Chapter 5 Flashcards

What is the distribution of water among body compartments?

The majority of the body's water content is intracellular, while the remaining one-third is distributed between the interstitium and plasma, with approximately 75% of that remaining portion found within the tissues.

Define and describe osmosis.

Osmosis is the movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration or from high solvent concentration to low until equilibrium is reached.

What is osmotic pressure?

Osmotic pressure is the pressure needed to prevent the inward flow of water across a semi-permeable membrane, driving fluids towards a compartment with a higher solute concentration.

How does osmolarity differ from molarity?

Molarity measures solute concentration in moles per liter, while osmolarity accounts for osmotically active particles in solution, making it more relevant in physiological contexts.

Distinguish between isosmotic, hyposmotic, and hyperosmotic.

Isosmotic: same osmotically active particles in both compartments; Hyperosmotic: higher concentration in one compartment; Hyposmotic: lower concentration in one compartment.

Contrast osmolarity and tonicity.

Osmolarity refers to total osmotically active particles in a solution; tonicity refers to effective osmolarity and its effect on cell volume, focusing on non-penetrating solutes.

Distinguish between isotonic, hypotonic, and hypertonic.

Isotonic: no net water movement, stable cell volume; Hypertonic: higher concentration of non-penetrating solutes, cell shrinks; Hypotonic: lower concentration of non-penetrating solutes, cell swells.

What is bulk flow?

Bulk flow is the overall movement of gases and fluids driven by a pressure gradient from high to low pressure.

What properties of a cell membrane contribute to its permeability?

Cell membrane permeability is influenced by lipid solubility, surface area, concentration gradient, and molecular size. Lipid-soluble substances can cross easily, whereas ions and large water-soluble molecules require assistance.

What is the difference between active transport and passive transport?

Active transport requires energy (ATP) to move substances against their concentration gradient, while passive transport moves substances down their gradient without energy.

Define diffusion.

Diffusion is a passive process where solutes move from high to low concentration due to a chemical gradient until equilibrium is achieved.

State Fick’s law.

Fick's law states diffusion rate is proportional to membrane surface area, concentration gradient, and permeability, and inversely proportional to molecular weight and size.

Differentiate between protein-mediated transport, facilitated diffusion, and active transport.

Protein-mediated transport involves any transport through proteins. Facilitated diffusion is passive transport using carrier/channel proteins, while active transport requires energy to move substances against their gradient.

What is the role of membrane receptor proteins?

Membrane receptor proteins bind to extracellular ligands, triggering cellular responses like signal transduction or receptor-mediated endocytosis.

Compare channel proteins and carrier proteins.

Channel proteins provide open passageways for ions/water to move freely. Carrier proteins bind substrates, leading to conformational changes for transport across the membrane.

Channel proteins provide open passageways for ions/water to move freely. Carrier proteins bind substrates, leading to conformational changes for transport across the membrane.

Open channels remain continuously open for movement, while gated channels open/close in response to stimuli.

Compare and contrast facilitated diffusion and simple diffusion.

Both are passive processes moving substances down their gradients. Simple diffusion involves direct passage through the membrane, while facilitated diffusion requires membrane proteins.

Diagram the structure and mechanism of the Na+-K+-ATPase.

The Na+-K+-ATPase is a primary active transporter that pumps three sodium ions out and two potassium ions into the cell per ATP, maintaining ion gradients.

Describe secondary active transport.

Secondary active transport utilizes the gradient established by primary transport to move another substance against its gradient, often via co-transport mechanisms.

Describe the process of phagocytosis.

Phagocytosis is a vesicular transport process where a cell engulfs large particles, forming a phagosome that enters the cytoplasm.

How is exocytosis related to endocytosis? Is exocytosis active or passive?

Exocytosis and endocytosis are opposing processes for membrane recycling. Both are active processes requiring energy.

Explain what is meant by an electrochemical gradient.

An electrochemical gradient combines the chemical gradient (ion concentration) and electrical gradient (charge differences) affecting ion movement across membranes.