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Stored Potatoes and Winter Hens: Food Molecules on a Farm

Grade 7 life science: analyze stored-potato carbon dioxide and dry-mass data and winter hen feed records to model how food is broken down and rearranged.

Grade 7ScienceInteractive · Printable

Aligned toMS-LS1-7

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
12 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students use storage data to show that stored potatoes break down food molecules in cellular respiration.
Students explain how cells rearrange small food molecules into new molecules such as cellulose and proteins.
Students use feed records to explain why animals break down more food to stay warm.

How to use

Read the model in paragraph 2 aloud and have students trace one glucose molecule through it before they start. Remind them that dry mass leaves out water.

Curriculum

NGSS standard covered

MS-LS1-7

Model how food is broken down and rearranged in cellular respiration to release energy and build new molecules.

Preview

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Name Date

Stored Potatoes and Winter Hens: Food Molecules on a Farm

Use potato storage data and coop records to model how cells break down and rebuild food molecules.

The potato bins

Read the passage and study Table 1. Then answer the questions.

What Happens to the Food?

1The Pham family farm grows potatoes on 12 hectares and keeps a flock of 200 laying hens. After the September harvest, the potatoes are stored in a cool cellar and sold through the winter, while the hens lay eggs in an unheated coop. Seventh grader Thuy Pham helps her uncle, Duc, on weekends. For her science fair project, she studied what happens to food molecules inside the stored potatoes and inside the hens.

2A potato tuber is mostly water and starch, a large molecule made of many glucose units linked together. A stored potato is still alive. Its cells break some starch into glucose and use it in cellular respiration: glucose + oxygen → carbon dioxide + water, releasing energy. When a potato sprouts, its cells also rearrange glucose and other small molecules into new large molecules, such as cellulose for cell walls and proteins for the growing sprout. Hens follow the same model with their feed. Digestion breaks the food into small molecules, such as glucose and amino acids, and the blood carries them to the cells. The cells use some of them in respiration and rearrange others into new body tissue and eggs.

3A county farm adviser, Ms. Lorraine Whitfield, helped Thuy set up a test. Thuy filled three bins with 5 kg of potatoes each and kept them at 4 °C, 10 °C and 20 °C for 8 weeks. Once a week she closed each bin's lid for two hours and used a carbon dioxide meter to find how fast the potatoes released carbon dioxide. In each bin she also marked a few potatoes that weighed 1 kg in all. At the start, the adviser's lab dried a matching 1 kg of potatoes, which had a dry mass of 210 g. After 8 weeks, the lab dried the marked potatoes from each bin, sprouts included, and also weighed the dried sprouts alone. Large potato warehouses run fans that push outside air through their piles all winter.

4In the coop, lights stay on 16 hours a day so the hens keep laying through the winter. Uncle Duc weighs the feed he puts out each day, and Thuy recorded the average temperature, the feed eaten and the eggs laid in four months (Table 2). The hens' average body mass stayed close to 1.8 kg all year. An egg white is made mostly of water and protein, and the yolk holds fats and proteins.