Questions and Answers
Which of the following is TRUE about passive transport?
What are two pathways for passing through the cell membrane by simple diffusion?
Diffusion through lipid bilayer and diffusion through protein channels
Passive diffusion requires energy to occur.
False
Which of the following substances can pass through the cell membrane via simple diffusion through the lipid bilayer?
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Name one macromolecule transport method.
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Study Notes
Transport across Cell Membrane
- Transport mechanisms for molecules are categorized into small (micro) and large (macromolecules).
Transport of Small Molecules
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Passive Transport:
- No energy required for movement across the cell membrane.
a- Passive Diffusion
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Involves movement of molecules from high to low concentration.
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Simple Diffusion:
- Molecules passively traverse the cell membrane through two main pathways:
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Diffusion through Lipid Bilayer:
- Lipid-soluble substances can easily dissolve in the bilayer, e.g., ( O_2 ), ( N_2 ), and alcohols.
- Water also diffuses due to its small molecular size and high kinetic energy.
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Diffusion through Protein Channels:
- Charged particles, such as ( Na^+ ) and ( K^+ ), move through specialized protein channels.
- Larger molecules like glucose cannot pass through the lipid bilayer without assistance.
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Diffusion through Lipid Bilayer:
- Molecules passively traverse the cell membrane through two main pathways:
Active Transport
- Requires energy (usually ATP) to move substances against their concentration gradient.
Transport of Large Molecules
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Large molecules and particles are transported via bulk transport mechanisms.
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Endocytosis:
- Process of engulfing substances into the cell by wrapping them in the membrane.
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Exocytosis:
- Mechanism for expelling materials from the cell by vesicle fusion with the plasma membrane.
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Description
Explore the mechanisms of transport across cell membranes in this quiz, which covers both small and large molecules. Learn about passive and active transport processes, including simple diffusion, facilitated diffusion, endocytosis, and exocytosis. Test your understanding of key concepts in cell biology.
