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Cause and Effect — Water Movement and Cell Shape
A cell is placed in a solution
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Cause
Water concentration differs across the selectively permeable membrane.
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Process
Osmosis moves water in or out of the cell.
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Effect
In weak solution the cell swells; in strong solution it shrinks.
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A plant cell keeps shape because of its rigid wall
Mind Map
Cell
The unit of life
2.1
How to Study Cells
Limit of resolution; magnification; light and electron microscopes.
2.2
Structure of a Cell
Membrane; cell wall; osmosis; diffusion; fluid-mosaic model.
2.3
The Cell Interior
Nucleus; organelles; prokaryotic and eukaryotic cells.
2.4
Growth and Division
Cell division; mitosis; meiosis; the cell cycle.
2.5
Cell Theory
Schleiden, Schwann, Virchow; contact inhibition; tumours.
Key Terms and Definitions
- Cell
- The basic unit of structure and function in all living organisms.
- Limit of resolution
- The smallest distance at which two points look separate (0.1 mm for the eye).
- Magnification
- Making a small object appear larger using lenses.
- Cell membrane
- The thin, selectively permeable boundary around a cell.
- Diffusion
- Net movement of particles from higher to lower concentration.
- Osmosis
- Diffusion of water across a selectively permeable membrane.
- Cell wall
- A rigid outer layer in plant, fungal and bacterial cells.
- Cytoplasm
- The semi-fluid, jelly-like substance filling the cell.
- Organelle
- A tiny part inside the cytoplasm, each with a special job.
- Prokaryotic cell
- A cell with no well-defined nucleus or membrane-bound organelles.
- Eukaryotic cell
- A cell with a well-defined nucleus and membrane-bound organelles.
- Nucleus
- The control centre of the cell that holds the DNA.
- Mitochondria
- Double-membrane organelles that release energy as ATP.
- Plastids
- Plant organelles for food synthesis and storage.
- Vacuole
- A sap-filled sac that stores materials and keeps a plant cell firm.
- Mitosis
- Division giving two genetically identical daughter cells.
- Meiosis
- Two-step division giving four cells with half the chromosomes.
- Cell Theory
- All organisms are made of cells, which arise from existing cells.
- Contact inhibition
- Animal cells stop dividing when they touch their neighbours.
