Why Do Scientists Convert Processes Into Equations?
- Scientists convert everyday biological processes into equations to:
- Simplify complex reactions: Equations reduce lengthy descriptions into concise statements.
- Ensure accuracy: Equations provide a clear and precise way to represent reactions.
- Aid communication: Standardized equations allow scientists worldwide to understand and replicate experiments.
Analogy
Think of equations as recipes that tell you exactly what ingredients you need and what products you'll get.
What Is a Word Equation?
A word equation describes the overall chemical change using names only, leaving out enzymes, energy transfers, or intermediate steps:
$$glucose + oxygen → carbon dioxide + water$$
Tip
- Word equations are useful when learning the core idea of a reaction before using formulas.
- To read them:
- Reactants appear on the left.
- The arrow means “reacts to form.”
- Products appear on the right.
- Order does not show timing or mechanism, only input and output.
What Is a Chemical Equation?
A chemical equation uses symbols and formulas to show how atoms rearrange. It's more precise than a word equation because it shows actual molecular formulas:
$$C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O$$
Common Mistake
- Students often swap coefficients and subscripts.
- Coefficients balance the equation.
- Subscripts define the molecule and cannot be changed.
Why Must Chemical Equations Be Balanced?
- The number of each type of atom must be the same on both sides.
- This follows the law of conservation of mass.
- You balance equations by adjusting coefficients, not subscripts.
Example
Respiration only becomes correct once oxygen, carbon, and hydrogen all match.
Exam technique
- Never alter subscripts to balance an equation.
- Only adjust the numbers in front of formulas.
How Do Equations Simplify Real Biological Reactions?
- Real biological reactions involve many steps, each controlled by enzymes.
- Writing every step would be too complex to study.
- An equation shows only the net chemical change, which is all that is needed for most analysis.
Example
- Cellular respiration involves many enzymes and dozens of intermediate compounds, but its core chemical change can be represented simply:
$$glucose + oxygen → carbon dioxide + water$$
- A chemical equation provides even more detail:
$$C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O$$
What Are Some Biological Equations You Should Recognize?
- Respiration: $C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O$
- Photosynthesis: $6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂$
- Lactose digestion: $lactose → glucose + galactose$
- Lactic acid fermentation: $glucose → lactic acid$
- Each highlights the core chemical change, not the enzyme mechanisms beneath it.
Self review
- What does a word equation show, and what does it leave out?
- What must be true for a chemical equation to be correctly balanced?
- Why do scientists prefer equations over everyday descriptions of reactions?
- Why is changing a subscript different from changing a coefficient?
- How does the respiration equation summarise a much larger metabolic pathway?
- Explain how equations help biologists compare processes across species.
