Database results:
examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Respiration and Photosynthesis
Respiration and photosynthesis are two fundamental biological processes that work together to maintain life on Earth. They form a beautiful cycle where the products of one process become the reactants for the other, creating a perfect balance in nature.
Key Definitions:
Plants capture sunlight energy in their chloroplasts to convert carbon dioxide and water into glucose and oxygen. This process is essential for all life as it produces oxygen for animals to breathe and glucose for energy.
Equation: 6CO2 + 6H2O → C6H12O6 + 6O2
All living organisms perform respiration to release energy from glucose. This energy is used for all life processes. Respiration produces carbon dioxide and water as waste products.
Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
There are two main types of respiration that organisms use to release energy from glucose:
Occurs in the presence of oxygen and releases a large amount of energy. It happens in the mitochondria of cells.
Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)
This is the most efficient form of respiration and produces approximately 38 ATP molecules per glucose molecule.
Occurs without oxygen and releases less energy. In humans and animals, it produces lactic acid. In plants and yeast, it results in ethanol (alcohol) and carbon dioxide.
In humans: Glucose → Lactic acid + Small amount of energy
In yeast: Glucose → Ethanol + Carbon dioxide + Small amount of energy
Photosynthesis occurs in two main stages, both taking place within the chloroplasts of plant cells:
These reactions happen in the thylakoid membranes of chloroplasts:
Also called the Calvin Cycle, these reactions occur in the stroma of chloroplasts:
Several environmental factors can limit the rate of photosynthesis:
More light generally means faster photosynthesis, up to a point. After that, other factors become limiting.
Enzymes work best at optimal temperatures (around 25-30°C for most plants). Too hot or too cold slows photosynthesis.
Higher CO2 levels increase photosynthesis rate until another factor becomes limiting.
Respiration and photosynthesis are key components of both the carbon cycle and oxygen cycle:
Carbon constantly moves between the atmosphere, oceans, soil and living organisms:
Oxygen is constantly being produced and consumed:
The Amazon rainforest is often called the "lungs of the Earth" because it produces about 20% of Earth's oxygen through photosynthesis. However, scientists have discovered that the rainforest ecosystem consumes almost all the oxygen it produces through respiration! The real benefit of the Amazon is its massive carbon storage capacity, helping to regulate global climate by removing CO2 from the atmosphere. This shows how the balance between photosynthesis and respiration is crucial for maintaining Earth's atmosphere.
Understanding respiration and photosynthesis has many real-world applications:
Farmers can optimize crop growth by controlling factors that affect photosynthesis:
The balance between photosynthesis and respiration affects global carbon levels:
| Feature | Photosynthesis | Respiration |
|---|---|---|
| Organisms | Plants, algae, some bacteria | All living organisms |
| Location in cell | Chloroplasts | Mitochondria (aerobic), cytoplasm (anaerobic) |
| Energy change | Stores energy (endothermic) | Releases energy (exothermic) |
| Reactants | CO2 and H2O | Glucose and O2 (aerobic) |
| Products | Glucose and O2 | CO2 and H2O |
| Light requirement | Required | Not required |
Plants perform both photosynthesis and respiration! During the day, photosynthesis usually produces more oxygen than the plant uses in respiration. But at night, when there's no light for photosynthesis, plants only perform respiration, consuming oxygen and releasing carbon dioxide just like animals do.
Respiration and photosynthesis create a beautiful balance in nature:
This interdependence between plants and animals highlights the importance of maintaining biodiversity and protecting ecosystems. Every organism plays a vital role in these nutrient cycles that sustain life on our planet.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.