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Cell Biology - Organelles and their Functions

Grade 6IB

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

🔑Concepts

The Cell Theory states that all living organisms are made of cells, and the cell is the basic unit of life.

The Nucleus acts as the control center of the cell and contains genetic material in the form of DNADNA (Deoxyribonucleic acid).

Mitochondria are known as the 'powerhouse' of the cell where aerobic respiration occurs to produce energy in the form of ATPATP.

Chloroplasts are found only in plant cells and some protists; they contain chlorophyll and are the site of photosynthesis where C6H12O6C_6H_{12}O_6 (glucose) is produced.

The Cell Membrane is a semi-permeable lipid bilayer that controls the movement of substances like H2OH_2O, O2O_2, and CO2CO_2 in and out of the cell.

The Cell Wall is a rigid outer layer made of cellulose, providing structural support to plant cells; it is absent in animal cells.

Ribosomes are small organelles responsible for protein synthesis.

Vacuoles store nutrients and waste products. Plant cells typically have one large central vacuole that maintains turgor pressure using H2OH_2O.

📐Formulae

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

Actual Size=Image SizeMagnification\text{Actual Size} = \frac{\text{Image Size}}{\text{Magnification}}

6CO2+6H2Olight energyC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light energy}} C_6H_{12}O_6 + 6O_2

C6H12O6+6O26CO2+6H2O+Energy (ATP)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}

💡Examples

Problem 1:

A student observes a plant cell under a microscope. The image size of a chloroplast is measured to be 5 mm5\text{ mm}, and the magnification used is 1000×1000\times. Calculate the actual size of the chloroplast in micrometers (μm\mu m).

Solution:

Actual Size=5 mm1000=0.005 mm=5μm\text{Actual Size} = \frac{5\text{ mm}}{1000} = 0.005\text{ mm} = 5\mu m

Explanation:

Using the magnification formula, we divide the image size by the magnification. Since 1 mm=1000μm1\text{ mm} = 1000\mu m, we convert the result to get the final answer in the correct unit.

Problem 2:

Identify which organelle would be most abundant in a muscle cell that requires a high amount of energy to function.

Solution:

The Mitochondria.

Explanation:

Mitochondria are responsible for cellular respiration, represented by the equation C6H12O6+6O26CO2+6H2O+ATPC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}. Since muscle cells require significant energy for contraction, they contain a higher density of mitochondria compared to other cells.

Organelles and their Functions - Revision Notes & Key Formulas | IB Grade 6 Science