IB MYP 4-5 Biology-Structure and Function- Study Notes - New Syllabus
IB MYP 4-5 Biology-Structure and Function- Study Notess- Study Notes – New syllabus
IB MYP 4-5 Biology-Structure and Function- Study Notes – IB MYP 4-5 Biology – per latest IB MYP Biology Syllabus.
Key Concepts:
- Adaptations of specialized cells (e.g., sperm, red blood cells, palisade cells).
- Surface-area-to-volume ratio (e.g., alveoli, root hairs).
- Comparative anatomy (e.g., fish gills vs. mammalian lungs).
Adaptations of Specialized Cells
🌱 What Are Specialized Cells?
📌 Specialized cells have unique structures to perform specific tasks. This is called cellular differentiation.
- All specialized cells come from stem cells 🌱
- As they mature, they change shape, organelles, and structure to suit their job
💡Note: Differentiation = the process of becoming special!
📎 Quick Fact:
🧬 One stem cell can specialize into over 200 different types of cells!
🧬 One stem cell can specialize into over 200 different types of cells!
🔬 Why Do Cells Specialize?
- To perform their roles more efficiently
- To divide work in multicellular organisms
- To help the body function as one smart system
🔍 Examples of Specialized Cells
🧪 1. Sperm Cell
| Feature | Adaptation Function |
|---|---|
| Long tail (flagellum) | Helps the sperm swim to the egg |
| Many mitochondria | Provides energy (ATP) for movement |
| Streamlined head | Reduces resistance in fluid |
| Acrosome | Contains enzymes to break through egg membrane |
| Minimal cytoplasm | Makes the cell lightweight and faster |
✏️ Memory Trick: S.P.E.E.D. = Streamlined, Powered, Enzymes, Energy, Direction (tail)
💡Note:
Sperm cells carry only half the DNA (haploid) – so they can merge with the egg! 🧬
Sperm cells carry only half the DNA (haploid) – so they can merge with the egg! 🧬
❤️ 2. Red Blood Cell (RBC)
| Feature | Adaptation Function |
|---|---|
| Biconcave shape | Increases surface area for oxygen exchange |
| No nucleus | More space for hemoglobin |
| Hemoglobin | Binds to oxygen efficiently |
| Flexible and small | Moves through narrow capillaries easily |
💡 Did You Know? Red blood cells live for only ~120 days and are constantly recycled by the liver and spleen!
🌿 3. Palisade Mesophyll Cell
Palisade cells are just below the upper leaf surface – where sunlight hits first!
| Feature | Adaptation Function |
|---|---|
| Many chloroplasts | More photosynthesis can happen |
| Column-shaped cells | Maximize light absorption at leaf top |
| Thin walls | Short diffusion path for CO₂ |
| Large vacuole | Pushes chloroplasts toward cell edge |
🍃 Note: These cells are crucial for plant energy – thanks to photosynthesis magic!
✅ Quick Comparison
| Cell Type | Main Function | Key Adaptations |
|---|---|---|
| Sperm Cell | Fertilizes the egg | Tail, enzymes, mitochondria |
| Red Blood Cell | Transports oxygen | Biconcave, no nucleus, hemoglobin |
| Palisade Cell | Photosynthesis | Chloroplasts, shape, vacuole |
Surface Area-to-Volume Ratio (SA:V)
🔍 What Is Surface Area-to-Volume Ratio?
📌 It’s how much surface area an object has compared to its volume.
✏️ Formula: SA:V ratio = Surface Area / Volume
⚠️ As cells grow bigger, their volume increases faster than their surface area. That means:
- SA:V ratio decreases
- Exchange of materials becomes less efficient
💡Note:
Smaller objects (like cells) have higher SA:V, which is why they are better at diffusion!
Smaller objects (like cells) have higher SA:V, which is why they are better at diffusion!
🧠 Why Does SA:V Matter?
- Higher SA:V = faster diffusion of gases, nutrients, and waste
- Lower SA:V = slower transport, harder to stay efficient
- Structures that rely on diffusion need a high SA:V ratio
💡 Did You Know?
