Transport Mechanisms and Membrane Properties
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Questions and Answers

What is Active Transport?

  • The diffusion of water across a membrane
  • The movement of a substance across a biological membrane against its concentration or electrochemical gradient (correct)
  • The process of molecules moving from an area of higher concentration to an area of lower concentration
  • The control of water balance in organisms

What defines an Amphipathic Molecule?

  • A molecule that is completely hydrophobic
  • A molecule that has both a hydrophilic region and a hydrophobic region (correct)
  • A molecule that allows for facilitated diffusion
  • A molecule that has only hydrophilic regions

What are Aquaporins?

A transport protein in the plasma membrane that facilitates the diffusion of water

Define Concentration Gradient.

<p>An increase or decrease in the density of a chemical substance in an area.</p> Signup and view all the answers

What is Cotransport?

<p>The coupling of the 'downhill' diffusion of one substance with the 'uphill' transport of another substance.</p> Signup and view all the answers

Diffusion is the process by which molecules move from lower concentration to higher concentration.

<p>False (B)</p> Signup and view all the answers

What is an Electrochemical Gradient?

<p>The diffusion gradient of an ion affected by concentration difference and membrane potential.</p> Signup and view all the answers

Define an Electrogenic Pump.

<p>An active transport protein that generates voltage across a membrane while pumping ions.</p> Signup and view all the answers

What is Endocytosis?

<p>The process where a cell membrane surrounds a particle and encloses it in a vesicle.</p> Signup and view all the answers

What occurs during Exocytosis?

<p>A substance is released from the cell through a vesicle that fuses with the membrane.</p> Signup and view all the answers

Define Facilitated Diffusion.

<p>The transport of substances through a membrane along a concentration gradient with the aid of carrier proteins.</p> Signup and view all the answers

What does Flaccid mean?

<p>Limp, lacking in stiffness or firmness.</p> Signup and view all the answers

Describe the Fluid Mosaic Model.

<p>The model of cell membrane structure envisioning a mosaic of protein molecules in a phospholipid bilayer.</p> Signup and view all the answers

What are Gated Channels?

<p>Protein channels in a membrane that open or close in response to a stimulus.</p> Signup and view all the answers

What are Glycolipids?

<p>Lipid substances with linked sugar groups important in cell membranes and signaling.</p> Signup and view all the answers

Define Glycoproteins.

<p>Proteins that have carbohydrates covalently bonded to them.</p> Signup and view all the answers

What does Hypertonic mean?

<p>The solution with greater concentration of solutes.</p> Signup and view all the answers

What is Hypotonic?

<p>The solution with the lesser concentration of solutes.</p> Signup and view all the answers

Define Integral Proteins.

<p>Proteins that extend entirely through the membrane with hydrophobic and hydrophilic ends.</p> Signup and view all the answers

What are Ion Channels?

<p>Transmembrane protein channels allowing specific ions to flow across the membrane.</p> Signup and view all the answers

Define Isotonic.

<p>Having a solute concentration equal to that of another solution.</p> Signup and view all the answers

What are Ligands?

<p>Molecules that bind specifically to a receptor site of another molecule.</p> Signup and view all the answers

Define Membrane Potential.

<p>The charge difference between a cell's cytoplasm and the extracellular fluid due to ion distribution.</p> Signup and view all the answers

What does Osmoregulation mean?

<p>The control of water balance in organisms.</p> Signup and view all the answers

What is Osmosis?

<p>Diffusion of molecules through a semipermeable membrane from higher to lower concentration.</p> Signup and view all the answers

Define Passive Transport.

<p>Movement of substances across a membrane without the use of energy by the cell.</p> Signup and view all the answers

What are Peripheral Proteins?

<p>Protein appendages loosely bound to the membrane surface.</p> Signup and view all the answers

Define Plasmolysis.

<p>When a cell in a hypertonic environment loses water and shrinks.</p> Signup and view all the answers

What is a Proton Pump?

<p>An active transport mechanism that consumes ATP to move hydrogen ions out of a cell.</p> Signup and view all the answers

Define Selective Permeability.

<p>A property of membranes that allows some substances to cross more easily than others.</p> Signup and view all the answers

What is the Sodium-Potassium Pump?

<p>A transport protein that moves sodium out of the cell and potassium into the cell.</p> Signup and view all the answers

Define Tonicity.

<p>The ability of a solution to cause a cell to gain or lose water.</p> Signup and view all the answers

What are Transport Proteins?

<p>Protein molecules that help transport substances across membranes.</p> Signup and view all the answers

Define Turgid.

<p>Firm, as a result of water entry from a hypotonic environment.</p> Signup and view all the answers

Study Notes

Transport Mechanisms

  • Active Transport: Movement of substances against concentration or electrochemical gradients, requiring energy.
  • Facilitated Diffusion: Movement of substances along a concentration gradient through carrier proteins, no energy required.
  • Diffusion: Spontaneous movement from high to low concentration areas.
  • Osmosis: Specific diffusion of water molecules through a semipermeable membrane, aiming for equal concentration.

Types of Transport Proteins

  • Aquaporins: Membrane proteins that facilitate water transport across cell membranes.
  • Ion Channels: Specialized protein channels allowing specific ions to pass through membranes.
  • Transport Proteins: Proteins aiding in the movement of substances through the cellular environment.

Membrane Properties

  • Fluid Mosaic Model: Describes membrane structure as a mix of proteins floating in a phospholipid bilayer.
  • Selective Permeability: Membrane characteristic allowing certain substances to pass easily while blocking others.
  • Integral Proteins: Proteins embedded within the membrane, functioning in transport and signaling.

Cellular Processes

  • Endocytosis: Process by which cells engulf particles, enclosing them in vesicles.
  • Exocytosis: Mechanism of releasing substances from cells via vesicles merging with the cell membrane.
  • Cotransport: Coupling of one substance's diffusion to drive the transport of another against its gradient.

Solutions and Tonicity

  • Hypertonic: Solution with a higher solute concentration than another, causing cells to lose water.
  • Hypotonic: Solution with lower solute concentration, leading to water entry and potential cell swelling.
  • Isotonic: Solutions with equal solute concentrations, maintaining cell size.
  • Tonicity: Describes a solution’s ability to affect water movement into or out of cells.

Cell Responses

  • Flaccid: Condition of a plant cell in an isotonic environment, lacking turgor pressure.
  • Turgid: Plant cells become firm when water enters from hypotonic surroundings.
  • Plasmolysis: Occurs when cells in hypertonic environments lose water, leading to cell shrinkage and membrane detachment.

Electrical and Chemical Gradients

  • Electrochemical Gradient: Determines the movement of ions based on both concentration differences and membrane electrical potential.
  • Membrane Potential: Voltage difference across a membrane due to ion distribution, influencing cell activity.
  • Electrogenic Pump: Active transport proteins generating voltage during ion transport, crucial for maintaining gradients.

Membrane Components

  • Amphipathic Molecules: Molecules with hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.
  • Glycolipids: Lipids with sugar groups, important for cell membrane structure and signaling.
  • Glycoproteins: Proteins with carbohydrate chains, playing roles in recognition and signaling.

Sodium-Potassium Pump

  • Transports sodium out and potassium into the cell, working against concentration gradients and generating membrane potential, vital for nerve impulses and muscle contraction.

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Description

Explore the diverse mechanisms through which substances move across cell membranes, including active transport, facilitated diffusion, and osmosis. Understand the structure and function of transport proteins and the fluid mosaic model that characterizes membrane properties. Test your knowledge of these essential biological concepts.

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