ap bio vocab

osmosis

the passive diffusion of water molecules across a selectively permeable membrane from a region of lower solute concentration (higher water potential) to a region of higher solute concentration (lower water potential)

facilitated diffusion

a type of passive transport where molecules move across a cell membrane from high to low concentration via helper proteins (channel or carrier proteins) without using energy

aquaporin

a protein channel in a cell's membrane that acts like a tiny tunnel, letting water molecules pass in and out quickly to maintain the cell's water balance

phagocytosis

The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells

hypertonic

A hypertonic solution has a higher concentration of solutes (like salt or sugar) outside a cell compared to inside it

hypotonic

A hypotonic solution has a lower concentration of solutes (like salt or sugar) compared to another solution, usually the inside of a cell

isotonic

An isotonic solution has the same concentration of solutes (like salt or sugar) as another solution or the inside of a cell.

water potential

quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and matrix effects such as capillary action

turgor pressure

Turgor pressure is the force of water inside a plant cell pushing outward against the rigid cell wall

plasmymolysis

the shrinking of a plant cell's cytoplasm and membrane away from its rigid cell wall, caused by water leaving the cell.

osmoregulation

the active, homeostatic process of balancing water and solute concentrations (salt) within an organism’s body fluids to prevent cells from becoming too dehydrated or bursting

ligand

a signaling molecule that specifically binds to a target receptor protein (usually larger) to initiate a cellular response

reception

the first stage of cell signaling, where a target cell detects and binds a signaling molecule (ligand) from outside the cell to a corresponding receptor protein.

transduction

the second step in cell signaling, where a cell converts an external message (like a hormone) into a specific internal response.

response

any behavioral or physiological change an organism makes in reaction to an internal or external environmental stimulus

phosphorylation cascade

a signal transduction pathway where a series of protein kinases add phosphate groups to the next kinase in line, activating it.

second messenger

amplify and distribute the original signal, greatly increasing the speed and magnitude of the cellular response

cAMP

a common second messenger used in signal transduction pathways to relay messages from extracellular signals (like hormones or neurotransmitters) to the inside of the cell.

kinase

an enzyme that plays a crucial role in cell signaling pathways by adding a phosphate group to other molecules, typically proteins

hormones

chemical messengers produced by endocrine glands that travel through the bloodstream (or body fluids) to act on specific target cells, regulating physiological processes like growth, metabolism, and homeostasis.

plasmodestmata

Plasmodesmata are microscopic, membrane-lined channels traversing the cell walls of adjacent plant cells, acting as junctions for direct intercellular communication and transport.

gap junctions

Gap junctions are specialized intercellular connections in animal cells that directly link the cytoplasm of adjacent cells via protein channels called connexons.

negative feedback

a regulatory mechanism that maintains homeostasis by counteracting or reversing a change, bringing a variable back to its ideal "set point,

positive feedback

a mechanism where the output or product of a process intensifies the original stimulus, amplifying the response and moving the system further from its starting point, rather than returning it to homeostasis.

apoptosis

a genetically regulated, orderly process of programmed cell death, often called "cell suicide," used by multicellular organisms to eliminate unneeded, damaged, or infected cells without triggering inflammation.