Biology Osmosis and Cell Transport
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Questions and Answers

What is the primary function of the Na+-K+ pump?

  • Transport glucose into the cell
  • Assist in exocytosis
  • Facilitate osmosis
  • Maintain the electric gradient by pumping Na+ out and K+ in (correct)
  • An isotonic solution has an osmolarity higher than 300 mOsm/l.

    False

    Define phagocytosis.

    It is the uptake of large particles or bacteria by cells, commonly performed by leukocytes.

    The delivery of free energy for active transport comes from _____.

    <p>ATP</p> Signup and view all the answers

    Match the types of active transport with their definitions:

    <p>Primary active transport = Using ATP to pump ions directly against a gradient Secondary active transport = Using the gradient of one substance to transport another Exocytosis = Release of large molecules from a cell Endocytosis = Intake of large molecules or particles into a cell</p> Signup and view all the answers

    Which of the following describes facilitated diffusion?

    <p>Passive transport of larger molecules with the assistance of a protein carrier</p> Signup and view all the answers

    How many Na+ ions does the Na+-K+ pump transport out of the cell per cycle?

    <p>3</p> Signup and view all the answers

    Osmosis only involves the movement of solutes.

    <p>False</p> Signup and view all the answers

    What is the primary driver for filtration?

    <p>Pressure gradient of hydrostatic pressure</p> Signup and view all the answers

    Osmotic fragility refers to the resistance of red blood cells to hemolysis in hypotonic solutions.

    <p>True</p> Signup and view all the answers

    What is the normal resting membrane potential (RMP) of a typical cell?

    <p>It is negative, typically around -70 mV.</p> Signup and view all the answers

    The protein channels that selectively allow ions to pass are known as ______ channels.

    <p>ion selective</p> Signup and view all the answers

    Match the type of transport with its characteristic:

    <p>Active Transport = Requires energy from ATP Simple Diffusion = Movement along the concentration gradient Facilitated Diffusion = Utilizes a protein carrier Osmosis = Water movement across a semipermeable membrane</p> Signup and view all the answers

    What is the main factor affecting the rate of simple diffusion?

    <p>Concentration gradient</p> Signup and view all the answers

    Ligand-gated protein channels open when a hormone binds to them.

    <p>True</p> Signup and view all the answers

    Name one example of active transport mechanisms in cells.

    <p>Na-K pump</p> Signup and view all the answers

    What type of transport mechanism across the cell membrane does not require energy?

    <p>Facilitated diffusion</p> Signup and view all the answers

    The surface membrane of a cell is primarily composed of a phospholipid bilayer.

    <p>True</p> Signup and view all the answers

    What is the primary role of the semipermeability of the cell membrane?

    <p>To regulate the movement of substances in and out of the cell.</p> Signup and view all the answers

    ______ refers to the electrical potential difference across the cell membrane during rest.

    <p>Resting potential</p> Signup and view all the answers

    Match the following mechanisms with their description:

    <p>Passive transport = Movement of molecules without energy Active transport = Movement against a concentration gradient requiring energy Osmosis = Diffusion of water across a semipermeable membrane Facilitated diffusion = Transport of molecules across a membrane using carrier proteins</p> Signup and view all the answers

    Which of the following is NOT a typical sign of a living cell?

    <p>Inactivity</p> Signup and view all the answers

    Cholesterol is an essential component of the cell membrane, comprising about 5% of its composition.

    <p>True</p> Signup and view all the answers

    What is one of the effects of radiation in medicine?

    <p>It can be used for diagnosis and treatment of diseases.</p> Signup and view all the answers

    Study Notes

    Osmosis and Solutions

    • Water naturally moves to dilute more concentrated solutions, as per Van Hoff's Law.
    • Normal osmolarity: 300 mOsm/L is isotonic, equivalent to 0.9% NaCl or 5% glucose.
    • Hypotonic solutions have osmolarity below 0.9%, while hypertonic solutions exceed 0.9%.
    • Red blood cells (RBCs) can experience osmotic fragility, leading to hemolysis when exposed to different osmotic conditions.

    Active Membrane Transport

    • Active transport enables molecule movement against concentration or electric gradients, requiring ATP energy.
    • Primary active transport involves selective ion channels, such as the Na⁺-K⁺ pump, Ca²⁺-pump (in muscle cells), and H⁺ proton pump (in stomach cells).
    • Secondary active transport uses a carrier mechanism where substances (like glucose) bind to ions (e.g., Na⁺) for membrane transport.
    • Exocytosis releases molecules from cells, while endocytosis (including phagocytosis) allows uptake of larger molecules.

    Na⁺-K⁺ Pump

    • Na⁺-K⁺ pump (Na⁺-K⁺ ATP-ase) is located in the cell membrane and actively transports ions.
    • It moves 3 Na⁺ ions out and 2 K⁺ ions into the cell, vital for maintaining electric charge renewal across body cells.
    • The pump operates at a maximum capacity of 200 Na⁺ and 133 K⁺ ions per second and necessitates ATP for function.

    Resting Membrane Potential (RMP)

    • RMP measures the electrical difference between the positively charged extracellular space and the negatively charged intracellular space.
    • The negative value results from selective permeability to K⁺, Na⁺, and Cl⁻ ions, influenced by their equilibrium potentials.

    Overview of Medical Biophysics

    • Medical biophysics integrates various medical sciences, addressing biological problems from atomic to organ levels.
    • It provides insights into radiation effects, safety guidelines, and new diagnostic or treatment methods.

    Human Cell Characteristics

    • Cells are the fundamental units of the body, totaling approximately 60 trillion, varying in size from 4 to 120 µm.
    • Key features include metabolism, excitability, and reproduction, organized into tissues forming organs.

    Surface Membrane (SM)

    • The surface membrane includes intracellular SM and plasmatic SM, providing functions such as semipermeability and protection.
    • Composed of a phospholipid bilayer (45% hydrophilic heads, 45% hydrophobic tails) and proteins (50%), it facilitates ion transport and charge storage.

    Membrane Transport Mechanisms

    • Transport mechanisms are crucial for solute movement, impacting cell metabolism and membrane potentials.
    • Passive transport includes diffusion (simple and facilitated) and osmosis, while active transport mechanisms require ATP.

    Types of Diffusion

    • Simple Diffusion: Passive transport of solutes from high to low concentration until equilibrium is reached. Influenced by concentration gradient, solubility, and temperature.
    • Facilitated Diffusion: Involves transport proteins that assist larger molecules across the membrane, changing conformation during the process.
    • Ion Channel Diffusion: Passive transport of ions like Na⁺ and K⁺ through selective protein channels, regulated by voltage or ligand binding.

    Filtration

    • Filtration is the passive movement of water and small particles driven by hydrostatic pressure gradients, distinct from concentration gradients, often seen in capillary actions.

    Osmosis

    • Osmosis is the passive movement of water through semipermeable membranes, moving from lower to higher osmotic pressure until equilibrium is established.

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    Description

    Explore the principles of osmosis, including the effects of hypotonic and hypertonic solutions on red blood cells. This quiz covers fundamental concepts such as Van Hoff's Law and active membrane transport mechanisms. Test your understanding of how these processes impact cellular environments.

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