CIE iGCSE Biology-3.3 Active transport- Study Notes- New Syllabus
CIE iGCSE Biology-3.3 Active transport- Study Notes – New syllabus
CIE iGCSE Biology-3.3 Active transport- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.
Supplement
- Explain the importance of active transport as a process for movement of molecules or ions across membranes, including ion uptake by root hairs.
- State that protein carriers move molecules or ions across a membrane during active transport.
Active Transport
🧠 Key Definition
Active transport is the movement of substances through a cell membrane from a region of lower concentration to a region of higher concentration, using energy from respiration. This process goes against the concentration gradient.
🔬 How Active Transport Works
- Unlike diffusion or osmosis, active transport requires energy (ATP).
- ATP is used to move particles from low to high concentration.
- Carrier proteins in the cell membrane perform this task.
📌 Key Features
| Feature | Description |
|---|---|
| Direction | Low → High concentration |
| Requires energy | Yes – from respiration (ATP) |
| Uses membrane proteins | Yes – carrier/transport proteins |
| Examples | Mineral ion uptake, glucose absorption |
🌱 Examples in Living Organisms
- Plants (Roots): Root hair cells actively absorb mineral ions (like nitrates) from the soil, even when their concentration is low.
- Animals (Small Intestine): After digestion, glucose is absorbed into the blood by active transport, even if glucose is already higher in the bloodstream.
🧪 Carrier Proteins in Action
Carrier proteins in the membrane are specific to certain substances.
They bind to particles and use ATP to change shape.
This allows the substance to be pushed against the concentration gradient.
⚠️ Why Active Transport Is Important
| Function | Why It Matters |
|---|---|
| Absorption of nutrients | Ensures complete absorption of glucose and amino acids even when their concentration is higher in the blood/gut |
| Uptake of minerals in plants | Plants can survive in nutrient-poor soils by absorbing scarce minerals |
| Nerve and muscle cell function | Maintains proper ion balance for impulses and muscle contraction |
Importance of Active Transport in Living Organisms
What Is Active Transport?
It works against the concentration gradient, unlike diffusion.
🌱 Importance in Plants: Ion Uptake by Root Hair Cells
- Soil has very low concentrations of minerals like nitrates, magnesium, and potassium.
- The inside of root cells already has a higher concentration of these ions.
- So, ions cannot enter by diffusion – they are absorbed by active transport.
Root hair cells use energy from respiration to actively transport mineral ions, which are essential for:
- Magnesium → Chlorophyll production
- Nitrates → Protein synthesis
- Overall → Healthy plant growth
Importance in Animals
| Function | Why Active Transport Is Needed |
|---|---|
| Glucose absorption (intestines) | Absorbs glucose into the blood even when blood glucose is already high — no glucose is wasted after digestion. |
| Reabsorption in kidneys | Recovers useful substances (e.g. glucose, salts) from urine back into the blood. |
| Nerve & muscle function | Maintains sodium/potassium balance for proper nerve impulses and muscle contractions. |
⚙️ Energy Requirement
Active transport uses energy in the form of ATP from aerobic respiration.
Cells that do a lot of active transport have many mitochondria (e.g. root hair cells, intestinal lining cells).
📌 Summary Points
- Active transport enables absorption of essential substances even when external concentration is low.
- It is vital for nutrient uptake, waste removal, and ion balance.
- Without it, plants can’t absorb minerals, and animals can’t fully absorb or regulate vital molecules.
Protein Carriers in Active Transport
Key Statement:
Protein carriers move molecules or ions across a membrane during active transport, using energy from respiration (ATP).
🧠 What Does This Mean?
- The cell membrane contains special carrier proteins.
- These act as molecular pumps for specific substances (e.g. ions, glucose).
- They push particles from low to high concentration (against the gradient).
- This requires energy from ATP (made during respiration).
🔬 How It Works – Step-by-Step
- The carrier protein binds to a specific molecule or ion on one side of the membrane.
- ATP provides energy, causing the protein to change shape.
- The substance is transported across the membrane and released on the other side.
- The carrier protein returns to its original shape, ready for reuse.
🧪 Real-Life Examples
- Small Intestine: Carrier proteins absorb glucose into the bloodstream, even when blood already has a high concentration.
- Root Hair Cells: Nitrate ions are pumped from the soil into plant roots against the concentration gradient.
📌 Summary Table
| Feature | Description |
|---|---|
| Structure | Specific carrier proteins in the membrane |
| Function | Move substances against the gradient |
| Energy used? | Yes – from ATP |
| Direction | Low → High concentration |