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Learn: Membrane Structure and Transport
Edexcel A Level Biology SNAB A
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Welcome!Today we'll explore membrane structure and transport mechanisms. These processes are key to understanding how substances move in and out of cells.
What is the Cell Membrane?The cell membrane is a thin barrier surrounding cells, made of a phospholipid bilayer. It controls what enters and exits the cell, maintaining internal balance (homeostasis).
Phospholipid BilayerThe phospholipid bilayer is made of two layers of phospholipids. Each phospholipid has a hydrophilic (water-loving) head and hydrophobic (water-hating) tails. This structure allows the membrane to be selectively permeable.
Quick check: What is the main role of the cell membrane?
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Transport MechanismsSubstances move through the cell membrane by diffusion, osmosis, and active transport. Each process works differently depending on the type of substance and energy requirements.
DiffusionDiffusion is the movement of particles from an area of high concentration to low concentration. It does not require energy and happens naturally, like perfume spreading in a room.
Diffusion moves particles from {{blank0}} concentration to {{blank1}} concentration.
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OsmosisOsmosis is the diffusion of water across a semi-permeable membrane from a region of high water concentration to low water concentration. It balances water levels in cells.
Which statement best describes osmosis?
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Active TransportActive transport moves substances against their concentration gradient (low to high concentration). This process requires energy (ATP) and involves transport proteins.
Which of the following are features of active transport? (Select all that apply)
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Review Time!Great work! You've learned about membrane structure, diffusion, osmosis, and active transport. Now, let's review these concepts with some questions.
Match the items on the left with their correct pairs on the right
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The cell membrane is made of a {{blank0}} bilayer, with hydrophilic heads and hydrophobic tails.
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Which process moves substances against their concentration gradient?
Start the lesson to answer this multiple choice question
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