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Cell Biology - Cell Theory

Grade 6IB

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

🔑Concepts

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Cells are the basic structural and functional units of all living organisms.

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The Cell Theory states that all living things are composed of one or more cells.

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New cells are produced only from existing cells through the process of cell division.

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Cells contain hereditary information (DNADNA) which is passed from 'parent' cells to 'daughter' cells during division.

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Energy flow, known as metabolism (such as respiration), occurs within cells to sustain life.

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Organisms can be unicellular (consisting of a single cell, like bacteria) or multicellular (consisting of many specialized cells, like humans).

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Biological measurements for cells are typically expressed in micrometers (μm\mu m) or nanometers (nmnm).

📐Formulae

Magnification(M)=Image size(I)Actual size(A)\text{Magnification} (M) = \frac{\text{Image size} (I)}{\text{Actual size} (A)}

Actual size(A)=Image size(I)Magnification(M)\text{Actual size} (A) = \frac{\text{Image size} (I)}{\text{Magnification} (M)}

1mm=103μm=1000μm1 mm = 10^3 \mu m = 1000 \mu m

1μm=103nm=1000nm1 \mu m = 10^3 nm = 1000 nm

💡Examples

Problem 1:

A student views a cheek cell under a microscope. The image of the cell measures 40mm40 mm in width. The microscope magnification is set to ×400\times 400. Calculate the actual width of the cell in micrometers (μm\mu m).

Solution:

A=IM=40mm400=0.1mmA = \frac{I}{M} = \frac{40 mm}{400} = 0.1 mm. Convert to μm\mu m: 0.1×1000=100μm0.1 \times 1000 = 100 \mu m.

Explanation:

First, use the formula for actual size (A=I/MA = I/M). Then, convert the result from millimeters (mmmm) to micrometers (μm\mu m) by multiplying by 10001000.

Problem 2:

A mitochondrion has an actual length of 2μm2 \mu m. If it is drawn with a magnification of ×5000\times 5000, how long will the drawing be in millimeters (mmmm)?

Solution:

I=A×M=2μm×5000=10,000μmI = A \times M = 2 \mu m \times 5000 = 10,000 \mu m. Convert to mmmm: 10,0001000=10mm\frac{10,000}{1000} = 10 mm.

Explanation:

To find the image/drawing size, multiply the actual size by the magnification. Since the question asks for millimeters, divide the result in μm\mu m by 10001000.

Cell Theory - Revision Notes & Key Formulas | IB Grade 6 Science