Ch. 5 Flashcards
What are the key ingredients of the plasma membrane?
phospholipids
What are amphipathic molecules?
contain both a hydrophillic region and a hydrophobic region
What is the Fluid Mosaic Model?
envisions the membrane as a “mosaic” of proteins drifting laterally in a fluid phospholipid bulayer
the currently accepted model of cell membrane structure
What are the functions of membrane proteins?
- transport
- signaling
- enzymes
What is selective permeability?
a property of biological membranes that allows them to regulate the passage of substances across them
What cannot easily pass through the cell membrane?
large molcules, polar molecules, ions
they require the help of membrane proteins!
What are transport proteins?
proteins embedded in the membrane that help certain substances cross it
What is an aquaporin?
a channel protein in the cell membrane that specifically facilitates osmosis
What is diffusion?
the movement of substances from an area of high concentration to an area of low concentration
will continue to move down the gradient until equilibrium is reached
What is passive transport?
the diffusion of a substance across a biological membrane with no energy expenditure
What is osmosis?
the diffusion of water across a cell membrane
What is tonicity?
the ability of a solution surrounding a cell to cause that cell to either gain or lose water
What is a hypotonic solution?
having a lower concentration of solute than another solution
causes a cell to take up water
lyse
What is a hypertonic solution?
having a higher concentration of solute than another solution
causes a cell to lose water
shrivel
What is an isotonic solution?
having the same solute concentration as another solution
causes no net movement of water
What is facilitated diffusion?
the passage of molecules across a membrane with the help of membrane proteins
requires no energy expenditure
What is active transport?
the movement of a substance across a membrane mediated by specific transport proteins
requires an expenditure of energy
What is membrane potential?
the voltage across a cell’s membrane, affects the activity of excitable cells and transmembrane movement
What are ion pumps?
carrier proteins that carry cations and anions across a cell membrane
influece action potential
What is cotransport?
occurs when active transport of a solute indirectly drives transport of other substances
What is exocytosis?
the release of substances out of a cell by the fusion of a vesicle with the membrane
What is endocytosis?
a process in which a cell engulfs extracellular material through an inward folding of its plasma membrane
What are the 3 types of endocytosis?
- phagocytosis
- pinocytosis
- receptor-mediated
What is phagocytosis?
a cell engulfs large particles or whole cells
cell eating
What is pinocytosis?
a cell ingests extracellular fluid and its dissolved solutes
cell drinking
What is receptor-mediated endocytosis?
the uptake of specific molecules based on a cell’s receptor proteins
enables cell to acquire bulk quantities of a substance
What are the 3 stages of cell signaling?
- reception
- transduction
- response
What is reception?
the binding of a signaling molecule to a receptor protein, activating the receptor by causing it to change shape
What is transduction?
the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway
occurs in a series of steps
What is reception?
the change in a specific cellular activity brought about by a transduced signal from outside the cell
What is a signal transduction pathway?
a series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response
