bio exam 2 (terms - basics + water transport)

Diffusion

random movement of molecules resulting in even distribution of particles when no barriers are present

simple diffusion

diffusion that does not involve a direct input of energy or assistance by carrier proteins

permeation

the process where molecules, like water or nutrients, move through a plant's cell membranes or outer layers (like the cuticle) by diffusing from an area of high concentration to an area of low concentration

facilitated diffusion

passive movement through a membrane involving a specific carrier protein, does not proceed against a concentration gradient

Channel protein

integral membrane protein that forms an aqueous passageway across the membrane which it is inserted and through which specific solutes may pass

carrier protein

proteins that bind another substance to transport it from one location to another

Primary active transport

active transport where atp is hydrolyzed, yielding energy required to transport an ion or molecule against its concentration gradient

secondary active transport

form of active transport that does not use atp as an energy source, but transport is coupled to ion diffusion down a concentration gradient established by primary active transport; also called co-transport

Fick’s Law of Diffusion

an equation that describes the factors that determine the rate of diffusion of a molecule from an area of higher concentration to an area of lower concentration

Electrochemical gradient

concentration gradient of an ion across a membrane plus the voltage difference across that membrane

electrochemical equilibrium

a state where the movement of ions across a cell membrane is balanced

Osmosis

the movement of water across a differentially permeable membrane, from one region to another region where water potential is more negative

osmolarity

concentration of osmotically active particles in a solution

isosmotic

a solution has the same osmotic pressure as the plant cell's internal environment, resulting in no net movement of water across the cell membrane

hyposmotic

a state of low osmotic pressure that can occur in root cells and cause water to move from the soil into the plant's vascular tissues

hyperosmotic

a condition where a plant experiences a higher concentration of solutes in its environment than in its cells, causing water to move out of the cells

Water potential

the tendency for a system to take up water from pure water though a differentially permeable membrane; relative to pressure potential and solute potential

Osmotic potential (or pressure)

the tendency of water to move across a semipermeable membrane due to the concentration of dissolved solutes within the cell sap

hydrostatic potential (or pressure)

the pressure exerted by water within a plant cell

Matrix potential

the component of water potential that arises from the attraction of water molecules to the solid surfaces within a plant cell wall

turgor pressure

the pressure exerted by the fluid inside a plant cell against its cell wall