Membrane Structure and Function

diffusion

passive movement of particles from an area of high concentration to low concentration

concentration gradient

the difference in the concentration of a substance between two areas, causing the substance to naturally move from an area of high concentration to an area of low concentration

osmosis

diffusion of water across a membrane

tonicity

ability of a surrounding solution to make a cell gain or lose water

hypotonic

solution that has a lower solute concentration which causes water to move into a cell

hypertonic

solution that has a higher solute concentration which causes water to move out of a cell

osmoregulation

control of water balance

facilitated diffusion

type of passive transport where hydrophilic molecules and ions need transport proteins to move across a membrane

sodium-potassium pump

protein that moves 3 sodium ions out and 2 potassium ions into a cell for every atp molecule it consumes

active transport

cell expends energy to move a solute against its concentration gradient

exocytosis

exports bulky materials by a vesicle that fuses with the plasma membrane

endocytosis

cell takes in large molecules or droplets of fluid

phagocytosis

type of endocytosis- cellular eating- a cell takes in large solids by engulfing them

receptor-mediated endocytosis

type of endocytosis- receptor proteins make a pit to release molecules into the cytoplasm

chemical energy

potential energy to release in a chemical reaction

thermodynamics

study of energy transformations that occur in a collection of matter

first law of thermodynamics

law that states energy in the universe is constant

second law of thermodynamics

every energy conversion increases entropy (disorder) of the universe

cellular respiration

process where chemical energy in organic molecules is used to produce atp

exergonic reaction

chemical reaction that releases energy

endergonic reaction

chemical reaction that absorbs energy from its surroundings

metabolism

sum of chemical reactions within a living organism

metabolic pathway

series of chemical reactions that either builds or breaks down a complex molecule

energy coupling

energy released from exergonic reactions to drive endergonic reactions

phosphorylation

the addition of a phosphate group to a molecule, to activate or deactivate its function

activation energy

minimum energy needed for a chemical reaction

substrate

reactant that an enzyme acts on

active site

place where a substrate fits on the surface of an enzyme

competitive inhibitor

reduces enzyme productivity by blocking substrate molecules from entering active site

noncompetitive inhibitor

reduces enzyme productivity by binding to the enzyme and changing its shape