released during cellular respiration ready to be used by the cell)
6 x 16-stud legos in blue or black (Carbon), 12 x 8-stud legos in red (Oxygen), 12 x 4-stud legos in white (Hydrogen). Oxygen gas has two bricks to make O2. Water has 2 hydrogens and 1 oxygen. Glucose sugar has 6 carbons, 6 oxygens, and 12 hydrogens.
Alternative materials: Cuisenaire rods. Robotics snap rods sized 4x 2x 1x. Dough shaped like legos 4x 2x 1x in size.
This fun activity is designed to show that cabbage juice turns from blue to red sooner after exercise than without exercise. The directions are on the student page.
One third red cabbage, bottled water, sieve, blender, teaspoon, two colorless drinking glasses or white cups, straws, timer/stopwatch, student able to exercise.
Hints for the activity: Stop the first bubbling as soon as the color goes pink. Save the first pink glass so there is an easy comparison with the second bubbling with exercise as to when to stop. Both resting and exercising will turn the color pink because cells at rest still do cellular respiration, therefore exercising may not turn the indicator pink faster even though in most cases it will.
The pink color is made by carbon dioxide turning the blue slightly basic cabbage juice indicator slightly acidic.
Students are invited to post to the group chat within Google Classroom to comment on where they think the extra carbon dioxide from exercise comes from. At this stage in the lesson set most students will not know the full answer though some will look it up. The main goal is to have students think about this at the cellular level as well as grasp that body systems: digestive system, muscle cells, blood circulation, and lungs all connect together to help us move.
What happened? The indicator went red from the carbon dioxide.
Did the amount of time change? Yes the exercise changed the red faster.
Why or why not? Because the muscle cells needed more ATP and so they burned more glucose and released more carbon dioxide.
Which organelle in what cell type did the extra carbon dioxide come from? Muscle mitochondria.
If it "didn't work" do you think other cells in your body are also working hard and producing carbon dioxide? Yes, my brain cells are thinking, my muscles in my fingers are writing.
Don't forget to do student post in the Google Classroom chat stream.
Students post in the class chatroom on Google Classroom* under the New Announcements/Stream tab.
*Only available to those signed up in the course.
A screenshot is shown for prospective parents to view.
Students are assigned to read the textbook. A video explains more advanced details. The textbook includes questions at the end to check for understanding. Hints and answers are given. Lexi, the ai chatbot answers individual student questions live if needed.
Access the Life Science for Homeschool textbook link on the Google Classroom* under the Classwork tab. This opens the Cellular Respiration section of the ck-12 Flexbook online.
*Only available to those signed up in the course.
A screenshot is shown for prospective parents to view.
This inquiry helps students identify that sugar as the source of cellular energy, rather than sweeteners or "energy" drinks with zero calories. Yeast is used as a model organism. In this case, yeast is performing fermentation as well as cellular respiration, producing both alcohol (fermentation) and carbon dioxide (cellular respiration). The sugary drinks should produce more bubbles and bigger balloons than the zero calorie drinks, low-cal "energy drinks," or water.
The activity details are on the student page.
Students are learning how to graph accurately, and it is important to take the time to do this well at this age. Students may confuse data tables with graphs: a graph has an x-axis and a y-axis. Data tables are numbers in columns, also known as spreadsheets.
Which "energy drinks" provide real energy for our cells? The higher calorie sugary drinks made more carbon dioxide.
What evidence supports your claim? We found the actual calories for each drink and measured yeast production of carbon dioxide to show these results. Yeast breaks down sugar to make carbon dioxide and water during cellular respiration and fermentation.
Use the graph to explain your thinking. The graph of bubble scores clearly show that drinks with more calories score higher than drinks with less, even if the drink tasted sweet from a sweetener such as stevia, and even if the drink was labeled an "energy drink." Energy drinks do not have real cell energy.
3 packets of Fleischmann's yeast (Rapid Rise).
6 balloons to fit on the neck of water bottles or conical flasks.
6 empty recyclable water bottles or conical flasks.
6 non-bubbly drinks to compare: tap water, two sugary drinks (such as apple juice, mango juice), two zero-calorie sweetened drinks (such as Zevia, Diet Coke), and a sugar-free "energy drink." Save the bottles so we can read the food labels.
A basin of warm water that the drinks can sit in for an hour prior to the activity.
7th grade Common Core math standards incorporate the base-10 exponents used in this example. However, students may need support for manipulating and dividing numbers above 10-squared, such as 10-to-the-power-of-22 (22 zeroes). All the math is written out in the student lesson.
Cellular Respiration Lesson Cluster: Unit 2, Week 4
Next Generation Science Standards (State)
MS-LS1-3 Use argument supported by evidence for how the body is a system of interacting subsystems.
MS-LS1-7 Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy.
College Board (National) Grades 6-8
Matter is transferred from organisms to the physical (abiotic) environment when molecules from food react with oxygen to produce carbon dioxide and water in a process called cellular respiration. Cellular respiration takes place in most species.
LSM-PE.4.1.1 Create a representation to describe the cycling of a carbon atom from the physical (abiotic) environment through the molecules of the biological (biotic) components of an ecosystem back to the physical (abiotic) environment. [BOUNDARY: The chemical structure of any of the molecules is not appropriate.]
LSM-PE.4.1.2 Make and justify a claim concerning whether a particular molecule of oxygen inhaled today could be made of the same atoms of oxygen inhaled by someone a hundred years ago. Make and justify a claim concerning whether a particular molecule of water consumed today could be made of the same atoms of hydrogen and oxygen consumed by someone a hundred years ago.