Transport

• How does the presence of a cell wall affect water movement in cells?

  In plants and fungi, the cell wall moderates the effects of osmosis, preventing cell rupture in hypotonic solutions and maintaining cell shape in hypertonic solutions.
• What is osmosis and how does it affect water movement across membranes?

  Osmosis is the passive movement of water across a semi-permeable membrane, from a region of low solute concentration to a region of high solute concentration, to equalize concentrations.
• Why is water movement important in biological systems?

  Water, as a solvent, is essential for transporting and dissolving polar or charged molecules (solute) in biological processes.
• What is simple diffusion across membranes?

  Simple diffusion is the passive, directional movement of molecules from an area of high concentration to an area of low concentration, continuing until equilibrium is reached.
• What is active transport and how does it differ from passive transport?

  Active transport is the movement of materials against a concentration gradient, requiring the expenditure of energy (ATP), unlike passive transport.
• What are the two main types of active transport and their differences?

  The two main types are primary active transport (using ATP to move a molecule against its gradient) and secondary active transport (coupling the movement of a molecule against its gradient to another molecule moving down an electrochemical gradient).
• What do hypertonic, hypotonic, and isotonic solutions mean?

  Hypertonic solutions have higher solute concentrations, causing cells to gain water; hypotonic solutions have lower solute concentrations, causing cells to lose water; isotonic solutions have equivalent solute concentrations, resulting in no net water flow.
• How do pump proteins function in active transport?

  Pump proteins in active transport use energy (ATP) to move molecules against their concentration gradient, either by direct ATP hydrolysis (primary) or by coupling with another molecule's gradient (secondary).
• What are channel proteins and carrier proteins in facilitated diffusion?

  Channel proteins are integral lipoproteins with a hydrophilic pore for ions, while carrier proteins are integral glycoproteins that bind specific molecules and undergo conformational changes to transport them.
• What are contractile vacuoles and their function?

  Contractile vacuoles, found in some unicellular organisms, regulate cell osmotic conditions by absorbing and expelling excess water to prevent cell damage.
• How does water movement in hypotonic and hypertonic solutions affect plant tissue?

  In hypertonic solutions, plant tissue loses water and in hypotonic solutions, it gains water, affecting the tissue's osmolarity and potentially leading to changes in turgor pressure.
• What are the medical applications of isotonic solutions?

  Isotonic solutions are used to preserve tissues or organs for medical procedures, prevent cellular damage due to osmosis, and restore fluid levels in patients with hypovolemia.
• What are the three main types of passive transport and their characteristics?

  The types are simple diffusion (for small or lipophilic molecules), osmosis (involving water movement), and facilitated diffusion (aided by transmembrane proteins for large or charged molecules).
• What factors can influence the rate of diffusion?

  The rate of diffusion can be influenced by temperature, molecular size, and the steepness of the concentration gradient.
• How do non-polar steroids pass through the phospholipid bilayer?

  Non-polar steroids pass through via simple diffusion, as they are small and lipophilic, unlike large or charged molecules which require facilitated diffusion or active transport.
• What is passive transport and what does it involve?

  Passive transport is the movement of materials along a concentration gradient (high to low concentration) without the expenditure of energy (ATP).
• What are the effects of uncontrolled osmosis in cells lacking a cell wall?

  In cells without a cell wall, uncontrolled osmosis can cause cell shrinkage (crenation) in hypertonic solutions and cell swelling or bursting (lysis) in hypotonic solutions.
• What is facilitated diffusion and how does it work?

  Facilitated diffusion is the passive movement of molecules across the cell membrane, aided by specific transmembrane proteins, for molecules unable to freely cross the bilayer.
• What is osmolarity and how is it measured?

  Osmolarity is a measure of solute concentration, defined by the number of osmoles of a solute per liter of solution (osmol/L).
• What are aquaporins, and how do they function in cell membranes to regulate water transport?

  Aquaporins are integral proteins in cell membranes, acting as water channels to facilitate faster water transport in response to solute concentrations, and their levels can be regulated to control cell osmotic conditions.