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entire contents of the cell, except the nucleus, bounded by the plasma membrane

transport proteins

special proteins embedded in the membrane that

selectively permeable

membranes regulate the exchange of materials in a very specific way


proteins embedded in the membranes that have sugars attached to the heads


lipids embedded in the membranes that have sugars attached to the heads


movement of a substance down its concentrated gradient from an area of higher concentration to an area of lower concentration; increases the entropy of the system

concentration gradient

difference in the concentration of a substance over a distance


movement of water down its concentration gradient


outward pressure of a cell against its cell wall

passive transport

diffusion of a substance through a biological membrane

active transport

movement of a substance through a biological membrane against a concentration gradient

facilitated diffusion

spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients


cellular uptake of materials where the plasma membrane surround and engulfs extracellular materials


release of macromolecules from a cell by the fusion of vesicles with the plasma membrane


air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place


waxy outlayer covering the surfaces of mos land-dwelling plants, animals, fungi


openings between two guard els in the epidermis of a plant leaf through which gases are exchanged with the air


the loss of water to the atmosphere by a plant through the stomates in its leaves


the balanced and controlled conditions in the internal environment of an organism


toxic nitrogen compound (NH3) excreted by some aquatic organisms; though to have been present Earth's early atmosphere


an organ that regulates water and salt levels, filters water and wastes from the lood, and excretes the end products


functional unit of a kidney consisting of a glomerulus, its associated capsule, and tubule, surrounded by capillaries

urinary system

vertebrate organism the regulates levels of water and dissolved substances in the body, execreting wastes as urine


the solution of wastes execreted from the kidney


carries urine from kidney to urinary bladder;

urinary bladder

an organ that stores urine before it is discharged from the body through the urethra


tube through which urine travels from the bladder to the outside of the body

glomerular capsule

the cup of a nephron, which filters blood


a ball of capillaries surrounded by a glomerular capsule in the nephron; the site of filtration in the kidneys


fluid from plasma passes into nephron; is filtered thru the glomerular capillaries


takes place in tubules of nephron; cells of tubule reabsorb substances needed by body into the capillaries


cells in tubule wall selectively remove from capillaries material left in blood after filtration or reabsorption and excrete it into filtrate; regulates hormones


a hormone secreted by the adrenal gland; helps regulate sodium and potassium concentrations and water balance

feedback regulation

the regulation of the activity of an enzyme by one of its products

antidiuretic hormone

hormone released from the posterior lobe of the pituitary; enhances conservation of water by the kidneys


colorless crystalline compound that is the main nitrogenous breakdown product of protein metabolism in mammals and is excreted in urine

uric acid

insoluble in H20; requires virtually no H20 for excretion; nontoxic form of nitrogenous waste

contractile vacuole

pumps excess water outside of a cell (using a pore in the membrane)


a state of balance


an endocrine gland in the brain

cell membrane

encloses the cell; composed of two thin layers of phospholipids and proteins


the materials that cross from the capillaries to the glomerular capsule


microscopic blood vessel penetrating the tissues and consisting of single layer of cells that allows exchange between the blood and tissue fluids

cellular respiration

the series of chemical reactions by which a living cell breaks down carbohydrates and obtains energy from them


net movement of water is into the cell; a lower osmotic pressure


net movement of water is out of the cell; a higher osmotic pressure

nitrogen waste

toxic by-product of metabolism proteins and nucleic acids

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