College Physics - Biology 2E Chapter 5

Flashcards on Plasma Membranes, Transport, and Cell Structure

Plasma Membrane Function

Defines the outer border of cells and organelles, manages entry/exit, receives external signals, adheres to neighbors.

Fluid Mosaic Model

Membrane structure with phospholipids, cholesterol, proteins, and carbohydrates, giving it a fluid character.

Phospholipids

Amphipathic molecules with a glycerol, phosphate group (polar), and 2 fatty acid chains (nonpolar); form the main fabric of cell membranes.

Amphipathic

Having both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Phospholipid Bilayer

Arrangement of phospholipids with polar heads facing outward and hydrophobic tails facing inward.

Integral Proteins

Proteins integrated completely into the phospholipid bilayer.

Transmembrane Proteins

Integral proteins that pass completely through the phospholipid bilayer.

Peripheral Proteins

Proteins occurring only on the surfaces of the phospholipid bilayer.

Glycoproteins

Carbohydrates bound to proteins on the exterior surface of the plasma membrane; function in cell-cell recognition.

Glycolipids

Carbohydrates bound to lipids on the exterior surface of the plasma membrane; function in cell-cell recognition.

Membrane Fluidity

The flexibility of the membrane, affected by phospholipid type, temperature, and cholesterol.

Saturated Fatty Acids and Membrane Rigidity

More saturated fatty acids in phospholipids lead to more rigid membranes.

Cholesterol's Role in Membrane Fluidity

Acts as a fluidity buffer, keeping membranes fluid when cold and preventing them from becoming too fluid when hot.

Selectively Permeable

Property of the plasma membrane that allows some molecules to pass through but not others.

Permeant Molecules

Molecules that can cross the phospholipid bilayer.

Passive Transport

Movement of substances across a membrane requiring no added energy.

Active Transport

Movement of substances across a membrane requiring energy (ATP or electrochemical gradient).

Diffusion

The movement of a substance from an area of high concentration to an area of low concentration.

Facilitated Transport

Passive transport of substances down their concentration gradients through transmembrane proteins.

Channel Proteins

Transmembrane proteins that form channels to allow specific molecules or ions to cross the membrane.

Carrier Proteins

Transmembrane proteins that bind to a substance and change shape to carry it across the membrane.

Osmosis

The diffusion of water across a selectively permeable membrane.

Tonicity

The ability of an extracellular solution to change the volume of a cell by affecting osmosis.

Hypertonic

Extracellular fluid with lower osmolarity than the cytosol; water leaves the cell.

Isotonic

Extracellular fluid with the same osmolarity as the cytosol; no net water movement.

Hypotonic

Extracellular fluid with higher osmolarity than the cytosol; water enters the cell.

Osmoregulation

The process by which organisms control the concentration of water and salt in their bodies.

Turgor Pressure

Pressure exerted by the plasma membrane against the cell wall in plant, fungi, and bacteria cells in hypotonic environments.

Plasmolysis

Detachment of the plasma membrane from the cell wall in hypertonic solutions.

Contractile Vacuoles

Organelles used by freshwater protists to pump water out of their cells.

Electrochemical Gradient

The combined effects of concentration gradients and electrical gradients on ions.

Primary Active Transport

Active transport that uses ATP to move substances against their concentration gradient.

Secondary Active Transport

Active transport that uses an electrochemical gradient created by primary active transport to move another substance.

Uniporter

Carrier protein that transports one molecule or ion.

Symporter

Carrier protein that transports two different molecules or ions in the same direction.

Antiporter

Carrier protein that transports two different molecules or ions in different directions.

Electrogenic Pump

A pump that contributes to the electrochemical gradient across a membrane.

Bulk Transport

Active transport of large molecules/particles across the plasma membrane.

Endocytosis

Importing molecules/particles into the cell by bulk transport.

Exocytosis

Exporting molecules/particles out of the cell by bulk transport.

Phagocytosis

A type of endocytosis where the cell membrane surrounds and engulfs a large particle.

Pinocytosis

A type of endocytosis where the cell membrane invaginates and surrounds a small volume of fluid.

Receptor-Mediated Endocytosis

Endocytosis where uptake of a specific substance is targeted by binding to receptors on the membrane surface.

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Solute

A substance that is dissolved in a solvent, forming a solution.

Solvent

A substance that dissolves a solute, forming a solution.

Solution

A homogeneous mixture of a solute dissolved in a solvent.

Hydrophilic

Having an affinity for water; polar molecules that dissolve in water.

Hydrophobic

Lacking affinity for water; nonpolar molecules that do not dissolve in water.

Cytoskeleton

A network of protein fibers within a cell that provides structure, support, and facilitates movement.

Extracellular Matrix

A collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells.