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Questions and Answers
Which type of molecule is least likely to diffuse freely through the phospholipid bilayer?
Which type of molecule is least likely to diffuse freely through the phospholipid bilayer?
- Oxygen
- Water
- Small uncharged molecules
- Glucose (correct)
What differentiates facilitated diffusion from simple diffusion?
What differentiates facilitated diffusion from simple diffusion?
- Facilitated diffusion can transport any type of molecule.
- Facilitated diffusion is limited to ions only.
- Facilitated diffusion requires energy.
- Facilitated diffusion occurs through protein channels. (correct)
In the context of osmosis, water moves towards areas of:
In the context of osmosis, water moves towards areas of:
- Low water potential.
- Equal distribution of solute.
- High concentration of water molecules.
- High concentration of solute. (correct)
Which of the following statements about passive transport is accurate?
Which of the following statements about passive transport is accurate?
Which statement correctly describes simple diffusion?
Which statement correctly describes simple diffusion?
Which of the following molecules would require facilitated diffusion to cross the phospholipid bilayer?
Which of the following molecules would require facilitated diffusion to cross the phospholipid bilayer?
What is the role of aquaporins in osmosis?
What is the role of aquaporins in osmosis?
Which of the following statements about membrane transport is false?
Which of the following statements about membrane transport is false?
What happens to a cell when it is placed in a hypertonic solution?
What happens to a cell when it is placed in a hypertonic solution?
How do protein pumps, such as the sodium-potassium pump, function in membrane transport?
How do protein pumps, such as the sodium-potassium pump, function in membrane transport?
Which solution causes a cell to swell and potentially burst?
Which solution causes a cell to swell and potentially burst?
What is an example of a bulk transport mechanism?
What is an example of a bulk transport mechanism?
What type of solution surrounds body cells if it is described as isotonic?
What type of solution surrounds body cells if it is described as isotonic?
Which of the following accurately describes passive transport mechanisms?
Which of the following accurately describes passive transport mechanisms?
What is the primary purpose of active transport in cellular processes?
What is the primary purpose of active transport in cellular processes?
The diffusion of water across a semi-permeable membrane is called what?
The diffusion of water across a semi-permeable membrane is called what?
What is the primary component responsible for the hydrophilic nature of a phospholipid?
What is the primary component responsible for the hydrophilic nature of a phospholipid?
Which type of transport does NOT require ATP?
Which type of transport does NOT require ATP?
What essential function is directly supported by the plasma membrane?
What essential function is directly supported by the plasma membrane?
Which statement describes simple diffusion?
Which statement describes simple diffusion?
What role do membrane proteins play in the context of the cell membrane?
What role do membrane proteins play in the context of the cell membrane?
What characteristic distinguishes active transport from passive transport mechanisms?
What characteristic distinguishes active transport from passive transport mechanisms?
How do prokaryotes differ from animal eukaryotes in terms of membrane structure?
How do prokaryotes differ from animal eukaryotes in terms of membrane structure?
In facilitated diffusion, what is the role of facilitator molecules?
In facilitated diffusion, what is the role of facilitator molecules?
What is the role of pseudopodia in phagocytosis?
What is the role of pseudopodia in phagocytosis?
Which type of endocytosis is characterized by the non-specific uptake of fluids?
Which type of endocytosis is characterized by the non-specific uptake of fluids?
In receptor-mediated endocytosis, which protein is commonly associated with the coated pits?
In receptor-mediated endocytosis, which protein is commonly associated with the coated pits?
What distinguishes phagocytosis from other types of endocytosis?
What distinguishes phagocytosis from other types of endocytosis?
What is the primary function of exocytosis?
What is the primary function of exocytosis?
How does endocytosis differ from active transport?
How does endocytosis differ from active transport?
Which of the following statements is accurate regarding bulk transport mechanisms?
Which of the following statements is accurate regarding bulk transport mechanisms?
What characteristic defines receptor-mediated endocytosis?
What characteristic defines receptor-mediated endocytosis?
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Study Notes
Osmosis and Mechanisms of Membrane Transport
- Osmosis is the diffusion of water across a selectively permeable membrane from a region of high water potential to low water potential.
- Hypertonic solutions have a higher solute concentration than the cell's cytoplasm; cells placed in these solutions lose water and shrink.
- Hypotonic solutions have a lower solute concentration; cells in these solutions gain water, swell, and may burst.
- Isotonic solutions have equal solute concentrations; water moves in and out of cells at an equal rate, maintaining cell volume.
Types of Membrane Transport
- Passive transport does not require ATP; molecules move along their concentration gradient.
- Active transport requires ATP to move molecules against their concentration gradient.
Passive Transport Mechanisms
- Diffusion: Movement of particles from high to low concentration without energy.
- Simple Diffusion: Small uncharged molecules like oxygen, carbon dioxide, and water can pass directly through the phospholipid bilayer.
- Facilitated Diffusion: Larger or charged molecules, such as glucose and ions, require transmembrane proteins to cross the membrane without energy.
Active Transport Mechanisms
- Protein Pumps: Transmembrane proteins that use ATP to transport ions and solutes against their concentration gradient. Types include uniport, symport, and antiport.
- Sodium-Potassium Pump: A specific antiport that actively exchanges Na+ out of the cell and K+ into the cell.
Bulk Transport Methods
- Endocytosis: Process of internalizing substances into the cell by engulfing them in the membrane to form vesicles.
- Phagocytosis: Engulfing large particles (e.g., bacteria) for immune defense, involving extensions called pseudopodia.
- Pinocytosis: Uptake of extracellular fluid and nutrients; the cell membrane invaginates and forms vesicles.
- Receptor-Mediated Endocytosis: Specific uptake of target substances through receptors clustered in coated pits.
Structural Components of Cell Membrane
- Composed of a phospholipid bilayer, proteins, and cholesterol, according to the fluid mosaic model.
- Phospholipids have hydrophilic (water-attracting) phosphate heads and hydrophobic (water-repelling) fatty acid tails.
Homeostasis Maintenance
- The cell membrane regulates internal conditions, such as pH, temperature, glucose levels, and water balance, ensuring a stable internal environment.
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