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Biology - Cell Biology (Structure, Transport, and Division)

Grade 10IB

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

🔑Concepts

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Cell Theory: All living organisms are composed of one or more cells, the cell is the basic unit of life, and cells arise from pre-existing cells.

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Prokaryotic vs. Eukaryotic: Prokaryotic cells (e.g., bacteria) lack a nucleus and membrane-bound organelles, whereas Eukaryotic cells (plant and animal) contain a nucleus and specialized organelles like mitochondria for ATPATP production.

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Surface Area to Volume Ratio (SA:VSA:V): As a cell increases in size, its volume increases faster than its surface area. A high SA:VSA:V ratio is essential for efficient diffusion and heat loss.

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Cell Membrane Structure: The fluid mosaic model describes a phospholipid bilayer with embedded proteins. Phospholipids have a hydrophilic (polar) head and two hydrophobic (non-polar) hydrocarbon tails.

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Passive Transport: The movement of substances across the membrane without energy expenditure. This includes simple diffusion, facilitated diffusion (via channel proteins), and osmosis (the movement of H2OH_2O molecules).

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Active Transport: The movement of substances against a concentration gradient (from low to high concentration) using energy in the form of ATPATP and protein pumps, such as the Na+/K+Na^+/K^+ pump.

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The Cell Cycle: Consists of Interphase (G1,S,G2G_1, S, G_2 phases) and the MM phase (Mitosis and Cytokinesis). DNA replication occurs during the SS phase.

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Mitosis: Nuclear division that produces two genetically identical diploid (2n2n) daughter cells. The stages are Prophase, Metaphase, Anaphase, and Telophase (PMATPMAT).

📐Formulae

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

I=A×MI = A \times M

Surface Area of a Cube=6s2\text{Surface Area of a Cube} = 6s^2

Volume of a Cube=s3\text{Volume of a Cube} = s^3

Percentage Change=Final Value−Initial ValueInitial Value×100\text{Percentage Change} = \frac{\text{Final Value} - \text{Initial Value}}{\text{Initial Value}} \times 100

💡Examples

Problem 1:

An image of a mitochondrion in a textbook is 35 mm35\text{ mm} long. The actual length of the mitochondrion is 5 \mum5\text{ \mu m}. Calculate the magnification of the image.

Solution:

M=35,000 \mum5 \mum=7000×M = \frac{35,000\text{ \mu m}}{5\text{ \mu m}} = 7000\times

Explanation:

First, convert the image size from millimeters to micrometers so the units are consistent: 35 mm×1000=35,000 \mum35\text{ mm} \times 1000 = 35,000\text{ \mu m}. Then apply the formula M=IAM = \frac{I}{A}.

Problem 2:

A dialysis tube containing a 10%10\% glucose solution is placed in a beaker of 5%5\% glucose solution. Describe the net movement of water molecules.

Solution:

Water will move into the dialysis tube via osmosis.

Explanation:

The 10%10\% solution is hypertonic (lower water potential) compared to the 5%5\% solution (higher water potential). Water moves from a region of higher water potential to a region of lower water potential across a semi-permeable membrane.

Problem 3:

If a parent cell has 2n=462n = 46 chromosomes, how many chromosomes and chromatids will be present in each daughter cell following Mitosis?

Solution:

Each daughter cell will have 4646 chromosomes and 4646 chromatids.

Explanation:

Mitosis is an equational division. During the SS phase, DNA replicates to form 9292 chromatids (4646 pairs). During Anaphase, sister chromatids separate, resulting in two identical nuclei each containing 4646 individual chromosomes.