Introduction
Fluid Movement Inside and Outside of the cell:
The cell membrane controls what enters or exits the cell. The cell membrane is called a selectively permeable membrane because only certain particles can pass through it.
Permeable means "let through." Impermeable means "not let through".
Osmosis is a type of diffusion that involves water. It is defined as the diffusion of water across a selectively permeable membrane from an area of higher concentration to an area of lower concentration (or higher solute concentration). Plasmolysis is the process of osmosis in plants. Adding a high concentration of minerals (ie salt or sugar solution) to the plants will cause the plant cells to shrink and this is referred to as Plasmolysis. A high concentration of minerals (ie salt), acts as a poison to most plants and stops photosynthesis.
Vocabulary:
Plasmolysis: the shrinking of protoplasm and vacuole (cytoplasm+nucleus) away from the cell wall of a plant cell.
Solution: A solution is a homogeneous (blends together) mixture of two or more substances.
Solute: A solution consists of a solute and a solvent. The solute (salt) is the substance that is dissolved in the solvent (water).
Concentration Gradient: when molecules of a solute or solvent are concentrated in one area.
Concentration: refers to how much of a solute or solvent.
Let's check some questions to activate prior knowledge :
Task
Let's recall what we studied before this and in chapter 5:
What are the structures found in plant cells, but not in animal cells?
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Chloroplast, Cell Wall, and a large Vacuole
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Chloroplast, Cell Wall, and Mitochondria
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Chloroplast, Nucleus
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Nucleus, Mitochondria
Which cell structure is responsible for controlling which molecules enter or leave the cell?
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Chloroplast
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Cell Wall
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Nucleus
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Cell Membrane
The movement of water from the level of higher concentration to an area of lower concentration is called___
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Diffusion
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Osmosis
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Concentration Gradient
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None of the above
Process
OSMOSIS IN CELLS:
Sugars, salts, and proteins are common solutes in cells. Water is the solvent. When water moves into or out of a cell, the concentration of the solution inside the cell changes.
Water moves from where it is more concentrated. If there is a lower concentration of water inside the cell than outside the cell, the water moves into the
Let's have a look at the following video in detail on how passive fluid movement (Diffusion and Osmosis) across the cell membrane occurs.
What happens when we place a plant cell in different types of solutions?
By examining the diagram, match the solution with its resulting cell type:
|
Solution |
Effects of Solution on cell |
|
a. Turgid Cell |
|
b. Flaccid Cell |
|
c. Plasmolysed Cell |
Evaluation
Let's check what we studied:
The movement of water from the level of higher concentration to an area of lower concentration is called___
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Diffusion
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Osmosis
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Active transport
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Hydrolysis
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Phagocytosis
More salty water is which type of solution?
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Hypotonic
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Hypertonic
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Isotonic
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Neutral
What will happen when we will place a plant cell in a hypertonic solution?
The cell will become plasmolyzed.
1. True
2. False
Which of the following helps plants stand up?
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Lysosomes
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Cell Wall
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Turgor pressure
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Cell Membrane
Conclusion
In conclusion, the cell membrane controls the materials and fluid movement inside the cell or outside the cell. It works like a security guard that allows some and does not allow others who are not able to cross it.
Fluid movement across the cell membrane is essential to keep the net balance ultimately to achieve normal Cell Homeostasis.
God / Mother nature has created cells physiology of living things in such a way that they tend to maintain a stable cell controlled environment.
Let's have a look at chapter 5 through this video:
Why passive (diffusion and Osmosis) and active transport (Facilitated diffusion, Endocytosis and Exocytosis) of materials through the cell membranes is crucial for living things?