Metabolism links building and breaking down
| English | 中文 | Pinyin |
|---|---|---|
| metabolism/məˈtæbəlɪzəm/ | 新陈代谢 | xīn chén dài xiè |
| urea/juːˈrɪə/ | 尿素 | niào sù |
What would explain this observation?
- Digestion breaks some molecules down while cells build others. Metabolism 新陈代谢 includes both directions, linked by enzymes, available materials and energy transfer.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Metabolism is the sum of all reactions in a cell or body. Energy transferred by respiration supports continual enzyme-controlled processes that synthesize new molecules. It includes glucose conversion into starch, glycogen and cellulose; formation of a lipid from one glycerol molecule and three fatty-acid molecules; and amino acids joining to form proteins.
- metabolism: The sum of reactions in a cell or body; urea 尿素: A waste product formed during breakdown of excess proteins and excreted from the body.
Which statement correctly describes metabolism?
In plants, glucose and nitrate ions provide materials for amino-acid production. Metabolism also includes respiration and the breakdown of excess proteins to form urea for excretion. Match each molecule to its role rather than treating every metabolic reaction as digestion or every product as an energy store. Urea formation and urea excretion are related but distinct processes.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- In plants, glucose and nitrate ions provide materials for amino-acid production. Metabolism also includes respiration and the breakdown of excess proteins to form urea for excretion. Match each molecule to its role rather than treating every metabolic reaction as digestion or every product as an energy store. Urea formation and urea excretion are related but distinct processes.
- Build a concept map with reactants, products and functions. Use one arrow for a specified conversion and annotate any needed additional material, such as nitrate. Trace where a material comes from and where a waste goes. Do not add advanced reaction pathways or treat the lipid particle-ratio model as a complete biochemical mechanism.
Which two habits make the investigation or model in this case more defensible?
Build a concept map with reactants, products and functions. Use one arrow for a specified conversion and annotate any needed additional material, such as nitrate. Trace where a material comes from and where a waste goes. Do not add advanced reaction pathways or treat the lipid particle-ratio model as a complete biochemical mechanism.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: the stated lipid-building model requires one glycerol and three fatty acids per lipid molecule. For 7 lipid molecules it needs 7 glycerol and 21 fatty-acid molecules. With 10 glycerol and 24 fatty acids, at most 8 lipid molecules can form in this model because fatty acids run out first, leaving 2 glycerol molecules unused.
In the stated model, each lipid needs three fatty acids. How many fatty-acid molecules are needed for 9 lipid molecules? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
In the stated model, each lipid needs three fatty acids. How many fatty-acid molecules are needed for 9 lipid molecules?
The result is 27 molecules. Known: the stated lipid-building model requires one glycerol and three fatty acids per lipid molecule. For 7 lipid molecules it needs 7 glycerol and 21 fatty-acid molecules. With 10 glycerol and 24 fatty acids, at most 8 lipid molecules can form in this model because fatty acids run out first, leaving 2 glycerol molecules unused.
Check the conclusion and its limits
- Metabolism includes synthesis and breakdown, not only reactions that release energy. Proteins are made from amino acids, while lipids use glycerol and fatty acids. Urea is a waste from excess protein breakdown and is not the same substance as glucose or lactic acid.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Metabolism includes only reactions that break molecules down. This claim is false: Metabolism includes synthesis and breakdown, not only reactions that release energy. Proteins are made from amino acids, while lipids use glycerol and fatty acids. Urea is a waste from excess protein breakdown and is not the same substance as glucose or lactic acid.
Metabolism links building and breaking down: In plants, glucose and nitrate ions provide materials for amino-acid production. Metabolism also includes respiration and the breakdown of excess proteins to form urea for excretion. Match each molecule to its role rather than treating every metabolic reaction as digestion or every product as an energy store. Urea formation and urea excretion are related but distinct processes.
Metabolism includes only reactions that break molecules down.
Metabolism includes synthesis and breakdown, not only reactions that release energy. Proteins are made from amino acids, while lipids use glycerol and fatty acids. Urea is a waste from excess protein breakdown and is not the same substance as glucose or lactic acid.
The sum of reactions in a cell or body: write the technical term.
metabolism means The sum of reactions in a cell or body.