Biology Chapter 5 Notes: Membrane Transport and Cell Signaling

Flashcards covering membrane structure, types of transport (passive, active, and bulk), and the three stages of cell signaling based on Chapter 5 lecture notes.

Plasma Membrane

A structure that separates the cell from its surroundings and regulates what enters and leaves the cell.

Fluid-Mosiac model

A model describing the membrane as proteins floating in a sea of lipids.

Phospholipid bilayer

A structure composed of two layers of phospholipids with polar heads facing toward water and nonpolar tails facing toward each other.

Fluidity

A measure of how flexible and dynamic the membrane is; it must be maintained at the correct level for the membrane to function properly.

Cholesterol

A steroid (lipid) that restricts phospholipid movement in warm temperatures and prevents solidification in cold temperatures.

Unsaturated phospholipids

Phospholipids with one or more double bonds; kinking prevents tight lipid packing at low temperatures.

Peripheral proteins

Proteins that are loosely bound to the membrane's surface.

Integral proteins

Amphipathic proteins that touch both polar and nonpolar membrane portions.

Channel proteins

Proteins that provide hydrophobic channels for the passage of polar or charged materials.

Carrier proteins

Proteins that bind to a molecule and change shape to move that molecule across the membrane.

Protein pumps

A type of carrier protein that requires energy to actively transport molecules.

Signal transduction

A process where a protein receptor in the membrane binds to its chemical messenger, relaying a message to the inside of the cell.

Cell-Cell recognition

A function where glycoproteins act as identification tags to other cells.

Intercellular joining

The hooking together of adjacent cells by attachment of membrane proteins, such as gap junctions or tight junctions.

Aquaporins

A protein channel that quickly allows $\text{H}_2\text{O}$ to pass through the membrane.

Passive transport

Movement of materials from high concentration to low concentration that does not require energy.

Diffusion

The passive transport of materials through a membrane.

Osmosis

The passive transport of $\text{H}_2\text{O}$ through a membrane.

Tonicity

The ability of a surrounding solution to cause a cell to gain or lose water, depending partly on concentration of solutes that cannot cross the membrane.

Hypotonic solution

A solution with a lower solute concentration (higher water) than the cell, causing the cell to swell.

Isotonic solution

A solution with equal solute concentration to the cell, resulting in no net movement of $\text{H}_2\text{O}$ and the cell staying the same size.

Hypertonic solution

A solution with a higher solute concentration (lower water) than the cell, causing the cell to shrivel.

Osmoregulation

The control of solute concentrations and water balance.

Facilitated diffusion

The passive movememnt of molecules through the membrane with the help of transport proteins like channel or carrier proteins.

Gated channels

Channel proteins that open and close in response to an electrical or chemical stimulus.

Active Transport

Transport of materials across the membrane from low to high concentration, requiring energy and transport proteins.

Sodium/potassium pump

A pump that uses phosphorylation from ATP to release $3\,\text{Na}^+$ outside the cell and take $2\,\text{K}^+$ into the cytoplasm.

Membrane potential

The voltage across the membrane caused by the separation of opposite charges.

Electrochemical gradient

The combination of the chemical force (ion concentration gradient) and electrical force (membrane potential) acting on an ion.

Electrogenic pumps

A transport protein that generates voltage across a membrane, such as a proton pump or the sodium potassium pump.

Cotransport

A process where a transport protein couples the downhill diffusion of one substance to the uphill transport of a second substance against its gradient.

Exocytosis

The secretion of molecules by the fusion of vesicles with the plasma membrane.

Endocytosis

The process of taking in materials by forming new vesicles from the plasma membrane.

Phagocytosis

A type of endocytosis commonly called cell eating, where the cell engulfs particles by extending pseudopods.

Pinocytosis

A type of endocytosis commonly called cell drinking, where a vesicle takes in surrounding fluid with dissolved materials.

Receptor mediated endocytosis

A specialized type of pinocytosis that only forms vesicles when enough target molecules bind to the cell surface.

Autocrine signaling

A local signaling method where a cell signals itself, common in the immune system.

Juxtacine signaling

Cell signaling between adjacent cells via gap junctions, plasmodesmata, or cell-cell recognition.

Paracrine signaling

Local signaling to cells in the nearby vicinity, such as growth factors or synaptic signaling.

Endocrine signaling

Long distance signaling involving hormones transported via the bloodstream.

Reception

The first stage of signaling where the target cell detects a signaling molecule (ligand) from outside the cell.

Ligand

A molecule that specifically binds to another molecule, such as a receptor protein.

Transduction

A multistep pathway that transmits and amplifies a signal to molecules inside the cell, often involving phosphorylation.

Protein kinase

An enzyme that transfers phosphate groups from ATP to a protein to change its shape.

Protein phosphates

Enzymes that remove phosphate groups from proteins (dephosphorylation) to inactivate protein kinases and stop a signaling pathway.

Second messengers

Small nonprotein molecules or ions involved in signaling, such as $\text{Ca}^{2+}$ or cyclic AMP (cAMP).