Why Cells Have Different Numbers of Mitochondria A Level Biology

Описание: In this video, we explain important A Level / O Level Biology exam questions related to mitochondria numbers in different cells and a comparison between yeast cells and bacterial cells.

These questions are very common in MCQs, structured questions, and data-handling questions.

🔬 Part 1: Differences in the Number of Mitochondria in Cells
📊 Data Interpretation from a Bar Chart

We analyze a bar chart showing the average number of mitochondria per cell:

❤️ Heart muscle cells → ~1500 mitochondria

🩸 Mature red blood cells → 0 mitochondria

🍽 Small intestine epithelial cells → ~1600 mitochondria

⚡ Why Heart Muscle Cells Have Many Mitochondria

Heart muscle contracts continuously throughout life

Requires a constant supply of ATP

Mitochondria are the site of aerobic respiration
✔ Therefore, heart muscle cells contain many mitochondria to meet high energy demands

🚫 Why Mature Red Blood Cells Have No Mitochondria

Main function: oxygen transport

No mitochondria means:

✔ More space for haemoglobin

✔ Oxygen is not used up for respiration
📌 This adaptation increases oxygen delivery to tissues

🔁 Why Small Intestine Epithelial Cells Have Many Mitochondria

Involved in active transport of nutrients

Active transport requires ATP

ATP is produced by mitochondria
✔ Hence, these cells contain large numbers of mitochondria

🧫 Part 2: Similarities & Differences Between Yeast Cell and Bacterial Cell
✅ Similarities (Very Common MCQ Topic)

Both yeast and bacterial cells have:

Cell membrane

Cell wall

Cytoplasm

Ribosomes

❌ Key Differences (Eukaryotic vs Prokaryotic)
Feature Yeast Cell Bacterial Cell
Nucleus Present Absent
DNA Linear chromosomes Circular DNA
Organelles Present (e.g. mitochondria) Absent
Size Larger Smaller
Reproduction Budding Binary fission

📌 Yeast = eukaryotic
📌 Bacteria = prokaryotic

🎓 Learning Outcomes

After watching this video, students will be able to:
✔ Explain why cells have different numbers of mitochondria
✔ Interpret bar charts confidently
✔ Compare yeast and bacterial cells accurately
✔ Avoid common exam mistakes
✔ Write full-mark biological explanations

📚 Helpful For

A Level Biology students

O Level / IGCSE Biology students

MCQ & structured question practice

Data-based biology questions

Exam revision & concept clarity

🔍 What Students Commonly Search For

Why red blood cells have no mitochondria

Heart muscle mitochondria explanation

Yeast vs bacterial cell differences

Prokaryotic vs eukaryotic cells

A level biology cell structure questions

❌ Common Student Mistakes

Saying RBCs have mitochondria

Forgetting ATP link with mitochondria

Mixing yeast and bacterial cell features

Writing vague explanations without function

💡 Exam Tip

🔑 More energy demand = more mitochondria
🔑 If the cell transports oxygen → no mitochondria

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A Level Biology
Mitochondria
Red blood cell
Heart muscle cell
Yeast vs bacteria
Cell structure biology
Prokaryotic vs eukaryotic
Biology past papers