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Cells and Life Processes - Specialized Cells

Grade 7IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Cell Differentiation: The process by which unspecialized cells (stem cells) undergo structural changes to perform specific functions within an organism.

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Red Blood Cells (Erythrocytes): Highly specialized for transporting oxygen. They have a biconcave shape to increase the surface area to volume ratio (SAV\frac{SA}{V}), contain hemoglobin (HbHb), and lack a nucleus to maximize space for oxygen carrying.

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Nerve Cells (Neurons): Adapted for rapid communication. They possess long axons to carry electrical impulses over long distances and branched dendrites to connect with other neuronsneurons.

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Sperm Cells: Specialized for reproduction. They feature a tail (flagellum) for movement, a midpiece packed with mitochondria to produce energy (ATPATP), and an acrosome containing enzymes to penetrate the egg.

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Root Hair Cells: Specialized plant cells for absorbing water (H2OH_2O) and mineral ions. They have long protrusions that significantly increase the surface area for osmosis and active transport.

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Palisade Mesophyll Cells: Located in leaves, these cells are packed with chloroplasts to maximize the rate of photosynthesis, converting light energy into chemical energy (C6H12O6C_6H_{12}O_6).

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Ciliated Epithelial Cells: Found in the respiratory tract; they have hair-like projections called cilia that move in a coordinated wave to push mucus and trapped dust/pathogens out of the lungs.

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Xylem Vessels: Specialized for water transport in plants. They are hollow, dead tubes reinforced with lignin to withstand the pressurepressure of water moving upwards.

📐Formulae

Magnification=Size of ImageActual Size of Object\text{Magnification} = \frac{\text{Size of Image}}{\text{Actual Size of Object}}

Total Magnification=Magnification of Eyepiece×Magnification of Objective Lens\text{Total Magnification} = \text{Magnification of Eyepiece} \times \text{Magnification of Objective Lens}

Surface Area to Volume Ratio=Surface AreaVolume\text{Surface Area to Volume Ratio} = \frac{\text{Surface Area}}{\text{Volume}}

💡Examples

Problem 1:

A student views a specialized root hair cell under a microscope. The image of the cell is 40 mm40\text{ mm} long. If the actual size of the cell is 0.2 mm0.2\text{ mm}, calculate the magnification used.

Solution:

Magnification=40 mm0.2 mm=200×\text{Magnification} = \frac{40\text{ mm}}{0.2\text{ mm}} = 200\times

Explanation:

To find the magnification, divide the measured image size by the known actual size. Ensure both values are in the same units (mm).

Problem 2:

Explain how the structure of a Red Blood Cell relates to the transport of Oxygen (O2O_2).

Solution:

The Red Blood Cell contains hemoglobin (HbHb), which chemically binds to O2O_2. The absence of a nucleus allows for a higher concentration of HbHb. The biconcave shape increases the SAV\frac{SA}{V}, allowing O2O_2 to diffuse more rapidly across the membrane.

Explanation:

Specialization involves structural adaptations (no nucleus, biconcave shape) that enhance a specific biological function (gas transport).

Problem 3:

Calculate the actual width of a chloroplast in a palisade cell if the image width is 5 mm5\text{ mm} and the magnification is 2000×2000\times. Give your answer in micrometers (μm\mu m).

Solution:

Actual Size=Image SizeMagnification=5 mm2000=0.0025 mm\text{Actual Size} = \frac{\text{Image Size}}{\text{Magnification}} = \frac{5\text{ mm}}{2000} = 0.0025\text{ mm} Converting to micrometers: 0.0025 mm×1000=2.5 μm0.0025\text{ mm} \times 1000 = 2.5\text{ }\mu m

Explanation:

First, rearrange the magnification formula to solve for actual size. Then, convert millimeters to micrometers by multiplying by 10310^3 because 1 mm=1000 μm1\text{ mm} = 1000\text{ }\mu m.

Specialized Cells - Revision Notes & Key Formulas | IB Grade 7 Science