Your alveoli cover an area of ~70 m² – that’s the size of a tennis court! 🎾
Your alveoli cover an area of ~70 m² – that’s the size of a tennis court! 🎾
🌬️ Example 1: Alveoli (Lungs)
| Adaptation | Why It Helps |
|---|---|
| Millions of tiny alveoli | Huge combined surface area |
| Thin walls (1 cell thick) | Short diffusion distance |
| Moist lining | Gases dissolve and diffuse easily |
| Rich blood supply | Maintains concentration gradient |
✅ Result: Alveoli have a massive SA:V ratio, making gas exchange super-efficient!
🌱 Example 2: Root Hair Cells
| Adaptation | Why It Helps |
|---|---|
| Long, thin projection | Increases surface area |
| Many root hairs | Boost total SA even more |
| Thin cell wall | Speeds up diffusion/osmosis |
| Close to moist soil | Keeps water potential gradient high |
🌿 Result: Root hairs have high SA:V, so they absorb water and nutrients very efficiently!
📌 Fun Fact:
Just one tiny root can have thousands of these cells!
Just one tiny root can have thousands of these cells!
🧬 Example 3: Small Cells
- Cells stay small to keep their SA:V ratio high
- Big cells = slower material movement = inefficient
- Multicellular organisms evolve specialized exchange surfaces to overcome this
✏️ Memory Trick:
“Small cells = Smart cells”
Small size = big surface = fast exchange!
“Small cells = Smart cells”
Small size = big surface = fast exchange!
📊 Summary Table: SA:V in Action
| Structure | Function | How SA:V Helps |
|---|---|---|
| Alveoli | Gas exchange | High SA = faster diffusion |
| Root Hair Cells | Absorbs water/nutrients | More SA for osmosis/transport |
| Small Cells | All cell processes | Efficient diffusion of substances |
Comparative Anatomy: Fish Gills vs. Mammalian Lungs
🌬️ What Is Comparative Anatomy?
📌 Comparative anatomy is the study of how different organisms’ structures compare – often because of adaptations to their environments.
👉 Example: Fish gills vs. Mammalian lungs
Both perform gas exchange but differently based on where they live!
💡 Did You Know?
Countercurrent exchange lets fish absorb up to 80% of the oxygen in water — way more efficient than lungs!
Countercurrent exchange lets fish absorb up to 80% of the oxygen in water — way more efficient than lungs!
🐟 Fish Gills: Adapted for Life in Water
| Feature | How It Helps |
|---|---|
| Thin filaments with lamellae | Increase surface area for diffusion |
| Water constantly flows over gills | Maintains high oxygen gradient |
| Countercurrent flow | Blood & water move in opposite directions → maximizes oxygen absorption |
| Dense capillary network | Fast diffusion of oxygen in, CO₂ out |
➡️ Fish extract oxygen from water, which has less O₂ than air – so their gills must be highly efficient!
🫱 Mammalian Lungs: Adapted for Life in Air
| Feature | How It Helps |
|---|---|
| Millions of alveoli | Massive surface area for gas exchange |
| Thin alveolar walls | Short diffusion distance |
| Moist lining | Gases dissolve for easier diffusion |
| Surrounded by capillaries | Maintains oxygen gradient |
| Ventilation using muscles | Diaphragm + intercostal muscles move air in/out |
➡️ Because air has more oxygen than water, lungs are optimized for fast exchange + constant ventilation.
⚖️ Comparison Table: Gills vs. Lungs
| Feature | Fish Gills 🐟 | Mammalian Lungs 🫱 |
|---|---|---|
| Respiratory Medium | Water | Air |
| Exchange Surface | Gill lamellae | Alveoli |
| Surface Area | High | Very High |
| Ventilation Method | Buccal pumping or swimming | Diaphragm & muscles |
| Flow Direction | Countercurrent | Tidal (same direction) |
| Oxygen Concentration | Lower in water | Higher in air |
| Efficiency | Up to 80% | ~25% |
✏️ Memory Tip: 🔄 “Countercurrent = Clever”
Fish gills use opposite flows to absorb more oxygen!
Fish gills use opposite flows to absorb more oxygen!
💬 Summary:
- ✅ Both gills and lungs are adapted for efficient gas exchange
- 🐟 Gills work in water (low O₂, high resistance) → countercurrent flow
- 🫱 Lungs work in air (high O₂, easier to ventilate) → constant breathing
- 🎯 Same goal: keeping cells supplied with oxygen and removing carbon dioxide