CIE iGCSE Biology-12.1 Respiration- Study Notes- New Syllabus
CIE iGCSE Biology-12.1 Respiration- Study Notes – New syllabus
CIE iGCSE Biology-12.1 Respiration- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- State the uses of energy in living organisms, including: muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses and the maintenance of a constant body temperature
- Investigate and describe the effect of temperature on respiration in yeast
Uses of Energy in Living Organisms
Organisms release energy (mainly from aerobic respiration) to carry out essential life processes. Here’s how that energy is used:
1. Muscle Contraction
- Needed for all movement: walking, breathing, pumping of the heart.
- Muscles use energy to contract and relax.
2. Protein Synthesis
- Energy is required to link amino acids together into proteins.
- Important for making enzymes, hormones, antibodies, and cell structures.
3. Cell Division
During mitosis or meiosis, cells use energy to:
- Copy DNA
- Build spindle fibres
- Separate chromosomes
Essential for growth, repair, and reproduction.
4. Active Transport
- Energy is used to move substances against a concentration gradient.
- Example: absorption of glucose and ions in the intestines and kidneys.
5. Growth
- Energy fuels cell enlargement and multiplication.
- Supports biosynthesis of complex molecules like proteins, lipids, and nucleic acids.
6. Transmission of Nerve Impulses
Nerve cells use energy to:
- Maintain ion gradients across membranes
- Transmit electrical signals quickly along neurons
7. Maintenance of Constant Body Temperature
- In warm-blooded animals (like mammals and birds), energy maintains homeostasis.
- Heat from respiration keeps internal temperature stable, even in cold environments.
Summary Table
| Process | How Energy Is Used |
|---|---|
| Muscle contraction | Enables movement and internal organ function |
| Protein synthesis | Builds new proteins for structure/function |
| Cell division | Supports growth, repair, and reproduction |
| Active transport | Moves substances against concentration gradient |
| Growth | Builds new cells and tissues |
| Nerve impulse transmission | Maintains ion balance and signal flow |
| Temperature regulation | Generates body heat for homeostasis |
Investigating the Effect of Temperature on Yeast Respiration
Yeast respires anaerobically (in the absence of oxygen), producing:
- Carbon dioxide (CO₂)
- Ethanol
- Energy
The rate of respiration is affected by temperature, as enzymes control the process.
Basic Experiment Setup
Aim:
To observe how temperature affects the rate of respiration in yeast.
Materials:
- Yeast suspension
- Sugar solution (glucose)
- Water bath
- Test tubes + delivery tube + gas syringe or inverted measuring cylinder
- Thermometer
- Timer
Method (summary):
- Mix yeast with glucose solution.
- Place in a water bath at a specific temperature (e.g., 20°C, 30°C, 40°C…).
- Measure the volume of CO₂ produced over time (e.g., per minute).
- Repeat for different temperatures.
Effect of Temperature
| Temperature (°C) | Effect on Respiration Rate |
|---|---|
| Low (e.g., 10–20°C) | Slow enzyme activity → low respiration rate |
| Optimum (~30–40°C) | Enzymes work fastest → highest rate of respiration |
| High (>45°C) | Enzymes start to denature → respiration slows down |
| Very high (>60°C) | Enzymes denature completely → respiration stops |
Explanation:
Respiration in yeast is controlled by enzymes.
As temperature increases:
- Kinetic energy increases → enzymes and substrates collide more often.
- Respiration rate increases until enzymes reach optimum temperature.
Beyond the optimum:
- Enzymes denature (lose shape) → rate rapidly drops.
Temperature directly affects the rate of yeast respiration.
There’s an optimum temperature (usually around 37°C).
Too low = slow reactions; too high = enzyme damage.