Human Anatomy and Physiology Chapter 03 Part B - Cells: The Living Units

Vocabulary flashcards covering active transport, vesicular transport, endocytosis/exocytosis, and membrane potential concepts from the lecture notes.

Active transport

Movement of solutes across a membrane that requires energy to move them against their electrochemical gradient.

Primary active transport

Direct use of ATP hydrolysis to power transport proteins that change shape and move solutes across membranes.

Secondary active transport

Transport that uses energy stored in ion gradients created by primary active transport to move solutes.

Na+-K+ ATPase (Na+-K+ pump)

Pump that moves 3 Na+ out and 2 K+ into the cell per ATP hydrolyzed; maintains electrochemical gradients, especially in excitable cells.

Antiporter

Carrier that moves one substance out of the cell while moving a different substance in (opposite directions).

Symporter

Carrier that moves two different substances in the same direction across the membrane.

Leakage channel

Ion channel that allows ions (e.g., Na+, K+) to passively leak down their concentration gradients.

Electrochemical gradient

Combined chemical and electrical driving force for ion movement across a membrane.

Calcium pump

Primary active transporter that moves Ca2+ across membranes to maintain low intracellular calcium.

Hydrogen (proton) pump

Primary active transporter that moves H+ across membranes, contributing to proton gradients.

Endocytosis

Process of taking substances into the cell via vesicle formation; includes phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Phagocytosis

Cell eating; engulfment of solid particles by pseudopods into a phagosome, used by macrophages and some WBCs.

Pinocytosis

Cell drinking; nonselective uptake of extracellular fluid and dissolved solutes; main nutrient absorption in the small intestine.

Receptor-mediated endocytosis

Selective uptake of specific molecules via receptors in clathrin-coated pits; examples include LDL, iron, insulin; can be hijacked by pathogens.

Clathrin-coated pits

Protein-coated membrane pits that mediate receptor-mediated endocytosis.

Caveolae

Small vesicular pits with a distinct coat; capture specific molecules and participate in transcytosis.

Transcytosis

Movement of a substance across the cell from one side to the other via vesicular transport.

Vesicular trafficking

Movement of substances within the cell using membrane-bound vesicles between compartments.

Exocytosis

Process of releasing material from the cell via secretory vesicles; docking involves v-SNARE and t-SNARE proteins.

v-SNARE

Vesicle-SNARE protein on the vesicle that interacts with t-SNAREs to trigger docking and fusion.

t-SNARE

Target-SNARE protein on the membrane that pairs with a v-SNARE to drive vesicle fusion.

Phagosome

Vesicle formed around a phagocytosed particle during phagocytosis.

Vesicular trafficking

Movement of substances through the cell via membrane-bound vesicles.

Pseudopods

Temporary cellular projections that engulf particles during phagocytosis and drive amoeboid movement.

Endocytosis vs Exocytosis

Endocytosis brings material into the cell; exocytosis ejects material from the cell.

Resting membrane potential (RMP)

Electrical potential energy across the plasma membrane of a cell at rest; typically negative inside.

K+ leakage channels

Leak channels that allow K+ to diffuse out, helping establish the RMP.

RMP range

Most cells have an RMP around -90 mV (range commonly cited as -50 to -100 mV).

Na+-K+ pump maintains RMP

The Na+-K+ ATPase continuously pumps Na+ out and K+ in, maintaining electrochemical gradients and the steady-state RMP.

Na+ effect on RMP

Na+ entry can depolarize the membrane and raise the RMP toward -70 mV when the membrane is more permeable to Na+.

Cl- role in RMP

Cl− gradients do not influence the RMP because their chemical and electrical gradients are balanced.

Inhibitors of Na+-K+ pump

Oleander toxin and digoxin/digitoxin (from foxglove) inhibit the Na+-K+ ATPase, affecting membrane potentials.