ANP 1105A - Anatomy & Physiology I Lecture 3 - Plasma Membrane, Transport, Diffusion and Osmosis

Flashcards covering key vocabulary related to the plasma membrane, types of transport, diffusion, and osmosis from the ANP 1105A Lecture 3 notes.

Plasma Membrane

Acts as a selective barrier separating intracellular fluid (ICF) from extracellular fluid (ECF), controlling what enters and leaves the cell. Also known as the cell membrane.

Lipid Bilayer

The flexible structure of the plasma membrane, primarily composed of membrane lipids, mainly phospholipids.

Phospholipids

Make up 75% of the lipid bilayer; consist of polar (hydrophilic) phosphate heads and nonpolar (hydrophobic) fatty acid tails.

Phosphate Heads

The polar (charged), hydrophilic (water-loving) part of a phospholipid molecule, facing the water inside and outside the cell.

Fatty Acid Tails

The nonpolar (no charge), hydrophobic (water-hating) part of a phospholipid molecule, facing inward away from water.

Glycolipids

Lipids with sugar groups on the outer membrane surface, making up about 5% of the lipid bilayer.

Cholesterol

Increases membrane stability and is a component of lipid rafts, making up about 20% of the lipid bilayer.

Amphipathic Molecules

Molecules that contain both a hydrophilic (water-loving) and a hydrophobic (water-hating) region, such as phospholipids.

Lipid Rafts

Formed by cholesterol, certain glycolipids, and other specialized lipids, they modify membrane fluidity and act as signaling islands.

Fluid Mosaic Model

Describes the plasma membrane as a constantly changing pattern where specialized plasma membrane proteins float in the fluid lipid bilayer.

Integral Membrane Proteins

Proteins inserted into the plasma membrane, most are transmembrane with hydrophobic and hydrophilic regions, functioning as transport proteins, enzymes, or receptors.

Peripheral Membrane Proteins

Proteins loosely attached to integral membrane proteins or anchored with covalently attached lipid groups on either the inner or outer leaflet of the membrane, functioning as enzymes, in signal transduction, or as scaffold proteins.

Glycocalyx

A coating formed by carbohydrates (on glycolipids and glycoproteins) on the outer surface of the cell, functioning as specific biological markers for cell-to-cell recognition and allowing the immune system to recognize 'self' from 'non-self'.

Tight Junctions

Impermeable junctions that form continuous seals around cells, preventing molecules from passing between cells.

Desmosomes

Anchoring junctions that bind adjacent cells together like molecular Velcro, helping to keep cells from tearing apart.

Gap Junctions

Communicating junctions formed by transmembrane proteins (connexons) that create tunnels between cells, allowing ions and small molecules to pass directly from cell to cell, important in heart cells and embryonic cells.

Passive Transport

Movement of substances across the plasma membrane that does not require cellular energy input, involving diffusion down a concentration gradient.

Active Transport

Movement of substances across the plasma membrane that requires energy (ATP) to move substances against their concentration gradient (uphill).

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration, driven by the intrinsic kinetic energy of molecules.

Concentration Gradient

A difference in the concentration of molecules between two areas, driving diffusion.

Simple Diffusion

The direct diffusion of small, nonpolar, lipid-soluble (hydrophobic) substances (e.g., oxygen, carbon dioxide, steroid hormones) through the phospholipid bilayer.

Facilitated Diffusion

The transport of larger, non-lipid soluble, or polar molecules across the membrane with the assistance of carrier molecules (carrier-mediated) or channel proteins (channel-mediated).

Carrier-mediated Facilitated Diffusion

Transport of specific hydrophilic molecules (e.g., glucose, amino acids) passively down their concentration gradient when they bind to a transmembrane protein carrier, causing it to change shape and move the molecule across the membrane.

Channel-mediated Facilitated Diffusion

Transport of ions across the membrane through integral membrane proteins that form channels, showing selectivity for particular types of ions based on size and charge.

Osmosis

The net diffusion of a solvent, such as water, across a selectively permeable membrane, moving from an area of higher water concentration (lower solute) to an area of lower water concentration (higher solute).

Aquaporins (AQPs)

Specific water channels in the plasma membrane through which most water diffuses during osmosis, though some may pass directly through the lipid bilayer.

Osmolarity

The total number of solute particles in a solution, influencing the movement of water by osmosis.

Hydrostatic Pressure

The outward pressure exerted on the cell side of the membrane caused by increases in the volume of the cell due to osmosis.

Osmotic Pressure

The inward pressure due to the tendency of water to be pulled into a cell with higher osmolarities (more solutes).

Isotonic Solution

A solution with the same non-penetrating solute concentration as inside cells; cells retain their normal size and shape (water moves in and out equally).

Hypertonic Solution

A solution that contains a higher concentration of non-penetrating solutes than are present inside cells; cells lose water by osmosis and shrink (crenate).

Hypotonic Solution

A solution that contains a lower concentration of non-penetrating solutes than are present inside cells; cells take on water by osmosis until they become bloated and burst (lyse).

Penetrating Solutes

Solutes that can freely cross the plasma membrane.

Non-penetrating Solutes

Solutes that cannot readily cross the plasma membrane, influencing tonicity and cell volume.